PANA Working Group D. Forsberg
Internet-Draft Nokia
Expires: November 11, 2005 Y. Ohba (Ed.)
Toshiba
B. Patil
Nokia
H. Tschofenig
Siemens
A. Yegin
Samsung
May 10, 2005
Protocol for Carrying Authentication for Network Access (PANA)
draft-ietf-pana-pana-08
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document defines the Protocol for Carrying Authentication for
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Network Access (PANA), a link-layer agnostic transport for Extensible
Authentication Protocol (EAP) to enable network access authentication
between clients and access networks. PANA can carry any
authentication method that can be specified as an EAP method, and it
can be used on any link that can carry IP. PANA protocol
specification covers the client-to-network access authentication part
of an overall secure network access framework, which additionally
includes other protocols and mechanisms for service provisioning,
access control as a result of initial authentication, and accounting.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1 Specification of Requirements . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . 9
4. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 11
4.1 Payload Encoding . . . . . . . . . . . . . . . . . . . . . 11
4.2 Discovery and Handshake Phase . . . . . . . . . . . . . . 12
4.3 Authentication and Authorization Phase . . . . . . . . . . 16
4.4 Access Phase . . . . . . . . . . . . . . . . . . . . . . . 18
4.5 Re-authentication Phase . . . . . . . . . . . . . . . . . 19
4.6 Termination Phase . . . . . . . . . . . . . . . . . . . . 21
4.7 Separate NAP and ISP Authentication . . . . . . . . . . . 22
4.7.1 Negotiating Separate NAP and ISP Authentication . . . 22
4.7.2 Execution of Separate NAP and ISP Authentication . . . 23
4.7.3 AAA-Key Calculation . . . . . . . . . . . . . . . . . 24
5. Protocol Design Details and Processing Rules . . . . . . . . 25
5.1 Transport Layer . . . . . . . . . . . . . . . . . . . . . 25
5.1.1 Fragmentation . . . . . . . . . . . . . . . . . . . . 25
5.2 Sequence Number and Retransmission . . . . . . . . . . . . 25
5.3 PANA Security Association . . . . . . . . . . . . . . . . 26
5.4 Message Authentication Code . . . . . . . . . . . . . . . 29
5.5 Message Validity Check . . . . . . . . . . . . . . . . . . 29
5.6 Device ID Choice . . . . . . . . . . . . . . . . . . . . . 31
5.7 PaC Updating its IP Address . . . . . . . . . . . . . . . 32
5.8 Session Lifetime . . . . . . . . . . . . . . . . . . . . . 32
5.9 Network Selection . . . . . . . . . . . . . . . . . . . . 33
5.10 Error Handling . . . . . . . . . . . . . . . . . . . . . 34
6. PANA Headers and Formats . . . . . . . . . . . . . . . . . . 35
6.1 IP and UDP Headers . . . . . . . . . . . . . . . . . . . . 35
6.2 PANA Header . . . . . . . . . . . . . . . . . . . . . . . 35
6.3 AVP Header . . . . . . . . . . . . . . . . . . . . . . . . 38
7. PANA Messages, Message Specifications and AVPs . . . . . . . 42
7.1 PANA Messages . . . . . . . . . . . . . . . . . . . . . . 42
7.2 PANA Message ABNF Specification . . . . . . . . . . . . . 42
7.2.1 PANA-PAA-Discover (PDI) . . . . . . . . . . . . . . . 44
7.2.2 PANA-Start-Request (PSR) . . . . . . . . . . . . . . . 45
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7.2.3 PANA-Start-Answer (PSA) . . . . . . . . . . . . . . . 45
7.2.4 PANA-Auth-Request (PAR) . . . . . . . . . . . . . . . 45
7.2.5 PANA-Auth-Answer (PAN) . . . . . . . . . . . . . . . . 46
7.2.6 PANA-Reauth-Request (PRAR) . . . . . . . . . . . . . . 46
7.2.7 PANA-Reauth-Answer (PRAA) . . . . . . . . . . . . . . 46
7.2.8 PANA-Bind-Request (PBR) . . . . . . . . . . . . . . . 46
7.2.9 PANA-Bind-Answer (PBA) . . . . . . . . . . . . . . . . 47
7.2.10 PANA-Ping-Request (PPR) . . . . . . . . . . . . . . 47
7.2.11 PANA-Ping-Answer (PPA) . . . . . . . . . . . . . . . 47
7.2.12 PANA-Termination-Request (PTR) . . . . . . . . . . . 48
7.2.13 PANA-Termination-Answer (PTA) . . . . . . . . . . . 48
7.2.14 PANA-Error-Request (PER) . . . . . . . . . . . . . . 48
7.2.15 PANA-Error-Answer (PEA) . . . . . . . . . . . . . . 49
7.2.16 PANA-FirstAuth-End-Request (PFER) . . . . . . . . . 49
7.2.17 PANA-FirstAuth-End-Answer (PFEA) . . . . . . . . . . 49
7.2.18 PANA-Update-Request (PUR) . . . . . . . . . . . . . 49
7.2.19 PANA-Update-Answer (PUA) . . . . . . . . . . . . . . 50
7.3 AVPs in PANA . . . . . . . . . . . . . . . . . . . . . . . 50
7.3.1 Cookie AVP . . . . . . . . . . . . . . . . . . . . . . 52
7.3.2 Device-Id AVP . . . . . . . . . . . . . . . . . . . . 52
7.3.3 EAP-Payload AVP . . . . . . . . . . . . . . . . . . . 53
7.3.4 Failed-AVP AVP . . . . . . . . . . . . . . . . . . . . 53
7.3.5 ISP-Information AVP . . . . . . . . . . . . . . . . . 53
7.3.6 Key-Id AVP . . . . . . . . . . . . . . . . . . . . . . 53
7.3.7 MAC AVP . . . . . . . . . . . . . . . . . . . . . . . 53
7.3.8 NAP-Information AVP . . . . . . . . . . . . . . . . . 54
7.3.9 Nonce AVP . . . . . . . . . . . . . . . . . . . . . . 54
7.3.10 Notification AVP . . . . . . . . . . . . . . . . . . 54
7.3.11 Post-PANA-Address-Configuration (PPAC) AVP . . . . . 55
7.3.12 Protection-Capability AVP . . . . . . . . . . . . . 56
7.3.13 Provider-Identifier AVP . . . . . . . . . . . . . . 56
7.3.14 Provider-Name AVP . . . . . . . . . . . . . . . . . 56
7.3.15 Result-Code AVP . . . . . . . . . . . . . . . . . . 56
7.3.16 Session-Id AVP . . . . . . . . . . . . . . . . . . . 61
7.3.17 Session-Lifetime AVP . . . . . . . . . . . . . . . . 61
7.3.18 Termination-Cause AVP . . . . . . . . . . . . . . . 61
8. Retransmission Timers . . . . . . . . . . . . . . . . . . . 62
8.1 Transmission and Retransmission Parameters . . . . . . . . 63
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . 65
9.1 PANA UDP Port Number . . . . . . . . . . . . . . . . . . . 65
9.2 PANA Multicast Address . . . . . . . . . . . . . . . . . . 65
9.3 PANA Header . . . . . . . . . . . . . . . . . . . . . . . 65
9.3.1 Message Type . . . . . . . . . . . . . . . . . . . . . 65
9.3.2 Flags . . . . . . . . . . . . . . . . . . . . . . . . 66
9.4 AVP Header . . . . . . . . . . . . . . . . . . . . . . . . 66
9.4.1 AVP Code . . . . . . . . . . . . . . . . . . . . . . . 66
9.4.2 Flags . . . . . . . . . . . . . . . . . . . . . . . . 67
9.5 AVP Values . . . . . . . . . . . . . . . . . . . . . . . . 67
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9.5.1 Algorithm Values of MAC AVP . . . . . . . . . . . . . 67
9.5.2 Post-PANA-Address-Configuration AVP Values . . . . . . 67
9.5.3 Protection-Capability AVP Values . . . . . . . . . . . 67
9.5.4 Result-Code AVP Values . . . . . . . . . . . . . . . . 67
9.5.5 Termination-Cause AVP Values . . . . . . . . . . . . . 68
10. Security Considerations . . . . . . . . . . . . . . . . . . 69
10.1 General Security Measures . . . . . . . . . . . . . . . 69
10.2 Discovery . . . . . . . . . . . . . . . . . . . . . . . 70
10.3 EAP Methods . . . . . . . . . . . . . . . . . . . . . . 71
10.4 Separate NAP and ISP Authentication . . . . . . . . . . 71
10.5 Cryptographic Keys . . . . . . . . . . . . . . . . . . . 71
10.6 Per-packet Ciphering . . . . . . . . . . . . . . . . . . 72
10.7 PAA-to-EP Communication . . . . . . . . . . . . . . . . 72
10.8 Liveness Test . . . . . . . . . . . . . . . . . . . . . 73
10.9 Updating PaC's IP Address . . . . . . . . . . . . . . . 73
10.10 Early Termination of a Session . . . . . . . . . . . . . 73
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 74
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 75
12.1 Normative References . . . . . . . . . . . . . . . . . . 75
12.2 Informative References . . . . . . . . . . . . . . . . . 76
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 77
A. Example Sequence of Separate NAP and ISP Authentication . . 79
Intellectual Property and Copyright Statements . . . . . . . 82
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1. Introduction
Providing secure network access service requires access control based
on the authentication and authorization of the clients and the access
networks. Client-to-network authentication provides parameters that
are needed to police the traffic flow through the enforcement points.
A protocol is needed to carry authentication methods between the
client and the access network.
Currently there is no standard network-layer solution for
authenticating clients for network access. Appendix A of [I-D.ietf-
pana-requirements] describes the problem statement that led to the
development of PANA.
Scope of this work is identified as designing a link-layer agnostic
transport for network access authentication methods. The Extensible
Authentication Protocol (EAP) [RFC3748] provides such authentication
methods. In other words, PANA will carry EAP which can carry various
authentication methods. By the virtue of enabling transport of EAP
above IP, any authentication method that can be carried as an EAP
method is made available to PANA and hence to any link-layer
technology. There is a clear division of labor between PANA (an EAP
lower layer), EAP and EAP methods as described in [RFC3748].
Various environments and usage models for PANA are identified in
Appendix A of [I-D.ietf-pana-requirements]. Potential security
threats for network-layer access authentication protocol are
discussed in [RFC4016]. These have been essential in defining the
requirements [I-D.ietf-pana-requirements] on the PANA protocol. Note
that some of these requirements are imposed by the chosen payload,
EAP [RFC3748].
There are components that are part of a complete secure network
solution but are outside of the PANA protocol specification,
including IP address configuration, authentication method choice,
filter rule installation, data traffic protection and PAA-EP
protocol. These components are described in separate documents (see
[I-D.ietf-pana-framework] and [I-D.ietf-pana-snmp]). The readers are
recommended to go through the PANA Framework document [I-D.ietf-pana-
framework] prior to reading this protocol specification document.
1.1 Specification of Requirements
In this document, several words are used to signify the requirements
of the specification. These words are often capitalized. 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].
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2. Terminology
PANA Client (PaC):
The client side of the protocol that resides in the access device
(e.g., laptop, PDA, etc.). It is responsible for providing the
credentials in order to prove its identity (authentication) for
network access authorization. The PaC and the EAP peer are co-
located in the same access device.
PANA Authentication Agent (PAA):
The protocol entity in the access network whose responsibility is
to verify the credentials provided by a PANA client (PaC) and
authorize network access to the device associated with the client
and identified by a Device Identifier (DI). The PAA and the EAP
authenticator (and optionally the EAP server) are co-located in
the same node. Note the authentication and authorization
procedure can, according to the EAP model, be also offloaded to
the backend AAA infrastructure.
PANA Session:
A PANA session begins with the handshake between the PANA Client
(PaC) and the PANA Authentication Agent (PAA), and terminates as a
result of an authentication or liveness test failure, a message
delivery failure after retransmissions reach maximum values,
session lifetime expiration, or an explicit termination message.
A fixed session identifier is maintained throughout a session. A
session cannot be shared across multiple network interfaces. Only
one device identifier of the PaC is allowed to be bound to a PANA
session for simplicity.
Session Identifier:
This identifier is used to uniquely identify a PANA session on the
PAA and PaC. It includes an identifier of the PAA, therefore it
cannot be shared across multiple PAAs. It is included in PANA
messages to bind the message to a specific PANA session. This
bidirectional identifier is allocated by the PAA following the
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handshake and freed when the session terminates.
PANA Security Association (PANA SA):
A PANA security association is formed between the PaC and the PAA
by sharing cryptographic keying material and associated context.
The formed duplex security association is used to protect the
bidirectional PANA signaling traffic between the PaC and the PAA.
Device Identifier (DI):
The identifier used by the network as a handle to control and
police the network access of a device. Depending on the access
technology, this identifier may contain an address that is carried
in protocol headers (e.g., IP or link-layer address), or a locally
significant identifier that is made available by the local
protocol stack (e.g., circuit id, PPP interface id) of a connected
device.
Enforcement Point (EP):
A node on the access network where per-packet enforcement policies
(i.e., filters) are applied on the inbound and outbound traffic of
access devices. Information such as the DI and (optionally)
cryptographic keys are provided by the PAA per client for
generating filters on the EP. The EP and PAA may be co-located.
Network Access Provider (NAP):
A service provider that provides physical and link-layer
connectivity to an access network it manages.
AAA-Key:
A key derived by the EAP peer and EAP server and transported to
the authenticator [I-D.ietf-eap-keying].
For additional terminology definitions see the PANA framework
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document [I-D.ietf-pana-framework].
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3. Protocol Overview
The PANA protocol is run between a client (PaC) and a server (PAA) in
order to perform authentication and authorization for the network
access service.
The protocol messaging consists of a series of request and responses,
some of which may be initiated by either ends. Each message can
carry zero or more AVPs as payload. The main payload of PANA is EAP
which performs authentication. PANA helps the PaC and PAA establish
an EAP session.
PANA is a UDP-based protocol. It has its own retransmission
mechanism to reliably deliver messages.
PANA messages are sent between the PaC and PAA as part of a PANA
session. A PANA session consists of distinct phases:
o Discovery and handshake phase: This is the phase that initiates a
new PANA session. The PaC discovers the PAA(s) by either
explicitly soliciting advertisements for them or receiving
unsolicited advertisements. The PaC's answer sent in response to
an advertisement starts a new session.
o Authentication and authorization phase: Immediately following the
discovery and handshake phase is the EAP execution between the PAA
and PaC. The EAP payload (which carry an EAP method inside) is
what is used for authentication. The PAA conveys the result of
authentication and authorization to the PaC at the end of this
phase. This phase may involve execution of two EAP sessions back-
to-back, one for the NAP and one for the ISP.
o Access phase: After a successful authentication and authorization
the host gains access to the network and can send and receive IP
data traffic through the EP(s). At any time during this phase,
the PaC and PAA may optionally ping each other to test liveness of
the PANA session on each end.
o Re-authentication phase: Following the access phase, the PAA must
initiate re-authentication before the PANA session lifetime
expires. Again EAP is carried by PANA to perform authentication.
