Network Working Group P. Calhoun
Internet-Draft B. O'Hara
Expires: October 2, 2005 Airespace
S. Kelly
Facetime Communications
R. Suri
Airespace
M. Williams
Nokia, Inc.
S. Hares
Nexthop Technologies, Inc.
N. Cam Winget
Cisco Systems, Inc.
March 31, 2005
Light Weight Access Point Protocol (LWAPP)
draft-ohara-capwap-lwapp-02
Status of this Memo
This document is an Internet-Draft and is subject to all provisions
of Section 3 of RFC 3667. By submitting this Internet-Draft, each
author represents that any applicable patent or other IPR claims of
which he or she is aware have been or will be disclosed, and any of
which he or she become aware will be disclosed, in accordance with
RFC 3668.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as
Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on October 2, 2005.
Copyright Notice
Calhoun, et al. Expires October 2, 2005 [Page 1]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Copyright (C) The Internet Society (2005).
Abstract
In the recent years, there has been a shift in wireless LAN product
architectures from autonomous access points to centralized control of
light weight access points. The general goal has been to move most
of the traditional wireless functionality such as access control
(user authentication and authorization), mobility and radio
management out of the access point into a centralized controller.
The IETF's CAPWAP WG has identified that a standards based protocol
is necessary between a wireless Access Controller and Wireless
Termination Points (the latter are also commonly referred to as Light
Weight Access Points). This specification defines the Light Weight
Access Point Protocol (LWAPP), which addresses the CAPWAP's protocol
requirements. Although the LWAPP protocol is designed to be flexible
enough to be used for a variety of wireless technologies, this
specific document describes the base protocol, and an extension that
allows it to be used with the IEEE's 802.11 wireless LAN protocol.
Calhoun, et al. Expires October 2, 2005 [Page 2]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 8
1.1 Conventions used in this document . . . . . . . . . . . 9
2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . 10
2.1 Wireless Binding Definition . . . . . . . . . . . . . . 11
2.2 LWAPP State Machine Definition . . . . . . . . . . . . . 12
3. LWAPP Transport Layers . . . . . . . . . . . . . . . . . . . 20
3.1 LWAPP Transport Header . . . . . . . . . . . . . . . . . 20
3.1.1 VER Field . . . . . . . . . . . . . . . . . . . . . 20
3.1.2 RID Field . . . . . . . . . . . . . . . . . . . . . 20
3.1.3 C Bit . . . . . . . . . . . . . . . . . . . . . . . 20
3.1.4 F Bit . . . . . . . . . . . . . . . . . . . . . . . 20
3.1.5 L Bit . . . . . . . . . . . . . . . . . . . . . . . 21
3.1.6 Fragment ID . . . . . . . . . . . . . . . . . . . . 21
3.1.7 Length . . . . . . . . . . . . . . . . . . . . . . . 21
3.1.8 Status and WLANS . . . . . . . . . . . . . . . . . . 21
3.1.9 Payload . . . . . . . . . . . . . . . . . . . . . . 21
3.2 Using IEEE 802.3 MAC as LWAPP transport . . . . . . . . 21
3.2.1 Framing . . . . . . . . . . . . . . . . . . . . . . 22
3.2.2 AC Discovery . . . . . . . . . . . . . . . . . . . . 22
3.2.3 LWAPP Message Header format over IEEE 802.3 MAC
transport . . . . . . . . . . . . . . . . . . . . . 22
3.2.4 Fragmentation/Reassembly . . . . . . . . . . . . . . 22
3.2.5 Multiplexing . . . . . . . . . . . . . . . . . . . . 23
3.3 Using IPv4/UDP as LWAPP transport . . . . . . . . . . . 23
3.3.1 Framing . . . . . . . . . . . . . . . . . . . . . . 23
3.3.2 AC Discovery . . . . . . . . . . . . . . . . . . . . 23
3.3.3 LWAPP Message Header format over IPv4/UDP transport 24
3.3.4 Fragmentation/Reassembly . . . . . . . . . . . . . . 24
3.3.5 Multiplexing . . . . . . . . . . . . . . . . . . . . 25
4. LWAPP Packet Definitions . . . . . . . . . . . . . . . . . . 26
4.1 LWAPP Data Messages . . . . . . . . . . . . . . . . . . 26
4.2 LWAPP Control Messages Overview . . . . . . . . . . . . 26
4.2.1 Control Message Format . . . . . . . . . . . . . . . 27
4.2.2 Message Element Format . . . . . . . . . . . . . . . 29
5. LWAPP Discovery Operations . . . . . . . . . . . . . . . . . 31
5.1 Discovery Request . . . . . . . . . . . . . . . . . . . 31
5.1.1 Discovery Type . . . . . . . . . . . . . . . . . . . 32
5.1.2 WTP Descriptor . . . . . . . . . . . . . . . . . . . 32
5.1.3 WTP Radio Information . . . . . . . . . . . . . . . 33
5.2 Discovery Response . . . . . . . . . . . . . . . . . . . 33
5.2.1 AC Address . . . . . . . . . . . . . . . . . . . . . 34
5.2.2 AC Descriptor . . . . . . . . . . . . . . . . . . . 34
5.2.3 AC Name . . . . . . . . . . . . . . . . . . . . . . 35
5.2.4 WTP Manager Control IP Address . . . . . . . . . . . 35
5.3 Primary Discovery Request . . . . . . . . . . . . . . . 36
5.3.1 Discovery Type . . . . . . . . . . . . . . . . . . . 36
Calhoun, et al. Expires October 2, 2005 [Page 3]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
5.3.2 WTP Descriptor . . . . . . . . . . . . . . . . . . . 36
5.3.3 WTP Radio Information . . . . . . . . . . . . . . . 36
5.4 Primary Discovery Response . . . . . . . . . . . . . . . 36
5.4.1 AC Descriptor . . . . . . . . . . . . . . . . . . . 37
5.4.2 AC Name . . . . . . . . . . . . . . . . . . . . . . 37
5.4.3 WTP Manager Control IP Address . . . . . . . . . . . 37
6. Control Channel Management . . . . . . . . . . . . . . . . . 38
6.1 Join Request . . . . . . . . . . . . . . . . . . . . . . 38
6.1.1 WTP Descriptor . . . . . . . . . . . . . . . . . . . 39
6.1.2 AC Address . . . . . . . . . . . . . . . . . . . . . 39
6.1.3 WTP Name . . . . . . . . . . . . . . . . . . . . . . 39
6.1.4 Location Data . . . . . . . . . . . . . . . . . . . 39
6.1.5 WTP Radio Information . . . . . . . . . . . . . . . 39
6.1.6 Certificate . . . . . . . . . . . . . . . . . . . . 40
6.1.7 Session ID . . . . . . . . . . . . . . . . . . . . . 40
6.1.8 Test . . . . . . . . . . . . . . . . . . . . . . . . 40
6.1.9 WNonce . . . . . . . . . . . . . . . . . . . . . . . 41
6.1.10 DH-Params . . . . . . . . . . . . . . . . . . . . . 41
6.2 Join Response . . . . . . . . . . . . . . . . . . . . . 42
6.2.1 Result Code . . . . . . . . . . . . . . . . . . . . 42
6.2.2 Status . . . . . . . . . . . . . . . . . . . . . . . 43
6.2.3 Certificate . . . . . . . . . . . . . . . . . . . . 43
6.2.4 Session Key . . . . . . . . . . . . . . . . . . . . 43
6.2.5 WTP Manager Data IP Address . . . . . . . . . . . . 44
6.2.6 AC List . . . . . . . . . . . . . . . . . . . . . . 44
6.2.7 ANonce . . . . . . . . . . . . . . . . . . . . . . . 45
6.2.8 PSK-MIC . . . . . . . . . . . . . . . . . . . . . . 45
6.2.9 DH-Params . . . . . . . . . . . . . . . . . . . . . 46
6.3 Join ACK . . . . . . . . . . . . . . . . . . . . . . . . 46
6.3.1 Session ID . . . . . . . . . . . . . . . . . . . . . 46
6.3.2 WNonce . . . . . . . . . . . . . . . . . . . . . . . 46
6.3.3 PSK-MIC . . . . . . . . . . . . . . . . . . . . . . 46
6.4 Join Confirm . . . . . . . . . . . . . . . . . . . . . . 46
6.4.1 Session ID . . . . . . . . . . . . . . . . . . . . . 47
6.4.2 ANonce . . . . . . . . . . . . . . . . . . . . . . . 47
6.4.3 PSK-MIC . . . . . . . . . . . . . . . . . . . . . . 47
6.5 Echo Request . . . . . . . . . . . . . . . . . . . . . . 47
6.6 Echo Response . . . . . . . . . . . . . . . . . . . . . 47
6.7 Key Update Request . . . . . . . . . . . . . . . . . . . 48
6.7.1 Session ID . . . . . . . . . . . . . . . . . . . . . 48
6.8 Key Update Response . . . . . . . . . . . . . . . . . . 48
6.8.1 Session Key . . . . . . . . . . . . . . . . . . . . 49
6.9 Key Update Trigger . . . . . . . . . . . . . . . . . . . 49
6.9.1 Session ID . . . . . . . . . . . . . . . . . . . . . 49
7. WTP Configuration Management . . . . . . . . . . . . . . . . 50
7.1 Configure Request . . . . . . . . . . . . . . . . . . . 50
7.1.1 Administrative State . . . . . . . . . . . . . . . . 50
7.1.2 AC Name . . . . . . . . . . . . . . . . . . . . . . 51
Calhoun, et al. Expires October 2, 2005 [Page 4]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
7.1.3 AC Name with Index . . . . . . . . . . . . . . . . . 51
7.1.4 WTP Board Data . . . . . . . . . . . . . . . . . . . 51
7.1.5 Statistics Timer . . . . . . . . . . . . . . . . . . 52
7.1.6 WTP Static IP Address Information . . . . . . . . . 52
7.1.7 WTP Reboot Statistics . . . . . . . . . . . . . . . 53
7.2 Configure Response . . . . . . . . . . . . . . . . . . . 53
7.2.1 Decryption Error Report Period . . . . . . . . . . . 54
7.2.2 Change State Event . . . . . . . . . . . . . . . . . 54
7.2.3 LWAPP Timers . . . . . . . . . . . . . . . . . . . . 55
7.2.4 AC List . . . . . . . . . . . . . . . . . . . . . . 55
7.2.5 WTP Fallback . . . . . . . . . . . . . . . . . . . . 55
7.2.6 Idle Timeout . . . . . . . . . . . . . . . . . . . . 56
7.3 Configuration Update Request . . . . . . . . . . . . . . 56
7.3.1 WTP Name . . . . . . . . . . . . . . . . . . . . . . 56
7.3.2 Change State Event . . . . . . . . . . . . . . . . . 57
7.3.3 Administrative State . . . . . . . . . . . . . . . . 57
7.3.4 Statistics Timer . . . . . . . . . . . . . . . . . . 57
7.3.5 Location Data . . . . . . . . . . . . . . . . . . . 57
7.3.6 Decryption Error Report Period . . . . . . . . . . . 57
7.3.7 AC List . . . . . . . . . . . . . . . . . . . . . . 57
7.3.8 Add Blacklist Entry . . . . . . . . . . . . . . . . 57
7.3.9 Delete Blacklist Entry . . . . . . . . . . . . . . . 58
7.3.10 Add Static Blacklist Entry . . . . . . . . . . . . . 58
7.3.11 Delete Static Blacklist Entry . . . . . . . . . . . 59
7.3.12 LWAPP Timers . . . . . . . . . . . . . . . . . . . . 59
7.3.13 AC Name with Index . . . . . . . . . . . . . . . . . 59
7.3.14 WTP Fallback . . . . . . . . . . . . . . . . . . . . 59
7.3.15 Idle Timeout . . . . . . . . . . . . . . . . . . . . 59
7.4 Configuration Update Response . . . . . . . . . . . . . 59
7.4.1 Result Code . . . . . . . . . . . . . . . . . . . . 60
7.5 Change State Event Request . . . . . . . . . . . . . . . 60
7.5.1 Change State Event . . . . . . . . . . . . . . . . . 60
7.6 Change State Event Response . . . . . . . . . . . . . . 60
7.7 Clear Config Indication . . . . . . . . . . . . . . . . 61
8. Device Management Operations . . . . . . . . . . . . . . . . 62
8.1 Image Data Request . . . . . . . . . . . . . . . . . . . 62
8.1.1 Image Download . . . . . . . . . . . . . . . . . . . 62
8.1.2 Image Data . . . . . . . . . . . . . . . . . . . . . 62
8.2 Image Data Response . . . . . . . . . . . . . . . . . . 63
8.3 Reset Request . . . . . . . . . . . . . . . . . . . . . 63
8.4 Reset Response . . . . . . . . . . . . . . . . . . . . . 63
8.5 WTP Event Request . . . . . . . . . . . . . . . . . . . 63
8.5.1 Decryption Error Report . . . . . . . . . . . . . . 64
8.5.2 Duplicate IP Address . . . . . . . . . . . . . . . . 64
8.6 WTP Event Response . . . . . . . . . . . . . . . . . . . 65
8.7 Data Transfer Request . . . . . . . . . . . . . . . . . 65
8.7.1 Data Transfer Mode . . . . . . . . . . . . . . . . . 65
8.7.2 Data Transfer Data . . . . . . . . . . . . . . . . . 66
Calhoun, et al. Expires October 2, 2005 [Page 5]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
8.8 Data Transfer Response . . . . . . . . . . . . . . . . . 66
9. Mobile Session Management . . . . . . . . . . . . . . . . . 67
9.1 Mobile Config Request . . . . . . . . . . . . . . . . . 67
9.1.1 Delete Mobile . . . . . . . . . . . . . . . . . . . 67
9.2 Mobile Config Response . . . . . . . . . . . . . . . . . 68
9.2.1 Result Code . . . . . . . . . . . . . . . . . . . . 68
10. Session Key Generation . . . . . . . . . . . . . . . . . . 69
10.1 Securing WTP-AC communications . . . . . . . . . . . . . 69
10.2 LWAPP Frame Encryption . . . . . . . . . . . . . . . . . 70
10.3 Authenticated Key Exchange . . . . . . . . . . . . . . . 71
10.3.1 Certificate Based Approach . . . . . . . . . . . . . 71
10.3.2 Pre-Shared Key Approach . . . . . . . . . . . . . . 74
11. IEEE 802.11 Binding . . . . . . . . . . . . . . . . . . . 78
11.1 Division of labor . . . . . . . . . . . . . . . . . . . 78
11.1.1 Split MAC . . . . . . . . . . . . . . . . . . . . . 78
11.1.2 Local MAC . . . . . . . . . . . . . . . . . . . . . 79
11.2 Transport specific bindings . . . . . . . . . . . . . . 79
11.2.1 Status and WLANS field . . . . . . . . . . . . . . . 79
11.3 Data Message bindings . . . . . . . . . . . . . . . . . 80
11.4 Control Message bindings . . . . . . . . . . . . . . . . 80
11.4.1 Mobile Config Request . . . . . . . . . . . . . . . 80
11.4.2 WTP Event Request . . . . . . . . . . . . . . . . . 85
11.5 802.11 Control Messages . . . . . . . . . . . . . . . . 87
11.5.1 IEEE 802.11 WLAN Config Request . . . . . . . . . . 87
11.5.2 IEEE 802.11 WLAN Config Response . . . . . . . . . . 91
11.5.3 IEEE 802.11 WTP Event . . . . . . . . . . . . . . . 91
11.6 Message Element Bindings . . . . . . . . . . . . . . . . 92
11.6.1 IEEE 802.11 WTP WLAN Radio Configuration . . . . . . 93
11.6.2 IEEE 802.11 Rate Set . . . . . . . . . . . . . . . . 94
11.6.3 IEEE 802.11 Multi-domain Capability . . . . . . . . 95
11.6.4 IEEE 802.11 MAC Operation . . . . . . . . . . . . . 95
11.6.5 IEEE 802.11 Tx Power . . . . . . . . . . . . . . . . 97
11.6.6 IEEE 802.11 Tx Power Level . . . . . . . . . . . . . 97
11.6.7 IEEE 802.11 Direct Sequence Control . . . . . . . . 97
11.6.8 IEEE 802.11 OFDM Control . . . . . . . . . . . . . . 98
11.6.9 IEEE 802.11 Antenna . . . . . . . . . . . . . . . . 99
11.6.10 IEEE 802.11 Supported Rates . . . . . . . . . . . 99
11.6.11 IEEE 802.11 CFP Status . . . . . . . . . . . . . . 100
11.6.12 IEEE 802.11 WTP Mode and Type . . . . . . . . . . 100
11.6.13 IEEE 802.11 Broadcast Probe Mode . . . . . . . . . 101
11.6.14 IEEE 802.11 WTP Quality of Service . . . . . . . . 101
11.6.15 IEEE 802.11 MIC Error Report From Mobile . . . . . 102
11.7 IEEE 802.11 Message Element Values . . . . . . . . . . . 103
12. LWAPP Protocol Timers . . . . . . . . . . . . . . . . . . 104
12.1 MaxDiscoveryInterval . . . . . . . . . . . . . . . . . . 104
12.2 SilentInterval . . . . . . . . . . . . . . . . . . . . . 104
12.3 NeighborDeadInterval . . . . . . . . . . . . . . . . . . 104
12.4 EchoInterval . . . . . . . . . . . . . . . . . . . . . . 104
Calhoun, et al. Expires October 2, 2005 [Page 6]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
12.5 DiscoveryInterval . . . . . . . . . . . . . . . . . . . 104
12.6 RetransmitInterval . . . . . . . . . . . . . . . . . . . 104
12.7 ResponseTimeout . . . . . . . . . . . . . . . . . . . . 105
12.8 KeyLifetime . . . . . . . . . . . . . . . . . . . . . . 105
13. LWAPP Protocol Variables . . . . . . . . . . . . . . . . . 106
13.1 MaxDiscoveries . . . . . . . . . . . . . . . . . . . . . 106
13.2 DiscoveryCount . . . . . . . . . . . . . . . . . . . . . 106
13.3 RetransmitCount . . . . . . . . . . . . . . . . . . . . 106
13.4 MaxRetransmit . . . . . . . . . . . . . . . . . . . . . 106
14. Security Considerations . . . . . . . . . . . . . . . . . 107
14.1 Certificate based Session Key establishment . . . . . . 107
14.2 PSK based Session Key establishment . . . . . . . . . . 108
15. IANA Considerations . . . . . . . . . . . . . . . . . . . 109
16. IPR Statement . . . . . . . . . . . . . . . . . . . . . . 110
17. References . . . . . . . . . . . . . . . . . . . . . . . . 111
17.1 Normative References . . . . . . . . . . . . . . . . . . 111
17.2 Informational References . . . . . . . . . . . . . . . . 112
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 112
Intellectual Property and Copyright Statements . . . . . . . 114
Calhoun, et al. Expires October 2, 2005 [Page 7]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
1. Introduction
Unlike wired network elements, Wireless Termination Points (WTPs)
require a set of dynamic management and control functions related to
their primary task of connecting the wireless and wired mediums.
Today, protocols for managing WTPs are either manual static
configuration via HTTP, proprietary Layer 2 specific or non-existent
(if the WTPs are self-contained). The emergence of simple 802.11
WTPs that are managed by a WLAN appliance or switch (also known as an
Access Controller, or AC) suggests that having a standardized,
interoperable protocol could radically simplify the deployment and
management of wireless networks. In many cases the overall control
and management functions themselves are generic and could apply to an
AP for any wireless Layer 2 protocol. Being independent of specific
wireless Layer 2 technologies, such a protocol could better support
interoperability between Layer 2 devices and enable smoother
intertechnology handovers.
The details of how these functions would be implemented are dependent
on the particular Layer 2 wireless technology. Such a protocol would
need provisions for binding to specific technologies.
LWAPP assumes a network configuration that consists of multiple WTPs
communicating either via layer 2 (MAC) or layer 3 (IP) to an AC. The
WTPs can be considered as remote RF interfaces, being controlled by
the AC. The AC forwards all L2 frames it wants to transmit to an WTP
via the LWAPP protocol. Packets from mobile nodes are forwarded by
the WTP to the AC, also via this protocol. Figure 1 illustrates this
arrangement as applied to an IEEE 802.11 binding.
+-+ 802.11frames +-+
| |--------------------------------| |
| | +-+ | |
| |--------------| |---------------| |
| | 802.11 PHY/ | | LWAPP | |
| | MAC sublayer | | | |
+-+ +-+ +-+
STA WTP AC
Figure 1: LWAPP Architecture
Security is another aspect of Wireless Termination Point management
that is not well served by existing solutions. Provisioning WTPs
with security credentials, and managing which WTPs are authorized to
provide service are today handled by proprietary solutions. Allowing
these functions to be performed from a centralized AC in an
interoperable fashion increases managability and allows network
operators to more tightly control their wireless network
Calhoun, et al. Expires October 2, 2005 [Page 8]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
infrastructure.
