PANA Working Group                                           D. Forsberg
Internet-Draft                                                     Nokia
Expires: November 5, 2004 January 15, 2005                                  Y. Ohba (Ed.)
                                                                 Toshiba
                                                                B. Patil
                                                                   Nokia
                                                           H. Tschofenig
                                                                 Siemens
                                                                A. Yegin
                                                                 Samsung
                                                             May 7,
                                                           July 17, 2004

     Protocol for Carrying Authentication for Network Access (PANA)
                        draft-ietf-pana-pana-04
                        draft-ietf-pana-pana-05

Status of this Memo

   This document is an Internet-Draft

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   patent or other IPR claims of which I am aware have been disclosed,
   and is any of which I become aware will be disclosed, in full conformance accordance with
   all provisions of Section 10 of RFC2026.
   RFC 3668.

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Copyright Notice

   Copyright (C) The Internet Society (2004).  All Rights Reserved.

Abstract

   This document defines the Protocol for Carrying Authentication for
   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 can
   be used on any link that can carry IP.  PANA 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  . . . . . . . . . . . . . . . . . . . . .   8
     3.1  Illustration of a Complete Message Sequence  . . . . . . .   9
   4.   Protocol Details . . . . . . . . . . . . . . . . . . . . .  10 .  11
     4.1  Common Processing Rules  . . . . . . . . . . . . . . . . .  10  11
       4.1.1  Payload Encoding . . . . . . . . . . . . . . . . . . . . .  10  11
       4.1.2  Transport Layer Protocol . . . . . . . . . . . . . . . . .  11  12
       4.1.3  Fragmentation  . . . . . . . . . . . . . . . . . . . . . .  11  12
       4.1.4  Sequence Number and Retransmission . . . . . . . . . . . .  11  12
       4.1.5  PANA Security Association  . . . . . . . . . . . . . . . .  12  13
       4.1.6  Message Authentication Code  . . . . . . . . . . . . . . .  14  15
       4.1.7  Message Validity Check . . . . . . . . . . . . . . . . . .  14  15
       4.1.8  Error Handling . . . . . . . . . . . . . . . . . . . . . .  15  17
     4.2  Discovery and Initial Handshake Phase  . . . . . . . . . .  16  17
       4.2.1  Discovery and Initial Handshake with NAP-ISP
              Authentication Separation  . . . . . . . . . . . . . .  20
     4.3  Authentication Phase . . . . . . . . . . . . . . . . . . .  19  21
     4.4  Re-authentication  . . . . . . . . . . . . . . . . . . . .  22  24
     4.5  Termination Phase  . . . . . . . . . . . . . . . . . . . .  23  26
     4.6    Illustration of a Complete Message  Example Sequence for NAP and ISP Separate
          Authentications  . . . . . . .  24 . . . . . . . . . . . . . .  26
     4.7  Responding to Duplicate Requests . . . . . . . . . . . . .  28
     4.8  Device ID Choice . . . . . . . . . . . . . . . . . . . . .  27
   4.8  29
     4.9  Updating PaC' Address  . . . . . . . . . . . . . . . . . .  29
     4.10   Session Lifetime . . . . . . . . . . . . . . . . . . . .  30
     4.11   Retransmission of Duplicate Answers  .  27
   4.9 . . . . . . . . .  31
     4.12   Mobility Handling  . . . . . . . . . . . . . . . . . . . .  28
   4.10  31
     4.13   Support for Separate EP  . . . . . . . . . . . . . . . . .  30  33
   5.   PANA Security Association Establishment  . . . . . . . . .  31 .  34
   6.   Message Formats  . . . . . . . . . . . . . . . . . . . . .  32 .  35
     6.1  IP and UDP Headers . . . . . . . . . . . . . . . . . . . .  32  35
     6.2  PANA Header  . . . . . . . . . . . . . . . . . . . . . . .  32  35
     6.3  AVP Header . . . . . . . . . . . . . . . . . . . . . . . .  34  37
     6.4  PANA Messages  . . . . . . . . . . . . . . . . . . . . . .  36  39
       6.4.1  Message Specifications . . . . . . . . . . . . . . . . . .  36  39
       6.4.2  PANA-PAA-Discover (PDI)  . . . . . . . . . . . . . . . . .  37  40
       6.4.3  PANA-Start-Request (PSR) . . . . . . . . . . . . . . . . .  37  40
       6.4.4  PANA-Start-Answer (PSA)  . . . . . . . . . . . . . . . . .  37  40
       6.4.5  PANA-Auth-Request (PAR)  . . . . . . . . . . . . . . . . .  38  41
       6.4.6  PANA-Auth-Answer (PAN) . . . . . . . . . . . . . . . . . .  38  41
       6.4.7  PANA-Bind-Request (PBR)  . . . . . . . . . . . . . . . . .  38  41
       6.4.8  PANA-Bind-Answer (PBA) . . . . . . . . . . . . . . . . . .  38  42
       6.4.9  PANA-Reauth-Request (PRAR) . . . . . . . . . . . . . . . .  39  42
       6.4.10   PANA-Reauth-Answer (PRAA)  . . . . . . . . . . . . . . . .  39  42
       6.4.11   PANA-Termination-Request (PTR) . . . . . . . . . . . . . .  39  42
       6.4.12   PANA-Termination-Answer (PTA)  . . . . . . . . . . . . . .  39  43
       6.4.13   PANA-Error (PER) . . . . . . . . . . . . . . . . . . . . .  40  43
       6.4.14   PANA-FirstAuth-End-Request (PFER)  . . . . . . . . . . . .  40  43
       6.4.15   PANA-FirstAuth-End-Answer (PFEA) . . . . . . . . . .  43
       6.4.16   PANA-Update-Request (PUR)  . . .  40 . . . . . . . . . .  44
       6.4.17   PANA-Update-Answer (PUA) . . . . . . . . . . . . . .  44
     6.5  AVPs in PANA . . . . . . . . . . . . . . . . . . . . . . .  40  44
       6.5.1  MAC AVP  . . . . . . . . . . . . . . . . . . . . . . . . .  41  44
       6.5.2  Device-Id AVP  . . . . . . . . . . . . . . . . . . . . . .  41  45
       6.5.3  Session-Id AVP . . . . . . . . . . . . . . . . . . . . . .  41  45
       6.5.4  Cookie AVP . . . . . . . . . . . . . . . . . . . . . . . .  42  45
       6.5.5  Protection-Capability AVP  . . . . . . . . . . . . . . . .  42  45
       6.5.6  Termination-Cause AVP  . . . . . . . . . . . . . . . . . .  42  45
       6.5.7  Result-Code AVP  . . . . . . . . . . . . . . . . . . . . .  42  46
       6.5.8  EAP-Payload AVP  . . . . . . . . . . . . . . . . . . . . .  46  50
       6.5.9  Session-Lifetime AVP . . . . . . . . . . . . . . . . . . .  46  50
       6.5.10   Failed-AVP AVP . . . . . . . . . . . . . . . . . . . . . .  46  50
       6.5.11   NAP-Information AVP  . . . . . . . . . . . . . . . . . . .  46  50
       6.5.12   ISP-Information AVP  . . . . . . . . . . . . . . . . . . .  47  50
       6.5.13   Provider-Identifier AVP  . . . . . . . . . . . . . . . . .  47  50
       6.5.14   Provider-Name AVP  . . . . . . . . . . . . . . . . . . . .  47  51
       6.5.15   EP-Device-Id AVP . . . . . . . . . . . . . . . . . . . . .  47  51
       6.5.16   Key-Id AVP . . . . . . . . . . . . . . . . . . . . . . . .  47  51
       6.5.17   Post-PANA-Address-Configuration (PPAC) AVP . . . . . . . .  47  51
       6.5.18   Nonce AVP  . . . . . . . . . . . . . . . . . . . . .  52
       6.5.19   IP-Address AVP . . . . . . . . . . . . . . . . .  48 . .  52
     6.6  AVP Occurrence Table . . . . . . . . . . . . . . . . . . .  49  52
   7.   PANA Protocol Message Retransmissions  . . . . . . . . . .  51 .  56
     7.1  Transmission and Retransmission Parameters . . . . . . . .  53  58
   8.   IANA Considerations  . . . . . . . . . . . . . . . . . . .  54 .  59
     8.1  PANA UDP Port Number . . . . . . . . . . . . . . . . . . .  54  59
     8.2  PANA Multicast Address . . . . . . . . . . . . . . . . . .  54  59
     8.3  PANA Header  . . . . . . . . . . . . . . . . . . . . . . .  54  59
       8.3.1  Message Type . . . . . . . . . . . . . . . . . . . . . . .  54  59
       8.3.2  Flags  . . . . . . . . . . . . . . . . . . . . . . . . . .  54  60
     8.4  AVP Header . . . . . . . . . . . . . . . . . . . . . . . .  54  60
       8.4.1  AVP Code . . . . . . . . . . . . . . . . . . . . . . . . .  54  60
       8.4.2  Flags  . . . . . . . . . . . . . . . . . . . . . . . . . .  55
   8.4.3  Vendor Id  . . . . . . . . . . . . . . . . . . . . . . . .  55  61
     8.5  AVP Values . . . . . . . . . . . . . . . . . . . . . . . .  55  61
       8.5.1  Algorithm Values of MAC AVP Values . . . . . .  . . . . . . . . . . . . . . . .  55  61
       8.5.2  Device-Id  Protection-Capability AVP Values . . . . . . . . . . . . . . . . . . .  55  61
       8.5.3  Protection-Capability  Termination-Cause AVP Values . . . . . . . . . . . . .  55  61
       8.5.4  Result-Code AVP Values . . . . . . . . . . . . . . . . . .  55  61
       8.5.5  Termination-Cause  Post-PANA-Address-Configuration AVP Values . . . . . .  62
   9.   Security Considerations  . . . . . . . . .  55
   8.5.6  Provider-Identifier AVP Values . . . . . . . . . . . .  63
   10.  Open Issues and Change History . .  55
   8.5.7  Post-PANA-Address-Configuration AVP Values . . . . . . . .  55
   9.     Security Considerations . . . . .  69
   11.  Acknowledgments  . . . . . . . . . . . .  56
   10.    Open Issues and Change History . . . . . . . . . .  70
   12.  References . . . .  62
   11.    Acknowledgments . . . . . . . . . . . . . . . . . . . . .  63  71
   12.1   Normative References . . . . . . . . . . . . . . . . . . .  64  71
   12.2   Informative References . . . . . . . . . . . . . . . . . .  66  72
        Authors' Addresses . . . . . . . . . . . . . . . . . . . .  69 .  75
        Intellectual Property and Copyright Statements . . . . . .  71 .  77