This phase may be optionally triggered by both the PaC and the PAA
without any respect to the session lifetime. The session moves to
this phase from the access phase, and returns back there upon
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successful re-authentication.
o Termination phase: The PaC or PAA may choose to discontinue the
access service at any time. An explicit disconnect message can be
sent by either end. If either the PaC or the PAA disconnects
without engaging in termination messaging, it is expected that
either the expiration of a finite session lifetime or failed
liveness tests would do the job.
PaC PAA Message
-----------------------------------------------------
// Discovery and handshake phase
-----> PANA-PAA-Discover
<----- PANA-Start-Request
-----> PANA-Start-Answer
// Authentication and authorization phase
<----- PANA-Auth-Request /* EAP Request */
-----> PANA-Auth-Answer
-----> PANA-Auth-Request /* EAP Response */
<----- PANA-Auth-Answer
<----- PANA-Bind-Request /* EAP Success */
-----> PANA-Bind-Answer
// Access phase (IP data traffic allowed)
<----- PANA-Ping-Request
-----> PANA-Ping-Answer
// Termination phase
-----> PANA-Termination-Request
<----- PANA-Termination-Answer
Figure 1: Illustration of PANA messages in a session
Note that depending on the environment and deployment the protocol
flow depicted in Figure 1 can be abbreviated.
Cryptographic protection of messages between the PaC and PAA is
possible as soon as EAP in conjunction with the EAP method exports a
shared key. That shared key is used to create a PANA SA. The PANA
SA helps generating per-message authentication codes that provide
integrity protection and authentication.
Throughout the lifetime of a session, various problems found with the
incoming messages can generate a PANA error message sent in response.
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4. Protocol Details
The following sections explain in detail the various phases of a PANA
session.
4.1 Payload Encoding
The payload of any PANA message consists of zero or more AVPs
(Attribute Value Pairs). The subsequent sections refer to these
AVPs, therefore the list of AVPs are provided with a brief
description before more extensive descriptions are included later in
the document.
o Cookie AVP: contains a random value that is generated by the PAA
and used for making PAA discovery robust against blind resource
consumption DoS attacks.
o Protection-Capability AVP: contains the type of per-packet
protection (link-layer vs. network-layer) when a cryptographic
mechanism should be enabled after PANA authentication.
o Device-Id AVP: contains a device identifier (link-layer address or
an IP address) of the PaC or an EP.
o EAP AVP: contains an EAP PDU.
o MAC AVP: contains a Message Authentication Code that integrity
protects the PANA message.
o Termination-Cause AVP: contains the reason of session termination.
o Result-Code AVP: contains information about the protocol execution
results.
o Session-Id AVP: contains the PANA session identifier value.
o Session-Lifetime AVP: contains the duration of authorized access.
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o Failed-AVP: contains an offending AVP that caused a failure.
o Provider-Identifier AVP: contains the identifier of a NAP or an
ISP.
o Provider-Name AVP: contains a name of a NAP or an ISP.
o NAP-Information AVP, ISP-Information AVP: contains the identifier
of a NAP and an ISP, respectively.
o Key-Id AVP: contains a AAA-Key identifier.
o PPAC AVP: Post-PANA-Address-Configuration AVP. Used to indicate
the available/chosen IP address configuration methods that can be
used by the PaC after successful PANA authentication.
o Nonce AVP: contains a randomly chosen value that is used in
cryptographic key computations.
o Notification AVP: contains a displayable message.
4.2 Discovery and Handshake Phase
When a PaC attaches to a network, and it does not already know the IP
address of the PAA, it MUST rely on dynamic discovery methods, such
as a multicast-based and a traffic-driven discovery.
The PaCs and PAAs MUST implement multicast-based discovery where the
PaC sends a PANA-PAA-Discover message to a well-known
administratively scoped multicast address (TBD) and UDP port (TBD).
The network administrator MUST configure the multicast scope such
that the discovery messages can reach only the designated PAA(s). In
case the PAA(s) is on the same link as the PaC, the administratively
scoped multicast messages MUST not be forwarded by the routers.
Details of scope configuration are discussed in [RFC2365].
The PAA(s) that receive the discovery message MUST respond with a
unicast PANA-Start-Request message sent to the soliciting PaC.
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Alternatively, the PaC MAY also choose to start sending data packets
before getting authenticated. The EP in an access network that
implements PANA SHOULD drop such unauthorized packets upon receipt.
Additionally, the EP MAY also take this traffic as an indication of
unauthorized PaC and notify the PAA. The EP-to-PAA notification
SHOULD be sent via [I-D.ietf-pana-snmp]. In response, the PAA SHOULD
send an unsolicited PANA-Start-Request message to the PaC. This is
called traffic-driven PAA discovery (an alternative to the PaC
explicitly soliciting for a PAA). Deployment of this alternate
scheme is optional.
The EP-to-PAA notification MAY also be generated in response to
receiving a link-up event notification on the EP [I-D.ietf-dna-link-
information].
Alternative PAA discovery schemes may be designed (e.g., DHCP-based)
but they are outside the scope of this specification.
If the PaC knows the IP address of the PAA, it can send a unicast
PANA-PAA-Discover message and initiate the PANA exchange.
When the PaC receives a PANA-Start-Request message from a PAA, it
responds with a PANA-Start-Answer message if it wishes to enter the
authentication and authorization phase.
There can be multiple PAAs on the link and the PaC may receive
multiple PANA-Start-Request messages from those PAAs. The
authentication and authorization result does not depend on which PAA
is chosen by the PaC. By default the PaC MAY choose the PAA that
sent the first response.
A PANA-Start-Request message MAY carry a Cookie AVP that contains a
random value generated by the PAA. The random value is referred to
as a cookie. The cookie is used for preventing the PAA from resource
consumption DoS attacks by blind attackers which bombard the PAA with
PANA-PAA-Discover messages. By relying on a cookie mechanism the PAA
can avoid per-PaC state creation until after the PaC can produce the
same cookie in its PANA-Start-Answer message. In order to do that,
the cookie MUST be computed in such a way that it does not require
any per-session state maintenance on the PAA in order to verify the
cookie returned in the PANA-Start-Answer message. The PAA discovery
that takes advantage of cookies is called "stateless PAA discovery".
The exact algorithms and syntax used by the PAA to generate cookies
does not affect interoperability and hence is not specified here. An
example algorithm is described below.
Cookie =
<secret-version> | HMAC_SHA1( <Device-Id of PaC> , <secret> )
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where <secret> is a randomly generated secret known only to the PAA,
<secret-version> is an index used for choosing the secret for
generating the cookie and '|' indicates concatenation. The secret-
version should be changed frequently enough to prevent replay
attacks. The secret key is valid for a certain time frame. The
device identifier of the PaC can be extracted from a link-layer or IP
header of PANA messages.
When the PaC sends a PANA-Start-Answer message in response to a PANA-
Start-Request containing a Cookie AVP, the answer MUST contain a
Cookie AVP with the cookie value copied from the request.
When the PAA receives the PANA-Start-Answer message from the PaC, it
verifies the cookie. The cookie is considered as valid if the
received cookie has the expected value. If the computed cookie is
valid, the protocol enters the authentication and authorization
phase. Otherwise, it MUST silently discard the received message.
The initial EAP Request message MAY be optionally carried by the
PANA-Start-Request (as opposed to by a later PANA-Auth-Request)
message in order to reduce the number of round-trips. This
optimization SHOULD NOT be used if the PAA discovery is desired to be
stateless since transmission of an EAP Request message creates a
state at EAP layer. See [I-D.ietf-eap-statemachine] for more
information on the EAP state machine and the allocation of state
information in the respective protocol steps.
A Protection-Capability AVP and a Post-PANA-Address-Configuration
(PPAC) AVP MAY be included in the PANA-Start-Request in order to
indicate required and available capabilities for the network access.
These AVPs MAY be used by the PaC for assessing the capability match
even before the authentication takes place. Since these AVPs are
provided during the insecure discovery and handshake phase, there are
certain security risks involved in using the provided information.
See Section 10 for further discussion on this.
If the initial EAP Request message is carried in the PANA-Start-
Request message, an EAP Response message MUST be carried in the PANA-
Start-Answer message returned to the PAA.
The PANA-Start-Request/Answer exchange is needed before entering the
authentication and authorization phase even when the PaC is pre-
configured with the IP address of the PAA and the PANA-PAA-Discover
message is unicast.
A Nonce AVP MUST be included in the PANA-Start-Request and PANA-
Start-Answer messages. The nonces are used to establish a fresh
PANA_MAC_KEY (see Section 5.3) which is a transient session key in
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the EAP key hierarchy [I-D.ietf-eap-keying] and is used only in the
PANA protocol. A Nonce AVP MUST be included in the PANA-Start-
Request and PANA-Start-Answer messages. The nonces are used to
establish a PANA SA.
A PANA-Start-Request message in stateless PAA discovery MUST NOT be
retransmitted as this voids the statelessness on the PAA. Instead,
the PaC MUST retransmit the PANA-PAA-Discover message until it
receives a PANA-Start-Request message, and retransmit the PANA-Start-
Answer message until it receives a PANA-Auth-Request message. The
PaC can determine whether the PAA is using stateless PAA discovery by
the presence of Cookie AVP. The PANA-Start-Request message MUST be
retransmitted instead of the PANA-Start-Answer message when stateless
PAA discovery is not used.
It is possible that both the PAA and the PaC initiate the discovery
and handshake procedure at the same time, i.e., the PAA sends a PANA-
Start-Request message while the PaC sends a PANA-PAA-Discover
message. To resolve the race condition, the PAA SHOULD silently
discard the PANA-PAA-Discover message received from the PaC after it
has sent a PANA-Start-Request message with creating a state (i.e., no
Cookie AVP is included in the message) for the PaC. In this case the
PAA will retransmit the PANA-Start-Request message based on a timer,
if the PaC doesn't respond in time (the message was lost for
example). If the PAA had sent a PANA-Start-Request message without
creating a state for the PaC (i.e., a Cookie AVP was included in the
message), then it SHOULD answer to the PANA-PAA-Discover message.
Figure 2 shows an example sequence for the discovery and handshake
phase when a PANA-PAA-Discover message is sent by the PaC. Figure 3
shows an example sequence for the discovery and handshake phase with
traffic-driven PAA discovery.
PaC PAA Message(sequence number)[AVPs]
------------------------------------------------------
-----> PANA-PAA-Discover(0)
<----- PANA-Start-Request(x)[Nonce, Cookie]
-----> PANA-Start-Answer(x)[Nonce, Cookie]
(continued to the authentication and
authorization phase)
Figure 2: Example sequence for the discovery and handshake phase when
PANA-PAA-Discover is sent by the PaC
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PaC EP PAA Message(sequence number)[AVPs]
------------------------------------------------------
---->o (Data packet arrival or L2 trigger)
------> PAA-to-EP protocol, or another mechanism
<------------ PANA-Start-Request(x)[Nonce, Cookie]
------------> PANA-Start-Answer(x)[Nonce, Cookie]
(continued to the authentication and
authorization phase)
Figure 3: Example sequence for the discovery and handshake phase with
traffic-driven PAA discovery
4.3 Authentication and Authorization Phase
The main task of the authentication and authorization phase is to
carry EAP messages between the PaC and the PAA. EAP Request and
Response messages are carried in PANA-Auth-Request messages. PANA-
Auth-Answer messages are simply used to acknowledge receipt of the
requests. As an optimization, a PANA-Auth-Answer message MAY include
the EAP Response message. This optimization MAY not be used when it
takes time to generate the EAP Response message (due to, e.g.,
intervention of human input), in which case returning an EAP-Auth-
Answer message without piggybacking an EAP Response message can avoid
unnecessary retransmission of the PANA-Auth-Request message. Another
optimization allows optionally carrying the first EAP Request/
Response message in PANA-Start-Request/Answer message as described in
Section 4.2.
PANA allows execution of two separate authentication methods, one
with NAP and one with ISP under the same PANA session. This optional
feature may be offered by the PAA and accepted by the PaC. When
performed separately, the result of the first EAP authentication is
signaled via PANA-FirstAuth-End-Request and PANA-FirstAuth-End-Answer
message exchange which delineates the first method execution from the
next. See Section 4.7 for a detailed discussion on separate NAP and
ISP authentication.
The result of PANA authentication is carried in a PANA-Bind-Request
message sent from the PAA to the PaC. This message carries the final
EAP authentication result (whether it is the second EAP
authentication result of NAP and ISP separate authentication, or the
sole EAP authentication result) and the result of PANA
authentication. The PANA-Bind-Request message MUST be acknowledged
with a PANA-Bind-Answer (PBA) message. Figure 4 shows an example
sequence in the authentication and authorization phase (no separate
authentication).
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PaC PAA Message(sequence number)[AVPs]
--------------------------------------------------------------------
(continued from the discovery and handshake phase)
<----- PANA-Auth-Request(x+1)
[Session-Id, EAP{Request}]
-----> PANA-Auth-Answer(x+1) // No piggybacking EAP Response
[Session-Id]
-----> PANA-Auth-Request(y)
[Session-Id, EAP{Response}]
<----- PANA-Auth-Answer(y)
[Session-Id]
<----- PANA-Auth-Request(x+2)
[Session-Id, EAP{Request}]
-----> PANA-Auth-Answer(x+2) // Piggybacking EAP Response
[Session-Id, EAP{Response}]
<----- PANA-Bind-Request(x+3)
[Session-Id, Result-Code, EAP{Success}, Device-Id,
Key-Id, Lifetime, Protection-Cap., PPAC, MAC]
-----> PANA-Bind-Answer(x+3)
[Session-Id, Device-Id, Key-Id, PPAC, MAC]
Figure 4: Example sequence for the authentication and authorization
phase
When an EAP method that is capable of deriving keys is used during
the authentication and authorization phase and the keys are
successfully derived, the PANA message that carries the EAP Success
message (i.e., a PANA-FirstAuth-End-Request or a PANA-Bind-Request
message) and any subsequent message MUST contain a MAC AVP.