This document describes the Light Weight Access Point Protocol
(LWAPP), allowing an AC to manage a collection of WTPs. The protocol
is defined to be independent of Layer 2 technology, but an 802.11
binding is provided for use in growing 802.11 wireless LAN networks.
Goals
The following are goals for this protocol:
1. Centralization of the bridging, forwarding, authentication and
policy enforcement functions for a wireless network. Optionally,
the AC may also provide centralized encryption of user traffic.
This will permit reduced cost and higher efficiency when applying
the capabilities of network processing silicon to the wireless
network, as it has already been applied to wired LANs.
2. Permit shifting of the higher level protocol processing burden
away from the WTP. This leaves the computing resource of the WTP
to the timing critical applications of wireless control and
access. This makes the most efficient use of the computing power
available in WTPs that are the subject of severe cost pressure.
3. Providing a generic encapsulation and transport mechanism, the
protocol may be applied to other access point type in the future
by adding the binding.
The LWAPP protocol concerns itself solely with the interface between
the WTP and the AC. Inter-AC, or mobile to AC communication is
strictly outside the scope of this document.
1.1 Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [1].
Calhoun, et al. Expires October 2, 2005 [Page 9]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
2. Protocol Overview
LWAPP is a generic protocol defining how Wireless Termination Points
communicate with Access Controllers. Wireless Termination Points and
Access Controllers may communicate either by means of Layer 2
protocols or by means of a routed IP network.
LWAPP messages and procedures defined in this document apply to both
types of transports unless specified otherwise. Transport
independence is achieved by defining formats for both MAC level and
IP level transport (see Section 3). Also defined are framing,
fragmentation/reassembly, and multiplexing services to LWAPP for each
transport type.
The LWAPP Transport layer carries two types of payload. LWAPP Data
Messages are forwarded wireless frames. LWAPP Control Messages are
management messages exchanged between an WTP and an AC. The LWAPP
transport header defines the "C-bit", which is used to distinguish
data and control traffic. When used over IP, the LWAPP data and
control traffic are also sent over separate UDP ports. Since both
data and control frames can exceed PMTU, the payload of an LWAPP data
or control message can be fragmented. The fragmentation behavior is
highly dependent upon the lower layer transport and is defined in
Section 3.
The Light Weight Access Protocol (LWAPP) begins with a discovery
phase. The WTPs send a Discovery Request frame, causing any Access
Controller (AC) , receiving that frame to respond with a Discovery
Response. From the Discovery Responses received, an WTP will select
an AC with which to associate, using the Join Request and Join
Response. The Join Request also provides an MTU discovery mechanism,
to determine whether there is support for the transport of large
frames between the WTP and it's AC. If support for large frames is
not present, the LWAPP frames will be fragmented to the maximum
length discovered to be supported by the network.
Once the WTP and the AC have joined, a configuration exchange is
accomplished that will cause both devices to agree on version
information. During this exchange the WTP may receive provisioning
settings. For the 802.11 binding, this information would typically
include a name (802.11 Service Set Identifier, SSID), and security
parameters, the data rates to be advertised as well as the radio
channel (channels, if the WTP is capable of operating more than one
802.11 MAC and PHY simultaneously) to be used. Finally, the WTPs are
enabled for operation.
When the WTP and AC have completed the version and provision exchange
and the WTP is enabled, the LWAPP encapsulates the wireless frames
Calhoun, et al. Expires October 2, 2005 [Page 10]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
sent between them. LWAPP will fragment its packets, if the size of
the encapsulated wireless user data (Data) or protocol control
(Management) frames causes the resultant LWAPP packet to exceed the
MTU supported between the WTP and AC. Fragmented LWAPP packets are
reassembled to reconstitute the original encapsulated payload.
In addition to the functions thus far described, LWAPP also provides
for the delivery of commands from the AC to the WTP for the
management of devices that are communicating with the WTP. This may
include the creation of local data structures in the WTP for the
managed devices and the collection of statistical information about
the communication between the WTP and the 802.11 devices. LWAPP
provides the ability for the AC to obtain any statistical information
collected by the WTP.
LWAPP also provides for a keep alive feature that preserves the
communication channel between the WTP and AC. If the AC fails to
appear alive, the WTP will try to discover a new AC to communicate
through.
This Document uses terminology defined in [5]
2.1 Wireless Binding Definition
This draft standard specifies a protocol independent of a specific
wireless access point radio technology. Elements of the protocol are
designed to accommodate specific needs of each wireless technology in
a standard way. Implementation of this standard for a particular
wireless technology must follow the binding requirements defined for
that technology. This specification includes a binding for the IEEE
802.11 (see Section 11).
When defining a binding for other technologies, the authors MUST
include any necessary definitions for technology-specific messages
and all technology-specific message elements for those messages. At
a minimum, a binding MUST provide the definition for a
binding-specific Statistics message element, which is carried in the
WTP Event Request message, and Add Mobile message element, which is
carried in the Mobile Configure Request. If any technology specific
message elements are required for any of the existing LWAPP messages
defined in this specification, they MUST also be defined in the
technology binding document.
The naming of binding-specific message elements MUST begin with the
name of the technology type, e.g., the binding for IEEE 802.11,
provided in this standard, begins with "IEEE 802.11"."
Calhoun, et al. Expires October 2, 2005 [Page 11]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
2.2 LWAPP State Machine Definition
The following state diagram represents the lifecycle of an WTP-AC
session:
/-------------\
| v
| +------------+
| C| Idle |<-----------------------------------\
| +------------+<-----------------------\ |
| ^ |a ^ | |
| | | \----\ | |
| | | |t u | |
| | | +-----------+------>+------------+ |
| / | C| Run | | Key Update | |
| / | r+-----------+<------+------------+ |
| / | ^ |s w x| |
| | v | | | |
| | +--------------+ | | v |y
| | C| Discovery | q| \--------------->+-------+
| | b+--------------+ +-------------+ | Reset |
| | |d f| ^ | Configure |------->+-------+
| | | | | +-------------+p ^
| |e v | | ^ ^ |
| +---------+ v |i |k 2| |
| C| Sulking | +------------+ +--------------+ |
| +---------+ C| Join |--->| Join-Confirm | |
| g+------------+z +--------------+ |
| |h m| 3| |4 |
| | | | v |o
|\ | | | +------------+
\\-----------------/ \--------+---->| Image Data |C
\------------------------------------/ +------------+n
Figure 2: LWAPP State Machine
The LWAPP state machine, depicted above, is used by both the AC and
the WTP. For every state defined, only certain messages are
permitted to be sent and received. In all of the LWAPP control
messages defined in this document, the state for which each command
is valid is specified.
Note that in the state diagram figure above, the 'C' character is
used to represent a condition that causes the state to remain the
same.
The following text discusses the various state transitions, and the
Calhoun, et al. Expires October 2, 2005 [Page 12]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
events that cause them.
Idle to Discovery (a): This is the initialization state.
WTP: The WTP enters the Discovery state prior to transmitting the
first Discovery Request (see Section 5.1). Upon entering this
state, the WTP sets the DiscoveryInterval timer (see
Section 12). The WTP resets the DiscoveryCount counter to zero
(0) (see Section 13). The WTP also clears all information from
ACs (e.g., AC Addresses) it may have received during a previous
Discovery phase.
AC: The AC does not need to maintain state information for the WTP
upon reception of the Discovery Request, but it MUST respond
with a Discovery Response (see Section 5.2).
Discovery to Discovery (b): This is the state the WTP uses to
determine which AC it wishes to connect to.
WTP: This event occurs when the DiscoveryInterval timer expires.
The WTP transmits a Discovery Request to every AC which the WTP
hasn't received a response to. For every transition to this
event, the WTP increments DisoveryCount counter. See
Section 5.1) for more information on how the WTP knows which
ACs it should transmit the Discovery Requests to. The WTP
restarts the DiscoveryInterval timer.
AC: This is a noop.
Discovery to Sulking (d): This state occurs on a WTP when Discovery
or connectivity to the AC fails.
WTP: The WTP enters this state when the DiscoveryInterval timer
expires and the DiscoveryCount variable is equal to the
MaxDiscoveries variable (see Section 13). Upon entering this
state, the WTP will start the SilentInterval timer. While in
the Sulking state, all LWAPP messages received are ignored.
AC: This is a noop.
Sulking to Idle (e): This state occurs on a WTP when it must restart
the discovery phase.
WTP: The WTP enters this state when the SilentInterval timer (see
Section 12) expires.
AC: This is a noop.
Discovery to Join (f): This state is used by the WTP to confirm its
commitment to an AC that it wishes to be provided service.
WTP: The WTP selects the best AC based on the information it
gathered during the Discovery Phase. It then transmits a Join
Request (see Section 6.1 to its preferred AC. The WTP starts
the WaitJoin Timer (see Section 12).
AC: The AC enters this state for the given WTP upon reception of a
Join Request. The AC processes the request and responds with a
Join Response.
Join to Join (g): This state transition occurs during the join phase.
Calhoun, et al. Expires October 2, 2005 [Page 13]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
WTP: The WTP enters this state when the WaitJoin timer expires,
and the underlying transport requires LWAPP MTU detection
Section 3).
AC: This state occurs when the AC receives a retransmission of a
Join Request. The WTP processes the request and responds with
the Join Response..
Join to Idle (h): This state is used when the join process failed.
WTP: This state transition occurs if the WTP is configured to use
PSK security and receives a Join Response that includes an
invalid PSK-MIC message element.
AC: The AC enters this state when it transmits an unsuccessful
Join Response.
Join to Discovery (i): This state is used when the join process
failed.
WTP: The WTP enters this state when it receives an unsuccessful
Join Response. Upon entering this state, the WTP sets the
DiscoveryInterval timer (see Section 12). The WTP resets the
DiscoveryCount counter to zero (0) (see Section 13). This
state transition may also occur if the PSK-MIC (see
Section 6.2.8) message element is invalid.
AC: This state transition is invalid.
Join to Join-Confirm (z): This state is used solely with the LWAPP
PSK Mode, and is used for the purposes of key confirmation.
WTP: This state is entered when the WTP receives a Join Response
that includes a valid PSK-MIC message element. The WTP MUST
respond with a Join ACK, which is used to provide key
confirmation.
AC: The AC enters this state when it receives a Join ACK that
includes a valid PSK-MIC message element. The AC MUST respond
with a Join Confirm message, which includes the Session Key
message element.
Join to Configure (k): This state is used by the WTP and the AC to
exchange configuration information.
WTP: The WTP enters this state when it receives a successful Join
Response, and determines that its version number and the
version number advertised by the AC are the same. The WTP
transmits the Configure Request (see Section 7.1) message to
the AC with a snapshot of its current configuration. This
state transition is only valid when the Certificate message
element is present in the Join Response, and not if the PSK-MIC
message element is present. The WTP also starts the
ResponseTimeout timer (see Section 12).
AC: This state transition occurs when the AC receives the
Configure Request from the WTP. Note that the AC MUST only
allow this state transition if the Join process used
certificate based security, through the presence on the
Certificate message element. The AC must transmit a Configure
Response (see Section 7.2) to the WTP, and may include specific
Calhoun, et al. Expires October 2, 2005 [Page 14]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
message elements to override the WTP's configuration.
Join to Image Data (m): This state is used by the WTP and the AC to
download executable firmware.
WTP: The WTP enters this state when it receives a successful Join
Response, and determines that its version number and the
version number advertised by the AC are different. This state
transition is only valid when the Certificate message element
is present in the Join Response, and not if the PSK-MIC message
element is present. The WTP transmits the Image Data Request
(see Section 8.1) message requesting that the AC's latest
firmware be initiated.
AC: This state transition occurs when the AC receives the Image
Data Request from the WTP. Note that the AC MUST only allow
this state transition if the Join process used certificate
based security, through the presence on the Certificate message
element. The AC must transmit a Image Data Response (see
Section 8.2) to the WTP, which includes a portion of the
firmware.
Join-Confirm to Idle (3): This state is used when the join process
failed.
WTP: This state transition occurs when the WTP receives an invalid
Join Confirm.
AC: The AC enters this state when it receives an invalid Join ACK.
Join-Confirm to Configure (2): This state is used by the WTP and the
AC to exchange configuration information.
WTP: The WTP enters this state when it receives a successful Join
Confirm, and determines that its version number and the version
number advertised by the AC are the same. The WTP transmits
the Configure Request (see Section 7.1) message to the AC with
a snapshot of its current configuration. The WTP also starts
the ResponseTimeout timer (see Section 12).
AC: This state transition occurs when the AC receives the
Configure Request from the WTP. The AC must transmit a
Configure Response (see Section 7.2) to the WTP, and may
include specific message elements to override the WTP's
configuration.
Join-Confirm to Image Data (4): This state is used by the WTP and the
AC to download executable firmware.
WTP: The WTP enters this state when it receives a successful Join
Confirm, and determines that its version number and the version
number advertised by the AC are different. The WTP transmits
the Image Data Request (see Section 8.1) message requesting
that the AC's latest firmware be initiated.
AC: This state transition occurs when the AC receives the Image
Data Request from the WTP. The AC must transmit a Image Data
Response (see Section 8.2) to the WTP, which includes a portion
of the firmware.
Calhoun, et al. Expires October 2, 2005 [Page 15]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Image Data to Image Data (n): This state is used by WTP and the AC
during the firmware download phase.
WTP: The WTP enters this state when it receives a Image Data
Response that indicates that the AC has more data to send.
AC: This state transition occurs when the AC receives the Image
Data Request from the WTP while already in this state, and it
detects that the firmware download has not completed.
Image Data to Reset (o): This state is used when the firmware
download is completed.
WTP: The WTP enters this state when it receives a Image Data
Response that indicates that the AC has no more data to send,
or if the underlying LWAPP transport indicates a link failure.
At this point, the WTP reboots itself.
AC: This state transition occurs when the AC receives the Image
Data Request from the WTP while already in this state, and it
detects that the firmware download has completed, or if the
underlying LWAPP transport indicates a link failure. Note that
the AC itself does not reset, but it places the specific WTPs
context it is communicating with in the reset state, meaning
that it clears all state associated with the WTP.
Configure to Reset (p): This state transition occurs if the Configure
phase fails.
WTP: The WTP enters this state when the reliable transport fails
to deliver the Configure Request, or if the ResponseTimeout
Timer (see Section 12)expires.
AC: This state transition occurs if the AC is unable to transmit
the Configure Response to a specific WTP. Note that the AC
itself does not reset, but it places the specific WTPs context
it is communicating with in the reset state, meaning that it
clears all state associated with the WTP.
Configure to Run (q): This state transition occurs when the WTP and
AC enters their normal state of operation.
WTP: The WTP enters this state when it receives a successful
Configure Response from the AC. The WTP initializes the
HeartBeat Timer (see Section 12), and transmits the Change
State Event Request message (see Section 7.5).
AC: This state transition occurs when the AC receives the Change
State Event Request (see Section 7.5) from the WTP. The AC
responds with a Change State Event Response (see Section 7.6)
message. The AC must start the Session ID and Neighbor Dead
timers (see Section 12).
Run to Run (r): This is the normal state of operation.
WTP: This is the WTP's normal state of operation, and there are
many events that cause this to occur:
Configuration Update: The WTP receives a Configuration Update
Request (see Section 7.3). The WTP MUST respond with a
Configuration Update Response (see Section 7.4).
Calhoun, et al. Expires October 2, 2005 [Page 16]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Change State Event: The WTP receives a Change State Event
Response, or determines that it must initiate a Change State
Event Request, as a result of a failure or change in the
state of a radio.
Echo Request: The WTP receives an Echo Request message
Section 6.5), which it MUST respond with an Echo Response
(see Section 6.6).
Clear Config Indication: The WTP receives a Clear Config
Indication message Section 7.7). The WTP MUST reset its
configuration back to manufacturer defaults.
WTP Event: The WTP generates a WTP Event Request to send
information to the AC Section 8.5). The WTP receives a WTP
Event Response from the AC Section 8.6).
Data Transfer: The WTP generates a Data Transfer Request to the
AC Section 8.7). The WTP receives a Data Transfer Response
from the AC Section 8.8).
WLAN Config Request: The WTP receives an WLAN Config Request
message Section 11.5.1), which it MUST respond with an WLAN
Config Response (see Section 11.5.2).
Mobile Config Request: The WTP receives an Mobile Config
Request message Section 9.1), which it MUST respond with an
Mobile Config Response (see Section 9.2).
AC: This is the AC's normal state of operation, and there are many
events that cause this to occur:
Configuration Update: The AC sends a Configuration Update
Request (see Section 7.3) to the WTP to update its
configuration. The AC receives a Configuration Update
Response (see Section 7.4) from the WTP.
Change State Event: The AC receives a Change State Event
Request (see Section 7.5), which it MUST respond to with the
Change State Event Response (see Section 7.6).
Echo: The AC sends an Echo Request message Section 6.5) or
receives the associated Echo Response (see Section 6.6) from
the WTP.
Clear Config Indication: The AC sends a Clear Config Indication
message Section 7.7).
WLAN Config: The AC sends an WLAN Config Request message
Section 11.5.1) or receives the associated WLAN Config
Response (see Section 11.5.2) from the WTP.
Mobile Config: The AC sends an Mobile Config Request message
Section 9.1) or receives the associated Mobile Config
Response (see Section 9.2) from the WTP.
Data Transfer: The AC receives a Data Transfer Request from the
AC (see Section 8.7) and MUST generate the associated Data
Transfer Response message (see Section 8.8).
Calhoun, et al. Expires October 2, 2005 [Page 17]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
WTP Event: The AC receives a WTP Event Request from the AC (see
Section 8.5) and MUST generate the associated WTP Event
Response message (see Section 8.6).
Run to Reset (s): This event occurs when the AC wishes for the WTP to
reboot.
WTP: The WTP enters this state when it receives a Reset Request
(see Section 8.3). It must respond with a Reset Response (see
Section 8.4), and once the reliable transport acknowledgement
has been received, it must reboot itself.
AC: This state transition occurs either through some
administrative action, or via some internal event on the AC
that causes it to request that the WTP disconnect. Note that
the AC itself does not reset, but it places the specific WTPs
context it is communicating with in the reset state.
Run to Idle (t): This event occurs when an error occurs in the
communication between the WTP and the AC.
WTP: The WTP enters this state when the underlying reliable
transport in unable to transmit a message within the
RetransmitInterval timer (see Section 12), and the maximum
number of RetransmitCount counter has reached the MaxRetransmit
variable (see Section 13).
AC: The AC enters this state when the underlying reliable
transport in unable to transmit a message within the
RetransmitInterval timer (see Section 12), and the maximum
number of RetransmitCount counter has reached the MaxRetransmit
variable (see Section 13).
Run to Key Update (u): This event occurs when the WTP and the AC are
to exchange new keying material, with which it must use to protect
all future messages.
WTP: This state transition occurs when the KeyLifetime timer
expires (see Section 12).
AC: The WTP enters this state when it receives a Key Update
Request (see Section 6.7). It must create new keying material
and include it in the Key Update Response (see Section 6.8).
Key Update to Run (w): This event occurs when the key exchange phase
is completed.
WTP: This state transition occurs when the WTP receives the Key
Update Response. The WTP must plumb the new keys in its crypto
module, allowing it to communicate with the AC using the new
key.
AC: The AC enters this state when it transmits the Key Update
Response message. The key is then plumbed into its crypto
module, allowing it to communicate with the WTP using the new
key.
Key Update to Reset (x): This event occurs when the key exchange
phase times out.
Calhoun, et al. Expires October 2, 2005 [Page 18]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
WTP: This state transition occurs when the WTP does not receive a
Key Update Response from the AC.
AC: The AC enters this state when it is unable to process a Key
Update Request.
Reset to Idle (y): This event occurs when the state machine is
restarted.
WTP: The WTP reboots itself. After reboot the WTP will start its
LWAPP state machine in the Idle state.
AC: The AC clears out any state associated with the WTP. The AC
generally does this as a result of the reliable link layer
timing out.
Calhoun, et al. Expires October 2, 2005 [Page 19]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
3. LWAPP Transport Layers
The LWAPP protocol can operate at layer 2 or 3. For layer 2 support,
the LWAPP messages are carried in a native Ethernet frame. As such,
the protocol is not routable and depends upon layer 2 connectivity
between the WTP and the AC. Layer 3 support is provided by
encapsulating the LWAPP messages within UDP.
