Network Working Group C. Shao
Internet-Draft H. Deng
Intended status: Informational China Mobile
Expires: November 10, 2013 F. Bari
AT&T
R. Zhang
China Telecom
S. Matsushima
SoftBank Telecom
May 09, 2013
Hybrid-MAC Model for CAPWAP
draft-ietf-opsawg-capwap-hybridmac-00
Abstract
The CAPWAP protocol supports two modes of operation: Split and Local
MAC (medium access control), which has been described in
[RFC5415].There are many functions in IEEE 802l.11 MAC layer that
have not yet been clearly defined whether they belong to either the
WTP (Wireless Termination Points) or the AC (Access Controller)in the
Split and Local modes. Because different vendors have their own
definition of these two models, depending upon the vendor many MAC
layer functions continue to be mapped differently to either the WTP
or AC. If there is no clear definition of split MAC and local MAC,
then operators will not only need to perform vendor specific
configurations in their network but will continue to experience
difficulty in interoperating WTPs and ACs from different vendors.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on November 10, 2013.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. The difference between Local MAC and Split MAC . . . . . . . 3
4. Functions in Local MAC and Split MAC . . . . . . . . . . . . 4
5. Hybrid-MAC model recommendation . . . . . . . . . . . . . . . 5
6. Hybrid-MAC model Frames Exchange . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
11. Normative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
The CAPWAP protocol supports two modes of operation: Split and Local
MAC (medium access control), which has been described in [RFC5415].In
Split MAC mode, all L2 wireless data and management frames are
encapsulated via the CAPWAP protocol and exchanged between the AC and
the WTP. The Local MAC mode of operation allows for the data frames
to be either locally bridged or tunneled as 802.3 frames. The latter
implies that the WTP performs the 802.11 Integration function.
Unfortunately, there are many functions that have not yet been
clearly defined whether they belong to either the WTP or the AC in
the Split and Local modes. Because different vendors have their own
definition of the two models, many MAC layer functions are mapped
differently to either the WTP or the AC by different vendors.
Therefore, depending upon the vendor, the operators in their
deployments have to perform different configurations based on
implementation of the two modes by their vendor. If there is no
clear definition of split MAC and local MAC, then operators will
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continue to experience difficulty in interoperating WTPs and ACs from
different vendors.
2. 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 [RFC2119].
3. The difference between Local MAC and Split MAC
The main difference between Local MAC and Split MAC lies in the
processing of the wireless frames. This is shown in Figure 1 where
depending upon the mode, either the WTP or the AC performs the 802.11
Integration function. According to the 802.11 protocol definition,
the 802.11 wireless frame is divided into three kinds of frames,
including wireless control frames, wireless management frames, and
wireless data frames.
Wireless control frames, such as TS, CTS, ACK, PS-POLL, etc., are
processed locally by WTP in both Local MAC and Split MAC. However,
wireless management frames, including Beacon, Probe, Association,
Authentication, are processed differently in the Local MAC and the
Split MAC. In the Local MAC, depending upon the vendor wireless
management frames can be processed in the WTP or the AC. In the case
of Split MAC, the real-time part of wireless frames are processed in
WTP, while the non-real-time frames are processed in the AC. This is
shown in Figure 1 quoted from [RFC5416]. In Split MAC mode, the
wireless data frames received from a mobile device are directly
encapsulated by the WTP and forwarded to the AC. The Local MAC mode
of operation allows data frames to be processed locally by the WTP
and then forwarded to the AC.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local MAC | Split MAC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | 802.3 MAC | |
+ 802.3 MAC + AC +-+-+-+-+-+-+-+-+- AC +
| | | 802.11MAC NonRT| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 802.11 MAC | | 802.11 MAC RT | |
+-+-+-+-+-+-+-+-+ WTP +-+-+-+-+-+-+-+-+- WTP +
| 802.11 PHY | | 802.11 PHY | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: The comparison between Local MAC and Split MAC
4. Functions in Local MAC and Split MAC
As shown in Figure 2 quoted from [RFC5416], main functions are
processed in different places in the Local MAC and Split MAC. In
addition, for some functions (for example, the Frag. / Defrag.
Assoc. / Disassoc / Reassoc., Etc.) the protocol does not
explicitly map processing of such functions to the WTP or the AC.