The PANA-Bind-Request and the PANA-Bind-Answer message exchange is
also used for binding device identifiers of the PaC and EP(s)to the
PANA SA. To achieve this, the PANA-Bind-Request message MUST contain
the device identifier in a Device-Id AVP for each EP if a Protection-
Capability AVP is included in the message. Otherwise, the message
SHOULD contain the device identifier in a Device-Id AVP for each EP
when a link-layer or IP address is used as the device identifier of
the PaC. The PANA-Bind-Answer message MUST contain the PaC's device
identifier in a Device-Id AVP when it is already presented with that
of EP(s) in the request with using the same type of device identifier
as contained in the request. If the PANA-Bind-Answer message sent
from the PaC does not contain a Device-Id AVP with the same device
identifier type contained in the request, the PAA sends a PANA-Error-
Request message with a PANA_MISSING_AVP result code, and wait for a
PANA-Error-Answer message to terminate the session. The PANA-Bind-
Request message with a PANA_SUCCESS result code MUST also contain a
Protection-Capability AVP if link-layer or network-layer ciphering is
enabled after the authentication and authorization phase. The PANA-
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Bind-Request message MAY also contain a Protection-Capability AVP to
indicate if link-layer or network-layer ciphering should be enabled
after the authentication and authorization phase. No link-layer or
network-layer specific information is included in the Protection-
Capability AVP. It is assumed that the PAA is aware of the security
capabilities of the access network. The PANA protocol does not
specify how the PANA SA and the Protection-Capability AVP will be
used to provide per-packet protection for data traffic.
Additionally, the PANA-Bind-Request message with a PANA_SUCCESS
result code MUST include a Post-PANA-Address-Configuration (PPAC)
AVP, which helps the PAA to inform the PaC about whether a new IP
address MUST be configured and the available methods to do so. In
this case, the PaC MUST include a PPAC AVP in the PANA-Bind-Answer
message in order to indicate its choice of method when there is a
match between the methods offered by the PAA and the methods
available on the PaC. When there is no match, the PaC MUST send a
PANA-Error-Request message with a PANA_PPAC_CAPABILITY_UNSUPPORTED
result code and terminate the PANA session.
PANA-Bind-Request and PANA-Bind-Answer messages MUST be retransmitted
based on the retransmission rule described in Section 5.2.
EAP authentication can fail at a pass-through authenticator without
sending an EAP Failure message [I-D.ietf-eap-statemachine]. When
this occurs, the PAA SHOULD send a PANA-Error-Request message to the
PaC with using PANA_UNABLE_TO_COMPLY result code. The PaC SHOULD not
change its state unless the error message is secured by PANA or
lower-layer. In any case, a more appropriate way is to rely on a
timeout on the PaC.
There is a case where EAP authentication succeeds with producing an
EAP Success message but network access authorization fails due to,
e.g., authorization rejected by a AAA or authorization locally
rejected by the PAA. When this occurs, the PAA MUST send a PANA-
Bind-Request with a result code PANA_AUTHORIZATION_REJECTED. If a
AAA-Key is established between the PaC and the PAA by the time when
the EAP Success message is generated by the EAP server (this is the
case when the EAP method provides protected success indication), the
PANA-Bind-Request and PANA-Bind-Answer messages MUST be protected
with a MAC AVP and carry a Key-Id AVP. The AAA-Key and the PANA
session MUST be deleted immediately after the PANA-Bind message
exchange.
4.4 Access Phase
Once the authentication and authorization phase or the re-
authentication phase successfully completes, the PaC gains access to
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the network and can send and receive IP data traffic through the
EP(s) and the PANA session enters the access phase. In this phase,
PANA-Ping-Request and PANA-Ping-Answer messages can be used for
testing the liveness of the PANA session on the PANA peer. Both the
PaC and the PAA are allowed to send a PANA-Ping-Request message to
the communicating peer whenever they need to make sure the
availability of the session on the peer and expect the peer to return
a PANA-Ping-Answer message. Both PANA-Ping-Request and PANA-Ping-
Answer messages MUST be protected with a MAC AVP when a PANA SA is
available.
Implementations MUST limit the rate of performing this test. The PaC
and the PAA can handle rate limitation on their own, they do not have
to perform any coordination with each other. There is no negotiation
of timers for this purpose.
Figure 5 and Figure 6 show liveness tests as they are initiated by
the PaC and the PAA respectively.
PaC PAA Message(sequence number)[AVPs]
------------------------------------------------------
-----> PANA-Ping-Request(q)[Session-Id, MAC]
<----- PANA-Ping-Answer(q)[Session-Id, MAC]
Figure 5: Example sequence for PaC-initiated liveness test
PaC PAA Message(sequence number)[AVPs]
------------------------------------------------------
<----- PANA-Ping-Request(p)[Session-Id, MAC]
-----> PANA-Ping-Answer(p)[Session-Id, MAC]
Figure 6: Example sequence for PAA-initiated liveness test
4.5 Re-authentication Phase
The PANA session in the access phase can enter the re-authentication
phase to extend the current session lifetime by re-executing EAP.
Once the re-authentication phase successfully completes, the session
re-enters the access phase. Otherwise, the session is deleted.
When the PaC wants to initiate re-authentication, it sends a PANA-
Reauth-Request message to the PAA. This message MUST contain a
Session-Id AVP which is used for identifying the PANA session on the
PAA. If the PAA already has an established PANA session for the PaC
with the matching session identifier, it MUST first respond with a
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PANA-Reauth-Answer message, followed by a PANA-Auth-Request that
starts a new EAP authentication. If the PAA cannot identify the
session, it MAY respond with a PANA-Error-Request message with a
result code PANA_UNKNOWN_SESSION_ID. Transmission of this error
request is made optional in case this behavior is leveraged for a DoS
attack on the PAA.
The PaC may receive a PANA-Auth-Request before receiving the answer
to its outstanding PANA-Reauth-Request. This condition can arise due
to packet re-ordering or a race condition between the PaC and PAA
when they both attempt to engage in re-authentication. The PaC MUST
keep discarding the received PANA-Auth-Requests until it receives the
answer to its request.
When the PAA initiates re-authentication, it sends a PANA-Auth-
Request message containing the session identifier for the PaC to
enter the re-authentication phase. The PAA SHOULD initiate EAP re-
authentication before the current session lifetime expires.
Re-authentication of an on-going PANA session MUST maintain the
existing sequence numbers.
For any re-authentication, if there is an established PANA SA, PANA-
Auth-Request and PANA-Auth-Answer messages MUST be protected by
adding a MAC AVP to each message. Any subsequent EAP authentication
MUST be performed with the same ISP and NAP that was selected during
the discovery and handshake phase. An example sequence for re-
authentication phase initiated by the PaC is shown in Figure 7.
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PaC PAA Message(sequence number)[AVPs]
------------------------------------------------------
-----> PANA-Reauth-Request(q)
[Session-Id, MAC]
<----- PANA-Reauth-Answer(q)
[Session-Id, MAC]
<----- PANA-Auth-Request(p)
[Session-Id, EAP{Request}, MAC]
-----> PANA-Auth-Answer(p) // No piggybacking EAP Response
[Session-Id, MAC]
-----> PANA-Auth-Request(q+1)
[Session-Id, EAP{Response}, MAC]
<----- PANA-Auth-Answer(q+1) // No piggybacking EAP Response
[Session-Id, MAC]
<----- PANA-Auth-Request(p+1)
[Session-Id, EAP{Request}, MAC]
-----> PANA-Auth-Answer(p+1) // Piggybacking EAP Response
[Session-Id, EAP{Response}, MAC]
<----- PANA-Bind-Request(p+2)
[Session-Id, Result-Code, EAP{Success}, Device-Id, Key-Id,
Lifetime, Protection-Cap., PPAC, MAC]
-----> PANA-Bind-Answer(p+2)
[Session-Id, Device-Id, Key-Id, PPAC, MAC]
Figure 7: Example sequence for the re-authentication phase initiated
by PaC
4.6 Termination Phase
A procedure for explicitly terminating a PANA session can be
initiated either from the PaC (i.e., disconnect indication) or from
the PAA (i.e., session revocation). The PANA-Termination-Request and
PANA-Termination-Answer message exchanges are used for disconnect
indication and session revocation procedures.
The reason for termination is indicated in the Termination-Cause AVP.
When there is an established PANA SA between the PaC and the PAA, all
messages exchanged during the termination phase MUST be protected
with a MAC AVP. When the sender of the PANA-Termination-Request
message receives a valid acknowledgment, all states maintained for
the PANA session MUST be deleted immediately.
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PaC PAA Message(sequence number)[AVPs]
------------------------------------------------------
-----> PANA-Termination-Request(q)[Session-Id, MAC]
<----- PANA-Termination-Answer(q)[Session-Id, MAC]
Figure 8: Example sequence for the termination phase triggered by PaC
4.7 Separate NAP and ISP Authentication
PANA allows running at most two EAP sessions in sequence in the
authentication and authorization phase to support separate NAP and
ISP authentication as described in this section. A typical network
access authentication includes execution of one EAP method with the
ISP. This separation allows the PaC to perform an additional
authentication method for receiving differentiated services from the
NAP.
Currently, running multiple EAP sessions in sequence in the
authentication and authorization phase is designed only for separate
NAP and ISP authentication. It is not for running arbitrary number
of EAP sessions in sequence, or giving the PaC another chance to try
another EAP authentication method within an integrated NAP and ISP
authentication when an EAP authentication method fails.
Within separate NAP and ISP authentication, the NAP authentication
and the ISP authentication are considered completely independent.
Presence or success of one should not effect the other. Making a
network access authorization decision based on the success or failure
of each authentication is a network policy issue.
4.7.1 Negotiating Separate NAP and ISP Authentication
When the PaC and PAA negotiates in the discovery and handshake phase
to perform separate NAP and ISP authentication, the PaC and the PAA
operate in the following way in addition to the behavior defined in
Section 4.2
In the discovery and handshake phase, the PAA MAY advertise
availability of separate NAP and ISP authentication ([I-D.ietf-pana-
framework]) by setting the S-flag on the PANA header of the PANA-
Start-Request message.
If the S-flag of the received PANA-Start-Request message is set, the
PaC can indicate its desire to perform separate NAP and ISP
authentication by setting the S-flag in the PANA-Start-Answer
message. If the S-flag of the received PANA-Start-Request message is
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not set, the PaC MUST NOT set the S-flag in the PANA-Start-Answer
message sent back to the PAA.
If the S-flag in the PANA-Start-Answer message is not set, only one
authentication is performed (ISP-only) and the processing occurs as
described in Section 4.2.
When the S-flag is set in a PANA-Start-Request message, the initial
EAP Request message MUST NOT be carried in the PANA-Start-Request
message. (If the initial EAP Request message were contained in the
PANA-Start-Request message during the S-flag negotiation, the PaC
cannot tell whether the EAP Request message is for NAP authentication
or ISP authentication.)
4.7.2 Execution of Separate NAP and ISP Authentication
When the PaC and PAA have negotiated in the discovery and handshake
phase to perform separate NAP and ISP authentication, the PaC and the
PAA operate in the following way in addition to the behavior defined
in Section 4.3
o The S-flag of PANA-Auth-Request and PANA-Auth-Answer messages MUST
be set.
o An EAP Success/Failure message is carried in a PANA-FirstAuth-End-
Request (PFER) message as well as a PANA-Bind-Request (PBR)
message. The PANA-FirstAuth-End-Request message MUST be used at
the end of the first EAP authentication and the PANA-Bind-Request
MUST be used for the second EAP authentication. The PANA-
FirstAuth-End-Request messages MUST be acknowledged with a PANA-
FirstAuth-End-Answer (PFEA) message.
o If the first EAP authentication has failed, the PAA can choose not
to perform the second EAP authentication by clearing the S-flag of
the PANA-FirstAuth-End-Request message. In this case, the S-flag
of the PANA-FirstAuth-End-Answer message sent by the PaC MUST be
cleared. If the S-flag of the PANA-FirstAuth-End-Request message
is set when the first EAP authentication has failed, the PaC can
choose not to perform the second EAP authentication by clearing
the S-flag of the PANA-FirstAuth-End-Answer message. If the first
EAP authentication failed and the S-flag is not set in the PANA-
FirstAuth-End-Answer message as a result of those operations, the
PANA session MUST be immediately deleted. Otherwise, the second
EAP authentication MUST be performed.
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o The PAA determines the execution order of NAP authentication and
ISP authentication. In this case, the PAA can indicate which
authentication (NAP authentication or ISP authentication) is
currently occurring by using N-flag in the PANA message header.
When NAP authentication is being performed, the N-flag MUST be
set. When ISP authentication is being performed, the N-flag MUST
NOT be set. The N-flag MUST NOT be set when S-flag is not set.
When the PaC and PAA have negotiated in the discovery and handshake
phase to perform separate NAP and ISP authentication, and the lower-
layer is insecure, the two EAP authentication methods used in the
separate authentication MUST be capable of deriving keys (AAA-Key).
4.7.3 AAA-Key Calculation
When the PaC and PAA have negotiated in the discovery and handshake
phase to perform separate NAP and ISP authentication, if the lower-
layer is insecure, the two EAP authentication methods used in the
separate authentication MUST be capable of deriving keys. In this
case, if the first EAP authentication is successful, the PANA-
FirstAuth-End-Request and PANA-FirstAuth-End-Answer messages as well
as PANA-Auth-Request and PANA-Auth-Answer messages in the second EAP
authentication MUST be protected with the key derived from the AAA-
Key for the first EAP authentication. The PANA-Bind-Request and
PANA-Bind-Answer messages and all subsequent PANA messages exchanged
in the access phase, re-authentication phase and termination phase
MUST be protected either with the AAA-Key for the first EAP
authentication if the first EAP authentication succeeds and the
second EAP authentication fails, or with the AAA-Key for the second
EAP authentication if the first EAP authentication fails and the
second EAP authentication succeeds, or with the compound AAA-Key
derived from the two AAA-Keys, one for the first EAP authentication
and the other from the second EAP authentication, if both the first
and second EAP authentication succeed. See Section 5.3 for how to
derive the AAA-Key.
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5. Protocol Design Details and Processing Rules
5.1 Transport Layer
PANA uses UDP as its transport layer protocol. The UDP port number
is TBD. All messages except for PANA-PAA-Discover are always
unicast. The PANA-PAA-Discover message MAY be unicast when the PaC
knows the IP address of the PAA.
5.1.1 Fragmentation
PANA does not provide fragmentation of PANA messages. Instead, it
relies on fragmentation provided by EAP methods and IP layer when
needed.
5.2 Sequence Number and Retransmission
PANA uses sequence numbers to provide ordered and reliable delivery
of messages.
The PaC and PAA maintain two sequence numbers: the next one to be
used for a request it initiates and the next one it expects to see in
a request from the other end. These sequence numbers are 32-bit
unsigned numbers. They are monotonically incremented by 1 as new
requests are generated and received, and wrapped to zero on the next
message after 2^32-1. Answers always contain the same sequence
number as the corresponding request. Retransmissions reuse the
sequence number contained in the original packet.
The initial sequence numbers (ISN) are randomly picked by the PaC and
PAA as they send their very first request messages. PANA-PAA-
Discover message carries sequence number 0.
When a request message is received, it is considered valid in terms
of sequence numbers if and only if its sequence number matches the
expected value. This check does not apply to the PANA-PAA-Discover,
PANA-Start-Request messages.