3.1 LWAPP Transport Header
All LWAPP protocol packets are encapsulated using a common header
format, regardless of the transport used to carry the frames.
However, certain flags are not applicable for a given transport, and
it is therefore necessary to refer to the specific transport section
in order to determine which flags are valid.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|VER| RID |C|F|L| Frag ID | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status/WLANs | Payload... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3.1.1 VER Field
A 2 bit field which contains the version of LWAPP used in this
packet. The value for this draft is 0.
3.1.2 RID Field
A 3 bit field which contains the Radio ID number for this packet.
WTPs with multiple radios but a single MAC Address use this field to
indicate which radio is associated with the packet.
3.1.3 C Bit
The Control Message 'C' bit indicates whether this packet carries a
data or control message. When this bit is zero (0), the packet
carries an LWAPP data message in the payload (see Section 4.1). When
this bit is one (1), the packet carries an LWAPP control message as
defined in section Section 4.2 for consumption by the addressed
destination.
3.1.4 F Bit
The Fragment 'F' bit indicates whether this packet is a fragment.
Calhoun, et al. Expires October 2, 2005 [Page 20]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
When this bit is one (1), the packet is a fragment and MUST be
combined with the other corresponding fragments to reassemble the
complete information exchanged between the WTP and AC.
3.1.5 L Bit
The Not Last 'L' bit is valid only if the 'F' bit is set and
indicates whether the packet contains the last fragment of a
fragmented exchange between WTP and AC. When this bit is 1, the
packet is not the last fragment. When this bit is 0, the packet is
the last fragment.
3.1.6 Fragment ID
An 8 bit field whose value is assigned to each group of fragments
making up a complete set. The fragment ID space is managed
individually for every WTP/AC pair. The value of Fragment ID is
incremented with each new set of fragments. The Fragment ID wraps to
zero after the maximum value has been used to identify a set of
fragments. LWAPP only supports up to 2 fragments per frame.
3.1.7 Length
The 16 bit length field contains the number of bytes in the Payload.
The field is encoded as an unsigned number. If the LWAPP packet is
encrypted, the length field includes the AES-CCM MIC (see
Section 10.2 for more information).
3.1.8 Status and WLANS
The interpretation of this 16 bit field is binding specific. Refer
to the transport portion of the binding for a wireless technology for
the specification.
3.1.9 Payload
This field contains the header for an LWAPP Data Message or LWAPP
Control Message, followed by the data associated with that message.
3.2 Using IEEE 802.3 MAC as LWAPP transport
This section describes how the LWAPP protocol is provided over native
ethernet frames. An LWAPP packet is formed from the MAC frame header
followed by the LWAPP message header. The following figure provides
an example of the frame formats used when LWAPP is used over the IEEE
802.3 transport.
Calhoun, et al. Expires October 2, 2005 [Page 21]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Layer 2 LWAPP Data Frame
+-----------------------------------------------------------+
| MAC Header | LWAPP Header [C=0] | Forwarded Data ... |
+-----------------------------------------------------------+
Layer 2 LWAPP Control Frame
+---------------------------------------------------+
| MAC Header | LWAPP Header [C=1] | Control Message |
+---------------------------------------------------+
| Message Elements ... |
+----------------------+
3.2.1 Framing
Source Address
A MAC address belonging to the interface from which this message is
sent. If multiple source addresses are configured on an interface,
then the one chosen is implementation dependent.
Destination Address
A MAC address belonging to the interface to which this message is to
be sent. This destination address MAY be either an individual
address or a multicast address, if more than one destination
interface is intended.
Ethertype
The Ethertype field is set to 0x88bb.
3.2.2 AC Discovery
When run over IEEE 802.3, LWAPP messages are distributed to a
specific MAC level broadcast domain. The AC discovery mechanism used
with this transport is for an WTP to transmit a Discovery Request
message to a broadcast destination MAC address. The ACs will receive
this message and reply based on their policy.
3.2.3 LWAPP Message Header format over IEEE 802.3 MAC transport
All of the fields described in Section 3.1 are used when LWAPP uses
the IEEE 802.3 MAC transport.
3.2.4 Fragmentation/Reassembly
Fragmentation at the MAC layer is managed using the F,L and Frag ID
Calhoun, et al. Expires October 2, 2005 [Page 22]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
fields of the LWAPP message header. The LWAPP protocol only allows a
single packet to be fragmented into 2, which is sufficient for a
frame that exceeds MTU due to LWAPP encapsulation. When used with
layer 2 (Ethernet) transport, both fragments MUST include the LWAPP
header.
3.2.5 Multiplexing
LWAPP control messages and data messages are distinguished by the C
Bit in the LWAPP message header.
3.3 Using IPv4/UDP as LWAPP transport
This section defines how LWAPP makes use of IPV4/UDP transport
between the WTP and the AC. When this transport is used, the MAC
layer is controlled by the IPv4 stack, and there are therefore no
special MAC layer requirements. The following figure provides an
example of the frame formats used when LWAPP is used over the
IPv4/UDP transport.
Layer 3 LWAPP Data Frame
+--------------------------------------------+
| MAC Header | IP | UDP | LWAPP Header [C=0] |
+--------------------------------------------+
|Forwarded Data ... |
+-------------------+
Layer 3 LWAPP Control Frame
+--------------------------------------------+
| MAC Header | IP | UDP | LWAPP Header [C=1] |
+--------------------------------------------+
| Control Message | Message Elements ... |
+-----------------+----------------------+
3.3.1 Framing
Communication between WTP and AC is established according to the
standard UDP client/server model. The connection is initiated by the
WTP (client) to the well-known UDP port of the AC (server) used for
control messages. This UDP port number of the AC is 12222 for LWAPP
data and 12223 for LWAPP control frames.
3.3.2 AC Discovery
When LWAPP is run over routed IPv4 networks, the WTP and the AC do
not need to reside in the same IP subnet (broadcast domain).
However, in the event the peers reside on separate subnets, there
Calhoun, et al. Expires October 2, 2005 [Page 23]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
must exist a mechanism for the WTP to discover the AC.
As the WTP attempts to establish communication with the AC, it sends
the Discovery Request message and receives the corresponding response
message from the AC. The WTP must send the Discovery Request message
to either the limited broadcast IP address (255.255.255.255), a well
known multicast address or to the unicast IP address of the AC. Upon
receipt of the message, the AC issues a Discovery Response message to
the unicast IP address of the WTP, regardless of whether Discovery
Request was sent as a broadcast, multicast or unicast message.
Whether the WTP uses a limited IP broadcast, multicast or unicast IP
address is implementation dependent.
In order for a WTP to transmit a Discovery Request to a unicast
address, the WTP must first obtain the IP address of the AC. Any
static configuration of an AC's IP address on the WTP non-volatile
storage is implementation dependent. However, additional dynamic
schemes are possible, for example:
DHCP: A comma delimited ASCII encoded list of AC IP addresses is
embedded inside a DHCP vendor specific option 43 extension. An
example of the actual format of the vendor specific payload is of
the form "10.1.1.1, 10.1.1.2".
DNS: The DNS name "LWAPP-AC-Address" MAY be resolvable to or more AC
addresses
3.3.3 LWAPP Message Header format over IPv4/UDP transport
All of the fields described in Section 3.1 are used when LWAPP uses
the IPv4/UDP transport, with the following exceptions:
3.3.3.1 F Bit
This flag field is not used with this transport, and MUST be set to
zero.
3.3.3.2 L Bit
This flag field is not used with this transport, and MUST be set to
zero.
3.3.3.3 Frag ID
This field is not used with this transport, and MUST be set to zero.
3.3.4 Fragmentation/Reassembly
When LWAPP is implemented at L3, the transport layer uses IP
Calhoun, et al. Expires October 2, 2005 [Page 24]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
fragmentation to fragment and reassemble LWAPP messages that are
longer than MTU size used by either WTP or AC. The details of IP
fragmentation are covered in [8]. When used with the IP transport,
only the first fragment would include the LWAPP header
[ed: IP fragmentation may raise security concerns and bring
additional configuration requirements for certain firewalls and NATs.
One alternative is to re-use the layer 2 (application layer)
fragmentation reassembly. Comments are welcomed.]
3.3.5 Multiplexing
LWAPP messages convey control information between WTP and AC, as well
as binding specific data frames or binding specific management
frames. As such, LWAPP messages need to be multiplexed in the
transport sub-layer and be delivered to the proper software entities
in the endpoints of the protocol. However, the 'C' bit is still used
to differentiate between data and control frames.
In case of Layer 3 connection, multiplexing is achieved by use of
different UDP ports for control and data packets (see Section 3.3.1.
As part of Join procedure, the WTP and AC may negotiate different IP
Addresses for data or control messages. The IP Address returned in
the AP Manager Control IP Address message element is used to inform
the WTP with the IP address to which it must sent all control frames.
The AP Manager Data IP Address message element MAY be present only if
the AC has a different IP Address which the WTP is to use to send its
data LWAPP frames.
In the event the WTP and AC are separated by a NAT, with the WTP
using private IP address space, it is the responsibility of the NAT
to manage appropriate UDP port mapping.
Calhoun, et al. Expires October 2, 2005 [Page 25]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
4. LWAPP Packet Definitions
This section contains the packet types and format. The LWAPP
protocol is designed to be transport agnostic by specifying packet
formats for both MAC frames and IP packets. An LWAPP packet consists
of an LWAPP Transport Layer packet header followed by an LWAPP
message.
Transport details can be found in Section 3.
4.1 LWAPP Data Messages
An LWAPP data message is a forwarded wireless frame. When forwarding
wireless frames, the sender simply encapsulates the wireless frame in
an LWAPP data packet, using the appropriate transport rules defined
in section Section 3.
In the event that the encapsulated frame would exceed the transport
layer's MTU, the sender is responsible for the fragmentation of the
frame, as specified in the transport specific section of Section 3.
The actual format of the encapsulated LWAPP data frame is subject to
the rules defined under the specific wireless technology binding.
4.2 LWAPP Control Messages Overview
The LWAPP Control protocol provides a control channel between the WTP
and the AC. The control channel is the series of control messages
between the WTP and AC, associated with a session ID and key.
Control messages are divided into the following distinct message
types:
Discovery: LWAPP Discovery messages are used to identify potential
ACs, their load and capabilities.
Control Channel Management: Messages that fall within this
classification are used for the discovery of ACs by the WTPs as
well as the establishment and maintenance of an LWAPP control
channel.
WTP Configuration: The WTP Configuration messages are used by the AC
to push a specific configuration to the WTPs it has a control
channel with. Messages that deal with the retrieval of statistics
from the WTP also fall in this category.
Mobile Session Management: Mobile session management messages are
used by the AC to push specific mobile policies to the WTP.
Firmware Management: Messages in this category are used by the AC to
push a new firmware image down to the WTP.
Control Channel, WTP Configuration and Mobile Session Management MUST
be implemented. Firmware Management MAY be implemented.
Calhoun, et al. Expires October 2, 2005 [Page 26]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
In addition, technology specific bindings may introduce new control
channel commands that depart from the above list.
4.2.1 Control Message Format
All LWAPP control messages are sent encapsulated within the LWAPP
header (see Section 3.1). Immediately following the header, is the
LWAPP control header, which has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Type | Seq Num | Msg Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Msg Element [0..N] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.2.1.1 Message Type
The Message Type field identifies the function of the LWAPP control
message. The valid values for Message Type are the following:
Calhoun, et al. Expires October 2, 2005 [Page 27]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Description Value
Discovery Request 1
Discovery Response 2
Join Request 3
Join Response 4
Join ACK 5
Join Confirm 6
Unused 7-9
Configure Request 10
Configure Response 11
Configuration Update Request 12
Configuration Update Response 13
WTP Event Request 14
WTP Event Response 15
Change State Event Request 16
Change State Event Response 17
Unused 18-21
Echo Request 22
Echo Response 23
Image Data Request 24
Image Data Response 25
Reset Request 26
Reset Response 27
Unused 28-29
Key Update Request 30
Key Update Response 31
Primary Discovery Request 32
Primary Discovery Response 33
Data Transfer Request 34
Data Transfer Response 35
Clear Config Indication 36
WLAN Config Request 37
WLAN Config Response 38
Mobile Config Request 39
Mobile Config Response 40
4.2.1.2 Sequence Number
The Sequence Number Field is an identifier value to match
request/response packet exchanges. When an LWAPP packet with a
request message type is received, the value of the sequence number
field is copied into the corresponding response packet.
When an LWAPP control frame is sent, its internal sequence number
counter is monotonically incremented, ensuring that no two requests
pending have the same sequence number. This field will wrap back to
zero.
Calhoun, et al. Expires October 2, 2005 [Page 28]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
4.2.1.3 Message Element Length
The Length field indicates the number of bytes following the Session
ID field. If the LWAPP packet is encrypted, the length field
includes the AES-CCM MIC (see Section 10.2 for more information).
4.2.1.4 Session ID
The Session ID is a 32-bit unsigned integer that is used to identify
the security context for encrypted exchanges between the WTP and the
AC. Note that a Session ID is a random value that MUST be unique
between a given AC and any of the WTP it may be communicating with.
4.2.1.5 Message Element[0..N]
The message element(s) carry the information pertinent to each of the
control message types. Every control message in this specification
specifies which message elements are permitted.
4.2.2 Message Element Format
The message element is used to carry information pertinent to a
control message. Every message element is identified by the Type
field, whose numbering space is managed via IANA (see Section 15).
The total length of the message elements is indicated in the Message
Element Length field.
All of the message element definitions in this document use a diagram
similar to the one below in order to depict its format. Note that in
order to simplify this specification, these diagrams do not include
the header fields (Type and Length). However, in every message
element description, the header's fields values will be defined.
Note that additional message elements may be defined in separate IETF
documents.
The format of a message element uses the TLV format shown here:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Value ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Where Type (8 bit) identifies the character of the information
carried in the Value field and Length (16 bits) indicates the number
of bytes in the Value field.
Calhoun, et al. Expires October 2, 2005 [Page 29]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
4.2.2.1 Generic Message Elements
This section includes message elements that are not bound to a
specific control message.
4.2.2.1.1 Vendor Specific
The Vendor Specific Payload is used to communicate vendor specific
information between the WTP and the AC. The value contains the
following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Element ID | Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 104 for Vendor Specific
Length: >= 7
Vendor Identifier: A 32-bit value containing the IANA assigned "SMI
Network Management Private Enterprise Codes" [11]
Element ID: A 16-bit Element Identifier which is managed by the
vendor.
Value: The value associated with the vendor specific element.
Calhoun, et al. Expires October 2, 2005 [Page 30]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
5. LWAPP Discovery Operations
The Discovery messages are used by an WTP to determine which ACs are
available to provide service, as well as the capabilities and load of
the ACs.
5.1 Discovery Request
The Discovery Request is used by the WTP to automatically discover
potential ACs available in the network. An WTP must transmit this
command even if it has a statically configured AC, as it is a
required step in the LWAPP state machine.
Discovery Requests MUST be sent by an WTP in the Discover state after
waiting for a random delay less than MaxDiscoveryInterval, after an
WTP first comes up or is (re)initialized. An WTP MUST send no more
than a maximum of MaxDiscoveries discoveries, waiting for a random
delay less than MaxDiscoveryInterval between each successive
discovery.
This is to prevent an explosion of WTP Discoveries. An example of
this occurring would be when many WTPs are powered on at the same
time.
Discovery requests MUST be sent by an WTP when no echo responses are
received for NeighborDeadInterval and the WTP returns to the Idle
state. Discovery requests are sent after NeighborDeadInterval, they
MUST be sent after waiting for a random delay less than
MaxDiscoveryInterval. An WTP MAY send up to a maximum of
MaxDiscoveries discoveries, waiting for a random delay less than
MaxDiscoveryInterval between each successive discovery.
If a discovery response is not received after sending the maximum
number of discovery requests, the WTP enters the Sulking state and
MUST wait for an interval equal to SilentInterval before sending
further discovery requests.
The Discovery Request message may be sent as a unicast, broadcast or
multicast message.
Upon receiving a discovery request, the AC will respond with a
Discovery Response sent to the address in the source address of the
received discovery request.
The following subsections define the message elements that MUST be
included in this LWAPP operation.
Calhoun, et al. Expires October 2, 2005 [Page 31]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
5.1.1 Discovery Type
The Discovery message element is used to configure an WTP to operate
in a specific mode.
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Discovery Type|
+-+-+-+-+-+-+-+-+
Type: 58 for Discovery Type
Length: 1
Discovery Type: An 8-bit value indicating how the AC was discovered.
The following values are supported:
0 - Broadcast
1 - Configured
5.1.2 WTP Descriptor
The WTP descriptor message element is used by the WTP to communicate
it's current hardware/firmware configuration. The value contains the
following fields.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hardware Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Software Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Boot Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max Radios | Radios in use | Encryption Capabilities |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 3 for WTP Descriptor
Length: 16
Hardware Version: A 32-bit integer representing the WTP's hardware
version number
Software Version: A 32-bit integer representing the WTP's Firmware
version number
Boot Version: A 32-bit integer representing the WTP's boot loader's
version number
Max Radios: An 8-bit value representing the number of radios (where
each radio is identified via the RID field) supported by the WTP
Calhoun, et al. Expires October 2, 2005 [Page 32]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Radios in use: An 8-bit value representing the number of radios
present in the WTP
Encryption Capabilities: This 16-bit field is used by the WTP to
communicate it's capabilities to the AC. Since most WTPs support
link layer encryption, the AC may make use of these services.
There are binding dependent encryption capabilites. An WTP that
does not have any encryption capabilities would set this field to
zero (0). Refer to the specific binding for the specification.
5.1.3 WTP Radio Information
The WTP radios information message element is used to communicate the
radio information in a specific slot. The Discovery Request MUST
include one such message element per radio in the WTP. The
Radio-Type field is used by the AC in order to determine which
technology specific binding is to be used with the WTP.
The value contains two fields, as shown.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Radio Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 4 for WTP Radio Information
Length: 2
Radio ID: The Radio Identifier, typically refers to some interface
index on the WTP
Radio Type: The type of radio present. The following values are
supported
1 - 802.11bg: An 802.11bg radio.
2 - 802.11a: An 802.11a radio.
3 - 802.16: An 802.16 radio.
4 - Ultra Wideband: An UWB radio.
7 - all: Used to specify all radios in the WTP.
5.2 Discovery Response
The Discovery Response is a mechanism by which an AC advertises its
services to requesting WTPs.
Discovery Responses are sent by an AC after receiving a Discovery
Request.
When an WTP receives a Discovery Response, it MUST wait for an
interval not less than DiscoveryInterval for receipt of additional
Discovery Responses. After the DiscoveryInterval elapses, the WTP
Calhoun, et al. Expires October 2, 2005 [Page 33]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
enters the Joining state and will select one of the ACs that sent a
Discovery Response and send a Join Request to that AC.
The following subsections define the message elements that MUST be
included in this LWAPP operation.
5.2.1 AC Address
The AC address message element is used to communicate the identity of
the AC. The value contains two fields, as shown.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 2 for AC Address
Length: 7
Reserved: MUST be set to zero
Mac Address: The MAC Address of the AC
5.2.2 AC Descriptor
The AC payload message element is used by the AC to communicate it's
current state. The value contains the following fields.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Hardware Version ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HW Ver | Software Version ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SW Ver | Stations | Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Limit | Radios | Max Radio |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max Radio | Security |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 6 for AC Descriptor
Length: 17
Calhoun, et al. Expires October 2, 2005 [Page 34]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Reserved: MUST be set to zero
Hardware Version: A 32-bit integer representing the AC's hardware
version number
Software Version: A 32-bit integer representing the AC's Firmware
version number
Stations: A 16-bit integer representing number of mobile stations
currently associated with the AC
Limit: A 16-bit integer representing the maximum number of stations
supported by the AC
Radios: A 16-bit integer representing the number of WTPs currently
attached to the AC
Max Radio: A 16-bit integer representing the maximum number of WTPs
supported by the AC
Security: A 8 bit bit mask specifying the security schemes supported
by the AC. The following values are supported:
1 - X.509 Certificate Based (Section 10.3.1)
2 - Pre-Shared Secret (Section 10.3.2)
5.2.3 AC Name
The AC name message element contains an ASCII representation of the
AC's identity. The value is a variable length byte string. The
string is NOT zero terminated.
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Name ...
+-+-+-+-+-+-+-+-+
Type: 31 for AC Name
Length: > 0
Name: A variable length ASCII string containing the AC's name
5.2.4 WTP Manager Control IP Address
The WTP Manager Control IP Address message element is sent by the AC
to the WTP during the discovery process and is used by the AC to
provide the interfaces available on the AC, and their current load.