1.  Introduction

   Providing secure network access service requires access control based
   on the authentication and authorization of the clients and the access
   networks.  Initial and subsequent 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.
   [I-D.ietf-pana-usage-scenarios]  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) [I-D.ietf-eap-rfc2284bis] [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, EAP and
   EAP methods.

   Various environments and usage models for PANA are identified in the
   [I-D.ietf-pana-usage-scenarios] Internet-Draft.
   Appendix A of [I-D.ietf-pana-requirements].  Potential security
   threats for network-layer access authentication protocol are
   discussed in [I-D.ietf-pana-threats-eval] draft. [I-D.ietf-pana-threats-eval].  These two drafts 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
   [I-D.ietf-eap-rfc2284bis]. [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
   [I-D.ietf-pana-framework][I-D.ietf-pana-snmp]. (see
   [I-D.ietf-pana-framework] and [I-D.ietf-pana-snmp]).

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].

2.  Terminology

   This section describes some terms introduced in this document:

   PANA Session:

      A PANA session is defined as begins with the exchange of messages initial handshake between the PANA
      Client (PaC) and the PANA Authentication Agent (PAA) to
      authenticate a user (PaC) for network access.  If the (PAA), and
      terminates by an authentication is unsuccessful, the session is terminated.  The failure, a timeout, or an explicit
      termination message.  A fixed session identifier is considered as active until there is maintained
      throughout a disconnect
      indication by the PaC or the PAA terminates it. session.  A session cannot be shared across multiple
      physical network interfaces.  A distinct PANA session is
      associated with a pair of the device identifiers of PaC and PAA.  For example, if the PaC has two interfaces connected to the
      same IP link with different IP addresses and IP address is used as
      a device identifier, a distinct PANA session will be created per
      interface if both interfaces addresses need to be authorized for
      network access.

   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
      initial handshake and freed when the session terminates.

   PANA Security Association:

      A PANA security association is a relationship between the PaC and
      PAA, formed by the sharing of cryptographic keying material and
      associated context.  Security associations are duplex.  That is,
      one security association is needed to protect the bidirectional
      traffic between the PaC and the PAA.

   PANA Client (PaC):

      The client side of the protocol that resides in the host device
      which is responsible for providing the credentials to prove its
      identity for network access authorization.

   Device Identifier (DI):

      The identifier used by the network as a handle to control and
      police the network access of a client.  Depending on the access
      technology, this identifier might contain any of IP address,
      link-layer address, switch port number, etc.  of a connected
      device.

   PANA Authentication Agent (PAA):

      The protocol entity in the access network side entity of the protocol whose
      responsibility is to verify the credentials provided by a PANA
      client and grant network access service to the device associated
      with the client and identified by a DI.  Note the authentication
      and authorization procedure can, according to the EAP model, be
      also offloaded to the backend AAA infrastructure.

   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
      client devices.  Information such as the DI and (optionally)
      cryptographic keys are provided by the PAA per client for
      constructing filters on the EP.

   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].

3.  Protocol Overview

   The PANA protocol involves two functional entities namely the PaC and
   the PAA.  The protocol resides above the transport layer and the
   details are explained in Section 4.

   The placement of the entities used in PANA largely depends on a
   certain
   selected architecture.  The PAA may optionally interact with a AAA
   backend to authenticate the user (PaC).  The EP, mentioned in the
   context with PANA, is a logical entity. There is, however, the option
   that the EP is not physically co-located with the PAA.  In case that the PAA and the
   EP are co-located only an API is required for intercommunication
   instead of a separate protocol.  In the case where the PAA is
   separated from the EP, a separate protocol will be used between the
   PAA and the EP for managing access control.  The  A description of this
   protocol
   and messaging between the PAA and EP for access authorization is outside the scope of this draft and will be dealt separately. is covered in
   [I-D.ietf-pana-snmp].

   Figure 1 illustrates the interactions in a simplified manner:

           PaC                   EP            PAA           AAA
           ---                   ---           ---           ---

                         PAA Discovery
            <---------------------o------------> (1)
                      PANA Authentication       AAA interaction
            <----------------------------------><------------> (2)

                                     Authorization
                                  <-------------  (3)

                        Figure 1: PANA Framework

   PANA supports authentication of a PaC using various EAP methods.  The
   EAP method used depends on the level of security required for the EAP
   messaging itself.  PANA does not secure the data traffic itself.
   However, EAP methods that enable key exchange may allow other
   protocols to be bootstrapped for securing the data traffic
   [I-D.ietf-pana-ipsec]. (e.g.,
   [I-D.ietf-pana-ipsec]).

   From a state machine aspect, point of view, the PANA protocol consists of
   three phases

   1.  Discovery and initial handshake phase

   2.  Authentication phase

   3.  Termination phase
   In the first phase, an IP address of PAA is discovered and a PANA
   session is established between PaC and PAA.  EAP messages are
   exchanged and a PANA SA is established in the second phase.  The
   established PANA
   session as well as a the PANA SA is deleted in the third phase.

4. Protocol Details

4.1 Common Processing Rules

4.1.1 Payload Encoding

   The payload

   In addition, PANA defines the following two types of any
   re-authentication procedures that are performed while an established
   PANA message consists session exists.

   1.  Re-authentication based on EAP

   2.  Re-authentication based on PANA-Reauth exchange

   The former type of zero re-authentication is used mainly for extending
   authorization lifetime or more AVPs
   (Attribute Value Pairs).  A brief description of for updating the AVPs defined in
   this document is listed below:

   o  Cookie AVP: contains cryptographic keying
   material of a random value that PANA SA.  The latter type of re-authentication is used
   mainly for making
      initial handshake robust against blind resource consumption DoS
      attacks.

   o  Protection-Capability AVP: contains information which protection
      should be initiated after maintaining the PANA exchange (e.g., link-layer or
      network layer protection).

   o  Device-Id AVP: contains a device identifier presence of the sender of communicating peers each
   other so that the
      message.  A device identifier is represented established PANA session can be terminated as soon
   as a pair of device
      identifier type and device identifier value.  Either a layer-2
      address or an IP address is used for the device identifier value.

   o  EP-Device-Id AVP: contains presence of the device identifier peer is lost.

3.1  Illustration of an EP.

   o  EAP AVP: contains an EAP PDU.

   o  MAC AVP: contains a Complete Message Authentication Code that protects a Sequence

   A complete PANA message PDU.

   o  Termination-Cause AVP: contains sequence is illustrated in Figure 2.  The
   example assumes the reason of session termination. following scenario:

   o  Result-Code AVP: contains information about  The PaC initiates the protocol execution
      results.

   o  Session-Id AVP: contains discovery and initial handshake phase by
      multicasting a PANA-PAA-Discover message.  The PAA responds with a
      PANA-Start-Request message with a cookie to be stateless in the session identifier value.

   o  Session-Lifetime AVP: contains
      discovery and initial handshake phase.  At the duration end of authorized access.

   o  Failed-AVP: contains the offending AVP that caused a failure.

   o  NAP-Information AVP, ISP-Information AVP: contains the information
      on a NAP
      discovery and an ISP, respectively.

   o  Key-Id AVP: contains initial handshake phase, the PaC sends a AAA-Key identifier.

   o  PPAC AVP: Post-PANA-Address-Configuration AVP.  Conveys
      PANA-Start-Answer message with a cookie in response to the list
      of IP address configuration methods available when sent by
      PANA-Start-Request.

   o  An EAP authentication method with a single round trip is used in
      the
      PAA, and authentication phase.  A AAA-Key is derived from the chosen EAP
      method when sent by the PaC. and used for establishing a PANA SA.

   o  Nonce AVP:  At the end of the authentication phase, the PAA sends a
      PANA-Bind-Request message and the PaC responds with a
      PANA-Bind-Answer message.  These messages contains a randomly chosen value.