When an answer message is received, it is considered valid in terms
of sequence numbers if and only if its sequence number matches that
of the currently outstanding request. A peer can only have one
outstanding request at a time.
PANA messages are retransmitted based on a timer until a response is
received (in which case the retransmission timer is stopped) or the
number of retransmission reaches the maximum value (in which case the
PANA session MUST be deleted immediately).
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The initial discovery and handshake phase requires special handling.
The PaC MUST retransmit the PANA-PAA-Discover message if a subsequent
PANA-Start-Request message is not received in time. Even though a
PANA-Start-Request message is received, the PANA-PAA-Discover message
may still have to be retransmitted. This is because stateless PAA
discovery requires one time transmission of a solicited PANA-Start-
Request message. The PAA MUST NOT start a timer and retransmit the
request in order to avoid state creation. If the received PANA-
Start-Request message included a Cookie AVP (an indication of
stateless PAA discovery), the PaC MUST retransmit the PANA-PAA-
Discover message until the first PANA-Auth-Request message is
received. Otherwise, the PaC can rely on the PAA to retransmit the
PANA-Start-Request message as soon as the PaC receives the first one
(i.e., the PaC can stop sending the PANA-PAA-Discover message).
The retransmission timers SHOULD be calculated as described in
[RFC2988] to provide congestion control. See Section 8 for default
timer and maximum retransmission count parameters.
The PaC and PAA MUST respond to duplicate requests. The last
transmitted answer MAY be cached in case it is not received by the
peer and that generates a retransmission of the last request. When
available, the cached answer can be used instead of fully processing
the retransmitted request and forming a new answer from scratch.
PANA MUST NOT generate EAP message duplication. EAP payload of a
retransmitted PANA message MUST NOT be passed to the EAP layer.
5.3 PANA Security Association
A PANA SA is created as an attribute of a PANA session when EAP
authentication succeeds with a creation of a AAA-Key. A PANA SA is
not created when the PANA authentication fails or no AAA-Key is
produced by any EAP authentication method. In the case where two EAP
sessions are performed in sequence in the PANA authentication and
authorization phase, it is possible that two AAA-Keys are derived.
If this happens, the PANA SA MUST be generated from both AAA-Keys.
When a new AAA-Key is derived in the PANA re-authentication phase,
any key derived from the old AAA-Key MUST be updated to a new one
that is derived from the new AAA-Key. In order to distinguish the
new AAA-Key from old ones, one Key-Id AVP MUST be carried in PANA-
Bind-Request and PANA-Bind-Answer messages or PANA-FirstAuth-End-
Request and PANA-FirstAuth-End-Answer messages at the end of the EAP
authentication which resulted in deriving a new AAA-Key. The Key-Id
AVP is of type Unsigned32 and MUST contain a value that uniquely
identifies the AAA-Key within the PANA session. The PANA-Bind-Answer
message (or the PANA-FirstAuth-End-Answer message) sent in response
to a PANA-Bind-Request message (or a PANA-FirstAuth-End-Request
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message) with a Key-Id AVP MUST contain a Key-Id AVP with the same
AAA-Key identifier carried in the request. PANA-Bind-Request, PANA-
Bind-Answer, PANA-FirstAuth-End-Request and PANA-FirstAuth-End-Answer
messages with a Key-Id AVP MUST also carry a MAC AVP whose value is
computed by using the new PANA_MAC_KEY derived from the new AAA-Key
(or the new pair of AAA-Keys when the PANA_MAC_KEY is derived from
two AAA-Keys). Although the specification does not mandate a
particular method for calculation of the Key-Id AVP value, a simple
method is to use monotonically increasing numbers.
The PANA session lifetime is bounded by the lifetime granted by the
authentication server (same as the AAA-Key lifetime). The lifetime
of the PANA SA (hence the PANA_MAC_KEY) is the same as the lifetime
of the PANA session. The created PANA SA is deleted when the
corresponding PANA session is deleted.
PANA SA attributes as well as PANA session attributes are listed
below:
PANA Session attributes:
* Session-Id
* Device-Id of PaC
* IP address and UDP port number of the PaC.
* IP address of PAA
* List of device identifiers of EPs
* Sequence number of the last transmitted request
* Sequence number of the last received request
* Last transmitted message payload
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* Retransmission interval
* Session lifetime
* Protection-Capability
* PANA SA attributes:
+ Nonce generated by PaC (PaC_nonce)
+ Nonce generated by PAA (PAA_nonce)
+ AAA-Key
+ AAA-Key Identifier
+ PANA_MAC_KEY
The PANA_MAC_KEY is derived from the available AAA-Key(s) and it is
used to integrity protect PANA messages. If there is only one AAA-
Key available, e.g., due to ISP-only authentication, or with one
failed and one successful separate NAP and ISP authentication (see
Section 4.7), the PANA_MAC_KEY computation is based on that single
key. Otherwise, two AAA-Keys available to PANA can be combined in
following way ('|' indicates concatenation):
AAA-Key = AAA-Key1 | AAA-Key2
The PANA_MAC_KEY is computed in the following way:
PANA_MAC_KEY = The first N bits of
HMAC_SHA1(AAA-Key, PaC_nonce | PAA_nonce | Session-ID)
where the value of N depends on the integrity protection algorithm in
use, i.e., N=160 for HMAC-SHA1. The length of the AAA-Key MUST be N
bits or longer. See Section Section 5.4 for the detailed usage of
the PANA_MAC_KEY.
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5.4 Message Authentication Code
A PANA message can contain a MAC (Message Authentication Code) AVP
for cryptographically protecting the message.
When a MAC AVP is included in a PANA message, the value field of the
MAC AVP is calculated by using the PANA_MAC_KEY in the following way:
MAC AVP value = PANA_MAC_PRF(PANA_MAC_KEY, PANA_PDU)
where PANA_PDU is the PANA message including the PANA header, with
the MAC AVP value field first initialized to 0. PANA_MAC_PRF
represents the pseudo random function corresponding to the MAC
algorithm specified in the MAC AVP. In this version of draft,
PANA_MAC_PRF is HMAC-SHA1. The PaC and PAA MUST use the same
algorithm to calculate a MAC AVP they originate and receive. The
algorithm is determined by the PAA when a PANA-Bind-Request with a
MAC AVP is sent. When the PaC does not support the MAC algorithm
specified in the PANA-Bind-Request message, it MUST silently discard
the message. The PAA MUST NOT change the MAC algorithm throughout
the continuation of the PANA session.
5.5 Message Validity Check
When a PANA message is received, the message is considered to be
invalid at least when one of the following conditions are not met:
o Each field in the message header contains a valid value including
sequence number, message length, message type, version number,
flags, etc.
o The message type is one of the expected types in the current
state. Specifically the following messages are unexpected and
invalid:
* In the discovery and handshake phase:
+ PANA-Termination-Request and PANA-Ping-Request.
+ PANA-Bind-Request.
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+ PANA-Update-Request.
+ PANA-Reauth-Request.
+ PANA-Error-Request.
* In the authentication and authorization phase and the re-
authentication phase:
+ PANA-PAA-Discover.
+ PANA-Update-Request.
+ PANA-Start-Request after a PaC receives the first valid
PANA-Auth-Request.
+ PANA-Termination-Request before the PaC receives the first
successful PANA-Bind-Request.
* In the access phase:
+ PANA-Start-Request as well as a non-duplicate PANA-Bind-
Request.
+ PANA-PAA-Discover.
* In the termination phase:
+ PANA-PAA-Discover.
+ All requests but PANA-Termination-Request.
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o The message payload contains a valid set of AVPs allowed for the
message type and there is no missing AVP that needs to be included
in the payload.
o Each AVP is decoded correctly.
o When a MAC AVP is included, the AVP value matches the MAC value
computed against the received message.
o When a Device-Id AVP is included, the AVP is valid if the device
identifier type contained in the AVP is supported (check performed
by both the PaC and the PAA) and is the requested one (check
performed by the PAA only). Note that a Device-Id AVP carries the
device identifier of the PaC in messages from the PaC to the PAA
and the device identifier(s) of the EP(s) in messages from the PAA
to the PaC.
Invalid messages MUST be discarded in order to provide robustness
against DoS attacks. In addition, an error notification message MAY
be returned to the sender. See Section 5.10 for details.
5.6 Device ID Choice
The device identifier used in the context of PANA can be an IP
address, a MAC address, or an identifier that is not carried in data
packets but has local significance in identifying a connected device
(e.g., circuit id, PPP interface id). The last type of identifiers
are commonly used in point-to-point links where MAC addresses are not
available and lower-layers are already physically or
cryptographically secured.
It is assumed that the PAA knows the link type and the security
mechanisms being provided or required on the access network (e.g.,
based on physical security, link-layer ciphers enabled before or
after PANA, or IPsec). Based on that information, the PAA can decide
what type of EP device id will be usedused when running PANA with the
client.
When IPsec-based security [I-D.ietf-pana-ipsec] is the choice of
access control, the PAA SHOULD provide IP address(es) as EP(s)'
device ID, and expect the PaC to provide its IP address in return.
Similarly, IP addresses are used when the EP(s) is not on the same IP
subnet as the PaC is.
In other cases, MAC addresses are used as device identifiers when
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they are available.
If non-IPsec access control is enabled, and a MAC address is not
available, locally-significant identifiers (e.g., as a circuit id)
MUST be used as device id. Note that these identifiers are not
exchanged within PANA messages. Instead, peers rely on lower-layers
to provide them along with received PANA messages.
5.7 PaC Updating its IP Address
A PaC's IP address can change in certain situations. For example,
the PANA framework [I-D.ietf-pana-framework] describes a case in
which a PaC replaces a pre-PANA address (PRPA) with a post-PANA
address (POPA). In order to establish reachability, the PAA needs to
be notified about the change of PaC address.
After the PaC has changed its address, it MUST send a PANA-Update-
Request message to the PAA. The PAA MUST update the PANA session
with the new PaC address (source IP address) and return a PANA-
Update-Answer message. If there is an established PANA SA, both
PANA-Update-Request and PANA-Update-Answer messages MUST be protected
with a MAC AVP.
5.8 Session Lifetime
The authentication and authorization phase determines the PANA
session lifetime when the network access authorization succeeds. The
Session-Lifetime AVP MAY be optionally included in the PANA-Bind-
Request message to inform the PaC about the valid lifetime of the
PANA session. It MUST be ignored when included in other PANA
messages.
The lifetime is a non-negotiable parameter that can be used by the
PaC to manage PANA-related state. The PaC does not have to perform
any actions when the lifetime expires, other than optionally purging
local state. The PAA SHOULD initiate the PANA re-authentication
phase before the current session lifetime expires.
The PaC and PAA MAY optionally rely on lower-layer indications to
expedite the detection of a disconnected peer. Availability and
reliability of such indications depend on the specific access
technologies. A PANA peer can use the PANA-Ping exchange to verify
the disconnection before taking an action.
The session lifetime parameter is not related to the transmission of
PANA-Ping-Request messages. These messages can be used for
asynchronously verifying the liveness of the peer. The decision to
send a PANA-Ping-Request message is taken locally and does not
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require coordination between the peers.
When separate ISP and NAP authentication is performed, it is possible
that different authorization lifetime values are associated with the
two EAP authentication sessions. In this case, the smaller
authorization lifetime value MUST be used for calculating the PANA
Session-Lifetime value. As a result, both NAP and ISP authentication
will be performed in the re-authentication phase.
5.9 Network Selection
The PANA discovery and handshake phase allows the PaC to learn
identity of the NAP and a list of ISPs that are available through the
NAP. The PaC can not only learn the ISPs but also convey the
selected ISP explicitly during the handshake phase. The PAA is
assumed to be pre-configured with the information of ISPs that are
served by the NAP.
A PANA-Start-Request message sent from the PAA MAY contain zero or
one NAP-Information AVP, and zero or more ISP-Information AVPs. The
PaC MAY indicate its choice of ISP by including an ISP-Information
AVP in the PANA-Start-Answer message. The PaC MAY convey its ISP
even when there is no ISP-Information AVP contained in the PANA-
Start-Request message. The PaC can do that when it is pre-configured
with ISP information.
In the absence of an ISP explicitly selected and conveyed by the PaC,
ISP selection is typically performed based on the client identifier
(e.g., using the realm portion of an NAI carried in EAP method). A
backend AAA protocol (e.g., RADIUS) will run between the AAA client
on the PAA and a AAA server in the selected ISP domain.
The PANA-based ISP selection mechanism dictates the next-hop AAA
proxy on the PAA. If the NAP requires all AAA traffic to go through
its local AAA proxy, it may have to rely on a mechanism to relay the
selected ISP information from PAA (AAA client) to the local AAA
proxy. The local AAA proxy can forward the AAA traffic to the
selected ISP domain upon processing. Further details, including how
the AAA client relays AAA routing information to the AAA proxy, are
outside the scope of PANA.
An alternative ISP discovery mechanism is outlined in [I-D.adrangi-
eap-network-discovery] which suggests advertising ISP information in-
band with the ongoing EAP method execution. Deployments using the
PANA's built-in ISP discovery mechanism need not use the other
mechanism.
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5.10 Error Handling
A PANA-Error-Request message MAY be sent by either the PaC or the PAA
when a badly formed PANA message is received or in case of other
errors. The receiver of this request MUST respond with a PANA-Error-
Answer message. If the cause of this error message was a request
message (e.g., PANA-PAA-Discover or *-Request), then the request MAY
be retransmitted immediately without waiting for its retransmission
timer to go off. If the cause of the error was a response message,
the receiver of the PANA-Error-Request message SHOULD NOT resend the
same response until it receives the next request.
Erroneous PANA messages may be exploited by adversaries to launch DoS
attacks on the victims. Unless the PaC or PAA rate-limits the
generated PANA-Error-Request messages it may be overburdened by
having to respond to bogus messages. Limiting the number of error
notifications sent to a given peer during a (configurable) period of
time may be useful.
When an error message is sent unprotected (i.e., no MAC AVP) and the
lower-layer is insecure, the error message is treated as an
informational message. The receiver of such an error message MUST
NOT change its state unless the error persists and the PANA session
is not making any progress.
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6. PANA Headers and Formats
This section defines message formats for PANA protocol.
6.1 IP and UDP Headers
When a PANA-PAA-Discover message is multicast, IP destination address
of the message is set to a well-known administratively scoped
multicast address (TBD). A PANA-PAA-Discover message MAY be unicast
in some cases as specified in Section 4.2. Any other PANA message is
unicast between the PaC and the PAA. The source and destination
addresses SHOULD be set to the addresses on the interfaces from which
the message will be sent and received, respectively.
When the PANA message is sent in response to a request, the UDP
source and destination ports of the response message MUST be copied
from the destination and source ports of the request message,
respectively.
The source port of an unsolicited PANA message MUST be set to a value
chosen by the sender. The destination port MUST be set to the peer's
port number if it has already been discovered via earlier PANA
exchanges, set to the assigned PANA port (TBD) otherwise.