Therefore the location of these features becomes vendor specific and
this increases the difficulty of interoperability between WTPs and
ACs from different vendors.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Functions describe | Local MAC | Split MAC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Distribution Service | WTP/AC | AC |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Integration Service | WTP | AC |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Beacon Generation | WTP | WTP |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Probe Response Generation| WTP | WTP |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Function |Power Mgmt | WTP | WTP |
+ |/Packet Buffering | | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Fragmentation | WTP | WTP/AC |
+ |/Defragmentation | | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Assoc/Disassoc/Reassoc | WTP/AC | AC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Classifying | WTP | AC |
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+ IEEE +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 802.11 QoS |Scheduling | WTP | WTP/AC |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Queuing | WTP | WTP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |IEEE 802.1X/EWTP | AC | AC |
+ IEEE +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 802.11 RSN |RSNA Key Management | WTP | AC |
+ (WPA2) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |IEEE 802.11 | WTP | WTP/AC |
+ |Encryption/Decryption | | |
|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Functions in Local MAC and Split MAC
5. Hybrid-MAC model recommendation
As discussed above, if the functions have been clearly defined to be
implemented in WTP or AC, the interoperability will be much better
between different vendors products. To achieve this goal a common
Hybrid-MAC model, as shown in Figure 3, is proposed.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Functions describe | Hybrid-MAC|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Distribution Service | AC |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Integration Service | AC |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Beacon Generation | WTP |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Probe Response Generation| WTP |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Function |Power Mgmt | WTP |
+ |/Packet Buffering | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Fragmentation | AC |
+ |/Defragmentation | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Assoc/Disassoc/Reassoc | AC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Classifying | AC |
+ IEEE +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 802.11 QoS |Scheduling | WTP |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Queuing | WTP |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |IEEE 802.1X/EWTP | AC |
+ IEEE +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 802.11 RSN |RSNA Key Management | AC |
+ (WPA2) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |IEEE 802.11 | WTP |
+ |Encryption/Decryption | |
|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Functions in Hybrid MAC
6. Hybrid-MAC model Frames Exchange
An example of frame exchange using the proposed Hybrid-MAC Model
shown in Figure 4.
+-+-+-+-+-+-+ +-+-+-+-+-+ +-+-+-+-+-+-+
| STA | | WTP | | AC |
+-+-+-+-+-+-+ +-+-+-+-+-+ +-+-+-+-+-+-+
| | |
| Beacon | |
|<-------------------------| |
| Probe | |
|<------------------------>| |
| 802.11 AUTH/Association |
|<-------------------------------------------------------->|
| |Station Configuration Request [|
| Add Station (Station MAC Address),|
| IEEE 802.11 Add Station (WLAN ID),|
| IEEE 802.11 Session Key(Flag=A)] |
| |<------------------------------|
| | |
| |Station Configuration Response |
| |------------------------------>|
| 802.1X Authentication & 802.11 Key Exchange |
|<-------------------------------------------------------->|
| |Station Configuration Request [|
| Add Station (Station MAC Address),|
| IEEE 802.11 Add Station (WLAN ID),|
| IEEE 802.11 Station Session Key] |
| |<------------------------------|
| | |
| |Station Configuration Response |
| |------------------------------>|
| 802.11 Action Frames |
|<-------------------------------------------------------->|
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| DATA Frame Exchange |
| 802.11 Data | 802.11 or 802.3 Data |
|<-------------------------+------------------------------>|
Figure 4: Hybrid-MAC model Frames Exchange
7. Security Considerations
This document doesn't specify security risk difference from
[RFC5416]. It could directly refer to Security section of [RFC5416]
8. IANA Considerations
This document make no request for IANA registration.
9. Contributors
Naibao Zhou zhounaibao@chinamobile.com
10. Acknowledgments
The author thanks the kind advices from Dorothy Stanley in the
development of this document.
The efforts of Margaret Wasserman, Wes George in reviewing this
document are gratefully acknowledged.
Guidance from management team: Melinda Shore, Scott Bradner, Chris
Liljenstolpe, Benoit Claise, Joel Jaeggli, Romascanu Dan are highly
appreciated.
11. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4564] Govindan, S., Cheng, H., Yao, ZH., Zhou, WH., and L. Yang,
"Objectives for Control and Provisioning of Wireless
Access Points (CAPWAP)", RFC 4564, July 2006.
[RFC5415] Calhoun, P., Montemurro, M., and D. Stanley, "Control And
Provisioning of Wireless Access Points (CAPWAP) Protocol
Specification", RFC 5415, March 2009.
[RFC5416] Calhoun, P., Montemurro, M., and D. Stanley, "Control and
Provisioning of Wireless Access Points (CAPWAP) Protocol
Binding for IEEE 802.11", RFC 5416, March 2009.
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Authors' Addresses
Chunju Shao
China Mobile
No.32 Xuanwumen West Street
Beijing 100053
China
Email: shaochunju@chinamobile.com
Hui Deng
China Mobile
No.32 Xuanwumen West Street
Beijing 100053
China
Email: denghui@chinamobile.com
Farooq Bari
AT&T
7277 164th Ave NE
Redmond WA 98052
USA
Email: farooq.bari@att.com
Rong Zhang
China Telecom
No.109 Zhongshandadao avenue
Guangzhou 510630
China
Email: zhangr@gsta.com
Satoru Matsushima
SoftBank Telecom
1-9-1 Higashi-Shinbashi, Munato-ku
Tokyo
Japan
Email: satoru.matsushima@g.softbank.co.jp
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