This message elemenet is useful for the WTP to perform load balancing
across multiple interfaces.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| WTP Count |
Calhoun, et al. Expires October 2, 2005 [Page 35]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 99 for WTP Manager Control IP Address
Length: 6
IP Address: The IP Address of an interface.
WTP Count: The number of WTPs currently connected to the interface.
5.3 Primary Discovery Request
The Primary Discovery Request is sent by the WTP in order to
determine whether its preferred (or primary) AC is available.
Primary Discovery Request are sent by an WTP when it has a primary AC
configured, and is connected to another AC. This generally occurs as
a result of a failover, and is used by the WTP as a means to discover
when its primary AC becomes available. As a consequence, this
message is only sent by a WTP when it is in the Run state.
The frequency of the Primary Discovery Requests should be no more
often than the sending of the Echo Request message.
Upon receiving a discovery request, the AC will respond with a
Primary Discovery Response sent to the address in the source address
of the received Primary Discovery Request.
The following subsections define the message elements that MUST be
included in this LWAPP operation.
5.3.1 Discovery Type
The Discovery Type message element is defined in section
Section 5.1.1.
5.3.2 WTP Descriptor
The WTP Descriptor message element is defined in section
Section 5.1.2.
5.3.3 WTP Radio Information
An WTP Radio Information message element must be present for every
radio in the WTP. This message element is defined in section
Section 5.1.3.
5.4 Primary Discovery Response
The Primary Discovery Response is a mechanism by which an AC
advertises its availability and services to requesting WTPs that are
Calhoun, et al. Expires October 2, 2005 [Page 36]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
configured to have the AC as its primary AC.
Primary Discovery Responses are sent by an AC after receiving a
Primary Discovery Request.
When an WTP receives a Primary Discovery Response, it may opt to
establish an LWAPP connection to its primary AC, based on the
configuration of the WTP Fallback Status message element on the WTP.
The following subsections define the message elements that MUST be
included in this LWAPP operation.
5.4.1 AC Descriptor
The Discovery Type message element is defined in section
Section 5.2.2.
5.4.2 AC Name
The AC Name message element is defined in section Section 5.2.3.
5.4.3 WTP Manager Control IP Address
An WTP Radio Information message element must be present for every
radio in the WTP. This message element is defined in section
Section 5.2.4.
Calhoun, et al. Expires October 2, 2005 [Page 37]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
6. Control Channel Management
The Control Channel Management messages are used by the WTP and AC to
create and maintain a channel of communication on which various other
commands may be transmitted, such as configuration, firmware update,
etc.
6.1 Join Request
The Join Request is used by an WTP to inform an AC that it wishes to
provide services through it.
Join Requests are sent by an WTP in the Joining state after receiving
one or more Discovery Responses. The Join Request is also used as an
MTU discovery mechanism by the WTP. The WTP issues a Join Request
with a Test message element, bringing the total size of the message
to exceed MTU.
If the transport used does not provide MTU path discovery, the
initial Join Request is padded with the Test message element to 1596
bytes. If a Join Response is received, the WTP can forward frames
without requiring any fragmentation. If no Join Response is
received, it issues a second Join Request padded with the Test
payload to a total of 1500 bytes. The WTP continues to cycle from
large (1596) to small (1500) packets until a Join Response has been
received , or until both packets sizes have been retransmitted 3
times . If the Join Response is not received after the maximum
number of retransmissions, the WTP MUST abandon the AC and restart
the discovery phase.
When an AC receives a Join Request it will respond with a Join
Response. If the certificate based security mechanism is used, the
AC validates the certificate found in the request. If valid, the AC
generates a session key which will be used to secure the control
frames it exchanges with the WTP. When the AC issues the Join
Response, the AC creates a context for the session with the WTP.
If the pre-shared session key security mechanism is used, the AC
saves the WTP's nonce, found in the WNonce message element, creates
its own nonce which it includes in the ANonce message element.
Finally, the AC creates the PSK-MIC, which is computed using a key
that is derived from the PSK.
A Join Request that includes both a WNonce and a Certificate message
element MUST be considered invalid.
Details on the key generation is found in Section 10.
Calhoun, et al. Expires October 2, 2005 [Page 38]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
The following subsections define the message elements that MUST be
included in this LWAPP operation.
6.1.1 WTP Descriptor
The WTP Descriptor message element is defined in section
Section 5.1.2.
6.1.2 AC Address
The AC Address message element is defined in section Section 5.2.1.
6.1.3 WTP Name
The WTP name message element value is a variable length byte string.
The string is NOT zero terminated.
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Name ...
+-+-+-+-+-+-+-+-+
Type: 5 for WTP Name
Length: > 0
Name: A non zero terminated string containing the WTP's name.
6.1.4 Location Data
The location data message element is a variable length byte string
containing user defined location information (e.g. "Next to
Fridge"). The string is NOT zero terminated.
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Location ...
+-+-+-+-+-+-+-+-+
Type: 35 for Location Data
Length: > 0
Location: A non zero terminated string containing the WTP's
location.
6.1.5 WTP Radio Information
An WTP Radio Information message element must be present for every
radio in the WTP. This message element is defined in section
Calhoun, et al. Expires October 2, 2005 [Page 39]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Section 5.1.3.
6.1.6 Certificate
The certificate message element value is a byte string containing a
DER-encoded x.509v3 certificate. This message element is only
included if the LWAPP security type used between the WTP and the AC
makes use of certificates (see Section 10 for more information).
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Certificate...
+-+-+-+-+-+-+-+-+
Type: 44 for Certificate
Length: > 0
Certificate: A non zero terminated string containing the device's
certificate.
6.1.7 Session ID
The session ID message element value contains a randomly generated
[4] unsigned 32-bit integer.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Session ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 45 for Session ID
Length: 4
Session ID: 32 bit random session identifier.
6.1.8 Test
The test message element is used as padding to perform MTU discovery,
and MAY contain any value, of any length.
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Padding ...
+-+-+-+-+-+-+-+-+
Calhoun, et al. Expires October 2, 2005 [Page 40]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Type: 18 for Test
Length: > 0
Padding: A variable length pad.
6.1.9 WNonce
The wnonce message element is sent by a WTP that is configured to
make use of the pre-shared key security mechanism. See
Section 10.3.2 for more information.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 107 for WNonce
Length: 16
Nonce: A 16 octet random nonce.
6.1.10 DH-Params
The DH-Params message element is used in order for the WTP and the AC
to perform a Diffie Hellman exchange. This message element contains
the g, p, g^x mod p - where x is the exponent chosen by the sender.
See Section 10.3.2 for more information.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Calhoun, et al. Expires October 2, 2005 [Page 41]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Type: 111 for DH-Params
Length: 16
Nonce: Contains g, p, g^x mod p, where 'x' is the exponent chosen by
the sender.
6.2 Join Response
The Join Response is sent by the AC to indicate to an WTP whether it
is capable and willing to provide service to it.
Join Responses are sent by the AC after receiving a Join Request.
Once the Join Response has been sent, the heartbeat timer is
initiated for the session to EchoInterval. Expiration of the timer
will result in deletion of the AC-WTP session. The timer is
refreshed upon receipt of the Echo Request.
If the security method used is certificate based, when a WTP receives
a Join Response it enters the Joined state and initiates either a
Configure Request or Image Data to the AC to which it is now joined.
Upon entering the Joined state, the WTP begins timing an interval
equal to NeighborDeadInterval. Expiration of the timer will result
in the transmission of the Echo Request.
If the security method used is pre-shared secret based, when a WTP
receives a Join Response that includes a valid PSK-MIC message
element, it responds with a Join ACK that also MUST include a locally
computed PSK-MIC message element.
The following subsections define the message elements that MUST be
included in this LWAPP operation.
6.2.1 Result Code
The Result Code message element value is a 32-bit integer value,
indicating the result of the request operation corresponding to the
sequence number in the message. The Result Code is included in a
successful Join Response.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Result Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 2 for Result Code
Calhoun, et al. Expires October 2, 2005 [Page 42]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Length: 4
Result Code: The following values are defined:
0 Success
1 Failure (AC List message element MUST be present)
6.2.2 Status
The Status message element is sent by the AC to the WTP in a
non-successful Join Response message. This message element is used
to indicate the reason for the failure and should only be accompanied
with a Result Code message element that indicates a failure.
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Status |
+-+-+-+-+-+-+-+-+
Type: 60 for Status
Length: 1
Status: The status field indicates the reason for an LWAPP failure.
The following values are supported:
1 - Reserved - do not use
2 - Resource Depletion
3 - Unknown Source
4 - Incorrect Data
6.2.3 Certificate
The Certificate message element is defined in section Section 6.1.6.
Note this message element is only included if the WTP and the AC make
use of certificate based security as defined in section Section 10.
6.2.4 Session Key
The Session Key message element is sent by the AC to the WTP and
includes the randomly generated session key, which is used to protect
the LWAPP control messages. More details are available in
Section 10. The value contains the following fields.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Security | Session Key ....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Calhoun, et al. Expires October 2, 2005 [Page 43]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Type: 46 for Session Key
Length: > 1
Security: The LWAPP security model used. The following values are
supported:
0 - Unused
1 - X.509 Certificate Based (Section 10.3.1)
2 - Pre-Shared Secret (Section 10.3.2)
Session Key: An Encrypted Session Key. The encryption procedures
used for this field depends upon the security model used, which
are defined in section Section 10.
6.2.5 WTP Manager Data IP Address
The WTP Manager Data IP Address message element is optionally sent by
the AC to the WTP during the join phase. If present, the IP Address
contained in this message element is the address the WTP is to use
when sending any of its LWAPP data frames.
Note this message element is only valid when LWAPP uses the IP/UDP
layer 3 transport
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD for WTP Manager Data IP Address
Length: 4
IP Address: The IP Address of an interface.
6.2.6 AC List
The AC List message element is used to configure an WTP with the
latest list of ACs in a cluster. This message element MUST be
included if the Join Response returns a failure indicating that the
AC cannot handle the WTP at this time, allowing the WTP to find an
alternate AC to connect to.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AC IP Address[] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Calhoun, et al. Expires October 2, 2005 [Page 44]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Type: 59 for AC List
Length: >= 4
AC IP Address: An array of 32-bit integers containing an AC's IP
Address.
6.2.7 ANonce
The anonce message element is sent by a AC that is configured to make
use of the pre-shared key security method. See Section 10.3.2 for
more information.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 108 for Test
Length: 16
Nonce: A 16 octet random nonce.
6.2.8 PSK-MIC
The PSK-MIC message element includes a message integrity check, whose
purpose is to provide confirmation to the peer that the sender has
the proper session key. This message element is only included if the
security method used between the WTP and the AC is the pre-shared
secret mechanism. See Section 10.3.2 for more information.
When present, the PSK-MIC message element MUST be the last message
element in the message. The MIC is computed over the complete LWAPP
packet, from the LWAPP control header as defined in Section 4.2.1 to
the end of the packet (which MUST be this PSK-MIC message element).
The MIC field in this message element and the sequence number field
in the LWAPP control header MUST be set to zeroes prior to computing
the MIC. The length field in the LWAPP control header must already
include this message element prior to computing the MIC.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SPI | MIC ...
Calhoun, et al. Expires October 2, 2005 [Page 45]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 109 for PSK-MIC
Length: > 1
SPI: The SPI field specifies the cryptographic algorithm used to
create the message integrity check. The following values are
supported:
0 - Unused
1 - HMAC-SHA-1 (RFC 2104 [14])
MIC: A 20 octet Message Integrity Check.
6.2.9 DH-Params
The Certificate message element is defined in section Section 6.1.10.
Note this message element is only included if the WTP and the AC make
use of pre-shared key based security as defined in section
Section 10.3.2.
6.3 Join ACK
The Join ACK message is sent by the WTP upon receiving a Join
Response, which has a valid PSK-MIC message element, as a means of
providing key confirmation to the AC. The Join ACK is only used in
the case where the WTP makes use of the pre-shared key LWAPP mode
(See Section 10.3.2 for more information).
Note that the AC should never receive this message unless the
security method used between the WTP and the AC is pre-shared secret
based.
The following subsections define the message elements that MUST be
included in this LWAPP operation.
6.3.1 Session ID
The Session ID message element is defined in section Section 6.1.7.
6.3.2 WNonce
The WNonce message element is defined in section Section 6.1.9.
6.3.3 PSK-MIC
The PSK-MIC message element is defined in section Section 6.2.8.
6.4 Join Confirm
The Join Confirm message is sent by the AC upon receiving a Join ACK,
Calhoun, et al. Expires October 2, 2005 [Page 46]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
which has a valid PSK-MIC message element, as a means of providing
key confirmation to the WTP. The Join Confirm is only used in the
case where the WTP makes use of the pre-shared key LWAPP mode (See
Section 10.3.2 for more information).
If the security method used is pre-shared key based, when an WTP
receives a Join Confirm it enters the Joined state and initiates
either a Configure Request or Image Data to the AC to which it is now
joined. Upon entering the Joined state, the WTP begins timing an
interval equal to NeighborDeadInterval. Expiration of the timer will
result in the transmission of the Echo Request.
This message is never received, or sent, when the security type used
between the WTP and the AC is certificated based.
The following subsections define the message elements that MUST be
included in this LWAPP operation.
6.4.1 Session ID
The Session ID message element is defined in section Section 6.1.7.
6.4.2 ANonce
The ANonce message element is defined in section Section 6.2.7.
6.4.3 PSK-MIC
The PSK-MIC message element is defined in section Section 6.2.8.
6.5 Echo Request
The Echo Request message is a keepalive mechanism for the LWAPP
control message.
Echo Requests are sent periodically by an WTP in the Run state (see
Figure 2) to determine the state of the connection between the WTP
and the AC. The Echo Request is sent by the WTP when the Heartbeat
timer expires, and it MUST start its NeighborDeadInterval timer.
The Echo Request carries no message elements.
When an AC receives an Echo Request it responds with an Echo
Response.
6.6 Echo Response
The Echo Response acknowledges the Echo Request, and are only
Calhoun, et al. Expires October 2, 2005 [Page 47]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
accepted while in the Run state (see Figure 2).
Echo Responses are sent by an AC after receiving an Echo Request.
After transmitting the Echo Response, the AC should reset its
Heartbeat timer to expire in the value configured for EchoInterval.
If another Echo request is not received by the AC when the timer
expires, the AC SHOULD consider the WTP to no longer be reachable.
The Echo Response carries no message elements.
When an WTP receives an Echo Response it stops the
NeighborDeadInterval timer, and starts the Heartbeat timer to
EchoInterval.
If the NeighborDeadInterval timer expires prior to receiving an Echo
Response, the WTP enters the Idle state.
6.7 Key Update Request
The Key Update Request updates the LWAPP session key used to secure
messages between the WTP and the AC.
Key Update Requests are sent by an WTP in the Run state to update a
session key. The Session ID message element MUST include a new
session identifier.
When an AC receives a Key Update Request it generates a new key (see
Section 10) and responds with a Key Update Response.
The following subsections define the message elements that MUST be
included in this LWAPP operation.
6.7.1 Session ID
The Session ID message element is defined in section Section 6.1.7.
6.8 Key Update Response
The Key Update Response updates the LWAPP session key used to secure
messages between the WTP and the AC, and acknowledges the Key Update
Request.
Key Update Responses are sent by a AC after receiving a Key Update
Request. The Key Update Responses is secured using public key
cryptography when certificates were used in the Join Request/Response
exchange. However, the session keys are AES Key-wrapped when the AC
and WTP invoked PSK-mode to establish the first session key.
Calhoun, et al. Expires October 2, 2005 [Page 48]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
When an WTP receives a Key Update Response it will use the
information contained in the Session Key message element to determine
the keying material used to encrypt the LWAPP communications between
the WTP and the AC.
The following subsections define the message elements that MUST be
included in this LWAPP operation.
6.8.1 Session Key
The Session Key message element is defined in section Section 6.2.4.
6.9 Key Update Trigger
The Key Update Trigger is used by the AC to request that a Key Update
Request be initiated by the WTP.
Key Update Trigger are sent by an AC in the Run state to inform the
WTP to initiate a Key Update Request message.
When a WTP receives a Key Update Trigger it generates a key Update
Request.
The following subsections define the message elements that MUST be
included in this LWAPP operation.
6.9.1 Session ID
The Session ID message element is defined in section Section 6.1.7.
Calhoun, et al. Expires October 2, 2005 [Page 49]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
7. WTP Configuration Management
The Wireless Termination Point Configuration messages are used to
exchange configuration between the AC and the WTP.
7.1 Configure Request
The Configure Request message is sent by an WTP to send its current
configuration to its AC.
Configure Requests are sent by an WTP after receiving a Join
Response, while in the Configure state.
The Configure Request carries binding specific message elements.
Refer to the appropriate binding for the definition of this
structure.
When an AC receives a Configure Request it will act upon the content
of the packet and respond to the WTP with a Configure Response.
The Configure Request includes multiple Administrative State message
Elements. There is one such message element for the WTP, and then
one per radio in the WTP.
The following subsections define the message elements that MUST be
included in this LWAPP operation.
7.1.1 Administrative State
The administrative event message element is used to communicate the
state of a particular radio. The value contains the following
fields.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Admin State |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 27 for Administrative State
Length: 2
Radio ID: An 8-bit value representing the radio to configure. The
Radio ID field may also include the value of 0xff, which is used
to identify the WTP itself. Therefore, if an AC wishes to change
the administrative state of an WTP, it would include 0xff in the
Radio ID field.
Calhoun, et al. Expires October 2, 2005 [Page 50]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Admin State: An 8-bit value representing the administrative state of
the radio. The following values are supported:
1 - Enabled
2 - Disabled
7.1.2 AC Name
The AC Name message element is defined in section Section 5.2.3.
7.1.3 AC Name with Index
The AC Name with Index message element is sent by the AC to the WTP
to configure preferred ACs. The number of instances where this
message element would be present is equal to the number of ACs
configured on the WTP.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Index | AC Name...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 90 for AC Name with Index
Length: 5
Index: The index of the preferred server (e.g., 1=primary,
2=secondary).
AC Name: A variable length ASCII string containing the AC's name.
7.1.4 WTP Board Data
The WTP Board Data message element is sent by the WTP to the AC and
contains information about the hardware present.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Card ID | Card Revision |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| WTP Model |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| WTP Model |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| WTP Serial Number ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ethernet MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Calhoun, et al. Expires October 2, 2005 [Page 51]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
| Ethernet MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 50 for WTP Board Data
Length: 26
Card ID: A hardware identifier.
Card Revision: 4 byte Revision of the card.
WTP Model: 8 byte WTP Model Number.
WTP Serial Number: 24 byte WTP Serial Number.
Reserved: A 4 byte reserved field that MUST be set to zero (0).
Ethernet MAC Address: MAC Address of the WTP's Ethernet interface.
7.1.5 Statistics Timer
The statistics timer message element value is used by the AC to
inform the WTP of the frequency which it expects to receive updated
statistics.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Statistics Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 37 for Statistics Timer
Length: 2
Statistics Timer: A 16-bit unsigned integer indicating the time, in
seconds
7.1.6 WTP Static IP Address Information
The WTP Static IP Address Information message element is used by an
AC to configure or clear a previously configured static IP address on
an WTP.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Netmask |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Gateway |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Static |
+-+-+-+-+-+-+-+-+
Calhoun, et al. Expires October 2, 2005 [Page 52]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Type: 82 for WTP Static IP Address Information
Length: 13
IP Address: The IP Address to assign to the WTP.
Netmask: The IP Netmask.
Gateway: The IP address of the gateway.
Netmask: The IP Netmask.
Static: An 8-bit boolean stating whether the WTP should use a static
IP address or not. A value of zero disables the static IP
address, while a value of one enables it.
7.1.7 WTP Reboot Statistics
The WTP Reboot Statistics message element is sent by the WTP to the
AC to communicate information about reasons why reboots have
occurred.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Crash Count | LWAPP Initiated Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Failure Count | Failure Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 67 for WTP Reboot Statistics
Length: 7
Crash Count: The number of reboots that have occurred due to an WTP
crash.
LWAPP Initiated Count: The number of reboots that have occured at
the request of some LWAPP message, such as a change in
configuration that required a reboot or an explicit LWAPP reset
request.
Link Failure Count: The number of times that an LWAPP connection
with an AC has failed.
Failure Type: The last WTP failure. The following values are
supported:
0 - Link Failure
1 - LWAPP Initiated
2 - WTP Crash
7.2 Configure Response
The Configure Response message is sent by an AC and provides an
opportunity for the AC to override an WTP's requested configuration.
Configure Responses are sent by an AC after receiving a Configure
Request.
Calhoun, et al. Expires October 2, 2005 [Page 53]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
The Configure Response carries binding specific message elements.