When the PANA message is sent in response to a request, the UDP
source and destination ports of the response message MUST be copied
from the destination and source ports of the request message,
respectively.
The source port of an unsolicited PANA message MUST be set to a value
chosen by the sender. The destination port MUST be set to the peer's
port number if it has already been discovered via earlier PANA
exchanges, set to the assigned PANA port (TBD) otherwise.
The maximum PANA message size is limited by the maximum UDP payload.
6.2 PANA Header
A summary of the PANA header format is shown below. The fields are
transmitted in network byte order.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Reserved | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVPs ...
+-+-+-+-+-+-+-+-+-+-+-+-+-
Version
This Version field MUST be set to 1 to indicate PANA Version 1.
Reserved
This 8-bit field is reserved for future use, and MUST be set to
zero, and ignored by the receiver.
Message Length
The Message Length field is three octets and indicates the length
of the PANA message including the header fields.
Flags
The Flags field is two octets. The following bits are assigned:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R S N r r r r r r r r r r r r r|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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R(equest)
If set, the message is a request. If cleared, the message is
an answer.
S(eparate)
When the S-flag is set in a PANA-Start-Request message it
indicates that PAA is willing to offer separate NAP and ISP
authentication. When the S-flag is set in a PANA-Start-Answer
message it indicates that the PaC accepts on performing
separate NAP and ISP authentication. The PaC may also respond
with the S-flag not set which implies the PaC has chosen to
authenticate with the ISP only. When the S-flag is set in a
PANA-Auth-Request/Answer, PANA-FirstAuth-End-Request/Answer and
PANA-Bind-Request/Answer messages it indicates that separate
NAP and ISP authentication is being performed in the
authentication and authorization phase. For other cases,
S-flag MUST NOT be set.
N(AP authentication)
When the N-flag is set in a PANA-Auth-Request message, it
indicates that the current EAP authentication is for NAP
authentication. When the N-flag is unset in a PANA-Auth-
Request message, it indicates that the current EAP
authentication is for ISP authentication. The PaC MUST copy
the value of the flag in its requests from the last received
request of the PAA. The value of the flag on an answer MUST be
copied from the request. The N-flag MUST NOT be set when
S-flag is not set.
r(eserved)
These flag bits are reserved for future use, and MUST be set to
zero, and ignored by the receiver.
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Message Type
The Message Type field is two octets, and is used in order to
communicate the message type with the message. The 16-bit address
space is managed by IANA [ianaweb]. PANA uses its own address
space for this field.
Sequence Number
The Sequence Number field contains a 32 bit value.
AVPs
AVPs are a method of encapsulating information relevant to the
PANA message. See section Section 6.3 for more information on
AVPs.
6.3 AVP Header
Each AVP of type OctetString MUST be padded to align on a 32-bit
boundary, while other AVP types align naturally. A number of zero-
valued bytes are added to the end of the AVP Data field till a word
boundary is reached. The length of the padding is not reflected in
the AVP Length field [RFC3588].
The fields in the AVP header are sent in network byte order. The
format of the header is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVP Code | AVP Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AVP Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Vendor-Id (opt) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data ...
+-+-+-+-+-+-+-+-+
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AVP Code
The AVP Code, combined with the Vendor-Id field, identifies the
attribute uniquely. AVP numbers are allocated by IANA [ianaweb].
PANA uses its own address space for this field although some of
the AVP formats are borrowed from Diameter protocol [RFC3588].
AVP Flags
The AVP Flags field is two octets. The following bits are
assigned:
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V M r r r r r r r r r r r r r r|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
M(andatory)
The 'M' Bit, known as the Mandatory bit, indicates whether
support of the AVP is required.
If an AVP with the 'M' bit set is received by the PaC or PAA
and either the AVP or its value is unrecognized, the message
MUST be rejected and the receiver MUST send a PANA-Error-
Request message. If the AVP was unrecognized the PANA-Error-
Request message result code MUST be PANA_AVP_UNSUPPORTED. If
the AVP value was unrecognized the PANA-Error-Request message
result code MUST be PANA_INVALID_AVP_DATA. In either case the
PANA-Error-Request message MUST carry a Failed-AVP AVP
containing the offending mandatory AVP.
AVPs with the 'M' bit cleared are informational only and a
receiver that receives a message with such an AVP that is not
supported, or whose value is not supported, MAY simply ignore
the AVP.
V(endor)
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The 'V' bit, known as the Vendor-Specific bit, indicates
whether the optional Vendor-Id field is present in the AVP
header. When set the AVP Code belongs to the specific vendor
code address space.
r(eserved)
These flag bits are reserved for future use, and MUST be set to
zero, and ignored by the receiver.
Unless otherwise noted, AVPs defined in this document will have
the following default AVP Flags field settings: The 'M' bit MUST
be set. The 'V' bit MUST NOT be set.
AVP Length
The AVP Length field is four octets, and indicates the number of
octets in this AVP including the AVP Code, AVP Length, AVP Flags,
and the AVP data.
Reserved
This two-octet field is reserved for future use, and MUST be set
to zero, and ignored by the receiver.
Vendor-Id
The Vendor-Id field is present if the 'V' bit is set in the AVP
Flags field. The optional four-octet Vendor-Id field contains the
IANA assigned "SMI Network Management Private Enterprise Codes"
[ianaweb] value, encoded in network byte order. Any vendor
wishing to implement a vendor-specific PANA AVP MUST use their own
Vendor-Id along with their privately managed AVP address space,
guaranteeing that they will not collide with any other vendor's
vendor-specific AVP(s), nor with future IETF applications.
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Data
The Data field is zero or more octets and contains information
specific to the Attribute. The format and length of the Data
field is determined by the AVP Code and AVP Length fields.
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7. PANA Messages, Message Specifications and AVPs
7.1 PANA Messages
Each Request/Answer message pair is assigned a message ID, and the
sub-type (i.e., request or answer) is identified via the 'R' bit in
the Message Flags field of the PANA header.
Every PANA message MUST contain a message ID in its header's
Message-Id field, which is used to determine the action that is to be
taken for a particular message. Figure 9 lists all PANA messages
defined in this document:
Message-Name Abbrev. ID PaC<->PAA Ref.
-----------------------------------------------------------
PANA-PAA-Discover PDI 1 --------> 7.2.1
PANA-Start-Request PSR 2 <-------- 7.2.2
PANA-Start-Answer PSA 2 --------> 7.2.3
PANA-Auth-Request PAR 3 <-------> 7.2.4
PANA-Auth-Answer PAN 3 <-------> 7.2.5
PANA-Reauth-Request PRAR 4 --------> 7.2.6
PANA-Reauth-Answer PRAA 4 <-------- 7.2.7
PANA-Bind-Request PBR 5 <-------- 7.2.8
PANA-Bind-Answer PBA 5 --------> 7.2.9
PANA-Ping-Request PPR 6 <-------> 7.2.10
PANA-Ping-Answer PPA 6 <-------> 7.2.11
PANA-Termination-Request PTR 7 <-------> 7.2.12
PANA-Termination-Answer PTA 7 <-------> 7.2.13
PANA-Error-Request PER 8 <-------> 7.2.14
PANA-Error-Answer PEA 8 <-------> 7.2.15
PANA-FirstAuth-End-Request PFER 9 <-------- 7.2.16
PANA-FirstAuth-End-Answer PFEA 9 --------> 7.2.17
PANA-Update-Request PUR 10 <-------> 7.2.18
PANA-Update-Answer PUA 10 <-------> 7.2.19
-----------------------------------------------------------
Figure 9: Table of PANA Messages
7.2 PANA Message ABNF Specification
Every PANA message defined MUST include a corresponding ABNF
[RFC2234] specification, which is used to define the AVPs that MUST
or MAY be present. The following format is used in the definition:
message-def = Message-Name "::=" PANA-message
message-name = PANA-name
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PANA-name = ALPHA *(ALPHA / DIGIT / "-")
PANA-message = header [ *fixed] [ *required] [ *optional]
[ *fixed]
header = "< PANA-Header: " Message-Id
[r-bit] [s-bit] [n-bit] ">"
Message-Id = 1*DIGIT
; The message code assigned to the message
r-bit = ", REQ"
; If present, the 'R' bit in the Message
; Flags is set, indicating that the message
; is a request, as opposed to an answer.
s-bit = ", SEP"
; If present, the 'S' bit in the Message
; Flags is set, indicating support for
; separate NAP and ISP authentication.
n-bit = ", NAP"
; If present, the 'N' bit in the Message
; Flags is set, indicating that current
; EAP authentication is for NAP authentication.
fixed = [qual] "<" avp-spec ">"
; Defines the fixed position of an AVP
required = [qual] "{" avp-spec "}"
; The AVP MUST be present and can appear
; anywhere in the message.
optional = [qual] "[" avp-name "]"
; The avp-name in the 'optional' rule cannot
; evaluate to any AVP Name which is included
; in a fixed or required rule. The AVP can
; appear anywhere in the message.
qual = [min] "*" [max]
; See ABNF conventions, RFC 2234 Section 6.6.
; The absence of any qualifiers depends on whether
; it precedes a fixed, required, or optional
; rule. If a fixed or required rule has no
; qualifier, then exactly one such AVP MUST
; be present. If an optional rule has no
; qualifier, then 0 or 1 such AVP may be
; present.
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;
; NOTE: "[" and "]" have a different meaning
; than in ABNF (see the optional rule, above).
; These braces cannot be used to express
; optional fixed rules (such as an optional
; MAC at the end). To do this, the convention
; is '0*1fixed'.
min = 1*DIGIT
; The minimum number of times the element may
; be present. The default value is zero.
max = 1*DIGIT
; The maximum number of times the element may
; be present. The default value is infinity. A
; value of zero implies the AVP MUST NOT be
; present.
avp-spec = PANA-name
; The avp-spec has to be an AVP Name, defined
; in the base or extended PANA protocol
; specifications.
avp-name = avp-spec / "AVP"
; The string "AVP" stands for *any* arbitrary
; AVP Name, which does not conflict with the
; required or fixed position AVPs defined in
; the message definition.
Example-Request ::= < "PANA-Header: 9999999, REQ >
< Session-Id >
{ Result-Code }
* [ AVP ]
0*1 < MAC >
7.2.1 PANA-PAA-Discover (PDI)
The PANA-PAA-Discover (PDI) message is used to discover the address
of PAA(s). The sequence number in this message is always set to zero
(0).
PANA-PAA-Discover ::= < PANA-Header: 1 >
[ Notification ]
* [ AVP ]
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7.2.2 PANA-Start-Request (PSR)
The PANA-Start-Request (PSR) message is sent by the PAA to the PaC to
advertise availability of the PAA and start PANA authentication. The
PAA sets the sequence number to an initial random value.
PANA-Start-Request ::= < PANA-Header: 2, REQ [, SEP] >
{ Nonce }
[ Cookie ]
[ EAP-Payload ]
[ NAP-Information ]
* [ ISP-Information ]
[ Protection-Capability]
[ PPAC ]
[ Notification ]
* [ AVP ]
7.2.3 PANA-Start-Answer (PSA)
The PANA-Start-Answer (PSA) message is sent by the PaC to the PAA in
response to a PANA-Start-Request message. This message completes the
handshake to start PANA authentication.
PANA-Start-Answer ::= < PANA-Header: 2 [, SEP] >
{ Nonce }
[ Cookie ]
[ EAP-Payload ]
[ ISP-Information ]
[ Notification ]
* [ AVP ]
7.2.4 PANA-Auth-Request (PAR)
The PANA-Auth-Request (PAR) message is either sent by the PAA or the
PaC. Its main task is to carry an EAP-Payload AVP.
PANA-Auth-Request ::= < PANA-Header: 3, REQ [, SEP] [, NAP] >
< Session-Id >
< EAP-Payload >
[ Notification ]
* [ AVP ]
0*1 < MAC >
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7.2.5 PANA-Auth-Answer (PAN)
THe PANA-Auth-Answer (PAN) message is sent by either the PaC or the
PAA in response to a PANA-Auth-Request message. It MAY carry an EAP-
Payload AVP.
PANA-Auth-Answer ::= < PANA-Header: 3 [, SEP] [, NAP] >
< Session-Id >
[ EAP-Payload ]
[ Notification ]
* [ AVP ]
0*1 < MAC >
7.2.6 PANA-Reauth-Request (PRAR)
The PANA-Reauth-Request (PRAR) message is sent by the PaC to the PAA
to re-initiate EAP authentication.
PANA-Reauth-Request ::= < PANA-Header: 4, REQ >
< Session-Id >
[ Notification ]
* [ AVP ]
0*1 < MAC >
7.2.7 PANA-Reauth-Answer (PRAA)
The PANA-Reauth-Answer (PRAA) message is sent by the PAA to the PaC
in response to a PANA-Reauth-Request message.
PANA-Reauth-Answer ::= < PANA-Header: 4 >
< Session-Id >
[ Notification ]
* [ AVP ]
0*1 < MAC >
7.2.8 PANA-Bind-Request (PBR)
The PANA-Bind-Request (PBR) message is sent by the PAA to the PaC to
deliver the result of PANA authentication.
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PANA-Bind-Request ::= < PANA-Header: 5, REQ [, SEP] [, NAP] >
< Session-Id >
{ Result-Code }
{ PPAC }
[ EAP-Payload ]
[ Session-Lifetime ]
[ Protection-Capability ]
[ Key-Id ]
* [ Device-Id ]
[ Notification ]
* [ AVP ]
0*1 < MAC >
7.2.9 PANA-Bind-Answer (PBA)
The PANA-Bind-Answer (PBA) message is sent by the PaC to the PAA in
response to a PANA-Bind-Request message.
PANA-Bind-Answer ::= < PANA-Header: 5 [,SEP] [, NAP] >
< Session-Id >
[ PPAC ]
[ Device-Id ]
[ Key-Id ]
[ Notification ]
* [ AVP ]
0*1 < MAC >
7.2.10 PANA-Ping-Request (PPR)
The PANA-Ping-Request (PPR) message is either sent by the PaC or the
PAA for performing liveness test.
PANA-Ping-Request ::= < PANA-Header: 6, REQ >
< Session-Id >
[ Notification ]
* [ AVP ]
0*1 < MAC >
7.2.11 PANA-Ping-Answer (PPA)
The PANA-Ping-Answer (PPA) message is sent in response to a PANA-
Ping-Request.
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PANA-Ping-Answer ::= < PANA-Header: 6 >
< Session-Id >
[ Notification ]
* [ AVP ]
0*1 < MAC >
7.2.12 PANA-Termination-Request (PTR)
The PANA-Termination-Request (PTR) message is sent either by the PaC
or the PAA to terminate a PANA session.