4.1.2 Transport Layer Protocol

   PANA uses UDP MAC AVP and a
      Key-Id AVP, as its transport layer protocol.  The UDP port number well as other AVPs for which usages are explained
      in Section 4, to securely establish a PANA session with a PANA SA.

   o  After the PANA SA is TBD.  All established, all messages except for PANA-PAA-Discover are always
   unicast.  PANA-PAA-Discover MAY be unicasted when integrity and
      replay protected with MAC AVPs.

   o  Re-authentication based on the PANA-Reauth-Request/ PANA-Reauth
      exchange is performed.

   o  The PaC knows the
   IP address initiates termination of the PAA.

4.1.3 Fragmentation

   PANA does not provide fragmentation of PANA messages. Instead, it
   relies on fragmentation provided session by EAP methods and IP layer when
   needed.

4.1.4 sending a
      PANA-Termination-Request message.

   o  Sequence Number and Retransmission

   PANA uses sequence numbers to provide ordered delivery of EAP
   messages.  The design involves use of two sequence numbers to prevent
   some of the DoS attacks on the sequencing scheme.  Every PANA packet
   include one transmitted sequence number (tseq) and one received
   sequence number (rseq) in the PANA header.  See [1] for detailed
   explanation on why two sequence numbers are needed.

   The two sequence number fields have the same length of 32 bits and
   appear in PANA header.  tseq starts from initial sequence number
   (ISN) and is monotonically increased by 1. The serial number
   arithmetic defined in [RFC1982] is used for sequence number
   operation. The ISNs headers are exchanged between not shown.

      PaC and      PAA during the
   discovery  Message[AVPs]
      -----------------------------------------------------
      // Discovery and initial handshake phase (see Section 4.2).
         ----->     PANA-PAA-Discover
         <-----     PANA-Start-Request[Nonce, Cookie]
         ----->     PANA-Start-Request-Answer[Nonce, Cookie]

      // Authentication phase
         <-----     PANA-Auth-Request[Session-Id, EAP]
         ----->     PANA-Auth-Answer[Session-Id, EAP]
         <-----     PANA-Auth-Request[Session-Id, EAP]
         ----->     PANA-Auth-Answer[Session-Id, EAP]
         <-----     PANA-Bind-Request[Session-Id, EAP{Success},
                         Device-Id, Lifetime, Protection-Cap., Key-Id, MAC]
         ----->     PANA-Bind-Answer[Session-Id, Device-Id, Key-Id, MAC]

      // Re-authentication based on PANA-Reauth exchange
         <-----     PANA-Reauth-Request[Session-Id, MAC]
         ----->     PANA-Reauth-Answer[Session-Id, MAC]

      // Termination phase
         ----->     PANA-Termination-Request[Session-Id, MAC]
         <-----     PANA-Termination-Answer[Session-Id, MAC]

                 Figure 2: A Complete Message Sequence

4.  Protocol Details

4.1  Common Processing Rules

4.1.1  Payload Encoding

   The rules
   that govern payload of any PANA message consists of zero or more AVPs
   (Attribute Value Pairs).  A brief description of the sequence numbers AVPs defined in other phases are described as
   follows.

   o  When a message
   this document is sent, listed below:

   o  Cookie AVP: contains a new sequence number random value that is placed on used for making
      initial handshake robust against blind resource consumption DoS
      attacks.

   o  Protection-Capability AVP: contains information which protection
      should be initiated after the
      tseq field PANA exchange (e.g., link-layer or
      network layer protection).

   o  Device-Id AVP: contains a device identifier of message regardless the sender of whether it the
      message.  A device identifier is sent represented as a result pair of retransmission or not.  When device
      identifier type and device identifier value.  Either a message is sent, rseq layer-2
      address or an IP address is copied
      from the tseq field of used for the last accepted message. device identifier value.

   o  When a message is received, it is considered valid in terms of
      sequence numbers if and only if (i) its tseq is greater than  EP-Device-Id AVP: contains the
      tseq device identifier of the last accepted an EP.

   o  EAP AVP: contains an EAP PDU.

   o  MAC AVP: contains a Message Authentication Code that protects a
      PANA message and (ii) its rseq falls in the
      range between PDU.

   o  Termination-Cause AVP: contains the tseq reason of session termination.

   o  Result-Code AVP: contains information about the last acknowledged message + 1 and protocol execution
      results.

   o  Session-Id AVP: contains the tseq session identifier value.

   o  Session-Lifetime AVP: contains the duration of authorized access.

   o  Failed-AVP: contains the last transmitted message.

   PANA relies on EAP-layer retransmissions, or for example NAS
   functionality [I-D.ietf-aaa-eap], for retransmitting EAP Requests
   based on timer.  Other PANA layer messages offending AVP that require caused a response
   from failure.

   o  NAP-Information AVP, ISP-Information AVP: contains the communicating peer are retransmitted based information
      on timer at
   PANA-layer until a response is received (in which case the
   retransmission timer is stopped) or NAP and an ISP, respectively.

   o  Key-Id AVP: contains a AAA-Key identifier.

   o  PPAC AVP: Post-PANA-Address-Configuration AVP.  Conveys the number list
      of retransmission
   reaches IP address configuration methods available when sent by the maximum value (in which case
      PAA, and the PANA session MUST be
   deleted immediately).  For PANA-layer retransmission, chosen method when sent by the
   retransmission timer SHOULD be calculated PaC.

   o  Nonce AVP: contains a randomly chosen value.

   o  IP-Address AVP: contains an IP Address of a PaC.

4.1.2  Transport Layer Protocol

   PANA uses UDP as described in [RFC2988]
   to provide congestion control.  See Section 7 for default timer and
   maximum retransmission count parameters.

4.1.5 PANA Security Association

   A PANA SA its transport layer protocol.  The UDP port number
   is created as an attribute of a PANA session TBD.  All messages except for PANA-PAA-Discover are always
   unicast.  PANA-PAA-Discover MAY be unicasted when EAP
   authentication succeeds with a creation the PaC knows the
   IP address of a AAA-Key.  A the PAA.

4.1.3  Fragmentation

   PANA SA is does not created when the provide fragmentation of PANA authentication fails or no AAA-Key is
   produced messages.  Instead, it
   relies on fragmentation provided by any EAP authentication method.  In the case where two methods and IP layer when
   needed.

4.1.4  Sequence Number and Retransmission

   PANA uses sequence numbers to provide ordered delivery of EAP
   authentications are performed in
   messages.  The design involves use of two sequence numbers to prevent
   some of the DoS attacks on the sequencing scheme.  Every PANA packet
   includes one transmitted sequence number (tseq) and one received
   sequence number (rseq) in a single the PANA
   authentication phase, it is possible that header.  See [1] for detailed
   explanation on why two AAA-Keys sequence numbers are derived.
   If this happens, needed.

   The two sequence number fields have the same length of 32 bits and
   appear in PANA SA MUST be generated header.  The transmission sequence number starts from both AAA-Keys.
   When a new AAA-Key
   initial sequence number (ISN) and is derived as a result of EAP-based
   re-authentication, any key derived from the old AAA-Key MUST be
   updated monotonically increased by 1.
   This rule applies to a new one that all PANA messages but PANA-PAA-Discover.  The
   serial number arithmetic defined in [RFC1982] 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. used for sequence
   number operation.  The Key-Id AVP is of type Unsigned32 ISNs are exchanged between PaC and MUST contain a
   value that uniquely identifies the AAA-Key within PAA during
   the PANA session. discovery and initial handshake phase (see Section 4.2).  The PANA-Bind-Answer message (or
   rules that govern the PANA-FirstAuth-End-Answer
   message) sent sequence numbers in response to other phases are described
   as follows.

   o  When a PANA-Bind-Request message (or a
   PANA-FirstAuth-End-Request 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 sent, a new AAA-Key (or sequence number is placed on the new pair
      tseq field of AAA-Keys when the
   PANA_MAC_KEY message regardless of whether it is derived from two AAA-Keys).  Although the
   specification does not mandate sent as a particular method for calculation result
      of
   Key-Id AVP value, retransmission or not.  When a simple method message is to use monotonically increasing
   numbers."