Refer to the appropriate binding for the definition of this
structure.
When an WTP receives a Configure Response it acts upon the content of
the packet, as appropriate. If the Configure Response message
includes a Change State Event message element that causes a change in
the operational state of one of the Radio, the WTP will transmit a
Change State Event to the AC, as an acknowledgement of the change in
state.
The following subsections define the message elements that MUST be
included in this LWAPP operation.
7.2.1 Decryption Error Report Period
The Decryption Error Report Period message element value is used by
the AC to inform the WTP how frequently it should send decryption
error report messages.
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Report Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 38 for Decryption Error Report Period
Length: 3
Radio ID: The Radio Identifier, typically refers to some interface
index on the WTP
Report Interval: A 16-bit unsigned integer indicating the time, in
seconds
7.2.2 Change State Event
The WTP radios information message element is used to communicate the
operational state of a radio. The value contains two fields, as
shown.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | State | Cause |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Calhoun, et al. Expires October 2, 2005 [Page 54]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Type: 26 for Change State Event
Length: 3
Radio ID: The Radio Identifier, typically refers to some interface
index on the WTP.
State: An 8-bit boolean value representing the state of the radio.
A value of one disables the radio, while a value of two enables
it.
Cause: In the event of a radio being inoperable, the cause field
would contain the reason the radio is out of service.
Cause: In the event of a radio being inoperable, the cause field
would contain the reason the radio is out of service. The
following values are supported:
0 - Normal
1 - Radio Failure
2 - Software Failure
7.2.3 LWAPP Timers
The LWAPP Timers message element is used by an AC to configure LWAPP
timers on an WTP.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Discovery | Echo Request |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 68 for LWAPP Timers
Length: 2
Discovery: The number of seconds between LWAPP Discovery packets,
when the WTP is in the discovery mode.
Echo Request: The number of seconds between WTP Echo Request LWAPP
messages.
7.2.4 AC List
The AC List message element is defined in section Section 6.2.6.
7.2.5 WTP Fallback
The WTP Fallback message element is sent by the AC to the WTP to
enable or disable automatic LWAPP fallback in the event that an WTP
detects its preferred AC, and is not currently connected to it.
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Mode |
Calhoun, et al. Expires October 2, 2005 [Page 55]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
+-+-+-+-+-+-+-+-+
Type: 91 for WTP Fallback
Length: 1
Mode: The 8-bit boolean value indicates the status of automatic
LWAPP fallback on the WTP. A value of zero disables the fallback
feature, while a value of one enables it. When enabled, if the
WTP detects that its primary AC is available, and it is not
connected to it, it SHOULD automatically disconnect from its
current AC and reconnect to its primary. If disabled, the WTP
will only reconnect to its primary through manual intervention
(e.g., through the Reset Request command).
7.2.6 Idle Timeout
The Idle Timeout message element is sent by the AC to the WTP to
provide it with the idle timeout that it should enforce on its active
mobile station entries.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timeout |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 97 for Idle Timeout
Length: 4
Timeout: The current idle timeout to be enforced by the WTP.
7.3 Configuration Update Request
Configure Update Requests are sent by the AC to provision the WTP
while in the Run state. This is used to modify the configuration of
the WTP while it is operational.
When an AC receives a Configuration Update Request it will respond
with a Configuration Update Response, with the appropriate Result
Code.
The following subsections define the message elements introduced by
this LWAPP operation.
7.3.1 WTP Name
The WTP Name message element is defined in section Section 6.1.3.
Calhoun, et al. Expires October 2, 2005 [Page 56]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
7.3.2 Change State Event
The Change State Event message element is defined in section
Section 7.2.2.
7.3.3 Administrative State
The Administrative State message element is defined in section
Section 7.1.1.
7.3.4 Statistics Timer
The Statistics Timer message element is defined in section
Section 7.1.5.
7.3.5 Location Data
The Location Data message element is defined in section
Section 6.1.4.
7.3.6 Decryption Error Report Period
The Decryption Error Report Period message element is defined in
section Section 7.2.1.
7.3.7 AC List
The AC List message element is defined in section Section 6.2.6.
7.3.8 Add Blacklist Entry
The Add Blacklist Entry message element is used by an AC to add a
blacklist entry on an WTP, ensuring that the WTP no longer provides
any service to the MAC addresses provided in the message. The MAC
Addresses provided in this message element are not expected to be
saved in non-volative memory on the WTP.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num of Entries| MAC Address[] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address[] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Calhoun, et al. Expires October 2, 2005 [Page 57]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Type: 65 for Add Blacklist Entry
Length: >= 7
Num of Entries: The number of MAC Addresses in the array.
MAC Address: An array of MAC Addresses to add to the blacklist
entry.
7.3.9 Delete Blacklist Entry
The Delete Blacklist Entry message element is used by an AC to delete
a previously added blacklist entry on an WTP, ensuring that the WTP
provides service to the MAC addresses provided in the message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num of Entries| MAC Address[] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address[] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 66 for Delete Blacklist Entry
Length: >= 7
Num of Entries: The number of MAC Addresses in the array.
MAC Address: An array of MAC Addresses to delete from the blacklist
entry.
7.3.10 Add Static Blacklist Entry
The Add Static Blacklist Entry message element is used by an AC to
add a permanent blacklist entry on an WTP, ensuring that the WTP no
longer provides any service to the MAC addresses provided in the
message. The MAC Addresses provided in this message element are
expected to be saved in non-volative memory on the WTP.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num of Entries| MAC Address[] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address[] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 70 for Delete Blacklist Entry
Length: >= 7
Num of Entries: The number of MAC Addresses in the array.
Calhoun, et al. Expires October 2, 2005 [Page 58]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
MAC Address: An array of MAC Addresses to add to the permanent
blacklist entry.
7.3.11 Delete Static Blacklist Entry
The Delete Static Blacklist Entry message element is used by an AC to
delete a previously added static blacklist entry on an WTP, ensuring
that the WTP provides service to the MAC addresses provided in the
message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num of Entries| MAC Address[] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address[] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 71 for Delete Blacklist Entry
Length: >= 7
Num of Entries: The number of MAC Addresses in the array.
MAC Address: An array of MAC Addresses to delete from the static
blacklist entry.
7.3.12 LWAPP Timers
The LWAPP Timers message element is defined in section Section 7.2.3.
7.3.13 AC Name with Index
The AC Name with Index message element is defined in section
Section 7.1.3.
7.3.14 WTP Fallback
The WTP Fallback message element is defined in section Section 7.2.5.
7.3.15 Idle Timeout
The Idle Timeout message element is defined in section Section 7.2.6.
7.4 Configuration Update Response
The Configuration Update Response is the acknowledgement message for
the Configuration Update Request.
Configuration Update Responses are sent by an WTP after receiving a
Configuration Update Request.
Calhoun, et al. Expires October 2, 2005 [Page 59]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
When an AC receives a Configure Update Response the result code
indicates if the WTP successfully accepted the configuration.
The following subsections define the message elements that must be
present in this LWAPP operation.
7.4.1 Result Code
The Result Code message element is defined in section Section 6.2.1.
7.5 Change State Event Request
The Change State Event is used by the WTP to inform the AC of a
change in the operational state.
The Change State Event message is sent by the WTP when it receives a
Configuration Response that includes a Change State Event message
element. It is also sent in the event that the WTP detects an
operational failure with a radio. The Change State Event may be sent
in either the Configure or Run state (see Figure 2.
When an AC receives a Change State Event it will respond with a
Change State Event Response and make any necessary modifications to
internal WTP data structures.
The following subsections define the message elements that must be
present in this LWAPP operation.
7.5.1 Change State Event
The Change State Event message element is defined in section
Section 7.2.2.
7.6 Change State Event Response
The Change State Event Response acknowledges the Change State Event.
Change State Event Response are sent by an WTP after receiving a
Change State Event.
The Change State Event Response carries no message elements. Its
purpose is to acknowledge the receipt of the Change State Event.
The WTP does not need to perform any special processing of the Change
State Event Response message.
Calhoun, et al. Expires October 2, 2005 [Page 60]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
7.7 Clear Config Indication
The Clear Config Indication is used to reset an WTP's configuration.
The Clear Config Indication is sent by an AC to request that an WTP
reset its configuration to manufacturing defaults. The Clear Config
Indication message is sent while in the Run LWAPP state.
The Reset Request carries no message elements.
When an WTP receives a Clear Config Indication it will reset its
configuration to manufacturing defaults.
Calhoun, et al. Expires October 2, 2005 [Page 61]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
8. Device Management Operations
This section defines LWAPP operations responsible for debugging,
gathering statistics, logging, and firmware management.
8.1 Image Data Request
The Image Data Request is used to update firmware on the WTP. This
message and its companion response are used by the AC to ensure that
the image being run on each WTP is appropriate.
Image Data Requests are exchanged between the WTP and the AC to
download a new program image to an WTP.
When an WTP or AC receives an Image Data Request it will respond with
a Image Data Response.
The format of the Image Data and Image Download message elements are
described in the following subsections.
8.1.1 Image Download
The image download message element is sent by the WTP to the AC and
contains the image filename. The value is a variable length byte
string. The string is NOT zero terminated.
8.1.2 Image Data
The image data message element is present when sent by the AC and
contains the following fields.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode | Checksum | Image Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Image Data ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 33 for Image Data
Length: >= 5
Opcode: An 8-bit value representing the transfer opcode. The
following values are supported:
3 - Image data is included
5 - An error occurred. Transfer is aborted
Calhoun, et al. Expires October 2, 2005 [Page 62]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Checksum: A 16-bit value containing a checksum of the image data
that follows
Image Data: The Image Data field contains 1024 characters, unless
the payload being sent is the last one (end of file)
8.2 Image Data Response
The Image Data Response acknowledges the Image Data Request.
An Image Data Responses is sent in response to an Image Data Request.
Its purpose is to acknowledge the receipt of the Image Data Request
packet.
The Image Data Response carries no message elements.
No action is necessary on receipt.
8.3 Reset Request
The Reset Request is used to cause an WTP to reboot.
Reset Requests are sent by an AC to cause an WTP to reinitialize its
operation.
The Reset Request carries no message elements.
When an WTP receives a Reset Request it will respond with a Reset
Response and then reinitialize itself.
8.4 Reset Response
The Reset Response acknowledges the Reset Request.
Reset Responses are sent by an WTP after receiving a Reset Request.
The Reset Response carries no message elements. Its purpose is to
acknowledge the receipt of the Reset Request.
When an AC receives a Reset Response it is notified that the WTP will
now reinitialize its operation.
8.5 WTP Event Request
WTP Event Request is used by an WTP to send an information to its AC.
These types of events may be periodical, or some asynchronous event
on the WTP. For instance, an WTP collects statistics and uses the
WTP Event Request to transmit this information to the AC.
Calhoun, et al. Expires October 2, 2005 [Page 63]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
When an AC receives a WTP Event Request it will respond with a WTP
Event Request.
The WTP Event Request message MUST contain one of the following
message element described in the next subsections, or a message
element that is defined for a specific technology.
8.5.1 Decryption Error Report
The Decryption Error Report message element value is used by the WTP
to inform the AC of decryption errors that have occured since the
last report.
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID |Num Of Entries | Mobile MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mobile MAC Address[] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 39 for Decryption Error Report
Length: >= 8
Radio ID: The Radio Identifier, typically refers to some interface
index on the WTP
Num Of Entries: An 8-bit unsigned integer indicating the number of
mobile MAC addresses.
Mobile MAC Address: An array of mobile station MAC addresses that
have caused decryption errors.
8.5.2 Duplicate IP Address
The Duplicate IP Address message element is used by an WTP to inform
an AC that it has detected another host using the same IP address it
is currently using.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Calhoun, et al. Expires October 2, 2005 [Page 64]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Type: 77 for Duplicate IP Address
Length: 10
IP Address: The IP Address currently used by the WTP.
MAC Address: The MAC Address of the offending device.
8.6 WTP Event Response
WTP Event Response acknowledges the WTP Event Request.
WTP Event Response are sent by an AC after receiving a WTP Event
Request.
The WTP Event Response carries no message elements.
8.7 Data Transfer Request
The Data Transfer Request is used to upload debug information from
the WTP to the AC.
Data Transfer Requests are sent by the WTP to the AC when it
determines that it has important information to send to the AC. For
instance, if the WTP detects that its previous reboot was caused by a
system crash, it would want to send the crash file to the AC. The
remote debugger function in the WTP also uses the data transfer
request in order to send console output to the AC for debugging
purposes.
When an AC receives an Data Transfer Request it will respond with a
Data Transfer Response. The AC may log the information received, as
it sees fit.
The data transfer request message MUST contain ONE of the following
message element described in the next subsection.
8.7.1 Data Transfer Mode
The Data Transfer Mode message element is used by the AC to request
information from the WTP for debugging purposes.
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Data Type |
+-+-+-+-+-+-+-+-+
Calhoun, et al. Expires October 2, 2005 [Page 65]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Type: 52 for Data Transfer Mode
Length: 1
Data Type: An 8-bit value the type of information being requested.
The following values are supported:
1 - WTP Crash Data
2 - WTP Memory Dump
8.7.2 Data Transfer Data
The Data Transfer Data message element is used by the WTP to provide
information to the AC for debugging purposes.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Type | Data Length | Data ....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 53 for Data Transfer Data
Length: >= 3
Data Type: An 8-bit value the type of information being sent. The
following values are supported:
1 - WTP Crash Data
2 - WTP Memory Dump
Data Length: Length of data field.
Data: Debug information.
8.8 Data Transfer Response
The Data Transfer Response acknowledges the Data Transfer Request.
An Data Transfer Response is sent in response to an Data Transfer
Request. Its purpose is to acknowledge the receipt of the Data
Transfer Request packet.
The Data Transfer Response carries no message elements.
Upon receipt of a Data Transfer Response, the WTP transmits more
information, if any is available.
Calhoun, et al. Expires October 2, 2005 [Page 66]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
9. Mobile Session Management
Messages in this section are used by the AC to create, modify or
delete mobile station session state on the WTPs.
9.1 Mobile Config Request
The Mobile Config Request message is used to create, modify or delete
mobile session state on an WTP. The message is sent by the AC to the
WTP, and may contain one or more message elements. The message
elements for this LWAPP control message include information that is
generally highly technology specific. Therefore, please refer to the
appropriate binding section or document for the definitions of the
messages elements that may be used in this control message.
This section defines the format of the Delete Mobile message element,
since it does not contain any technology specific information.
9.1.1 Delete Mobile
The Delete Mobile message element is used by the AC to inform an WTP
that it should no longer provide service to a particular mobile
station. The WTP must terminate service immediately upon receiving
this message element.
The transmission of a Delete Mobile message element could occur for
various reasons, including for administrative reaons, as a result of
the fact that the mobile has roamed to another WTP, etc.
Once access has been terminated for a given station, any future
packets received from the mobile must result in a deauthenticate
message, as specified in [6].
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 30 for Delete Mobile
Length: 7
Radio ID: An 8-bit value representing the radio
MAC Address: The mobile station's MAC Address
Calhoun, et al. Expires October 2, 2005 [Page 67]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
9.2 Mobile Config Response
The Mobile Configuration Response is used to acknowledge a previously
received Mobile Configuration Request, and includes a Result Code
message element which indicates whether an error occured on the WTP.
This message requires no special processing, and is only used to
acknowledge the Mobile Configuration Request.
The data transfer request message MUST contain the message elements
described in the next subsection.
9.2.1 Result Code
The Result Code message element is defined in section Section 6.2.1.
Calhoun, et al. Expires October 2, 2005 [Page 68]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
10. Session Key Generation
Note: This version only defines a certificate and a shared secret
based mechanism to secure control LWAPP traffic exchanged between the
WTP and the AC.
10.1 Securing WTP-AC communications
While it is generally straightforward to produce network
installations in which the communications medium between the WTP and
AC is not accessible to the casual user (e.g. these LAN segments are
isolated, no RJ45 or other access ports exist between the WTP and the
AC), this will not always be the case. Furthermore, a determined
attacker may resort to various more sophisticated monitoring and/or
access techniques, thereby compromising the integrity of this
connection.
In general, a certain level of threat on the local (wired) LAN is
expected and accepted in most computing environments. That is, it is
expected that in order to provide users with an acceptable level of
service and maintain reasonable productivity levels, a certain amount
of risk must be tolerated. It is generally believed that a certain
perimeter is maintained around such LANs, that an attacker must have
access to the building(s) in which such LANs exist, and that they
must be able to "plug in" to the LAN in order to access the network.
With these things in mind, we can begin to assess the general
security requirements for AC-WTP communications. While an in-depth
security analysis of threats and risks to these communication is
beyond the scope of this document, some discussion of the motivation
for various security-related design choices is useful. The
assumptions driving the security design thus far include the
following:
o WTP-AC communications take place over a wired connection which may
be accessible to a sophisticated attacker
o access to this connection is not trivial for an outsider (i.e.
someone who does not "belong" in the building) to access
o if authentication and/or privacy of end to end traffic for which
the WTP and AC are intermediaries is required, this may be
provided via IPsec [13].
o privacy and authentication for at least some WTP-AC control
traffic is required (e.g. WEP keys for user sessions, passed from
AC to WTP)
o the AC can be trusted to generate strong cryptographic keys
AC-WTP traffic can be considered to consist of two types: data
traffic (e.g. to or from an end user), and control traffic which is
strictly between the AC and WTP. Since data traffic may be secured
Calhoun, et al. Expires October 2, 2005 [Page 69]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
using IPsec (or some other end-to-end security mechanism), we confine
our solution to control traffic. The resulting security consists of
two components: an authenticated key exchange, and control traffic
security encapsulation. The security encapsulation is accomplished
using AES CCM, described in [3]. This encapsulation provides for
strong AES-based authentication and encryption. The exchange of
cryptographic keys used for CCM is described below.
10.2 LWAPP Frame Encryption
While, the LWAPP protocol uses AES-CCM to encrypt control traffic, it
is important to note that not all control frames are encrypted. The
LWAPP discovery and join phase are not encrypted. The Discovery
messages are sent in the clear since there does not exist a security
association between the WTP and the AC during the discovery phase.
The Join phase is an authenticated exchange used to negotiate
symmetric session keys (see Section 6.2.4).
Once the join phase has been successfully completed, the LWAPP state
machine Figure 2 will move to the Configure state, at which time all
LWAPP control frames are encrypted using AES-CCM.
Encryption of a control message begins at the Message Element field,
meaning the Msg Type, Seq Num, Msg Element Length and Session ID
fields are left intact (see Section 4.2.1).
The AES-CCM 12 byte authentication data is appended to the end of the
message. The authentication data is calculated from the start of the
LWAPP packet, and includes the complete LWAPP control header (see
Section 4.2.1).
The AES-CCM block cipher protocol requires an initialization vector.
The LWAPP protocol requires that the WTP and the AC maintain two
separate IVs, one for transmission and one for reception. The IV is
initialized on both the WTP and the AC to the Session ID, and the IV
is monotonically increased for every packet transmitted. Note that
the IV is implicit, and is not transmitted in the LWAPP header, and
therefore an LWAPP device MUST keep track of both bi-directional IVs.
The IV is 13 bytes long, and the first byte is set to zero, while the
remaining twelve bytes are set to the monotonically increasing 32 bit
counter previously mentioned. The following pseudo code provides an
example of how the IVs are managed for a transmitted packet.
Calhoun, et al. Expires October 2, 2005 [Page 70]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
void SetNonce(char *buffer, int sessionId, int xmitIv)
{
if (xmitIv == 0) {
xmitIv = sessionId;
memset(buffer, '\0', 13);
/* Initialize the IV Buffer */
buffer[1] = (xmitIv >> 24) & 0xff;
buffer[2] = (xmitIv >> 16) & 0xff;
buffer[3] = (xmitIv >> 8) & 0xff;
buffer[4] = (xmitIv & 0xff);
buffer[5] = (xmitIv >> 24) & 0xff;
buffer[6] = (xmitIv >> 16) & 0xff;
buffer[7] = (xmitIv >> 8) & 0xff;
buffer[8] = (xmitIv & 0xff);
buffer[9] = (xmitIv >> 24) & 0xff;
buffer[10] = (xmitIv >> 16) & 0xff;
buffer[11] = (xmitIv >> 8) & 0xff;
buffer[12] = (xmitIv & 0xff);
} else {
xmitIv = bignuminc-12(xmitIv);
}
return;
}
10.3 Authenticated Key Exchange
This section describes the key management component of the LWAPP
protocol. There are two modes supported by LWAPP; certificate and
pre-shared key.
10.3.1 Certificate Based Approach
This section details the key management protocol which makes use of
X.509 certificates.