PANA-Termination-Request ::= < PANA-Header: 7, REQ >
< Session-Id >
< Termination-Cause >
[ Notification ]
* [ AVP ]
0*1 < MAC >
7.2.13 PANA-Termination-Answer (PTA)
The PANA-Termination-Answer (PTA) message is sent either by the PaC
or the PAA in response to PANA-Termination-Request.
PANA-Termination-Answer ::= < PANA-Header: 7 >
< Session-Id >
[ Notification ]
* [ AVP ]
0*1 < MAC >
7.2.14 PANA-Error-Request (PER)
The PANA-Error-Request (PER) message is sent either by the PaC or the
PAA to report an error with the last received PANA message.
PANA-Error-Request ::= < PANA-Header: 8, REQ >
< Session-Id >
< Result-Code >
* [ Failed-AVP ]
[ Notification ]
* [ AVP ]
0*1 < MAC >
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7.2.15 PANA-Error-Answer (PEA)
The PANA-Error-Answer (PEA) message is sent in response to a PANA-
Error-Request.
PANA-Error-Answer ::= < PANA-Header: 8 >
< Session-Id >
[ Notification ]
* [ AVP ]
0*1 < MAC >
7.2.16 PANA-FirstAuth-End-Request (PFER)
The PANA-FirstAuth-End-Request (PFER) message is sent by the PAA to
the PaC to signal the result of the first EAP authentication method
when separate NAP and ISP authentication is performed.
PANA-FirstAuth-End-Request ::= < PANA-Header: 9, REQ [, SEP] [, NAP] >
< Session-Id >
{ Result-Code }
[ EAP-Payload ]
[ Key-Id ]
[ Notification ]
* [ AVP ]
0*1 < MAC >
7.2.17 PANA-FirstAuth-End-Answer (PFEA)
The PANA-FirstAuth-End-Answer (PFEA) message is sent by the PaC to
the PAA in response to a PANA-FirstAuth-End-Request message.
PANA-FirstAuth-End-Answer ::= < PANA-Header: 9, REQ [, SEP] [, NAP] >
< Session-Id >
[ Key-Id ]
[ Notification ]
* [ AVP ]
0*1 < MAC >
7.2.18 PANA-Update-Request (PUR)
The PANA-Update-Request (PUR) message is sent either by the PaC or
the PAA to deliver attribute updates and notifications. In the scope
of this specification only the PaC IP address can be updated via this
mechanism.
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PANA-Update-Request ::= < PANA-Header: 10, REQ >
< Session-Id >
[ Notification ]
* [ AVP ]
0*1 < MAC >
7.2.19 PANA-Update-Answer (PUA)
The PANA-Update-Answer (PUA) message is sent by the PAA to the PaC in
response to a PANA-Update-Request.
PANA-Update-Answer ::= < PANA-Header: 10 >
< Session-Id >
[ Notification ]
* [ AVP ]
0*1 < MAC >
7.3 AVPs in PANA
PANA defines several AVPs that are specific to the protocol. A
number of others AVPs are reused. These are specified in other
documents such as [RFC3588].
The following tables lists the AVPs used in this document, and
specifies in which PANA messages they MAY, or MAY NOT be present.
The table uses the following symbols:
0 The AVP MUST NOT be present in the message.
0+ Zero or more instances of the AVP MAY be present in the
message.
0-1 Zero or one instance of the AVP MAY be present in the message.
It is considered an error if there are more than one instance
of the AVP.
1 One instance of the AVP MUST be present in the message.
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1+ At least one instance of the AVP MUST be present in the
message.
+---------------------------------------------+
| Message |
| Type |
+---+---+---+---+---+----+----+---+---+---+---+
Attribute Name |PDI|PSR|PSA|PAR|PAN|PRAR|PRAA|PBR|PBA|PPR|PPA|
--------------------+---+---+---+---+---+----+----+---+---+---+---+
Cookie | 0 |0-1|0-1| 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Device-Id | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0+|0-1| 0 | 0 |
EAP-Payload | 0 |0-1|0-1| 1 |0-1| 0 | 0 |0-1| 0 | 0 | 0 |
Failed-AVP | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
ISP-Information | 0 | 0+|0-1| 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Key-Id | 0 | 0 | 0 | 0 | 0 | 0 | 0 |0-1|0-1| 0 | 0 |
MAC | 0 | 0 | 0 |0-1|0-1|0-1 |0-1 |0-1|0-1|0-1|0-1|
NAP-Information | 0 |0-1| 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Nonce | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Notification |0-1|0-1|0-1|0-1|0-1|0-1 |0-1 |0-1|0-1|0-1|0-1|
PPAC | 0 |0-1| 0 | 0 | 0 | 0 | 0 | 1 |0-1| 0 | 0 |
Protection-Cap. | 0 |0-1| 0 | 0 | 0 | 0 | 0 |0-1| 0 | 0 | 0 |
Result-Code | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 |
Session-Id | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
Session-Lifetime | 0 | 0 | 0 | 0 | 0 | 0 | 0 |0-1| 0 | 0 | 0 |
Termination-Cause | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
--------------------+---+---+---+---+---+----+----+---+---+---+---+
Figure 10: AVP Occurrence Table (1/2)
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+---------------------------------+
| Message |
| Type |
+---+---+---+---+----+----+---+---+
Attribute Name |PTR|PTA|PER|PEA|PFER|PFEA|PUR|PUA|
--------------------+---+---+---+---+----+----+---+---+
Cookie | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Device-Id | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
EAP-Payload | 0 | 0 | 0 | 0 |0-1 | 0 | 0 | 0 |
Failed-AVP | 0 | 0 | 0+| 0 | 0 | 0 | 0 | 0 |
ISP-Information | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Key-Id | 0 | 0 | 0 | 0 |0-1 |0-1 | 0 | 0 |
MAC |0-1|0-1|0-1|0-1|0-1 |0-1 |0-1|0-1|
NAP-Information | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Nonce | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Notification |0-1|0-1|0-1|0-1|0-1 |0-1 |0-1|0-1|
PPAC | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Protection-Cap. | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Result-Code | 0 | 0 | 1 | 0 | 1 | 0 | 0 | 0 |
Session-Id | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 |
Session-Lifetime | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
Termination-Cause | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
--------------------+---+---+---+---+----+----+---+---+
Figure 11: AVP Occurrence Table (2/2)
7.3.1 Cookie AVP
The Cookie AVP (AVP Code 1) is used for carrying a random value
generated by the PAA. The AVP data is of type OctetString. The
random value is referred to as a cookie and used for making PAA
discovery robust against blind resource consumption DoS attacks. The
exact algorithms and syntax used by the PAA to generate a cookie does
not affect interoperability and not specified in this document. An
example cookie generation algorithm is shown in Section 4.2.
7.3.2 Device-Id AVP
The Device-Id AVP (AVP Code 2) is used for carrying device
identifiers of PaC and EP(s). The AVP data is of Address type
[RFC3588]. IPv4 and IPv6 addresses are encoded as specified in
[RFC3588]. The content and format of data (including byte and bit
ordering) for link-layer addresses is expected to be specified in
specific documents that describe how IP operates over different link-
layers. For instance, [RFC2464]. Address families other than that
are defined for link-layer or IP addresses MUST NOT be used for this
AVP.
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7.3.3 EAP-Payload AVP
The EAP-Payload AVP (AVP Code 3) is used for encapsulating the actual
EAP message that is being exchanged between the EAP peer and the EAP
authenticator. The AVP data is of type OctetString.
7.3.4 Failed-AVP AVP
The Failed-AVP AVP (AVP Code 4) provides debugging information in
cases where a request is rejected or not fully processed due to
erroneous information in a specific AVP. The AVP data is of type
Grouped. The format of the Failed-AVP AVP is defined in [RFC3588].
In case of a failed grouped AVP, the Failed-AVP contains the whole
grouped AVP. In case of a failed AVP inside a grouped AVP, the
Failed-AVP contains the single offending AVP.
7.3.5 ISP-Information AVP
The ISP-Information AVP (AVP Code 5) contains zero or one Provider-
Identifier AVP which carries the identifier of the ISP and one
Provider-Name AVP which carries the name of the ISP. The AVP data is
of type Grouped, and it has the following ABNF grammar:
ISP-Information ::= < AVP Header: 5 >
0*1 { Provider-Identifier }
{ Provider-Name }
* [ AVP ]
7.3.6 Key-Id AVP
The Key-Id AVP (AVP Code 6) is of type Integer32, and contains an
AAA-Key identifier. The AAA-Key identifier is assigned by PAA and
MUST be unique within the PANA session.
7.3.7 MAC AVP
The MAC (Message Authentication Code) AVP is used to integrity
protect PANA messages. The first octet of the this AVP (AVP Code 7)
data contains the MAC algorithm type. Rest of the AVP data payload
contains the MAC encoded in network byte order. The 8-bit Algorithm
name space is managed by IANA [ianaweb]. The AVP length varies
depending on the used algorithm.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm | MAC...
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Algorithm
1 HMAC-SHA1 (20 bytes)
MAC
The Message Authentication Code is encoded in network byte order.
7.3.8 NAP-Information AVP
The NAP-Information AVP (AVP Code 8) contains zero or one Provider-
Identifier AVP which carries the identifier of the NAP and one
Provider-Name AVP which carries the name of the NAP. The AVP data is
of type Grouped, and it has the following ABNF grammar:
NAP-Information ::= < AVP Header: 8 >
0*1 { Provider-Identifier }
{ Provider-Name }
* [ AVP ]
7.3.9 Nonce AVP
The Nonce AVP (AVP Code 9) carries a randomly chosen value that is
used in cryptographic key computations. The AVP data is of type
OctetString and it contains a randomly generated value in opaque
format. The data length MUST be between 8 and 256 bytes inclusive.
7.3.10 Notification AVP
The Notification AVP (AVP Code 10) is optionally used to convey a
displayable message sent by either the PaC or the PAA. It can be
included in any message, whether it is a request or answer. In case
a notification needs to be sent but there is no outgoing PANA message
to deliver this AVP, a PANA-Update-Request that only carries a
Notification AVP SHOULD be generated.
Receipt this AVP does not change PANA state.
AVP data is of type OctetString and it contains UTF-8 encoded ISO
10646 characters [RFC2279]. The length of the displayable message is
determined by the AVP Length field. The message MUST NOT be null
terminated.
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7.3.11 Post-PANA-Address-Configuration (PPAC) AVP
The PPAC AVP (AVP Code 11) is used for conveying the available types
of post-PANA IP address configuration mechanisms when sent by the
PAA, and the chosen one when sent by the PaC. Each possible
mechanisms is represented by a flag. At least one or more of the
flags MUST be set when sent by the PAA, and exactly one flag MUST be
set when sent by the PaC. The AVP data is of type Unsigned32.
The format of the AVP data is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N|D|A|T|I| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PPAC Flags
N (No configuration)
The PaC does not have to (if sent by PAA) or will not (if sent
by PaC) configure a new IP address after PANA.
D (DHCP)
The PaC can (if sent by PAA) or will (if sent by PaC) use DHCP
[RFC2131] [RFC3315] to configure a new IP address after PANA.
A (stateless autoconfiguration)
The PaC can/will use stateless IPv6 address autoconfiguration
[RFC2462] to configure a new IP address after PANA.
T (DHCP with IPsec tunnel mode)
The PaC can/will use [RFC3456] to configure a new IP address
after PANA.
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I (IKEv2)
The PaC can/will use [I-D.ietf-ipsec-ikev2] to configure a new
IP address after PANA.
Reserved
These flag bits are reserved for future use, and MUST be set to
zero, and ignored by the receiver.
Unless the N-flag is set, the PaC MUST configure a new IP address
using one of the methods indicated by the other flags. Refer to
[I-D.ietf-pana-framework] for a detailed discussion on when these
methods can be used.
7.3.12 Protection-Capability AVP
The Protection-Capability AVP (AVP Code 12) indicates the
cryptographic data protection capability supported and required by
the EPs. The AVP data is of type Unsigned32. Below is a list of
valid data values and associated protection capabilities:
0 L2_PROTECTION
1 IPSEC_PROTECTION
7.3.13 Provider-Identifier AVP
The Provider-Identifier AVP (AVP Code 13) is of type Unsigned32, and
contains an IANA assigned "SMI Network Management Private Enterprise
Codes" [ianaweb] value, encoded in network byte order.
7.3.14 Provider-Name AVP
The Provider-Name AVP (AVP Code 14) is of type UTF8String, and
contains the UTF8-encoded name of the provider.
7.3.15 Result-Code AVP
The Result-Code AVP (AVP Code 15) is of type Unsigned32 and indicates
whether an EAP authentication was completed successfully or whether
an error occurred. Here are Result-Code AVP values taken from
[RFC3588] and adapted for PANA.
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7.3.15.1 Authentication Results Codes
These result code values inform the PaC about the authentication and
authorization result. The authentication result and authorization
result can be different as described below, but only one result is
returned to the PaC. These codes are used with PANA-Bind-Request and
PANA-FirstAuth-End-Request messages.
PANA_SUCCESS 2001
Both authentication and authorization processes are successful.
PANA_AUTHENTICATION_REJECTED 4001
Authentication has failed. When this error is returned, it is
assumed that authorization is automatically failed.
PANA_AUTHORIZATION_REJECTED 5003
The authorization process has failed. This error could occur when
authorization is rejected by a AAA server or rejected locally by a
PAA, even if the authentication procedure has succeeded.
7.3.15.2 Protocol Error Result Codes
These codes are used with PANA-Error-Request messages. Unless stated
otherwise, they can be generated by both the PaC and the PAA.
PANA_MESSAGE_UNSUPPORTED 3001
Message type not recognized or supported.
PANA_UNABLE_TO_DELIVER 3002
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The PAA was unable to deliver the EAP payload to the
authentication server. Only the PAA can generate this code.
PANA_INVALID_HDR_BITS 3008
A message was received whose bits in the PANA header were either
set to an invalid combination, or to a value that is inconsistent
with the message type definition.
PANA_INVALID_AVP_FLAGS 3009
A message was received that included an AVP whose flag bits are
set to an unrecognized value, or that is inconsistent with the
AVP's definition.
PANA_AVP_UNSUPPORTED 5001
The received message contained an AVP that is not recognized or
supported and was marked with the Mandatory bit. A PANA message
with this error MUST contain one or more Failed-AVP AVP containing
the AVPs that caused the failure.
PANA_UNKNOWN_SESSION_ID 5002
The message contained an unknown Session-Id. A PANA message
indicating this error MUST include the unknown Session-Id AVP
within a Failed-AVP AVP.
PANA_INVALID_AVP_DATA 5004
The message contained an AVP with an invalid value in its data
portion. A PANA message indicating this error MUST include the
offending AVPs within a Failed-AVP AVP.
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PANA_MISSING_AVP 5005
The message did not contain an AVP that is required by the message
type definition. If this value is sent in the Result-Code AVP, a
Failed-AVP AVP SHOULD be included in the message. The Failed-AVP
AVP MUST contain an example of the missing AVP complete with the
Vendor-Id if applicable. The value field of the missing AVP
should be of correct minimum length and contain zeroes.