   The created PANA SA sent, rseq is deleted when copied
      from the corresponding PANA session is
   deleted.  The lifetime tseq field of the PANA SA last accepted message.

   o  When a message is the same as the lifetime received, it is considered valid in terms of
      sequence numbers if and only if (i) its tseq is greater than the PANA session for simplicity.

   PANA SA attributes as well as PANA session attributes are listed
   below:

   PANA Session attributes:

      *  Session-Id

      *  Device-Id of PaC

      *  Device-Id of PAA

      *  List of device identifiers of EPs

      *  Initial
      tseq of PaC (ISN_pac)

      *  Initial the last accepted message and (ii) its rseq falls in the
      range between the tseq of PAA (ISN_paa)

      *  Last transmitted the last acknowledged message and the
      tseq value

      *  Last received rseq value

      *  Last of the last transmitted message payload

      *  Retransmission interval

      *  Session lifetime

      *  Protection-Capability

      * message.

   PANA SA attributes:

         +  AAA-Key

         +  AAA-Key Identifier

         +  PANA_MAC_Key

   The PANA_MAC_Key is used to integrity protect relies on EAP-layer retransmissions, or for example NAS
   functionality [I-D.ietf-aaa-eap], for retransmitting EAP Requests
   based on timer.  Other PANA messages.  When
   the PANA_MAC_Key is derived layer messages that require a response
   from the communicating peer are retransmitted based on timer at
   PANA-layer until a single AAA-Key, it response is computed in received (in which case the following way:

      PANA_MAC_KEY = The first N bits
   retransmission timer is stopped) or the number of
                     HMAC_SHA1(AAA-Key, ISN_pac | ISN_paa | Session-ID)

   where retransmission
   reaches the maximum value of N depends on (in which case the integrity protection algorithm in
   use, i.e., N=160 for HMAC-SHA1.

   When PANA session MUST be
   deleted immediately).  For PANA-layer retransmission, the PANA_MAC_Key is derived from two AAA-Keys, it is computed
   retransmission timer SHOULD be calculated as described in
   the following way:

      PANA_MAC_KEY = The first N bits of
                     HMAC_SHA1(AAA-Key1 | AAA-Key2, ISN_pac | ISN_paa |
                               Session-ID)

   where AAA-Key1 and AAA-Key2 are AAA-Keys [RFC2988]
   to provide congestion control.  See Section 7 for the first default timer and second EAP
   authentication in a single
   maximum retransmission count parameters.

4.1.5  PANA authentication phase, respectively.

   The length of AAA-Key, AAA-Key1 and AAA-Key2 MUST be N bits or
   longer.  See Section 4.1.6 for the detailed usage of the
   PANA_MAC_Key.

4.1.6 Message Authentication Code Security Association

   A PANA message can contain a MAC (Message Authentication Code) AVP
   for cryptographically protecting the message.

   When a MAC AVP SA is included in created as an attribute of a PANA message, the value field session when EAP
   authentication succeeds with a creation of a AAA-Key.  A PANA SA is
   not created when the
   MAC AVP PANA authentication fails or no AAA-Key is calculated
   produced by using the PANA_MAC_Key in any EAP authentication method.  In the following way:

      MAC AVP value = PANA_MAC_PRF(PANA_MAC_Key, PANA_PDU) case where PANA_PDU is the two EAP
   authentications are performed in sequence in a single PANA message including
   authentication phase, it is possible that two AAA-Keys are derived.
   If this happens, the PANA header, with SA MUST be generated from both AAA-Keys.
   When a new AAA-Key is derived as a result of EAP-based
   re-authentication, any key derived from the MAC AVP value field first initialized old AAA-Key MUST be
   updated to 0.  PANA_MAC_PRF
   represents a new one that is derived from the pseudo random function corresponding new AAA-Key.  In order
   to distinguish the MAC
   algorithm specified 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 MAC AVP.  In this version end of draft,
   PANA_MAC_PRF is HMAC-SHA1. The PaC and PAA MUST use the same
   algorithm to calculate EAP authentication which resulted in deriving a MAC AVP they originate and receive. new
   AAA-Key.  The
   algorithm Key-Id AVP is determined by of type Unsigned32 and MUST contain a
   value that uniquely identifies the PAA when 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 message) with a
   MAC Key-Id AVP is sent.  When the PaC does not support MUST contain a
   Key-Id AVP with the MAC algorithm
   specified same AAA-Key identifier carried in the PANA-Bind-Request message, it request.
   PANA-Bind-Request, PANA-Bind-Answer, PANA-FirstAuth-End-Request and
   PANA-FirstAuth-End-Answer messages with a Key-Id AVP MUST silently discard also carry
   a MAC AVP whose value is computed by using the message.  The PAA MUST NOT change new PANA-MAC-KEY
   derived from the MAC algorithm throughout new AAA-Key (or the continuation new pair of AAA-Keys when the PANA session.

4.1.7 Message Validity Check

   When a PANA message is received, the message
   PANA_MAC_KEY is considered to be
   invalid at least when one of derived from two AAA-Keys).  Although the following conditions are
   specification does not met:

   o  The IP Hop Limit (or TTL) field has mandate a value particular method for calculation of 255, i.e., the
      packet could not possibly have been forwarded by a router.

   o  Each field in the message header contains a valid value including
      sequence number, message length, message type, version number,
      flags, etc.

   o  When
   Key-Id AVP value, a device identifier of the communication peer simple method is bound to the use monotonically increasing
   numbers.

   The created PANA session, it matches the device identifier carried in MAC and/
      or IP header(s), or other auxiliary indetifier provided by SA is deleted when the
      lower-layers (e.g., circuit ID).

   o  The message type corresponding PANA session is one
   deleted.  The lifetime of the expected types in PANA SA is the current
      state.

   o  The message payload contains a valid set same as the lifetime of AVPs allowed for
   the
      message type and there is no missing AVP that needs to PANA session for simplicity.

   PANA SA attributes as well as PANA session attributes are listed
   below:

   PANA Session attributes:

      *  Session-Id

      *  Device-Id of PaC

      *  Device-Id of PAA

      *  IP address of PaC (may 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 same as the received message.

   o  When a Device-Id AVP is included, of PaC)

      *  IP address of PAA (may be the AVP is valid if same as the Device-Id of PAA)

      *  List of device
      identifier type contained in the AVP is supported (this check is
      for both identifiers of EPs

      *  Last transmitted tseq value

      *  Last received rseq value

      *  Last transmitted message payload

      *  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 used to integrity protect PANA messages and PAA)
   derived from AAA-Key(s).  When two AAA-Keys (AAA-Key1 and is AAA-Key2)
   are generated as a result of double EAP authentication (see Section
   4.3) the requested one (this check compound AAA-Key can be computed as follows ('|' indicates
   concatenation):

      AAA-Key = AAA-Key1 | AAA-Key2
    The PANA_MAC_KEY is for
      PAA only) and the device identifier value contained computed in the AVP
      matches following way:

      PANA_MAC_KEY = The first N bits of
                     HMAC_SHA1(AAA-Key, PaC_nonce | PAA_nonce | Session-ID)

   where the value extracted from of N depends on the lower-layer encapsulation
      header corresponding to the device identifier type contained in
      the AVP.  Note that a Device-Id AVP carries the PaC's device
      identifier in messages from PaC to PAA and PAA's device identifier integrity protection algorithm in messages from PAA to PaC.

   Invalid messages
   use, i.e., N=160 for HMAC-SHA1.  The length of AAA-Key MUST be discarded in order to provide robustness
   against DoS attacks and an unprotected.  In addition, a
   non-acknowledged error notification message MAY be returned to the
   sender. N bits
   or longer.  See Section 4.1.8 Section 4.1.6 for details.

4.1.8 Error Handling

   PANA-Error message MAY be sent by either PaC or PAA when a badly
   formed PANA message is received or in case of other errors.  If the
   cause detailed usage of this error the
   PANA_MAC_KEY.

4.1.6  Message Authentication Code

   A PANA message was can contain a request message (e.g.,
   PANA-PAA-Discover or *-Request), then the request MAY be
   retransmitted immediately without waiting MAC (Message Authentication Code) AVP
   for its retransmission
   timer to go off.  If the cause of cryptographically protecting the error was message.

   When a response MAC AVP is included in a PANA message, the receiver value field of the PANA-Error message SHOULD NOT resend
   MAC AVP is calculated by using the same
   response until it receives PANA_MAC_KEY in the next request.

   To defend against DoS attacks a timer MAY be used.  One (1) error
   notification is sent to each different sender each N seconds.  N following way:

      MAC AVP value = PANA_MAC_PRF(PANA_MAC_KEY, PANA_PDU)

   where PANA_PDU is a
   configurable parameter.

   When an error the PANA message is sent unprotected including the PANA header, with
   the MAC AVP and value field first initialized to 0.  PANA_MAC_PRF
   represents the
   lower-layer is insecure, pseudo random function corresponding to the error message MAC
   algorithm specified in the MAC AVP.  In this version of draft,
   PANA_MAC_PRF is treated as an
   informational message. HMAC-SHA1.  The receiver of such an error message MUST
   NOT change its state unless the error persists PaC and PAA MUST use the PANA session
   is not making any progress.