The following notations are used throughout this section:
o Kpriv - the private key of a public-private key pair
o Kpub - the public key of the pair
o KeyMaterial - output of KDF-256(key, WTP-MAC)
o K1 - AES-CCM Encryption Key
o K2 - AES Key-Wrap Key
Calhoun, et al. Expires October 2, 2005 [Page 71]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
o SessionID - randomly generated LWAPP session identifier, provided
by the WTP in the Join Request
o M - a clear-text message
o C - a cipher-text message.
o S - signed cipher-text message.
o PKCS1(z) - the PKCS#1 encapsulation of z
o E-x{Kpriv, M} - RSA encryption of M using X's private key
o E-x{Kpub, M} - RSA encryption of M using X's public key
o S-x{M} - an RSA digital signature over M produced by X
o V-x{S-x, M} - RSA verification of X's digital signature over M
o D-x{Kpriv, C} - RSA decryption of C using X's private key
o D-x{Kpub, C} - RSA decryption of C using X's public key
o Certificate-AC - AC's Certificate
o Certificate-WTP - WTP's Certificate
10.3.1.1 Session Key Generation
The AC and WTP accomplish mutual authentication and a cryptographic
key exchange in a single round trip using the Join Request and
Response pair (see Section 6.1).
Note that the constant 'x' is used in the above notations to
represent one of the parties in the LWAPP exchange. For instance, if
the WTP must encrypt some text, it would use its own private key, and
therefore the notation "E-wtp{Kpriv, M}" would be used.
The following text describes the exchange between the WTP and the AC
that creates a session key, which is used to secure LWAPP control
messages.
o The WTP adds the Certificate message element (see Section 6.1.6)
with the contents set to Certificate-WTP in the Join Request.
o The WTP adds the Session ID message element (see Section 6.1.7)
with the contents set to a randomly generated session identifer
(see RFC 1750 [4]) in the Join Request. The WTP MUST save the
Session ID in order to validate the Join Response.
o Upon receiving the Join Request, the AC verifies Certificate-WTP,
encoded in the Certificate message element. The AC SHOULD also
perform some authorization check, ensuring that the WTP is allowed
to connect to the AC.
o The AC generates a 32 byte random session key. The first 16
bytes, K1 are used to protect the LWAPP traffic while the latter
16 bytes, K2 are used to keywrap the keys in the Key Update
Response using RFC 3394 [10].
o The AC encrypts the key into cipher-text (C), using E-wtp{Kpub ,
PKCS1(KeyMaterial)}. This encrypts the PKCS#1-encoded key
material with the public key of the WTP, so that only the WTP can
decrypt it and determine the session keys.
Calhoun, et al. Expires October 2, 2005 [Page 72]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
o The AC encrypts the concatenation of sessionID and cipher text (C)
into cipher text(Cª), using E-ac{Kpriv, SessionID|C}. This
encrypts using the private key of AC and can be decrypted using
the public key of AC, proving that AC produced this; this forms
the basis of trust for WTP with respect to the source of the
session keys. The cipher-text (Cª) is then copied into the
session key field within the Session Key message element.
o AC creates the Join Response, and includes two message elements.
Certificate-AC is included in the Certificate message element.
The Session Key message element is added, with the Security field
set to one (1 - X.509 Certificate Based), and the cipher-text (Cª)
is included in the Session Key field. The resulting Join Response
is sent to the WTP.
o WTP verifies authenticity of Certificate-AC in the Join Response's
Certificate message element.
o WTP computes D-ac{Kpub, 'Cª}, where 'Cª is the content of Session
Key field in Session Key Message element. The resulting data
includes the SessionID and cipher text (C). SessionID is
validated against the SessionID that was sent in the Join Request.
o WTP computes PKCS1(KeyMaterial) = D-ac{Kpriv , C}, decrypting the
session keys using its private key, where C is the cipher text
retrieved by decrypting the session key field in earlier step.
Since these were encrypted with the WTP's public key, only the WTP
can successfully decrypt the session key. The resulting 32 octet
KeyMaterial is split into two 16 octet keys, K1 and K2,
respectively.
o K1 is now plumbed into the crypto engine as the AES-CCM session
key. From this point on, all control protocol payloads between
the WTP and AC are encrypted and authenticated using the new
session key.
10.3.1.2 Refreshing Cryptographic Keys
Since AC-WTP associations will tend to be relatively long-lived, it
is sensible to periodically refresh the encryption and authentication
keys; this is referred to as "rekeying". When the key lifetime
reaches 95% of the configured value, identified in the KeyLifetime
timer (see Section 12), the rekeying will proceed as follows:
o WTP generates a fresh random Session identier value and encodes it
within the Key Update Request's Session ID message element. The
new session identifier is saved on the WTP in order to verify the
Key Update Response. The protected Key Update Request is sent to
the AC.
o The AC generates a 32 byte random session key. The first 16
bytes, K1 are used to protect the LWAPP traffic while the latter
16 bytes, K2 are used to keywrap the keys in the Key Update
Response using RFC 3394 [10].
Calhoun, et al. Expires October 2, 2005 [Page 73]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
o The AC encrypts the key into cipher-text (C), using E-wtp{Kpub ,
PKCS1(KeyMaterial)}. This encrypts the PKCS#1-encoded key
material with the public key of the WTP, so that only the WTP can
decrypt it and determine the session keys.
o The AC encrypts the concatenation of sessionID and cipher text (C)
into cipher text(Cª), using E-ac{Kpriv, SessionID|C}. This
encrypts using the private key of AC and can be decrypted using
the public key of AC, proving that AC produced this; this forms
the basis of trust for WTP with respect to the the source of the
session keys. The cipher-text (Cª) is then copied into the
session key field within the Session Key message element.
o AC creates the Key Update Response message, and includes the
Session Key message element with the Security field set to one (1
- X.509 Certificate Based), and the cipher-text (Cª) is included
in the Session Key field. The resulting encrypted Key Update
Response is sent to the WTP.
o WTP computes D-ac{Kpub, Cª}, where Cª is the conten of Session Key
field in Session Key Message element. The resulting data includes
the SessionID and cipher text (C). SessionID is validated against
the SessionID that was sent in the Join Request.
o WTP computes PKCS1(KeyMaterial) = D-ac{Kpriv , C}, decrypting the
session keys using its private key, where C is the cipher text
retrieved by decrypting the session key field in earlier step.
Since these were encrypted with the WTP's public key, only the WTP
can successfully decrypt the session key. The resulting 32 octet
KeyMaterial is split into two 16 octet keys, K1 and K2,
respectively.
o K1 is now plumbed into the crypto engine as the AES-CCM session
key. From this point on, all control protocol payloads between
the WTP and AC are encrypted and authenticated using the new
session key.
If WTP does not receive the Key Update Response by the time the
ResponseTimeout timer expires (see Section 12), the WTP MUST delete
the new and old session information, and reset the state machine to
the Idle state.
Following a rekey process, both the WTP and the AC keep the previous
encryption for one second in order to be able to process packets that
arrive out of order.
10.3.2 Pre-Shared Key Approach
This section details the key management protocol which makes use of
pre-shared secrets.
The following notations are used throughout this section:
Calhoun, et al. Expires October 2, 2005 [Page 74]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
o PSK - the pre-shared key shared between the WTP and the AC
o K0 - the result of a KDF using the PSK and the WTP's MAC Address
o K1 - the confirmation Key
o K2 - the encryption Key
o K3 - the keywrap Key (see RFC 3394 [10])
o KeyMaterial - concatenation of K1, K2 and K3
o SessionID - randomly generated LWAPP session identifier, provided
by the WTP in the Join Request
o MIC(K1, packet) - A message integrity check, using HMAC-SHA1 and
K1, of the complete LWAPP packet, with the sequence number field
set to zero.
o E(K0E, plaintext) - Plaintext is encrypted with K0E, using
AES-CBC.
o D(K0E, cryptotext) - Cryptotext is decrypted with K0E, using
AES-CBC.
o WNonce - The WTP's randomly generated Nonce.
o ANonce - The AC's randomly generated Nonce.
o EWNonce - The payload of the WNonce message element, which
includes the WNonce.
o EANonce - The payload of the ANonce message element, which
includes the ANonce.
o WTP-MAC - The WTP's MAC Address.
o AC-MAC - The AC's MAC Address.
10.3.2.1 Session Key Generation
The AC and WTP accomplish mutual authentication and a cryptographic
key exchange in a dual round trip using the Join Request, Join
Response, Join ACK and Join Confirm (see Section 6.1).
The following text describes the exchange between the WTP and the AC
that creates a session key, which is used to secure LWAPP control
messages.
o The WTP creates K0 through the following algorithm: K0 =
KDF-256{PSK, "LWAPP PSK Top K0" || Session ID || WTP-MAC ||
AC-MAC}, where WTP-MAC is the WTP's MAC Address in the form
"xx:xx:xx:xx:xx:xx". Similarly, the AC-MAC is an ASCII encoding
of the AC's MAC Address, of the form "xx:xx:xx:xx:xx:xx". The
first 16 octets is the K0 encryption key (K0E), and the second 16
octets is the K0 Derivation key (K0D).
o The WTP creates a random nonce, known as WNonce, and encrypts it
using the following algorithm: EWNonce = E{K0E, WNonce}. The
encrypted nonce is added to the Join Request's WNonce message
element (see Section 6.1.9).
o The WTP adds the Session ID message element (see Section 6.1.7)
with the contents set to a randomly generated session identifer
(see RFC 1750 [4]) in the Join Request. The WTP MUST save the
Session ID in order to validate the Join Response.
Calhoun, et al. Expires October 2, 2005 [Page 75]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
o Upon receiving the Join Request, the AC creates K0, using K0 =
KDF-256{PSK, "LWAPP PSK Top K0" || Session ID || WTP-MAC ||
AC-MAC}. WNonce = D{K0E, EWNonce}, where EWNonce is found in the
WNonce message element.
o The AC then creates its own random nonce, known as ANonce. The
WANonce is then created, through E{K0E, NOT WNonce || ANonce}.
"NOT WNonce" means that the AC takes WNonce and inverts all of the
bits within the field. The results of the encryption is inserted
in the Join Response's ANonce message element (see Section 6.1.9).
o The AC then uses the KDF function to create a 48 octet session
key. The KDF function used is as follows: KDF-384{K0D, "LWAPP Key
Generation", WNonce || ANonce || WTP-MAC || AC-MAC}. The KDF
function is defined in [7]. The resulting octets are split into
three 16 octet keys (K1, K2 and K3, in that exact order).
o The AC creates the PSK-MIC (see Section 6.2.8) message element
whose payload includes MIC{K1, Join Response} using K1 as the
confirmation key, which is added to the Join Response. The
resulting Join Response is sent to the WTP.
o Upon receiving the Join Response, the WTP decrypts ANonce from the
contents of the ANonce message element, using ANonce = D{K0E,
WANonce}
o The WTP uses a KDF function to create a 48 octet session key. The
KDF function used is as follows: KDF-384{K0D, "LWAPP Key
Generation", WNonce || ANonce || WTP-MAC || AC-MAC}. The KDF
function is defined in [7]. The resulting octets are split into
three 16 octet keys (K1, K2 and K3, in that exact order).
o WTP verifies authenticity of the PSK-MIC field by using MIC{K1,
Join Response}.
o The WTP creates the PSK-MIC message element whose payload includes
MIC{K1, Join ACK}, which is added to the Join ACK, as well as the
WNonce message element. The resulting Join ACK is sent to the AC.
o AC verifies that WTP's Nonce in the Join ACK's WNonce message
element matches the value it had received in the Join Request.
o AC verifies authenticity of the PSK-MIC message element, by using
its own saved version of K1. It then creates another PSK-MIC
message element, whose payload includes MIC{K1, Join Confirm},
which is added to the Join Confirm, as well as the Session ID
message element. The resulting Join Confirm is sent to the WTP.
o WTP verifies authenticity of the PSK-MIC message element, by using
its own saved version of K1, using the SessionID it had used in
the original Join Request.
o K2 is now plumbed into the crypto engine as the AES-CCM session
key. From this point on, all control protocol payloads between
the WTP and AC are encrypted and authenticated using the new
session key.
Calhoun, et al. Expires October 2, 2005 [Page 76]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
10.3.2.2 Refreshing Cryptographic Keys
Since AC-WTP associations will tend to be relatively long-lived, it
is sensible to periodically refresh the encryption and authentication
keys; this is referred to as "rekeying". When the key lifetime
reaches 95% of the configured value, identified in the KeyLifetime
timer (see Section 12), the rekeying will proceed as follows:
o WTP generates a fresh random Session identier value and encodes it
within the Key Update Request's Session ID message element. The
new session identifier is saved on the WTP in order to verify the
Key Update Response. The Key Update Request is sent to the AC.
o The AC generates 2 new random 16 octet, which are the new K2 and
K3. This new K3 is the AES Key Wrap key that will be used in the
next rekey event. These two session keys are concatenated into a
32 octet value, which is encrypted using the AES Key Wrap (see RFC
3384 [9]), and using K3, which was either created in the KDF
function during the Join phase, or communicated in the previous
Key Update Response to the WTP. The output of the AES Key Wrap
function is used as the Payload of the Session Key message
element.
o AC then sends a protected Key Update Response message to the WTP
using the old session key. Once the message has been sent, the
new K2 session key is plumbed into the AC's crypto engine.
o WTP verifies that SessionID in the Key Update Response's Session
Key message element matches an outstanding request
o WTP uses the AES Key Wrap function, with the K3 which it had
received from the AC in the original Join phase, or mututally
generated in the previous Join Update Request exchange. The
output of the Key Wrap function is a 32 octet value, which is
split into two separate 16 octet session keys, K2 and K3.
o K2 is now plumbed into the crypto engine as the AES-CCM session
key. From this point on, all control protocol payloads between
the WTP and AC are encrypted and authenticated using the new
session key.
If WTP does not receive the Key Update Response by the time the
ResponseTimeout timer expires (see Section 12), the WTP MUST delete
the new and old session information, and reset the state machine to
the Idle state.
Following a rekey process, both the WTP and the AC keep the previous
encryption for one second in order to be able to process packets that
arrive out of order.
Calhoun, et al. Expires October 2, 2005 [Page 77]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
11. IEEE 802.11 Binding
This section defines the extensions required for the LWAPP protocol
to be used with the IEEE 802.11 protocol.
11.1 Division of labor
The LWAPP protocol, when used with IEEE 802.11 devices, requires a
specific behavior from the WTP and the AC, specifically in terms of
which 802.11 protocol functions are handled.
11.1.1 Split MAC
This section discusses the roles and responsibilities of the WTP and
the AC when the LWAPP protocol is used in a Split MAC mode.
The responsibility of the WTP is to handle the following functions:
o 802.11 Control Protocol. These functions are very latency
sensitive, and include such functions as packet acknowledgement,
retransmissions, etc.
o 802.11 Beacons. The information elements to be included in the
beacon is controlled by the AC. Since inter-beacon timing is very
critical, the actual beacons are generated by the WTP. Any 802.11
protocol extension that requires changes within the beacon on a
per frame basis (e.g., 802.11e's QBSS) must be handled solely
within the WTP.
o 802.11 Probe Response. As with the beacons, the information to
include in the probe responses is sent by the AC. Stations
generally expect probe requests to be responded to within 3 to 10
milliseconds, and as a consequence it is very difficult to provide
this function in the AC. Note that the WTP does forward the Probe
Requests received to the AC, for its own information. Whether the
AC makes use of these frames is implementation dependent, and is
outside the scope of this document.
o 802.11e Frame Queuing. The 802.11e standard defines a control
protocol, which is carried within the 802.11 MAC management
protocol, as well as defines how packet prioritization is handled
through various timing parameters. The actual packet
prioritization must be handled in the WTP, since only the WTP has
complete visibility into the RF.
o 802.11i Frame Encryption. The 802.11i standard defines a control
protocol used for the establishment of a security association, as
well as a means to encrypt and decrypt 802.11 data frames. The
actual encryption and decryption services MAY occur in the WTP.
The responsibility of the AC is to handle the following functions:
Calhoun, et al. Expires October 2, 2005 [Page 78]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
o 802.11 MAC Management. All 802.11 MAC Management frames not
listed above are handled exclusively within the AC. This includes
the 802.11 (re)association request, action frames, etc.
o 802.11 Data. The WTP simply encapsulates all 802.11 data frames
received, and forwards them to the AC.
o 802.11e Resource Reservat. The 802.11e standard defines a control
protocol, which is carried within the 802.11 MAC management
protocol, as well as defines how packet prioritization is handled
through various timing parameters. The signaling defined in this
specification is handled within the AC.
o 802.11i Authentication and Key Exchange. The 802.11i standard
defines a control protocol used for the establishment of a
security association, as well as a means to encrypt and decrypt
802.11 data frames. The authentication (802.1X/EAP) and key
exchange component of this standard is handled within the AC.
11.1.2 Local MAC
This section discusses the roles and responsibilities of the WTP and
the AC when the LWAPP protocol is used in a Local MAC mode.
TBD
11.2 Transport specific bindings
All LWAPP transports have the following IEEE 802.11 specific
bindings:
11.2.1 Status and WLANS field
The interpretation of this 16 bit field depends on the direction of
transmission of the packet. Refer to the figure in Section
Section 3.1.
Status
When an LWAPP packet is transmitted from an WTP to an AC, this field
is called the status field and indicates radio resource information
associated with the frame. When the message is an LWAPP control
message this field is transmitted as zero.
The status field is divided into the signal strength and signal to
noise ratio with which an IEEE 802.11 frame was received, encoded in
the following manner:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
Calhoun, et al. Expires October 2, 2005 [Page 79]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RSSI | SNR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
RSSI: RSSI is a signed, 8-bit value. It is the received signal
strength indication, in dBm.
SNR: SNR is a signed, 8-bit value. It is the signal to noise ratio
of the received IEEE 802.11 frame, in dB.
WLANs field: When an LWAPP data message is transmitted from an AC to
an WTP, this 16 bit field indicates on which WLANs the
encapsulated IEEE 802.11 frame is to be transmitted. For unicast
packets, this field is not used by the WTP. For broadcast or
multicast packets, the WTP might require this information if it
provides encryption services.
Given that a single broadcast or multicast packet might need to be
sent to multiple wireless LANs (presumably each with a different
broadcast key), this field is defined as a bit field. A bit set
indicates a WLAN ID (see Section Section 11.5.1.1) which will be
sent the data. The WLANS field is encoded in the following
manner:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| WLAN ID(s) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
11.3 Data Message bindings
There are no LWAPP Data Message bindings for IEEE 802.11.
11.4 Control Message bindings
The IEEE 802.11 binding has the following Control Message
definitions.
11.4.1 Mobile Config Request
This section contains the 802.11 specific message elements that are
used with the Mobile Config Request.
11.4.1.1 Add Mobile
The Add Mobile Request is used by the AC to inform an WTP that it
should forward traffic from a particular mobile station. The add
mobile request may also include security parameters that must be
enforced by the WTP for the particular mobile.
Calhoun, et al. Expires October 2, 2005 [Page 80]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
When the AC sends an Add Mobile Request, it includes any security
parameters that may be required. An AC that wishes to update a
mobile's policy on an WTP may be done by simply sending a new Add
Mobile message element.
When an WTP receives an Add Mobile message element, it must first
override any existing state it may have for the mobile station in
question. The latest Add Mobile overrides any previously received
messages. If the Add Mobile message element's EAP Only bit is set,
the WTP MUST drop all 802.11 packets that do not contain EAP packets.
Note that when EAP Only is set, the Encryption Policy field MAY have
additional values, and therefore it is possible to inform an WTP to
only accept encrypted EAP packets. Once the mobile station has
successfully completed EAP authentication, the AC must send a new Add
Mobile message element to push the session key down to the WTP as
well as to remove the EAP Only restriction.
If the QoS field is set, the WTP MUST observe and provide policing of
the 802.11e priority tag to ensure that it does not exceed the value
provided by the AC.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Association ID | MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address |E|C| Encryption Policy |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Encrypt Policy | Session Key... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pairwise TSC... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pairwise RSC... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Capabilities | WLAN ID | WME Mode |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 802.11e Mode | Qos | Supported Rates |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Supported Rates |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 29 for Add Mobile
Length: 36
Calhoun, et al. Expires October 2, 2005 [Page 81]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Radio ID: An 8-bit value representing the radio
Association ID: A 16-bit value specifying the 802.11 Association
Identifier
MAC Address: The mobile station's MAC Address
E: The one bit field is set by the AC to inform the WTP that is MUST
NOT accept any 802.11 data frames, other than 802.1X frames. This
is the equivalent of the WTP's 802.1X port for the mobile station
to be in the closed state. When set, the WTP MUST drop any
non-802.1X packets it receives from the mobile station.