PANA_RESOURCES_EXCEEDED 5006
A message was received that cannot be authorized because the
client has already expended allowed resources. An example of this
error condition is a client that is restricted to one PANA session
and attempts to establish a second session. Only the PAA can
generate this code.
PANA_CONTRADICTING_AVPS 5007
The PAA has detected AVPs in the message that contradicted each
other, and is not willing to provide service to the client. One
or more Failed-AVP AVPs MUST be present, containing the AVPs that
contradicted each other. Only the PAA can generate this code.
PANA_AVP_NOT_ALLOWED 5008
A message was received with an AVP that MUST NOT be present. The
Failed-AVP AVP MUST be included and contain a copy of the
offending AVP.
PANA_AVP_OCCURS_TOO_MANY_TIMES 5009
A message was received that included an AVP that appeared more
often than permitted in the message definition. The Failed-AVP
AVP MUST be included and contain a copy of the first instance of
the offending AVP that exceeded the maximum number of occurrences.
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PANA_UNSUPPORTED_VERSION 5011
This error is returned when a message was received, whose version
number is unsupported.
PANA_UNABLE_TO_COMPLY 5012
This error is returned when a request is rejected for unspecified
reasons. For example, when an EAP authentication fails at an EAP
pass-through authenticator without passing an EAP Failure message
to the PAA, a Result-Code AVP with this error code is carried in
the PANA-Error-Request message.
PANA_INVALID_AVP_LENGTH 5014
The message contained an AVP with an invalid length. The PANA-
Error-Request message indicating this error MUST include the
offending AVPs within a Failed-AVP AVP.
PANA_INVALID_MESSAGE_LENGTH 5015
This error is returned when a message is received with an invalid
message length.
PANA_PROTECTION_CAPABILITY_UNSUPPORTED 5016
This error is returned when the PaC receives a PANA-Bind-Request
message with a Protection-Capability AVP and a valid MAC AVP but
does not support the protection capability specified in the
Protection-Capability AVP. Only the PaC can generate this code.
PANA_PPAC_CAPABILITY_UNSUPPORTED 5017
This error is returned when there is no match between the list of
PPAC methods offered by the PAA and the ones available on the PaC.
Only the PaC can generate this code.
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7.3.16 Session-Id AVP
All messages pertaining to a specific PANA session MUST include a
Session-Id AVP (AVP Code 16) which carries a PAA-assigned fixed
session identifier value throughout the lifetime of a session. When
present, the Session-Id AVP SHOULD appear immediately following the
PANA header.
The Session-Id MUST be globally and eternally unique, as it is meant
to identify a PANA session without reference to any other
information, and may be needed to correlate historical authentication
information with accounting information. The PANA Session-Id AVP has
the same format as the Diameter Session-Id AVP [RFC3588].
7.3.17 Session-Lifetime AVP
The Session-Lifetime AVP (AVP Code 17) contains the number of seconds
remaining before the current session is considered expired. The AVP
data is of type Unsigned32.
7.3.18 Termination-Cause AVP
The Termination-Cause AVP (AVP Code 18) is used for indicating the
reason why a session is terminated by the requester. The AVP data is
of type Enumerated. The following Termination-Cause data values are
used with PANA.
LOGOUT 1 (PaC -> PAA)
The client initiated a disconnect
ADMINISTRATIVE 4 (PAA -> PaC)
The client was not granted access, or was disconnected, due to
administrative reasons.
SESSION_TIMEOUT 8 (PAA -> PaC)
The session has timed out, and service has been terminated.
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8. Retransmission Timers
The PANA protocol provides retransmissions for the PANA-PAA-Discover
message and all request messages, with the exception that the PANA-
Start-Answer message is retransmitted instead of the PANA-Start-
Request message in stateless PAA discovery.
PANA retransmission timers are based on the model used in DHCPv6
[RFC3315]. Variables used here are also borrowed from this
specification. PANA is a request response like protocol. The
message exchange terminates when either the request sender
successfully receives the appropriate answer, or when the message
exchange is considered to have failed according to the retransmission
mechanism described below.
The retransmission behavior is controlled and described by the
following variables:
RT Retransmission timeout
IRT Initial retransmission time
MRC Maximum retransmission count
MRT Maximum retransmission time
MRD Maximum retransmission duration
RAND Randomization factor
With each message transmission or retransmission, the sender sets RT
according to the rules given below. If RT expires before the message
exchange terminates, the sender recomputes RT and retransmits the
message.
Each of the computations of a new RT include a randomization factor
(RAND), which is a random number chosen with a uniform distribution
between -0.1 and +0.1. The randomization factor is included to
minimize synchronization of messages.
The algorithm for choosing a random number does not need to be
cryptographically sound. The algorithm SHOULD produce a different
sequence of random numbers from each invocation.
RT for the first message transmission is based on IRT:
RT = IRT + RAND*IRT
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RT for each subsequent message transmission is based on the previous
value of RT:
RT = 2*RTprev + RAND*RTprev
MRT specifies an upper bound on the value of RT (disregarding the
randomization added by the use of RAND). If MRT has a value of 0,
there is no upper limit on the value of RT. Otherwise:
if (RT > MRT)
RT = MRT + RAND*MRT
MRC specifies an upper bound on the number of times a sender may
retransmit a message. Unless MRC is zero, the message exchange fails
once the sender has transmitted the message MRC times.
MRD specifies an upper bound on the length of time a sender may
retransmit a message. Unless MRD is zero, the message exchange fails
once MRD seconds have elapsed since the client first transmitted the
message.
If both MRC and MRD are non-zero, the message exchange fails whenever
either of the conditions specified in the previous two paragraphs are
met.
If both MRC and MRD are zero, the client continues to transmit the
message until it receives a response.
8.1 Transmission and Retransmission Parameters
This section presents a table of values used to describe the message
retransmission behavior of PANA requests and answers that are
retransmitted (REQ_*) and PANA-PAA-Discover message (PDI_*). The
table shows default values.
Parameter Default Description
------------------------------------------------
PDI_IRT 1 sec Initial PDI timeout.
PDI_MRT 120 secs Max PDI timeout value.
PDI_MRC 0 Configurable.
PDI_MRD 0 Configurable.
REQ_IRT 1 sec Initial Request timeout.
REQ_MRT 30 secs Max Request timeout value.
REQ_MRC 10 Max Request retry attempts.
REQ_MRD 0 Configurable.
So for example the first RT for the PBR message is calculated using
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REQ_IRT as the IRT:
RT = REQ_IRT + RAND*REQ_IRT
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9. IANA Considerations
This section provides guidance to the Internet Assigned Numbers
Authority (IANA) regarding registration of values related to the PANA
protocol, in accordance with BCP 26 [IANA]. The following policies
are used here with the meanings defined in BCP 26: "Private Use",
"First Come First Served", "Expert Review", "Specification Required",
"IETF Consensus", "Standards Action".
This section explains the criteria to be used by the IANA for
assignment of numbers within namespaces defined within this document.
For registration requests where a Designated Expert should be
consulted, the responsible IESG area director should appoint the
Designated Expert. For Designated Expert with Specification
Required, the request is posted to the PANA WG mailing list (or, if
it has been disbanded, a successor designated by the Area Director)
for comment and review, and MUST include a pointer to a public
specification. Before a period of 30 days has passed, the Designated
Expert will either approve or deny the registration request and
publish a notice of the decision to the PANA WG mailing list or its
successor. A denial notice must be justified by an explanation and,
in the cases where it is possible, concrete suggestions on how the
request can be modified so as to become acceptable.
9.1 PANA UDP Port Number
PANA uses one well-known UDP port number (Section 5.1, Section 4.2
and Section 6.1), which needs to be assigned by the IANA.
9.2 PANA Multicast Address
PANA uses one well-known administratively scoped IPv4 multicast
address, and one well-known administratively scoped IPv6 multicast
address (Section 4.2 and Section 6.1), which need to be assigned by
the IANA.
9.3 PANA Header
As defined in Section 6.2, the PANA header contains two fields that
requires IANA namespace management; the Message Type and Flags field.
9.3.1 Message Type
The Message Type namespace is used to identify PANA messages. Values
0-65,533 are for permanent, standard message types, allocated by IETF
Consensus [IANA]. This document defines the Message Types 1-10. See
Section 7.2.1 through Section 7.2.19 for the assignment of the
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namespace in this specification.
The values 65,534 and 65,535 (hexadecimal values 0xfffe - 0xffff) are
reserved for experimental messages. As these codes are only for
experimental and testing purposes, no guarantee is made for
interoperability between the communicating PaC and PAA using
experimental commands, as outlined in [IANA-EXP].
9.3.2 Flags
There are 16 bits in the Flags field of the PANA header. This
document assigns bit 0 ('R'equest), bit 1 ('S'eparate) and bit 2
('N'AP Authentication). The remaining bits MUST only be assigned via
a Standards Action [IANA].
9.4 AVP Header
As defined in Section 6.3, the AVP header contains three fields that
requires IANA namespace management; the AVP Code, AVP Flags and
Vendor-Id fields where only the AVP Code and AVP Flags create new
namespaces.
9.4.1 AVP Code
The AVP Code namespace is used to identify attributes. There are
multiple namespaces. Vendors can have their own AVP Codes namespace
which will be identified by their Vendor-ID (also known as
Enterprise-Number) and they control the assignments of their vendor-
specific AVP codes within their own namespace. The absence of a
Vendor-ID or a Vendor-ID value of zero (0) identifies the IETF IANA
controlled AVP Codes namespace. The AVP Codes and sometimes also
possible values in an AVP are controlled and maintained by IANA.
AVP Code 0 is not used. This document defines the AVP Codes 1-18.
See Section 7.3.1 through Section 7.3.18 for the assignment of the
namespace in this specification.
AVPs may be allocated following Designated Expert with Specification
Required [IANA]. Release of blocks of AVPs (more than 3 at a time
for a given purpose) should require IETF Consensus.
Note that PANA defines a mechanism for Vendor-Specific AVPs, where
the Vendor-Id field in the AVP header is set to a non-zero value.
Vendor-Specific AVPs codes are for Private Use and should be
encouraged instead of allocation of global attribute types, for
functions specific only to one vendor's implementation of PANA, where
no interoperability is deemed useful. Where a Vendor-Specific AVP is
implemented by more than one vendor, allocation of global AVPs should
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be encouraged instead.
9.4.2 Flags
There are 16 bits in the AVP Flags field of the AVP header, defined
in Section 6.3. This document assigns bit 0 ('V'endor Specific) and
bit 1 ('M'andatory). The remaining bits should only be assigned via
a Standards Action .
9.5 AVP Values
Certain AVPs in PANA define a list of values with various meanings.
For attributes other than those specified in this section, adding
additional values to the list can be done on a First Come, First
Served basis by IANA [IANA].
9.5.1 Algorithm Values of MAC AVP
As defined in Section 7.3.7, the Algorithm field of MAC AVP (AVP Code
7) defines the value of 1 (one) for HMAC-SHA1.
All remaining values are available for assignment via IETF Consensus
[IANA].
9.5.2 Post-PANA-Address-Configuration AVP Values
As defined in Section 7.3.11, the Post-PANA-Address-Configuration AVP
(AVP Code 11) defines the bits 0 ('N': no configuration), 1 ('D':
DHCP), 2 ('A' stateless autoconfiguration), 3 ('T': DHCP with IPsec
tunnel mode) and 4 ('I': IKEv2).
All remaining values are available for assignment via a Standards
Action [IANA].
9.5.3 Protection-Capability AVP Values
As defined in Section 7.3.12, the Protection-Capability AVP (AVP Code
12) defines the values 0 and 1.
All remaining values are available for assignment via a Standards
Action [IANA].
9.5.4 Result-Code AVP Values
As defined in Section 7.3.15.1 and Section 7.3.15.2 the Result-Code
AVP (AVP Code 15) defines the values 2001, 3001-3002, 3008-3009,
4001, 5001-5009 and 5011-5017.
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All remaining values are available for assignment via IETF Consensus
[IANA].
9.5.5 Termination-Cause AVP Values
As defined in Section 7.3.18, the Termination-Cause AVP (AVP Code 18)
defines the values 1, 4 and 8.
All remaining values are available for assignment via IETF Consensus
[IANA].
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10. Security Considerations
The PANA protocol defines a UDP-based EAP encapsulation that runs
between two IP-enabled nodes on the same IP link. Various security
threats that are relevant to a protocol of this nature are outlined
in [RFC4016]. Security considerations stemming from the use of EAP
and EAP methods are discussed in [RFC3748]. This section provides a
discussion on the security-related issues that are related to PANA
framework and protocol design.
An important element in assessing security of PANA design and
deployment in a network is the presence of lower-layer (physical and
link-layer) security. In the context of this document, lower-layers
are said to be secure if they can prevent eavesdropping and spoofing
of packets. Examples of such networks are physically-secured DSL
networks and 3GPP2 networks with crytographically-secured cdma2000
link-layer. In these examples, the lower-layer security is enabled
even before running the first PANA-based authentication. In the
absence of such a pre-established secure channel, one needs to be
created in conjunction with PANA using a link-layer or network-layer
cryptographic mechanism (e.g., IPsec).
10.1 General Security Measures
PANA provides multiple mechanisms to secure a PANA session.
PANA messages carry sequence numbers, which are monotonically
incremented by 1 with every new request message. These numbers are
randomly initialized at the beginning of the session, and verified
against expected numbers upon receipt. A message whose sequence
number is different than the expected one is silently discarded. In
addition to accomplishing orderly delivery of EAP messages and
duplicate elimination, this scheme also helps prevent an adversary
spoof messages to disturb ongoing PANA and EAP sessions unless it can
also eavesdrop to synchronize on the expected sequence number.
Furthermore, impact of replay attacks is reduced as any stale message
(i.e., a request or answer with an unexpected sequence number) and
any duplicate answer are immediately discarded, and a duplicate
request can trigger transmission of the cached answer (i.e., no need
to process the request and generate a new answer).
The PANA framework defines EP which is ideally located on a network
device that can filter traffic from the PaCs before the traffic
enters the Internet/intranet. A set of filters can be used to
discard unauthorized packets, such as a PANA-Start-Request message
that is received from the segment of the access network where only
the PaCs are supposed to be connected.
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The protocol also provides authentication and integrity protection to
PANA messages when the used EAP method can generate cryptographic
session keys. A PANA SA is generated based on the AAA-Key exported
by the EAP method. This SA is used for generating per-packet MAC to
protect the PANA header and payload (including the complete EAP
message).
The cryptographic protection prevents an adversary from acting as a
man-in-the-middle, injecting messages, replaying messages and
modifying the content of the exchanged messages. Any packet that
fails to pass the MAC verification is silently discarded. The
earliest this protection can be enabled is when the very first PANA-
Bind-Request or PANA-FirstAuth-End-Request message that signals a
successful authentication is generated. Starting with these
messages, any subsequent PANA message until the session gets torn
down can be cryptographically protected.