4.2 Discovery and Initial Handshake Phase

   When a PaC attaches same
   algorithm to calculate a network, MAC AVP they originate and knows that it has to discover receive.  The
   algorithm is determined by the PAA for PANA, it SHOULD send when a PANA-PAA-Discover message to PANA-Bind-Request with a
   well-known link local multicast address (TBD) and UDP port (TBD).
   PANA PAA discovery assumes that PaC and PAA are one hop away from
   each other.  If
   MAC AVP is sent.  When the PaC knows does not support the IP address of MAC algorithm
   specified in the PAA (some
   pre-configuration), PANA-Bind-Request message, it MAY unicast MUST silently discard
   the PANA discovery message to that
   address. message.  The PAA SHOULD answer to MUST NOT change the PANA-PAA-Discover message with a
   PANA-Start-Request message.

   When MAC algorithm throughout
   the PAA receives such a request, or upon receiving some lower
   layer indications continuation of the PANA session.

4.1.7  Message Validity Check

   When a new PaC, PAA SHOULD unicast a
   PANA-Start-Request message.

   There can PANA message is received, the message is considered to be multiple PAAs on
   invalid at least when one of the link. following conditions are not met:

   o  The authentication and
   authorization result does IP Hop Limit (or TTL) field has a value of 255, i.e., the
      packet could not depend on which PAA is chosen possibly have been forwarded by a router.

   o  Each field in the
   PaC.  By default the PaC MAY choose the PAA that sent the first
   response.

   PaC MAY also choose to start sending packets before getting
   authenticated.  In that case, the network MAY detect this and send an
   unsolicited PANA-Start-Request message to PaC in addition to
   filtering the unauthorized traffic.  EP is the node that can detect
   such activity.  PAA-to-EP protocol MAY be used for this purpose.

   A PANA-Start-Request message MAY carry a Cookie AVP that header contains a
   cookie.  The rseq field valid value including
      sequence number, message length, message type, version number,
      flags, etc.

   o  When a device identifier of the header communication peer is set bound to zero (0).  The tseq
   field of the header contains the initial sequence number.  The cookie
   is used for preventing the PAA from resource consumption DoS attacks
   by blind attackers. The cookie is computed in such a way that
      PANA session, it does
   not require any per-session state maintenance on matches the PAA device identifier carried in order to
   verify MAC and/
      or IP header(s), or other auxiliary indetifier provided by the cookie returned in a PANA-Start-Answer message.
      lower-layers (e.g., circuit ID).

   o  The exact
   algorithms and syntax used for generating cookies does not affect
   interoperability and hence is not specified here.  An example
   algorithm message type is described below.

      Cookie =
        <secret-version> | HMAC_SHA1( <Device-Id one of PaC> | <secret> )

   where <secret> is a randomly generated secret known only to the PAA,
   <secret-version> is an index used for choosing expected types in the secret for
   generating current
      state.  Specifically the cookie following messages are unexpected and '|' indicates concatenation.  The secret-
   version should be changed frequently enough to prevent replay
   attacks.  The secret key is locally known to the PAA only
      invalid:

      *  In discovery and initial handshake phase:

         +  PANA-Termination-Request and PANA-Reauth-Request.

         +  PANA-Bind-Request.

         +  PANA-Update-Request.

      *  In authentication phase:

         +  PANA-PAA-Discover.

         +  PANA-Termination-Request and PANA-Reauth-Request.

         +  PANA-Update-Request.

         +  PANA-Start-Request after a PaC receives the first valid
            PANA-Auth-Request.

      *  After successful PANA authentication:

         +  PANA-Start-Request as well as a non-duplicate
            PANA-Bind-Request (see section Section 4.7 for definition of
            duplicate requests).

         +  PANA-PAA-Discover without a certain time frame.

   Protection-Capability and Post-PANA-Address-Configuration Session-Id AVP.

      *  In termination phase:

         +  PANA-PAA-Discover.

         +  All requests but PANA-Termination-Request.

   o  The message payload contains a valid set of AVPs MAY allowed for the
      message type and there is no missing AVP that needs to be
   optionally included
      in the PANA-Start-Request in order to indicate
   required and available capabilities for payload.

   o  Each AVP is decoded correctly.

   o  When a MAC AVP is included, the network access.  These
   AVPs MAY be used by AVP value matches the PaC for assessing MAC value
      computed against the capability match even
   before received message.

   o  When a Device-Id AVP is included, the authentication takes place.  But these AVPs are provided
   during AVP is valid if the insecure discovery phase, there are certain security risks
   involved device
      identifier type contained in using the provided information. See Section 9 AVP is supported (this check is
      for further
   discussion on this.

   PAA MAY enable NAP-ISP authentication separation by setting the
   S-flag of both PaC and PAA) and is the message header of requested one (this check is for
      PAA only) and the PANA-Start-Request. Also, device identifier value contained in the
   PANA-Start-Request MAY contain zero or one NAP-Information AVP and
   zero or more ISP-Information AVPs to advertise
      matches the information on value extracted from the
   NAP and/or ISPs.

   When lower-layer encapsulation
      header corresponding to the device identifier type contained in
      the AVP.  Note that a PaC receives Device-Id AVP carries the PANA-Start-Request message PaC's device
      identifier in response messages from PaC to the
   PANA-PAA-Discover message, it responds with PAA and PAA's device identifier
      in messages from PAA to PaC.

   Invalid messages MUST be discarded in order to provide robustness
   against DoS attacks.  In addition, a PANA-Start-Answer non-acknowledged error
   notification message if it wishes MAY be returned to enter the authentication phase.  The
   PANA-Start-Answer sender.  See Section
   4.1.8 for details.

4.1.8  Error Handling

   PANA-Error message contains the initial sequence numbers MAY be sent by either PaC or PAA when a badly
   formed PANA message is received or in
   the tseq and rseq fields case of other errors.  If the PANA header, a copy
   cause of this error message was a request message (e.g.,
   PANA-PAA-Discover or *-Request), then the received
   Cookie (if any) as the PANA payload. request MAY be
   retransmitted immediately without waiting for its retransmission
   timer to go off.  If the S-flag cause of the received PANA-Start-Request error was a response message,
   the receiver of the PANA-Error message is not set,
   PaC MUST SHOULD NOT set resend the S-flag in same
   response until it receives the PANA-Start-Answer message next request.

   To defend against DoS attacks a timer MAY be used.  One (1) error
   notification is sent
   back to the PAA.  In this case, PaC MAY indicate its choice of ISP by
   including each different sender each N seconds.  N is a
   configurable parameter.

   When an ISP-Information error message is sent unprotected with MAC AVP in and the PANA-Start-Answer message.
   When a AAA backend
   lower-layer is used, insecure, the identity of the destination AAA
   server or realm error message is treated as an
   informational message.  The receiver of such an error message MUST be determined based on
   NOT change its state unless the explicitly chosen
   ISP.  When error persists and the ISP-Information AVP PANA session
   is not present, making any progress.

4.2  Discovery and Initial Handshake Phase

   When a PaC attaches to a network, and knows that it has to discover a
   PAA, it SHOULD send a PANA-PAA-Discover message to a well-known link
   local multicast address (TBD) and UDP port (TBD).  The PANA PAA
   discovery assumes that PaC and PAA are one hop away from each other.
   If the access network
   MAY rely on PaC knows the client identifier carried in IP address of the EAP authentication
   method PAA (based on
   pre-configuration), it MAY unicast the PANA discovery message to that
   address.  The PAA SHOULD respond to make this determination.

   If the S-flag PANA-PAA-Discover message
   with a PANA-Start-Request message.

   When the PAA receives such a request, or upon receiving some lower
   layer indications of a new PaC, the received PAA SHOULD unicast a
   PANA-Start-Request message is set, PaC message.

   There can indicate its desire to perform separate EAP be multiple PAAs on the link.  The authentication for
   NAP and ISP
   authorization result does not depend on which PAA is chosen by setting the S-flag in
   PaC.  By default the PANA-Start-Answer message.
   If PaC MAY choose the S-flag in PAA that sent the PANA-Start-Answer message is not set, only one
   authentication is performed first
   response.

   The PaC MAY also choose to start sending packets before getting
   authenticated.  In that case, the network may detect this and the processing occurs as described
   earlier.  If PAA
   MAY send an unsolicited PANA-Start-Request message to the S-flag PaC in
   addition to filtering the PANA-Start-Answer message unauthorized traffic.  The EP is set, the
   determination of the destination AAA server or realm for ISP
   authentication is performed as described earlier.  In addition, where
   backend AAA servers are node
   that can detect such activity.  The PAA-to-EP protocol MAY be used
   for NAP authentication, this purpose.