C: The one bit field is set by the AC to inform the WTP that
encryption services will be provided by the AC. When set, the WTP
SHOULD police frames received from stations to ensure that they
comply to the stated encryption policy, but does not need to take
specific cryptographic action on the frame. Similarly, for
transmitted frames, the WTP only needs to forward already
encrypted frames.
Encryption Policy: The policy field informs the WTP how to handle
packets from/to the mobile station. The following values are
supported:
0 - Encrypt WEP 104: All packets to/from the mobile station must
be encrypted using standard 104 bit WEP.
1 - Clear Text: All packets to/from the mobile station do not
require any additional crypto processing by the WTP.
2 - Encrypt WEP 40: All packets to/from the mobile station must
be encrypted using standard 40 bit WEP.
3 - Encrypt WEP 128: All packets to/from the mobile station must
be encrypted using standard 128 bit WEP.
4 - Encrypt AES-CCMP 128: All packets to/from the mobile station
must be encrypted using 128 bit AES CCMP [7]
5 - Encrypt TKIP-MIC: All packets to/from the mobile station must
be encrypted using TKIP and authenticated using Michael [15]
Session Key: A 32 octet session key the WTP is to use when
encrypting traffic to or decrypting traffic from the mobile
station. The type of key is determined based on the Encryption
Policy field.
Pairwise TSC: The TSC to use for unicast packets transmitted to the
mobile.
Pairwise RSC: The RSC to use for unicast packets received from the
mobile.
Capabilities: A 16-bit field containing the 802.11 capabilities to
use with the mobile.
WLAN ID: An 8-bit value specifying the WLAN Identifier
WME Mode: A 8-bit boolean used to identify whether the station is
WME capable. A value of zero is used to indicate that the station
is not WME capable, while a value of one means that the station is
WME capable.
Calhoun, et al. Expires October 2, 2005 [Page 82]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
802.11e Mode: A 8-bit boolean used to identify whether the station
is 802.11e capable. A value of zero is used to indicate that the
station is not 802.11e capable, while a value of one means that
the station is 802.11e capable.
QoS: An 8-bit value specifying the QoS policy to enforce for the
station. The following values are supported: PRC: TO CHECK
0 - Silver (Best Effort)
1 - Gold (Video)
2 - Platinum (Voice)
3 - Bronze (Background)
Supported Rates: The supported rates to be used with the mobile
station.
11.4.1.2 IEEE 802.11 Mobile Session Key
The Mobile Session Key Payload message element is sent when the AC
determines that encryption of a mobile station must be performed in
the WTP. This message element MUST NOT be present without the Add
Mobile (see Section 11.4.1.1) message element, and MUST NOT be sent
if the WTP had not specifically advertised support for the requested
encryption scheme (see ???).
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address | Encryption Policy |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encryption Policy | Session Key... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 105 for IEEE 802.11 Mobile Session Key
Length: >= 11
MAC Address: The mobile station's MAC Address
Encryption Policy: The policy field informs the WTP how to handle
packets from/to the mobile station. The following values are
supported:
0 - Encrypt WEP 104: All packets to/from the mobile station must
be encrypted using standard 104 bit WEP.
1 - Clear Text: All packets to/from the mobile station do not
require any additional crypto processing by the WTP.
2 - Encrypt WEP 40: All packets to/from the mobile station must
be encrypted using standard 40 bit WEP.
3 - Encrypt WEP 128: All packets to/from the mobile station must
be encrypted using standard 128 bit WEP.
Calhoun, et al. Expires October 2, 2005 [Page 83]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
4 - Encrypt AES-CCMP 128: All packets to/from the mobile station
must be encrypted using 128 bit AES CCMP [7]
5 - Encrypt TKIP-MIC: All packets to/from the mobile station must
be encrypted using TKIP and authenticated using Michael [15]
Session Key: The session key the WTP is to use when encrypting
traffic to/from the mobile station.
11.4.1.3 QoS Profile
The QoS Profile Payload message element contains the maximum 802.11e
priority tag that may be used by the station. Any packets received
that exceeds the value encoded in this message element must either be
dropped or tagged using the maximum value permitted by to the user.
The priority tag must be between zero (0) and seven (7).
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address | 802.1P Precedence Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD for IEEE 802.11 QOS Profile
Length: 12
MAC Address: The mobile station's MAC Address
802.1P Precedence Tag: The maximum 802.1P precedence value that the
WTP will allow in the TID field in the extended 802.11e QOS Data
header.
11.4.1.4 IEEE 802.11 Update Mobile QoS
The Update Mobile QoS message element is used to change the Quality
of Service policy on the WTP for a given mobile station.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Association ID | MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address | QoS Profile | Vlan Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DSCP Tag | 802.1P Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Calhoun, et al. Expires October 2, 2005 [Page 84]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Type: 106 for IEEE 802.11 Update Mobile QoS
Length: 14
Radio ID: The Radio Identifier, typically refers to some interface
index on the WTP
Association ID: The 802.11 Association Identifier.
MAC Address: The mobile station's MAC Address.
QoS Profile: An 8-bit value specifying the QoS policy to enforce for
the station. The following values are supported:
0 - Silver (Best Effort)
1 - Gold (Video)
2 - Platinum (Voice)
3 - Bronze (Background)
VLAN Identifier: PRC.
DSCP Tag: The DSCP label to use if packets are to be DSCP tagged.
802.1P Tag: The 802.1P precedence value to use if packets are to be
802.1P tagged.
11.4.2 WTP Event Request
This section contains the 802.11 specific message elements that are
used with the WTP Event Request message.
11.4.2.1 IEEE 802.11 Statistics
The statistics message element is sent by the WTP to transmit it's
current statistics. The value contains the following fields.
Calhoun, et al. Expires October 2, 2005 [Page 85]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Tx Fragment Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Tx Fragment Cnt| Multicast Tx Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mcast Tx Cnt | Failed Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Failed Count | Retry Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retry Count | Multiple Retry Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Multi Retry Cnt| Frame Duplicate Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Frame Dup Cnt | RTS Success Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|RTS Success Cnt| RTS Failure Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|RTS Failure Cnt| ACK Failure Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|ACK Failure Cnt| Rx Fragment Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Rx Fragment Cnt| Multicast RX Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mcast Rx Cnt | FCS Error Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FCS Error Cnt| Tx Frame Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tx Frame Cnt | Decryption Errors |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Decryption Errs|
+-+-+-+-+-+-+-+-+
Type: 38 for Statistics
Length: 57
Radio ID: An 8-bit value representing the radio.
Tx Fragment Count: A 32-bit value representing the number of
fragmented frames transmitted.
Multicast Tx Count: A 32-bit value representing the number of
multicast frames transmitted.
Failed Count: A 32-bit value representing the transmit excessive
retries.
Retry Count: A 32-bit value representing the number of transmit
retries.
Calhoun, et al. Expires October 2, 2005 [Page 86]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Multiple Retry Count: A 32-bit value representing the number of
transmits that required more than one retry.
Frame Duplicate Count: A 32-bit value representing the duplicate
frames received.
RTS Success Count: A 32-bit value representing the number of
successfully transmitted Ready To Send (RTS).
RTS Failure Count: A 32-bit value representing the failed
transmitted RTS.
ACK Failure Count: A 32-bit value representing the number of failed
acknowledgements.
Rx Fragment Count: A 32-bit value representing the number of
fragmented frames received.
Multicast RX Count: A 32-bit value representing the number of
multicast frames received.
FCS Error Count: A 32-bit value representing the number of FCS
failures.
Decryption Errors: A 32-bit value representing the number of
Decryption errors that occured on the WTP. Note that this field
is only valid in cases where the WTP provides
encryption/decryption services.
11.5 802.11 Control Messages
This section will define LWAPP Control Messages that are specific to
the IEEE 802.11 binding.
11.5.1 IEEE 802.11 WLAN Config Request
The IEEE 802.11 WLAN Configuration Request is sent by the AC to the
WTP in order to change services provided by the WTP. This control
message is used to either create, update or delete a WLAN on the WTP.
The IEEE 802.11 WLAN Configuration Request is sent as a result of
either some manual admistrative process (e.g., deleting a WLAN), or
automatically to create a WLAN on an WTP. When sent automatically to
create a WLAN, this control message is sent after the LWAPP
Configuration Request message has been received by the WTP.
Upon receiving this control message, the WTP will modify the
necessary services, and transmit an IEEE 802.11 WLAN Configuration
Response.
An WTP MAY provide service for more than one WLAN, therefore every
WLAN is identified through a numerical index. For instance, an WTP
that is capable of supporting up to 16 SSIDs, could accept up to 16
IEEE 802.11 WLAN Configuration Request messages that include the Add
WLAN message element.
Calhoun, et al. Expires October 2, 2005 [Page 87]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Since the index is the primary identifier for a WLAN, an AC SHOULD
attempt to ensure that the same WLAN is identified through the same
index number on all of its WTPs. An AC that does not follow this
approach MUST find some other means of maintaining a WLAN Identifier
to SSID mapping table.
The following subsections define the message elements that are value
for this LWAPP operation. Only one message MUST be present.
11.5.1.1 IEEE 802.11 Add WLAN
The Add WLAN message element is used by the AC to define a wireless
LAN on the WTP. The value contains the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | WLAN Capability | WLAN ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encryption Policy |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key Index | Shared Key | WPA Data Len |WPA IE Data ...|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RSN Data Len |RSN IE Data ...| Reserved .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| WME Data Len |WME IE Data ...| 11e Data Len |11e IE Data ...|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| QoS | Auth Type |Broadcast SSID | Reserved... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SSID ... |
+-+-+-+-+-+-+-+-+
Type: 7 for IEEE 802.11 Add WLAN
Length: >= 298
Radio ID: An 8-bit value representing the radio.
WLAN Capability: A 16-bit value containing the capabilities to be
advertised by the WTP within the Probe and Beacon messages.
WLAN ID: A 16-bit value specifying the WLAN Identifier.
Encryption Policy: A 32-bit value specifying the encryption scheme
to apply to traffic to and from the mobile station.
The following values are supported:
0 - Encrypt WEP 104: All packets to/from the mobile station must
be encrypted using standard 104 bit WEP.
Calhoun, et al. Expires October 2, 2005 [Page 88]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
1 - Clear Text: All packets to/from the mobile station do not
require any additional crypto processing by the WTP.
2 - Encrypt WEP 40: All packets to/from the mobile station must
be encrypted using standard 40 bit WEP.
3 - Encrypt WEP 128: All packets to/from the mobile station must
be encrypted using standard 128 bit WEP.
4 - Encrypt AES-CCMP 128: All packets to/from the mobile station
must be encrypted using 128 bit AES CCMP [7]
5 - Encrypt TKIP-MIC: All packets to/from the mobile station must
be encrypted using TKIP and authenticated using Michael [15]
6 - Encrypt CKIP: All packets to/from the mobile station must be
encrypted using Cisco TKIP.
Key: A 32 byte Session Key to use with the encryption policy.
Key-Index: The Key Index associated with the key.
Shared Key: A 1 byte boolean that specifies whether the key included
in the Key field is a shared WEP key. A value of zero is used to
state that the key is not a shared WEP key, while a value of one
is used to state that the key is a shared WEP key.
WPA Data Len: Length of the WPA IE.
WPA IE: A 32 byte field containing the WPA Information Element.
RSN Data Len: Length of the RSN IE.
RSN IE: A 64 byte field containing the RSN Information Element.
Reserved: A 49 byte reserved field, which MUST be set to zero (0).
WME Data Len: Length of the WME IE.
WME IE: A 32 byte field containing the WME Information Element.
DOT11E Data Len: Length of the 802.11e IE.
DOT11E IE: A 32 byte field containing the 802.11e Information
Element.
QOS: An 8-bit value specifying the QoS policy to enforce for the
station.
The following values are supported:
0 - Silver (Best Effort)
1 - Gold (Video)
2 - Platinum (Voice)
3 - Bronze (Background)
Auth Type: An 8-bit value specifying the station's authentication
type.
The following values are supported:
0 - Open System
1 - WEP Shared Key
2 - WPA/WPA2 802.1X
3 - WPA/WPA2 PSK
Broadcast SSID: A boolean indicating whether the SSID is to be
broadcast by the WTP. A value of zero disables SSID broadcast,
while a value of one enables it.
Calhoun, et al. Expires October 2, 2005 [Page 89]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Reserved: A 40 byte reserved field.
SSID: The SSID attribute is the service set identifier that will be
advertised by the WTP for this WLAN.
11.5.1.2 IEEE 802.11 Delete WLAN
The delete WLAN message element is used to inform the WTP that a
previously created WLAN is to be deleted. The value contains the
following fields:
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | WLAN ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 28 for IEEE 802.11 Delete WLAN
Length: 3
Radio ID: An 8-bit value representing the radio
WLAN ID: A 16-bit value specifying the WLAN Identifier
11.5.1.3 IEEE 802.11 Update WLAN
The Update WLAN message element is used by the AC to define a
wireless LAN on the WTP. The value contains the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | WLAN ID |Encrypt Policy |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encryption Policy | Key... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key Index | Shared Key | WLAN Capability |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 34 for IEEE 802.11 Update WLAN
Length: 43
Radio ID: An 8-bit value representing the radio.
WLAN ID: A 16-bit value specifying the WLAN Identifier.
Encryption Policy: A 32-bit value specifying the encryption scheme
to apply to traffic to and from the mobile station.
The following values are supported:
Calhoun, et al. Expires October 2, 2005 [Page 90]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
0 - Encrypt WEP 104: All packets to/from the mobile station must
be encrypted using standard 104 bit WEP.
1 - Clear Text: All packets to/from the mobile station do not
require any additional crypto processing by the WTP.
2 - Encrypt WEP 40: All packets to/from the mobile station must
be encrypted using standard 40 bit WEP.
3 - Encrypt WEP 128: All packets to/from the mobile station must
be encrypted using standard 128 bit WEP.
4 - Encrypt AES-CCMP 128: All packets to/from the mobile station
must be encrypted using 128 bit AES CCMP [7]
5 - Encrypt TKIP-MIC: All packets to/from the mobile station must
be encrypted using TKIP and authenticated using Michael [15]
6 - Encrypt CKIP: All packets to/from the mobile station must be
encrypted using Cisco TKIP.
Key: A 32 byte Session Key to use with the encryption policy.
Key-Index: The Key Index associated with the key.
Shared Key: A 1 byte boolean that specifies whether the key included
in the Key field is a shared WEP key. A value of zero means that
the key is not a shared WEP key, while a value of one is used to
state that the key is a shared WEP key.
WLAN Capability: A 16-bit value containing the capabilities to be
advertised by the WTP within the Probe and Beacon messages.
11.5.2 IEEE 802.11 WLAN Config Response
The IEEE 802.11 WLAN Configuration Response is sent by the WTP to the
AC as an acknowledgement of the receipt of an IEEE 802.11 WLAN
Configuration Request.
This LWAPP control message does not include any message elements.
11.5.3 IEEE 802.11 WTP Event
The IEEE 802.11 WTP Event LWAPP message is used by the WTP in order
to report asynchronous events to the AC. There is no reply message
expected from the AC, except that the message is acknowledged via the
reliable transport.
When the AC receives the IEEE 802.11 WTP Event, it will take whatever
action is necessary, depending upon the message elements present in
the message.
The IEEE 802.11 WTP Event message MUST contain one of the following
message element described in the next subsections.
11.5.3.1 IEEE 802.11 MIC Countermeasures
The MIC Countermeasures message element is sent by the WTP to the AC
Calhoun, et al. Expires October 2, 2005 [Page 91]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
to indicate the occurrence of a MIC failure.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | WLAN ID | MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 61 for IEEE 802.11 MIC Countermeasures
Length: 8
Radio ID: The Radio Identifier, typically refers to some interface
index on the WTP.
WLAN ID: This 8-bit unsigned integer includes the WLAN Identifier,
on which the MIC failure occurred.
MAC Address: The MAC Address of the mobile station that caused the
MIC failure.
11.5.3.2 IEEE 802.11 WTP Radio Fail Alarm Indication
The WTP Radio Fail Alarm Indication message element is sent by the
WTP to the AC when it detects a radio failure.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Type | Status | Pad |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 95 for WTP Radio Fail Alarm Indication
Length: 4
Radio ID: The Radio Identifier, typically refers to some interface
index on the WTP
Type: The type of radio failure detected. The following values are
supported:
1 - Receiver
2 - Transmitter
Status: An 8-bit boolean indicating whether the radio failure is
being reported or cleared. A value of zero is used to clear the
event, while a value of one is used to report the event.
Pad: Reserved field MUST be set to zero (0).
11.6 Message Element Bindings
The IEEE 802.11 Message Element binding has the following
definitions:
Calhoun, et al. Expires October 2, 2005 [Page 92]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Conf Conf Conf Add
Req Resp Upd Mobile
IEEE 802.11 WTP WLAN Radio Configuration X X X
IEEE 802.11 Rate Set X X
IEEE 802.11 Multi-domain Capability X X X
IEEE 802.11 MAC Operation X X X
IEEE 802.11 Tx Power X X X
IEEE 802.11 Tx Power Level X
IEEE 802.11 Direct Sequence Control X X X
IEEE 802.11 OFDM Control X X X
IEEE 802.11 Supported Rates X X
IEEE 802.11 Antenna X X X
IEEE 802.11 CFP Status X X
IEEE 802.11 Broadcast Probe Mode X X
IEEE 802.11 WTP Mode and Type X? X
IEEE 802.11 WTP Quality of Service X X
IEEE 802.11 MIC Error Report From Mobile X
IEEE 802.11 Update Mobile QoS X
IEEE 802.11 Mobile Session Key X
VOIP STUFF
11.6.1 IEEE 802.11 WTP WLAN Radio Configuration
The WTP WLAN radio configuration is used by the AC to configure a
Radio on the WTP. The message element value contains the following
Fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Reserved | Occupancy Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CFP Per | CFP Maximum Duration | BSS ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BSS ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BSS ID | Beacon Period | DTIM Per |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Country String |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 8 for IEEE 802.11 WTP WLAN Radio Configuration
Length: 20
Calhoun, et al. Expires October 2, 2005 [Page 93]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Radio ID: An 8-bit value representing the radio to configure.
Reserved: MUST be set to zero
Occupancy Limit: This attribute indicates the maximum amount of
time, in TU, that a point coordinator MAY control the usage of the
wireless medium without relinquishing control for long enough to
allow at least one instance of DCF access to the medium. The
default value of this attribute SHOULD be 100, and the maximum
value SHOULD be 1000.
CFP Period: The attribute describes the number of DTIM intervals
between the start of CFPs.
CFP Maximum Duration: The attribute describes the maximum duration
of the CFP in TU that MAY be generated by the PCF.
BSSID: The WLAN Radio's base MAC Address. For WTPs that support
more than a single WLAN, the value of the WLAN Identifier is added
to the last octet of the BSSID. Therefore, a WTP that supports 16
WLANs MUST have 16 MAC Addresses reserved for it, and the last
nibble is used to represent the WLAN ID.
Beacon Period: This attribute specifies the number of TU that a
station uses for scheduling Beacon transmissions. This value is
transmitted in Beacon and Probe Response frames.
DTIM Period: This attribute specifies the number of beacon intervals
that elapses between transmission of Beacons frames containing a
TIM element whose DTIM Count field is 0. This value is
transmitted in the DTIM Period field of Beacon frames.
Country Code: This attribute identifies the country in which the
station is operating. The first two octets of this string is the
two character country code as described in document ISO/IEC 3166-
1. The third octet MUST be one of the following:
1. an ASCII space character, if the regulations under which the
station is operating encompass all environments in the
country,
2. an ASCII 'O' character, if the regulations under which the
station is operating are for an outdoor environment only, or
3. an ASCII 'I' character, if the regulations under which the
station is operating are for an indoor environment only
11.6.2 IEEE 802.11 Rate Set
The rate set message element value is sent by the AC and contains the
supported operational rates. It contains the following fields.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Rate Set |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Calhoun, et al. Expires October 2, 2005 [Page 94]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Type: 16 for IEEE 802.11 Rate Set
Length: 4
Radio ID: An 8-bit value representing the radio to configure.
Rate Set: The AC generates the Rate Set that the WTP is to include
in it's Beacon and Probe messages.
11.6.3 IEEE 802.11 Multi-domain Capability
The multi-domain capability message element is used by the AC to
inform the WTP of regulatory limits. The value contains the
following fields.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Reserved | First Channel # |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Channels | Max Tx Power Level |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 10 for IEEE 802.11 Multi-Domain Capability
Length: 8
Radio ID: An 8-bit value representing the radio to configure.