The PANA SA enables authenticated and integrity protected exchange of
the device ID information between the PaC and PAA. This ensures
there were no man-in-the-middle during the PANA authentication.
The lifetime of the PANA SA is set to PANA session lifetime which is
bounded by the lifetime granted by the authentication server. An
implementation MAY add a tolerance period to that value. Unless the
PANA session is extended by executing another EAP authentication, the
PANA SA is removed when the current session expires.
The ability to use cryptographic protection within PANA is determined
by the used EAP method, which is generally dictated by the deployment
environment. Insecure lower-layers necessitate use of key-generating
EAP methods. In networks where lower-layers are already secured,
cryptographic protection of PANA messages is not necessary.
10.2 Discovery
The discovery and handshake phase is vulnerable to spoofing attacks
as these messages are not authenticated and integrity protected. In
order to prevent very basic denial-of service attacks an adversary
should not be able to cause state creation by sending discovery
messages to the PAA. This protection is achieved by using a cookie-
based scheme (similar to [RFC2522] which allows the responder (PAA)
to be stateless in the first round of message exchange. A return-
routability test does not provide additional protection as PANA
traffic is not routed but simply forwarded on-link. It is difficult
to prevent this threat entirely.
In networks where lower-layers are not secured prior to running PANA,
the capability discovery enabled through inclusion of Protection-
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Capability and Post-PANA-Address-Configuration AVPs in a PANA-Start-
Request message is susceptible to spoofing leading to denial-of
service attacks. Therefore, usage of these AVPs during the discovery
and handshake phase in such insecure networks is NOT RECOMMENDED.
The same AVPs are delivered via an integrity-protected PANA-Bind-
Request upon successful authentication.
10.3 EAP Methods
Eavesdropping EAP messages might cause problems when the EAP method
is weak and enables dictionary or replay attacks or even allows an
adversary to learn the long-term password directly. Furthermore, if
the optional EAP Response/Identity payload is used then it allows the
adversary to learn the identity of the PaC. In such a case a privacy
problem is prevalent.
To prevent these threats, [I-D.ietf-pana-framework] suggests using
proper EAP methods for particular environments. Depending on the
deployment environment an EAP authentication method which supports
user identity confidentiality, protection against dictionary attacks
and session key establishment must be used. It is therefore the
responsibility of the network operators and users to choose a proper
EAP method.
10.4 Separate NAP and ISP Authentication
The PANA design allows running two separate EAP sessions for the same
PaC in the authentication and authorization phase: one with the NAP,
and one with the ISP. The process of arriving at the resultant
authorization, which is a combination of the individual
authorizations obtained from respective service providers, is outside
the scope of this protocol. In the absence of lower-layer security,
both authentications MUST be able to generate a AAA-Key, leading to
generation of a PANA SA. The resultant PANA SA cryptographically
binds the two AAA-Keys together, hence it prevents man-in-the-middle
attacks.
10.5 Cryptographic Keys
When the EAP method exports a AAA-Key, this key is used to produce a
PANA SA with PANA_MAC_KEY with a distinct key ID. The PANA_MAC_KEY
is unique to the PANA session, and takes PANA-based nonce values into
computation to cryptographically separate itself from the AAA-Key.
The PANA_MAC_KEY is solely used for authentication and integrity
protection of the PANA messages within the designated session.
Two AAA-Keys may be generated as a result of separate NAP and ISP
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authentication. In that case, the AAA-Key used with the PANA SA is
the combination of both keys.
The PANA SA lifetime is bounded by the AAA-Key lifetime. Another
execution of EAP method yields in a new AAA-Key, and updates the PANA
SA, PANA_MAC_KEY and key ID.
When link-layer or network-layer ciphering [I-D.ietf-pana-ipsec] is
enabled as a result of successful PANA authentication, a separate
PaC-EP master key is generated based on the AAA-Key, session
identifier, key identifier, and EP device identifier.
The lifetime of PaC-EP master key is bounded by the lifetime of the
PANA SA. This key may be used with a secure association protocol
[I-D.ietf-ipsec-ikev2] to produce further cipher-specific and
transient keys.
10.6 Per-packet Ciphering
Networks that are not secured at the lower-layers prior to running
PANA can rely on enabling per-packet data traffic ciphering upon
successful PANA session establishment. The PANA framework allows
generation of a PaC-EP master key from AAA-Key for using with a per-
packet protection mechanism, such as link-layer or IPsec-based
ciphering [I-D.ietf-pana-ipsec]. In case the master key is not
readily useful to the ciphering mechanism, an additional secure
association protocol [I-D.ietf-ipsec-ikev2] may be needed to produce
the required keying material. These mechanisms ultimately establish
a cryptographic binding between the data traffic generated by and for
a client and the authenticated identity of the client. Data traffic
must be minimally data origin authenticated, replay and integrity
protected, and optionally encrypted.
10.7 PAA-to-EP Communication
The PANA framework allows separation of PAA from EP(s). SNMPv3
[I-D.ietf-pana-snmp] is used between the PAA and EP for provisioning
authorized PaC information on the EP. This exchange MUST be always
physically or cryptographically protected for authentication,
integrity and replay protection. It MUST also be privacy-protected
when PaC-EP master key for per-packet ciphering is transmitted to the
EP.
The PaC-EP master key MUST be unique to the PaC and EP pair. The
session identifier and the device identifier of the EP are taken into
computation for achieving this effect [I-D.ietf-pana-ipsec].
Compromise of an EP does not automatically lead to compromise of
another EP or the PAA.
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10.8 Liveness Test
A PANA session is associated with a session lifetime. The session is
terminated unless it is refreshed by a new round of EAP
authentication before it expires. Therefore, at the latest a
disconnected client can be detected when its session expires. A
disconnect may also be detected earlier by using PANA ping messages.
A request message can be generated by either PaC or PAA at any time
and the peer must respond with an answer message. A successful
round-trip of this exchange is a simple verification that the peer is
alive.
This test can be engaged when there is a possibility that the peer
might have disconnected (e.g., after the discontinuation of data
traffic for an extended period of time). Periodic use of this
exchange as a keep-alive requires additional care as it might result
in congestion and hence false alarms.
This exchange is cryptographically protected when a PANA SA is
available in order to prevent threats associated with the abuse of
this functionality.
Any valid PANA answer message received in response to a recently sent
request message can be taken as an indication of peer's liveness.
The PaC or PAA MAY forgo sending an explicit PANA-Ping-Request if a
recent exchange has already confirmed that the peer is alive.
10.9 Updating PaC's IP Address
There is no way to prove the ownership of the IP address presented by
the PaC. Hence an authorized PaC can launch a redirect attack by
spoofing a victim's IP address.
10.10 Early Termination of a Session
The PANA protocol supports the ability for both the PaC and the PAA
to transmit a tear-down message before the session lifetime expires.
This message causes state removal, a stop of the accounting procedure
and removes the installed per-PaC state on the EP(s). This message
is cryptographically protected when PANA SA is present.
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11. Acknowledgments
We would like to thank Jari Arkko, Mohan Parthasarathy, Julien
Bournelle, Rafael Marin Lopez, Pasi Eronen, Randy Turner, Erik
Nordmark, Lionel Morand, Avi Lior, Susan Thomson, Giaretta Gerardo
and all members of the PANA working group for their valuable comments
to this document.
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12. References
12.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.
[RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC2365] Meyer, D., "Administratively Scoped IP Multicast", BCP 23,
RFC 2365, July 1998.
[RFC2462] Thomson, S. and T. Narten, "IPv6 Stateless Address
Autoconfiguration", RFC 2462, December 1998.
[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Networks", RFC 2464, December 1998.
[RFC2988] Paxson, V. and M. Allman, "Computing TCP's Retransmission
Timer", RFC 2988, November 2000.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC3456] Patel, B., Aboba, B., Kelly, S., and V. Gupta, "Dynamic
Host Configuration Protocol (DHCPv4) Configuration of
IPsec Tunnel Mode", RFC 3456, January 2003.
[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, "Extensible Authentication Protocol (EAP)",
RFC 3748, June 2004.
[I-D.ietf-eap-keying]
Aboba, B., "Extensible Authentication Protocol (EAP) Key
Management Framework", draft-ietf-eap-keying-06 (work in
progress), April 2005.
[IANA] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
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12.2 Informative References
[RFC2522] Karn, P. and W. Simpson, "Photuris: Session-Key Management
Protocol", RFC 2522, March 1999.
[RFC4016] Parthasarathy, M., "Protocol for Carrying Authentication
and Network Access (PANA) Threat Analysis and Security
Requirements", RFC 4016, March 2005.
[I-D.ietf-pana-requirements]
Yegin, A. and Y. Ohba, "Protocol for Carrying
Authentication for Network Access (PANA)Requirements",
draft-ietf-pana-requirements-09 (work in progress),
August 2004.
[I-D.ietf-pana-ipsec]
Parthasarathy, M., "PANA enabling IPsec based Access
Control", draft-ietf-pana-ipsec-05 (work in progress),
December 2004.
[I-D.ietf-pana-framework]
Jayaraman, P., "PANA Framework",
draft-ietf-pana-framework-03 (work in progress),
December 2004.
[I-D.ietf-pana-snmp]
Mghazli, Y., "SNMP usage for PAA-EP interface",
draft-ietf-pana-snmp-03 (work in progress), February 2005.
[I-D.ietf-eap-statemachine]
Vollbrecht, J., Eronen, P., Petroni, N., and Y. Ohba,
"State Machines for Extensible Authentication Protocol
(EAP) Peer and Authenticator",
draft-ietf-eap-statemachine-06 (work in progress),
December 2004.
[I-D.ietf-ipsec-ikev2]
Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
draft-ietf-ipsec-ikev2-17 (work in progress),
October 2004.
[I-D.ietf-dna-link-information]
Yegin, A., "Link-layer Event Notifications for Detecting
Network Attachments", draft-ietf-dna-link-information-01
(work in progress), February 2005.
[I-D.adrangi-eap-network-discovery]
Adrangi, F., "Identity selection hints for Extensible
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Authentication Protocol (EAP)",
draft-adrangi-eap-network-discovery-12 (work in progress),
April 2005.
[ianaweb] IANA, "Number assignment", http://www.iana.org.
[IANA-EXP]
Narten, T., "Assigning Experimental and Testing Numbers
Considered Useful", BCP 82, RFC 3692, January 2004.
[RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO
10646", RFC 2279, January 1998.
Authors' Addresses
Dan Forsberg
Nokia Research Center
P.O. Box 407
FIN-00045 NOKIA GROUP
Finland
Phone: +358 50 4839470
Email: dan.forsberg@nokia.com
Yoshihiro Ohba
Toshiba America Research, Inc.
1 Telcordia Drive
Piscataway, NJ 08854
USA
Phone: +1 732 699 5305
Email: yohba@tari.toshiba.com
Basavaraj Patil
Nokia
6000 Connection Dr.
Irving, TX 75039
USA
Phone: +1 972-894-6709
Email: Basavaraj.Patil@nokia.com
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Hannes Tschofenig
Siemens Corporate Technology
Otto-Hahn-Ring 6
81739 Munich
Germany
Email: Hannes.Tschofenig@siemens.com
Alper E. Yegin
Samsung Advanced Institute of Technology
75 West Plumeria Drive
San Jose, CA 95134
USA
Phone: +1 408 544 5656
Email: alper.yegin@samsung.com
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Appendix A. Example Sequence of Separate NAP and ISP Authentication
A PANA message sequence with separate NAP and ISP authentication is
illustrated in Figure 12. The example assumes the following
scenario:
o The PaC initiates the discovery and handshake phase.
o The PAA offers separate NAP and ISP authentication, as well as a
choice of ISP from "ISP1" and "ISP2". The PaC accepts the offer
from PAA, with choosing "ISP1" as the ISP.
o NAP authentication and ISP authentication is performed in this
order in the authentication and authorization phase.
o An EAP authentication method with a single round trip is used in
each EAP sequence.
o After a PANA SA is established, all messages are integrity and
replay protected with MAC AVPs.
o The access, re-authentication and termination phases are not
shown.
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PaC PAA Message(sequence number)[AVPs]
-----------------------------------------------------
// Discovery and handshake phase
-----> PANA-PAA-Discover(0)
<----- PANA-Start-Request(x) // S-flag set
[Nonce, Cookie,
ISP-Information("ISP1"),
ISP-Information("ISP2"),
NAP-Information("MyNAP")]
-----> PANA-Start-Answer(x) // S-flag set
[Nonce, Cookie, // PaC chooses "ISP1"
ISP-Information("ISP1")]
// Authentication and authorization phase
<----- PANA-Auth-Request(x+1) // NAP authentication
[Session-Id, EAP{Request}] // S- and N-flags set
-----> PANA-Auth-Answer(x+1) // S- and N-flags set
[Session-Id] // No piggybacking
-----> PANA-Auth-Request(y) // S- and N-flags set
[Session-Id, EAP{Response}]
<----- PANA-Auth-Answer(y)[Session-Id] // S- and N-flags set
<----- PANA-Auth-Request(x+2) // S- and N-flags set
[Session-Id, EAP{Request}]
-----> PANA-Auth-Answer(x+2) // S- and N-flags set
[Session-Id, EAP{Response}] // Piggybacking
<----- PANA-FirstAuth-End-Request(x+3) // S- and N-flags set
[Session-Id, EAP{Success}, Key-Id, MAC]
-----> PANA-FirstAuth-End-Answer(x+3) // S- and N-flags set
[Session-Id, Key-Id, MAC]
<----- PANA-Auth-Request(x+4) // ISP authentication
[Session-Id, EAP{Request}, MAC] // S-flag set
-----> PANA-Auth-Answer(x+4) // S-flag set
[Session-Id, MAC] // No piggybacking
-----> PANA-Auth-Request(y+1) // S-flag set
[Session-Id, EAP{Response}, MAC]
<----- PANA-Auth-Answer(y+1) // S-flag set
[Session-Id, MAC]
<----- PANA-Auth-Request(x+5) // S-flag set
[Session-Id, EAP{Request}, MAC]
-----> PANA-Auth-Answer(x+5) // S-flag set
[Session-Id, EAP{Response}, MAC] // Piggybacking
<----- PANA-Bind-Request(x+6) // S-flag set
[Session-Id, Result-Code, EAP{Success}, Device-Id,
Key-Id, Lifetime, Protection-Cap., PPAC, MAC]
-----> PANA-Bind-Answer(x+6) // S-flag set
[Session-Id, Device-Id, Key-Id,
PPAC, MAC]
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Figure 12: A Complete Message Sequence for Separate NAP and ISP
Authentication
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Forsberg, et al. Expires November 11, 2005 [Page 82]