   A PANA-Start-Request message MAY carry a Cookie AVP that contains a
   cookie.  The rseq field of the NAP header is
   considered set to zero (0).  The tseq
   field of the ultimate AAA realm, and header contains the destination AAA server for
   this authentication initial sequence number.  The cookie
   is determined entirely by used for preventing the local configuration PAA from resource consumption DoS attacks
   by blind attackers.  The cookie is computed in such a way that it
   does not require any per-session state maintenance on the access server hosting PAA (NAS).

   The PaC can choose an ISP and contain an ISP-Information AVP for in
   order to verify the
   chosen ISP cookie returned in a PANA-Start-Answer message even when there message.
   The exact algorithms and syntax used for generating cookies does not
   affect interoperability and hence is no
   ISP-Information AVP contained in not specified here.  An example
   algorithm is described below.

      Cookie =
        <secret-version> | HMAC_SHA1( <Device-Id of PaC> , <secret> )

   where <secret> is a randomly generated secret known only to the PANA-Start-Request message. 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.

   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 phase.  Otherwise, it
   MUST silently discard the received message.

   Initial EAP Request 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.

   When the S-flag is set

   Protection-Capability and Post-PANA-Address-Configuration AVPs MAY be
   optionally included in a the PANA-Start-Request message, in order to indicate
   required and available capabilities for the initial
   EAP Request MUST NOT network access.  These
   AVPs MAY be carried in used by the PANA-Start-Request message.
   (If PaC for assessing the initial EAP Request were contained in capability match even
   before the PANA-Start-Request
   message authentication takes place.  But these AVPs are provided
   during the S-flag negotiation, the PaC cannot tell whether insecure discovery phase, there are certain security risks
   involved in using the EAP Request is provided information.  See Section 9 for NAP authentication or ISP authentication.)
   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.

   In any case, PANA MUST NOT generate an EAP message on behalf of EAP
   peer or EAP (pass-through) authenticator.

   The PANA-Start-Request/Answer exchange is needed before entering
   authentication phase even when the PaC is pre-configured with PAAs IP
   address and the PANA-PAA-Discover message is unicast.

   A Nonce AVP MUST be included in PANA-Start-Request and
   PANA-Start-Answer messages.

   A PANA-Start-Request message that carries a Cookie AVP is never
   retransmitted.  A PANA-Start-Request message that does not carry a
   Cookie AVP is retransmitted based on timer.  A PANA-Start-Answer
   message that carries a Cookie AVP is retransmitted based on timer.  A
   PANA-Start-Answer message that does not carry a Cookie AVP is never
   retransmitted based on timer.

   It is possible that both PAA and PaC initiate the discovery and
   initial 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 included) for the PaC.  In this case PAA will retransmit
   PANA-Start-Request based on a timer, if PaC doesn't respond in time
   (message was lost for example).  If PAA had sent stateless
   PANA-Start-Request message (i.e., a Cookie AVP was included), then it
   SHOULD answer to the PANA-PAA-Discover message.

   Figure 3 shows an example sequence for the discovery and initial
   handshake phase when a PANA-PAA-Discover message is sent by a PaC.
   Figure 4 shows an example sequence for the discovery and initial
   handshake phase that is triggered by data traffic.

      PaC      PAA         Message         Message(tseq,rseq)[AVPs]
      ------------------------------------------------------
         ----->            PANA-PAA-Discover(0,0)
         <-----            PANA-Start-Request(x,0)[Cookie]            PANA-Start-Request(x,0)[Nonce, Cookie]
         ----->            PANA-Start-Answer(y,x)[Cookie]            PANA-Start-Answer(y,x)[Nonce, Cookie]
                           (continued to authentication phase)

 Figure 2: 3: Example Sequence for Discovery and Initial Handshake Phase
                 when PANA-PAA-Discover is sent by PaC

      PaC   EP      PAA    Message    Message(tseq,rseq)[AVPs]
      ------------------------------------------------------
       ---->o              (Data packet arrival or L2 trigger)
             ------>       PAA-to-EP protocol, or another mechanism
       <------------       PANA-Start-Request(x,0)[Cookie]       PANA-Start-Request(x,0)[Nonce, Cookie]
       ------------>       PANA-Start-Answer(y,x)[Cookie]       PANA-Start-Answer(y,x)[Nonce, Cookie]
                           (continued to authentication phase)

  Figure 3: 4: Example Sequence for Discovery and Initial Handshake when
                 discovery is triggered by data traffic

4.3 Authentication Phase

   The main task in authentication phase is to carry EAP messages
   between PaC and PAA.  EAP Request messages are carried in PANA-
   Auth-Request messages

4.2.1  Discovery and optionally carried in PANA-Start-Request
   messages.  EAP Response messages are carried in PANA-Auth-Answer
   messages Initial Handshake with NAP-ISP Authentication
      Separation

   In the discovery and optionally carried in PANA-Start-Answer messages.  When
   an EAP Success/Failure message is sent from initial handshake phase, a PAA, PAA MAY enable
   NAP-ISP authentication separation ([I-D.ietf-pana-framework]) by
   setting the message is
   carried in a PANA-Bind-Request (PBR) or PANA-FirstAuth-End-Request
   (PFER) message.  The PANA-FirstAuth-End-Reques message MUST be used
   at S-flag of the end message header of the first EAP when the PaC and PAA have negotiated
   during PANA-Start-Request.
   Also, the discovery PANA-Start-Request MAY contain zero or one NAP-Information
   AVP and initial handshake phase zero or more ISP-Information AVPs to perform separate advertise the
   information on the NAP and ISP authentications in and/or ISPs.

   When a single PANA authentication phase.
   Otherwise, PaC receives the PANA-Bind-Request PANA-Start-Request message MUST be used.  The
   PANA-Bind-Request and PANA-FirstAuth-End-Request messages MUST be
   acknowledged in response to the
   PANA-PAA-Discover message, it responds with a PANA-Bind-Answer (PBA) and a
   PANA-FirstAuth-End-Answer (PFEA) messages, respectively.

   When PANA-Start-Answer
   message if it wishes to enter the PaC and PAA have negotiated during authentication phase.  The
   PANA-Start-Answer message contains the discovery and initial
   handshake phase to perform separate NAP sequence numbers in
   the tseq and ISP authentications, rseq fields of the
   S-flag PANA header, a copy of PANA-Auth-Request and PANA-Auth-Answer messages MUST be
   set.  Otherwise, the received
   Cookie (if any) as the PANA payload.

   If the S-flag of the received PANA-Start-Request message is not set,
   PaC MUST NOT be set.

   When separate NAP and ISP authentications are performed, set the PAA
   determines S-flag in the execution order of NAP authentication and ISP
   authentication. PANA-Start-Answer message sent
   back to the PAA.  In this case, the PAA can PaC MAY indicate which EAP
   authentication is currently occurring its choice of ISP by using N-flag
   including an ISP-Information AVP in the PANA
   message header. PANA-Start-Answer message.
   When NAP authentication a AAA backend is performed, used, the N-flag identity of the destination AAA
   server or realm MUST be set. determined based on the explicitly chosen
   ISP.  When ISP authentication is performed, the N-flag MUST
   NOT be set. The N-flag MUST NOT be set when S-flag ISP-Information AVP is not set.

   When separate NAP and ISP authentications are performed, if present, the access network
   MAY rely on the client identifier carried in the first EAP authentication has failed,
   method to make this determination.

   If the PAA S-flag of the received PANA-Start-Request message is set, PaC
   can choose not indicate its desire to perform the
   second separate EAP authentication for
   NAP and ISP by clearing setting the S-flag of in the
   PANA-FirstAuth-End-Request PANA-Start-Answer message.  In this case,
   If the S-flag of in the
   PANA-FirstAuth-End-Answer PANA-Start-Answer message sent by is not set, only one
   authentication is performed and the PaC MUST be cleared. processing occurs as described in
   Section 4.2.  If the S-flag of in the PANA-FirstAuth-End-Request PANA-Start-Answer message is set when set,
   the first EAP determination of the destination AAA server or realm for ISP
   authentication has failed, is performed as described earlier.  In addition, where
   backend AAA servers are used for NAP authentication, the PaC can choose not to
   perform NAP is
   considered the second EAP ultimate AAA realm, and the destination AAA server for
   this authentication is determined entirely by clearing the S-flag of the
   PANA-FirstAuth-End-Answer message.  If local configuration
   on the first EAP authentication
   failed access server hosting PAA (NAS).

   The PaC can choose an ISP and contain an ISP-Information AVP for the
   chosen ISP in a PANA-Start-Answer message even when there is no
   ISP-Information AVP contained in the PANA-Start-Request message.

   When 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, PANA-Start-Request message, the second initial
   EAP authentication Request MUST NOT be
   performed.