Reserved: MUST be set to zero
First Channnel #: This attribute indicates the value of the lowest
channel number in the subband for the associated domain country
string.
Number of Channels: This attribute indicates the value of the total
number of channels allowed in the subband for the associated
domain country string.
Max Tx Power Level: This attribute indicates the maximum transmit
power, in dBm, allowed in the subband for the associated domain
country string.
11.6.4 IEEE 802.11 MAC Operation
The MAC operation message element is sent by the AC to set the 802.11
MAC parameters on the WTP. The value contains the following fields.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Reserved | RTS Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Short Retry | Long Retry | Fragmentation Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tx MSDU Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Calhoun, et al. Expires October 2, 2005 [Page 95]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
| Rx MSDU Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 11 for IEEE 802.11 MAC Operation
Length: 16
Radio ID: An 8-bit value representing the radio to configure.
Reserved: MUST be set to zero
RTS Threshold: This attribute indicates the number of octets in an
MPDU, below which an RTS/CTS handshake MUST NOT be performed. An
RTS/CTS handshake MUST be performed at the beginning of any frame
exchange sequence where the MPDU is of type Data or Management,
the MPDU has an individual address in the Address1 field, and the
length of the MPDU is greater than this threshold. Setting this
attribute to be larger than the maximum MSDU size MUST have the
effect of turning off the RTS/CTS handshake for frames of Data or
Management type transmitted by this STA. Setting this attribute
to zero MUST have the effect of turning on the RTS/CTS handshake
for all frames of Data or Management type transmitted by this STA.
The default value of this attribute MUST be 2347.
Short Retry: This attribute indicates the maximum number of
transmission attempts of a frame, the length of which is less than
or equal to RTSThreshold, that MUST be made before a failure
condition is indicated. The default value of this attribute MUST
be 7.
Long Retry: This attribute indicates the maximum number of
transmission attempts of a frame, the length of which is greater
than dot11RTSThreshold, that MUST be made before a failure
condition is indicated. The default value of this attribute MUST
be 4.
Fragmentation Threshold: This attribute specifies the current
maximum size, in octets, of the MPDU that MAY be delivered to the
PHY. An MSDU MUST be broken into fragments if its size exceeds
the value of this attribute after adding MAC headers and trailers.
An MSDU or MMPDU MUST be fragmented when the resulting frame has
an individual address in the Address1 field, and the length of the
frame is larger than this threshold. The default value for this
attribute MUST be the lesser of 2346 or the aMPDUMaxLength of the
attached PHY and MUST never exceed the lesser of 2346 or the
aMPDUMaxLength of the attached PHY. The value of this attribute
MUST never be less than 256.
Tx MSDU Lifetime: This attribute speficies the elapsed time in TU,
after the initial transmission of an MSDU, after which further
attempts to transmit the MSDU MUST be terminated. The default
value of this attribute MUST be 512.
Rx MSDU Lifetime: This attribute specifies the elapsed time in TU,
after the initial reception of a fragmented MMPDU or MSDU, after
which further attempts to reassemble the MMPDU or MSDU MUST be
terminated. The default value MUST be 512.
Calhoun, et al. Expires October 2, 2005 [Page 96]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
11.6.5 IEEE 802.11 Tx Power
The Tx power message element value is bi-directional. When sent by
the WTP, it contains the current power level of the radio in
question. When sent by the AC, it contains the power level the WTP
MUST adhere to.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Reserved | Current Tx Power |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 12 for IEEE 802.11 Tx Power
Length: 4
Radio ID: An 8-bit value representing the radio to configure.
Reserved: MUST be set to zero
Current Tx Power: This attribute contains the transmit output power
in mW.
11.6.6 IEEE 802.11 Tx Power Level
The Tx power level message element is sent by the WTP and contains
the different power levels supported. The value contains the
following fields.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Num Levels | Power Level [n] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 13 for IEEE 802.11 Tx Power Level
Length: >= 4
Radio ID: An 8-bit value representing the radio to configure.
Num Levels: The number of power level attributes.
Power Level: Each power level fields contains a supported power
level, in mW.
11.6.7 IEEE 802.11 Direct Sequence Control
The direct sequence control message element is a bi-directional
element. When sent by the WTP, it contains the current state. When
sent by the AC, the WTP MUST adhere to the values. This element is
only used for 802.11b radios. The value has the following fields.
Calhoun, et al. Expires October 2, 2005 [Page 97]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Reserved | Current Chan | Current CCA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Energy Detect Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 14 for IEEE 802.11 Direct Sequence Control
Length: 8
Radio ID: An 8-bit value representing the radio to configure.
Reserved: MUST be set to zero
Current Channel: This attribute contains the current operating
frequency channel of the DSSS PHY.
Current CCA: The current CCA method in operation. Valid values are:
1 - energy detect only (edonly)
2 - carrier sense only (csonly)
4 - carrier sense and energy detect (edandcs)
8 - carrier sense with timer (cswithtimer)
16 - high rate carrier sense and energy detect (hrcsanded)
Energy Detect Threshold: The current Energy Detect Threshold being
used by the DSSS PHY.
11.6.8 IEEE 802.11 OFDM Control
The OFDM control message element is a bi-directional element. When
sent by the WTP, it contains the current state. When sent by the AC,
the WTP MUST adhere to the values. This element is only used for
802.11a radios. The value contains the following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Reserved | Current Chan | Band Support |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TI Threshold |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 15 for IEEE 802.11 OFDM Control
Length: 8
Radio ID: An 8-bit value representing the radio to configure.
Reserved: MUST be set to zero
Current Channel: This attribute contains the current operating
frequency channel of the OFDM PHY.
Band Supported: The capability of the OFDM PHY implementation to
operate in the three U-NII bands. Coded as an integer value of a
three bit field as follows:
Calhoun, et al. Expires October 2, 2005 [Page 98]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
capable of operating in the lower (5.15-5.25 GHz) U-NII band
capable of operating in the middle (5.25-5.35 GHz) U-NII band
capable of operating in the upper (5.725-5.825 GHz) U-NII band
For example, for an implementation capable of operating in the
lower and mid bands this attribute would take the value
TI Threshold: The Threshold being used to detect a busy medium
(frequency). CCA MUST report a busy medium upon detecting the
RSSI above this threshold.
11.6.9 IEEE 802.11 Antenna
The antenna message element is communicated by the WTP to the AC to
provide information on the antennas available. The AC MAY use this
element to reconfigure the WTP's antennas. The value contains the
following fields:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Diversity | Combiner | Antenna Cnt |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Antenna Selection [0..N] |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 41 for IEEE 802.11 Antenna
Length: >= 8
Radio ID: An 8-bit value representing the radio to configure.
Diversity: An 8-bit value specifying whether the antenna is to
provide receive diversity. The following values are supported:
0 - Disabled
1 - Enabled (may only be true if the antenna can be used as a
receive antenna)
Combiner: An 8-bit value specifying the combiner selection. The
following values are supported:
1 - Sectorized (Left)
2 - Sectorized (Right)
3 - Omni
4 - Mimo
Antenna Count: An 8-bit value specifying the number of Antenna
Selection fields.
Antenna Selection: One 8-bit antenna configuration value per antenna
in the WTP. The following values are supported:
1 - Internal Antenna
2 - External Antenna
11.6.10 IEEE 802.11 Supported Rates
The supported rates message element is sent by the WTP to indicate
Calhoun, et al. Expires October 2, 2005 [Page 99]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
the rates that it supports. The value contains the following fields.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Supported Rates |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 16 for IEEE 802.11 Supported Rates
Length: 4
Radio ID: An 8-bit value representing the radio.
Supported Rates: The WTP includes the Supported Rates that it's
hardware supports. The format is identical to the Rate Set
message element.
11.6.11 IEEE 802.11 CFP Status
The CFP Status message element is sent to provide the CF Polling
configuration.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 48 for IEEE 802.11 CFP Status
Length: 2
Radio ID: The Radio Identifier, typically refers to some interface
index on the WTP
Status: An 8-bit boolean containing the status of the CF Polling
feature. A value of zero disables CFP Status, while a value of
one enables it.
11.6.12 IEEE 802.11 WTP Mode and Type
The WTP Mode and Type message element is used to configure an WTP to
operate in a specific mode.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mode | Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Calhoun, et al. Expires October 2, 2005 [Page 100]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Type: 54 for IEEE 802.11 WTP Mode and Type
Length: 2
Mode: An 8-bit value the type of information being sent. The
following values are supported:
0 - Normal Mode
1 - Monitoring Mode
2 - REAP Mode
3 - Rogue Detector Mode
4 - Sniffer Mode
Type: The type field is not currently used.
11.6.13 IEEE 802.11 Broadcast Probe Mode
The Broadcast Probe Mode message element indicates whether an WTP
will respond to NULL SSID probe requests. Since broadcast NULL
probes are not sent to a specific BSSID, the WTP cannot know which
SSID the sending station is querying. Therefore, this behavior must
be global to the WTP.
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| Status |
+-+-+-+-+-+-+-+-+
Type: 51 for IEEE 802.11 Broadcast Probe Mode
Length: 1
Status: An 8-bit boolean indicating the status of whether an WTP
shall response to a NULL SSID probe request. A value of zero
disables NULL SSID probe response, while a value of one enables
it.
11.6.14 IEEE 802.11 WTP Quality of Service
The WTP Quality of Service message element value is sent by the AC to
the WTP to communicate quality of service configuration information.
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | Tag Packets |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 57 for IEEE 802.11 WTP Quality of Service
Length: 12
Calhoun, et al. Expires October 2, 2005 [Page 101]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Radio ID: The Radio Identifier, typically refers to some interface
index on the WTP
Tag Packets: An value indicating whether LWAPP packets should be
tagged with for QoS purposes. The following values are currently
supported:
0 - Untagged
1 - 802.1P
2 - DSCP
Immediately following the above header is the following data
structure. This data structure will be repeated five times; once
for every QoS profile. The order of the QoS profiles are Uranium,
Platinum, Gold, Silver and Bronze.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Queue Depth | CWMin | CWMax |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CWMax | AIFS | CBR |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Dot1P Tag | DSCP Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Queue Depth: The number of packets that can be on the specific QoS
transmit queue at any given time.
CWMin: The Contention Window minimum value for the QoS transmit
queue.
CWMax: The Contention Window maximum value for the QoS transmit
queue.
AIFS: The Arbitration Inter Frame Spacing to use for the QoS
transmit queue.
CBR: The CBR value to observe for the QoS transmit queue.
Dot1P Tag: The 802.1P precedence value to use if packets are to be
802.1P tagged.
DSCP Tag: The DSCP label to use if packets are to be DSCP tagged.
11.6.15 IEEE 802.11 MIC Error Report From Mobile
The MIC Error Report From Mobile message element is sent by an AC to
an WTP when it receives a MIC failure notification, via the Error bit
in the EAPOL-Key frame.
Calhoun, et al. Expires October 2, 2005 [Page 102]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Client MAC Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Client MAC Address | BSSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BSSID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | WLAN ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: 79 for IEEE 802.11 MIC Error Report From Mobile
Length: 14
Client MAC Address: The Client MAC Address of the station reporting
the MIC failure.
BSSID: The BSSID on which the MIC failure is being reported.
Radio ID: The Radio Identifier, typically refers to some interface
index on the WTP
WLAN ID: The WLAN ID on which the MIC failure is being reported.
11.7 IEEE 802.11 Message Element Values
This section lists IEEE 802.11 specific values for any generic LWAPP
message elements which include fields whose values are technology
specific.
IEEE 802.11 uses the following values:
4 - Encrypt AES-CCMP 128: WTP supports AES-CCMP, as defined in [7].
5 - Encrypt TKIP-MIC: WTP supports TKIP and Michael, as defined in
[15].
Calhoun, et al. Expires October 2, 2005 [Page 103]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
12. LWAPP Protocol Timers
An WTP or AC that implements LWAPP discovery MUST implement the
following timers.
12.1 MaxDiscoveryInterval
The maximum time allowed between sending discovery requests from the
interface, in seconds. Must be no less than 2 seconds and no greater
than 180 seconds.
Default: 20 seconds.
12.2 SilentInterval
The minimum time, in seconds, an WTP MUST wait after failing to
receive any responses to its discovery requests, before it MAY again
send discovery requests.
Default: 30
12.3 NeighborDeadInterval
The minimum time, in seconds, an WTP MUST wait without having
received Echo Responses to its Echo Requests, before the destination
for the Echo Request may be considered dead. Must be no less than
2*EchoInterval seconds and no greater than 240 seconds.
Default: 60
12.4 EchoInterval
The minimum time, in seconds, between sending echo requests to the AC
with which the WTP has joined.
Default: 30
12.5 DiscoveryInterval
The minimum time, in seconds, that an WTP MUST wait after receiving a
Discovery Response, before sending a join request.
Default: 5
12.6 RetransmitInterval
The minimum time, in seconds, which a non-acknowledged LWAPP packet
will be retransmitted.
Calhoun, et al. Expires October 2, 2005 [Page 104]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Default: 3
12.7 ResponseTimeout
The minimum time, in seconds, which an LWAPP Request message must be
responded to.
Default: 1
12.8 KeyLifetime
The maximum time, in seconds, which an LWAPP session key is valid.
Default: 28800
Calhoun, et al. Expires October 2, 2005 [Page 105]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
13. LWAPP Protocol Variables
An WTP or AC that implements LWAPP discovery MUST allow for the
following variables to be configured by system management; default
values are specified so as to make it unnecessary to configure any of
these variables in many cases.
13.1 MaxDiscoveries
The maximum number of discovery requests that will be sent after an
WTP boots.
Default: 10
13.2 DiscoveryCount
The number of discoveries transmitted by a WTP to a single AC. This
is a monotonically increasing counter.
13.3 RetransmitCount
The number of retransmissions for a given LWAPP packet. This is a
monotonically increasing counter.
13.4 MaxRetransmit
The maximum number of retransmissions for a given LWAPP packet before
the link layer considers the peer dead.
Default: 5
Calhoun, et al. Expires October 2, 2005 [Page 106]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
14. Security Considerations
LWAPP uses either an authenticated key exchange or key agreement
mechanism to ensure peer authenticity and establish fresh session
keys to protect the LWAPP communications.
Fresh keying material is ensured in certificated based construction
as the AC generates new keying material in either the Join Response
or Key Update Response (see RFC 1750 [4]. In the PSK construction
both parties, WTP and AC mutually derive new keying material through
the exchange of the nonces in the Join Request/Response exchange.
The rekeys are ensured new keying material through the Key Update
Response.
It is important to note that Perfect Forward Secrecy is not a
requirement for the LWAPP protocol.
14.1 Certificate based Session Key establishment
LWAPP uses public key cryptography to ensure trust between the WTP
and the AC. During the Join phase, the AC generates a session key,
which is used to secure future control messages. The WTP does not
participate in the key generation, but public key cryptography is
used to authenticate the resulting key material. A secured delivery
mechanism to place the certificate in the devices is required. In
order to maximize session key security, the WTP and AC periodically
update the session keys, which are encrypted using public key
cryptography. This ensures that a potentially previously compromised
key does not affect the security of communication with new key
material.
One question that periodically arises is why the Join Request is not
signed. It was felt that requiring a signature in this messages was
not required for the following reasons:
1. The Join Request is replayable, so requiring a signature doesn't
provide much protection unless the switches keep track of all
previous Join Requests from a given WTP. One alternative would
have been to add a timestamp, but this introduces clock
synchronization issues. Further, authentication occurs in a later
exchange anyway (see point 2 below).
2. The WTP is authenticated by virtue of the fact that it can
decrypt and then use the session keys (encrypted with its own
public key), so it *is* ultimately authenticated.
3. A signed Join Request provides a potential Denial of Service
attack on the AC, which would have to authenticate each
(potentially malicious) message.
The WTP-Certificate that is included in the Join Request MUST be
Calhoun, et al. Expires October 2, 2005 [Page 107]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
validated by the AC. It is also good practice that the AC perform
some form of authorization, ensuring that the WTP in question is
allowed to establish an LWAPP session with it.
14.2 PSK based Session Key establishment
Use of a fixed shared secret of limited entropy (for example, a PSK
that is relatively short, or was chosen by a human and thus may
contain less entropy than its length would imply) may allow an
attacker to perform a brute-force or dictionary attack to recover the
secret.
It is RECOMMENDED that implementations that allow the administrator
to manually configure the PSK also provide a functionality for
generating a new random PSK, taking RFC 1750 [4] into account.
Since the key generation does not expose the nonces in plaintext,
there are no practical passive attacks possible.
Calhoun, et al. Expires October 2, 2005 [Page 108]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
15. IANA Considerations
This document requires no action by IANA.
Calhoun, et al. Expires October 2, 2005 [Page 109]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
16. IPR Statement
The IETF has been notified of intellectual property rights claimed in
regard to some or all of the specification contained in this
document. For more information consult the online list of claimed
rights.
Please refer to http://www.ietf.org/ietf/IPR for more information.
Calhoun, et al. Expires October 2, 2005 [Page 110]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
17. References
17.1 Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] National Institute of Standards and Technology, "Advanced
Encryption Standard (AES)", FIPS PUB 197, November 2001,
<http://csrc.nist.gov/publications/fips/fips197/fips-197.pdf>.
[3] Whiting, D., Housley, R. and N. Ferguson, "Counter with CBC-MAC
(CCM)", RFC 3610, September 2003.
[4] Eastlake, D., Crocker, S. and J. Schiller, "Randomness
Recommendations for Security", RFC 1750, December 1994.
[5] Manner, J. and M. Kojo, "Mobility Related Terminology",
RFC 3753, June 2004.
[6] "Information technology - Telecommunications and information
exchange between systems - Local and metropolitan area networks
- Specific requirements - Part 11: Wireless LAN Medium Access
Control (MAC) and Physical Layer (PHY) specifications",
IEEE Standard 802.11, 1999,
<http://standards.ieee.org/getieee802/download/802.11-1999.pdf>
.
[7] "Information technology - Telecommunications and information
exchange between systems - Local and metropolitan area networks
- Specific requirements - Part 11: Wireless LAN Medium Access
Control (MAC) and Physical Layer (PHY) specifications Amendment
6: Medium Access Control (MAC) Security Enhancements",
IEEE Standard 802.11i, July 2004,
<http://standards.ieee.org/getieee802/download/802.11i-2004.pdf
>.
[8] Clark, D., "IP datagram reassembly algorithms", RFC 815, July
1982.
[9] Stokes, E., Weiser, R., Moats, R. and R. Huber, "Lightweight
Directory Access Protocol (version 3) Replication
Requirements", RFC 3384, October 2002.
[10] Schaad, J. and R. Housley, "Advanced Encryption Standard (AES)
Key Wrap Algorithm", RFC 3394, September 2002.
Calhoun, et al. Expires October 2, 2005 [Page 111]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
17.2 Informational References
[11] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by an
On-line Database", RFC 3232, January 2002.
[12] Bradner, S., "The Internet Standards Process -- Revision 3",
BCP 9, RFC 2026, October 1996.
[13] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
[14] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed-Hashing
for Message Authentication", RFC 2104, February 1997.
[15] "WiFi Protected Access (WPA) rev 1.6", April 2003.
Authors' Addresses
Pat R. Calhoun
Airespace
110 Nortech Parkway
San Jose, CA 95134
Phone: +1 408-635-2000
Email: pcalhoun@airespace.com
Bob O'Hara
Airespace
110 Nortech Parkway
San Jose, CA 95134
Phone: +1 408-635-2025
Email: bob@airespace.com
Scott Kelly
Facetime Communications
1159 Triton Dr
Foster City, CA 94404
Phone: +1 650 572-5846
Email: scott@hyperthought.com
Calhoun, et al. Expires October 2, 2005 [Page 112]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Rohit Suri
Airespace
110 Nortech Parkway
San Jose, CA 95134
Phone: +1 408-635-2026
Email: rsuri@airespace.com
Michael Glenn Williams
Nokia, Inc.
313 Fairchild Drive
Mountain View, CA 94043
Phone: +1 650-714-7758
Email: Michael.G.Williams@Nokia.com
Sue Hares
Nexthop Technologies, Inc.
825 Victors Way, Suite 100
Ann Arbor, MI 48108
Phone: +1 734 222 1610
Email: shares@nexthop.com
Nancy
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134
Phone: +1 408-853-0532
Email: ncamwing@cisco.com
Calhoun, et al. Expires October 2, 2005 [Page 113]
Internet-Draft Light Weight Access Point Protocol (LWAPP) March 2005
Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment
Funding for the RFC Editor function is currently provided by the
Internet Society.
Calhoun, et al. Expires October 2, 2005 [Page 114]