   Currently, use of multiple carried in the PANA-Start-Request message.
   (If the initial EAP methods Request were contained in PANA the PANA-Start-Request
   message during the S-flag negotiation, the PaC cannot tell whether
   the EAP Request is designed only for
   NAP-ISP NAP authentication separation.  It is not for arbitrary EAP
   method sequencing, or giving the PaC another chance when an
   authentication method fails.  The NAP and ISP authentication.)

4.3  Authentication Phase

   The main task in 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 phase is a network
   policy issue.

   When an to carry EAP method that is capable of deriving keys is used during
   the authentication phase messages
   between PaC and the keys PAA.  EAP Request messages are successfully derived, the
   PANA-FirstAuth-End-Request and PANA-FirstAuth-End-Answer and/or
   PANA-Bind-Request and PANA-Bind-Answer messages, and all subsequent
   PANA carried in
   PANA-Auth-Request messages MUST contain a MAC AVP.

   When separate NAP and ISP authentications optionally carried in
   PANA-Start-Request messages.  EAP Response messages are performed carried in
   PANA-Auth-Answer messages and the
   lower-layer optionally carried in PANA-Start-Answer
   messages.  When an EAP Success/Failure message is insecure, sent from a PAA,
   the two EAP methods message is carried in a PANA-Bind-Request (PBR) or
   PANA-FirstAuth-End-Request (PFER) message.  The
   PANA-FirstAuth-End-Reques message MUST be capable used at the end of
   deriving keys.  In this case, if the
   first EAP authentication is
   successful, when the PANA-FirstAuth-End-Request PaC and
   PANA-FirstAuth-End-Answer messages as well as PANA-Auth-Request PAA have negotiated during the discovery
   and
   PANA-Auth-Answer messages initial handshake phase to perform separate NAP and ISP
   authentications in the second EAP a single PANA authentication phase.  Otherwise,
   the PANA-Bind-Request message MUST be
   protected with the key derived from the AAA-Key for the first EAP
   authentication. used.  The PANA-Bind-Request
   and PANA-Bind-Answer messages
   and all subsequent PANA PANA-FirstAuth-End-Request messages MUST be protected either acknowledged with the
   AAA-Key a
   PANA-Bind-Answer (PBA) and a PANA-FirstAuth-End-Answer (PFEA)
   messages, respectively.  Figure 5 shows an example sequence for the first EAP
   authentication if phase without separating NAP and ISP authentications.

      PaC      PAA  Message(tseq,rseq)[AVPs]
      -------------------------------------------------
                    (continued from discovery and initial handshake phase)
         <-----     PANA-Auth-Request(x+1,y)[Session-Id, EAP{Request}]
         ----->     PANA-Auth-Answer(y+1,x+1)[Session-Id, EAP{Response}]
           .
           .
         <-----     PANA-Auth-Request (x+2,y+1)[Session-Id, EAP{Request}]
         ----->     PANA-Auth-Answer (y+2,x+2)[Session-Id, EAP{Response}]
         <-----     PANA-Bind-Request(x+3,y+2)
                       [Session-Id, EAP{Success}, Device-Id, Lifetime,
                        Protection-Cap., PPAC, MAC]
         ----->     PANA-Bind-Answer(y+3,x+3)
                       [Session-Id, Device-Id, PPAC, MAC]

           Figure 5: Example Sequence in Authentication Phase

   When the first EAP PaC and PAA have negotiated during the discovery and initial
   handshake phase to perform separate NAP and ISP authentications, the
   S-flag of PANA-Auth-Request and PANA-Auth-Answer messages MUST be
   set.  Otherwise, the S-flag MUST NOT be set.

   When separate NAP and ISP authentications are performed, the PAA
   determines the execution order of NAP authentication succeeds and ISP
   authentication.  In this case, the second PAA can indicate which EAP
   authentication fails, or
   with is currently occurring by using N-flag in the AAA-Key for PANA
   message header.  When NAP authentication is performed, the second EAP N-flag
   MUST be set.  When ISP authentication is performed, the N-flag MUST
   NOT be set.  The N-flag MUST NOT be set when S-flag is not set.

   When separate NAP and ISP authentications are performed, if the first
   EAP authentication fails and has failed, the PAA can choose not to perform the
   second EAP authentication succeeds, or
   with by clearing the compound key derived from S-flag of the two AAA-Keys, one for
   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 and has failed, the other from PaC can choose not to
   perform the second EAP
   authentication, if both authentication by clearing the S-flag of the
   PANA-FirstAuth-End-Answer message.  If the first and second EAP authentications
   succeed (see Section 4.1.5 for how authentication
   failed and the compound key S-flag is derived).

   The PANA-Bind-Request and not set in the PANA-Bind-Answer PANA-FirstAuth-End-Answer
   message exchange is
   also used for binding device identifiers as a result of the PaC and the PAA to those operations, the PANA SA when session MUST be
   immediately deleted.  Otherwise, the identifiers are either IP second EAP authentication MUST
   be performed.

   Currently, use of multiple EAP methods in PANA is designed only for
   NAP-ISP authentication separation.  It is not for arbitrary EAP
   method sequencing, or MAC addresses.  To
   achieve this, giving the PANA-Bind-Request PaC another chance when an
   authentication method fails.  The NAP and the PANA-Bind-Answer SHOULD
   contain a device identifier ISP authentication are
   considered completely independent.  Presence or success of one should
   not effect the PAA and other.  Making a network access authorization decision
   based on the PaC, respectively, in success or failure of each authentication is a Device-Id AVP.  Device identifier exchange network
   policy issue.

   When an EAP method that is protected by a
   MAC AVP prevents man-in-the-middle attacks.  The PaC MUST use the
   same type capable of device identifier as contained in deriving keys is used during
   the authentication phase and the keys are successfully derived, the
   PANA-FirstAuth-End-Request and PANA-FirstAuth-End-Answer and/or
   PANA-Bind-Request
   message.  The PANA-Bind-Request message MAY also and PANA-Bind-Answer messages, and all subsequent
   PANA messages MUST contain a
   Protection-Capability AVP to indicate if link-layer or network-layer
   ciphering should be initiated after PANA.  No link layer or network
   layer specific information is included in the Protection-Capability MAC AVP.

   When separate NAP and ISP authentications are performed and the information
   lower-layer is preconfigured on the PaC and insecure, the PAA
   this AVP can two EAP methods MUST be omitted.  It is assumed that at least PAA is aware of
   the security capabilities capable of
   deriving keys.  In this case, if the access network.  The PANA protocol
   does not specify how first EAP authentication is
   successful, the PANA SA PANA-FirstAuth-End-Request and the Protection-Capability AVP
   will be used to provide per-packet protection for data traffic.

   Additionally, PANA-Bind-Request MUST include a
   Post-PANA-Address-Configuration AVP, which helps PAA to inform PaC
   about whether a new IP address MUST be configured
   PANA-FirstAuth-End-Answer messages as well as PANA-Auth-Request and the available
   methods to do so.  PaC MUST include a PPAC AVP
   PANA-Auth-Answer messages 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, a PPAC AVP second EAP authentication MUST NOT be included and
   protected with the Result-Code AVP
   MUST be set to PANA_PPAC_CAPABILITY_UNSUPPORTED in key derived from the
   PANA-Bind-Answer message. AAA-Key for the first EAP
   authentication.  The PANA-Bind-Request and PANA-Bind-Answer messages
   and all subsequent PANA messages MUST be retransmitted
   based on protected either with the retransmission rule described in Section 4.1.4.
   AAA-Key for the first EAP authentication can fail at a pass-through authenticator without
   sending an EAP-Failure message [I-D.ietf-eap-statemachine].  When
   this occurs, if the PAA SHOULD send a PANA-Error message to first EAP
   authentication succeeds and the PaC second EAP authentication fails, or
   with
   using PANA_UNABLE_TO_COMPLY result code.  The PaC SHOULD ignore the
   message unless it is secured by PANA or lower layer.  In any case, a
   more appropriate way is to rely on a timeout on AAA-Key for the PaC.

   There is a case where second EAP authentication if the first EAP
   authentication succeeds with producing an
   EAP-Success message but network access authorization fails due to,
   e.g., authorization rejected by a AAA proxy or authorization locally
   rejected by a PAA. When this occurs, and the PAA MUST send
   PANA-Bind-Request second EAP authentication succeeds, or
   with a result code PANA_AUTHORIZATION_REJECTED.  If
   a 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 authentications
   succeed.

   The PANA-Bind-Request and the PANA-Bind-Answer message exchange is established between
   also used for binding device identifiers of the PaC and the PAA by to
   the time PANA SA when the
   EAP-Success is generated by identifiers are either IP or MAC addresses.  To
   achieve this, the EAP server (this is PANA-Bind-Request and the case when PANA-Bind-Answer SHOULD
   contain a device identifier of the
   EAP method provides protected success indication), PAA and the this PANA-Bind
   message PaC, respectively, in
   a Device-Id AVP.  Device identifier exchange MUST be that is protected with by a
   MAC AVP and with carrying a
   Key-Id AVP. prevents man-in-the-middle attacks.  The AAA-Key and the PANA session PaC MUST be deleted after use the PANA-Bind message exchange.

      PaC      PAA  Message(tseq,rseq)[AVPs]
      -------------------------------------------------
                    (continued from discovery and initial handshake phase)
         <-----     PANA-Auth-Request(x+1,y)[EAP{Request}]
         ----->     PANA-Auth-Answer(y+1,x+1)[EAP{Response}]
           .
           .
         <-----     PANA-Auth-Request (x+2,y+1)[EAP{Request}]
         ----->     PANA-Auth-Answer (y+2,x+2)[EAP{Response}]
         <-----     PANA-Bind-Request(x+3,y+2)
                       [EAP{Success}, Device-Id, Lifetime, Protection-Cap.,
                        PPAC, MAC]
         ----->     PANA-Bind-Answer(y+3,x+3)[Device-Id, PPAC, MAC]

           Figure 4: Example Sequence in Authentication Phase

4.4 Re-authentication

   There are two types of re-authentication supported by PANA.

   The first
   same type of re-authentication is based on EAP by entering an
   authentication phase.  In this case, some or all message exchanges
   for discovery and initial handshake phase MAY be omitted device identifier as contained in the
   following way.  When PANA-Bind-Request
   message.  The PANA-Bind-Request message MAY also contain a PaC wants to initiate EAP-based
   re-authentication, it sends a unicast PANA-PAA-Discovery message to
   the PAA.  This message MUST contain a Session-Id
   Protection-Capability AVP which to indicate if link-layer or network-layer
   ciphering should be initiated after PANA.  No link layer or network
   layer specific information is used
   for identifying the PANA session on included in the PAA.  If Protection-Capability
   AVP.  When the PAA already has
   an established PANA session for information is preconfigured on the PaC with the matching identifier,
   it sends a PANA-Auth-Request message containing the same identifier
   to start an authentication phase.  If and the PAA
   this AVP can be omitted.  It is assumed that at least PAA is aware of
   the security capabilities of the access network.  The PANA protocol
   does not recognize specify how the
   session identifier, it proceeds with regular authentication by
   sending back PANA-Start-Request.  When PANA SA and the Protection-Capability AVP
   will be used to provide per-packet protection for data traffic.

   Additionally, PANA-Bind-Request MUST include a
   Post-PANA-Address-Configuration AVP, which helps PAA initiates EAP-based
   re-authentication, it sends to inform PaC
   about whether a PANA-Auth-Request message containing
   the session identifier for new IP address MUST be configured and the available
   methods to do so.  PaC MUST include a PPAC AVP in order to enter an authentication phase.
   PAA SHOULD initiate EAP authentication before indicate
   its choice of method when there is a match between the current session
   lifetime expires. In both cases, methods
   offered by the tseq PAA and rseq values are
   inherited from the previous (re-)authentication.  For any EAP-based
   re-authentication, if methods available on the PaC.  When there
   is an established PANA SA,
   PANA-Auth-Request no match, a PPAC AVP MUST NOT be included and PANA-Auth-Answer messages the Result-Code AVP
   MUST be protected by
   adding a MAC AVP set to each PANA_PPAC_CAPABILITY_UNSUPPORTED in the
   PANA-Bind-Answer message.

   The second type of re-authentication is

   PANA-Bind-Request and PANA-Bind-Answer messages MUST be retransmitted
   based on a single protected
   message exchange without entering the retransmission rule described in Section 4.1.4.

   EAP authentication phase.
   PANA-Reauth-Request and PANA-Reauth-Answer messages are used for this
   purpose.  If there is can fail at a pass-through authenticator without
   sending an established PANA SA, both the PaC and EAP-Failure message [I-D.ietf-eap-statemachine].  When
   this occurs, the PAA are allowed to SHOULD send a PANA-Reauth-Request PANA-Error message to the
   communicating peer whenever it needs to make sure the availability of PaC with
   using PANA_UNABLE_TO_COMPLY result code.  The PaC SHOULD ignore the
   message unless it is secured by PANA SA or lower layer.  In any case, a
   more appropriate way is to rely on a timeout on the peer and expect 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 proxy or authorization locally
   rejected by a PAA.  When this occurs, the peer to return PAA MUST send
   PANA-Bind-Request with a PANA-
   Reauth-Answer message.  Both PANA-Reauth-Request/ PANA-Reauth-Answer
   messages result code PANA_AUTHORIZATION_REJECTED.  If
   a AAA-Key is established between PaC and PAA by the time when the
   EAP-Success is generated by the EAP server (this is the case when the
   EAP method provides protected success indication), the this PANA-Bind
   message exchange MUST be protected with a MAC AVP and with carrying a
   Key-Id AVP.

   Implementations  The AAA-Key and the PANA session MUST limit be deleted after
   the rate of performing re-authentication
   for both PANA-Bind message exchange.

4.4  Re-authentication

   There are two types of re-authentication. re-authentication supported by PANA.

   The PaC and the PAA can handle
   rate limitation on their own, they don't have to perform any
   coordination with each other. There is no negotiation first type of timers for re-authentication is based on EAP by entering an
   authentication phase.  In this purpose.

      PaC      PAA     Message(tseq,rseq)[AVPs]
      ------------------------------------------------------
         ----->        PANA-Reauth-Request(q,p)[MAC]
         <-----        PANA-Reauth-Answer(p+1,q)[MAC]

        Figure 5: Example Sequence for PaC-initiated second type
                           Re-authentication

      PaC      PAA     Message(tseq,rseq)[AVPs]
      ------------------------------------------------------
         <-----        PANA-Reauth-Request(p,q)[MAC]
         ----->        PANA-Reauth-Answer(q+1,p)[MAC]

        Figure 6: Example Sequence for PAA-initiated second type
                           Re-authentication

4.5 Termination Phase

   A procedure for explicitly terminating a PANA session can be
   initiated either from PaC (i.e., disconnect indication) case, some or from PAA
   (i.e., session revocation).  The PANA-Termination-Request and the
   PANA-Termination-Answer all message exchanges are used
   for disconnect
   indication discovery and session revocation procedures.

   The reason for termination is indicated initial handshake phase MAY be omitted in the Termination-Cause AVP.
   following way.  When there a PaC wants to initiate EAP-based
   re-authentication, it sends a unicast PANA-PAA-Discovery 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 SA established between session for the PaC and with the PAA, all messages exchanged during matching identifier,
   it sends a PANA-Auth-Request message containing the termination phase MUST be
   protected same identifier
   to start an authentication phase.  If the PAA can not recognize the
   session identifier, it proceeds with a MAC AVP. regular authentication by
   sending back PANA-Start-Request.  When the sender of the
   PANA-Termination-Request receives PAA initiates EAP-based
   re-authentication, it sends a valid acknowledgment, all states
   maintained for PANA-Auth-Request message containing
   the PANA session MUST be deleted immediately. identifier for the PaC to enter an authentication phase.
   PAA     Message(tseq,rseq)[AVPs]
      ------------------------------------------------------
         ----->        PANA-Termination-Request(q,p)[MAC]
         <-----        PANA-Termination-Answer(p+1,q)[MAC]

           Figure 7: Example Sequence for Session Termination

4.6 Illustration of a Complete Message Sequence

   A complete PANA message sequence is illustrated in Figure 8. The
   example assumes SHOULD initiate EAP authentication before the following scenario:

   o  PaC multicasts PANA-PAA-Discover message

   o  The ISNs used by current session
   lifetime expires.  In both cases, the PAA tseq and the PaC rseq values are x and y, respectively.

   o  A single EAP sequence is used in authentication phase.

   o  An EAP authentication method with a single round trip is used in
   inherited from the EAP sequence.

   o  The EAP authentication method derives keys.  The PANA SA previous (re-)authentication.  For any EAP-based
   re-authentication, if there is an established based on the unique and fresh session key provided by
      the EAP method.

   o  After PANA SA is established, all messages are integrity SA,
   PANA-Auth-Request and
      replay PANA-Auth-Answer messages MUST be protected with the by
   adding a MAC AVP.

   o  Re-authentication based on AVP to each message.  Any subsequent EAP-based
   authentication MUST be performed with the PANA-Reauth-Request/ PANA-Reauth-
      Answer exchange is performed.

   o  The PANA session is terminated as a result of same ISP and NAP that was
   selected during the PANA-
      Termination-Request indication from initial authentication.  An example sequence for
   the PaC. EAP-based re-authentication initiated by a PaC is shown in Figure
   6.

      PaC      PAA  Message(tseq,rseq)[AVPs]
      -----------------------------------------------------
      // Discovery and initial handshake phase
         ----->     PANA-PAA-Discover (0,0)
         <-----     PANA-Start-Request (x,0)[Cookie]  Message
      ------------------------------------------------------
         ----->     PANA-Start-Request-Answer (y,x)[Cookie]

      // Authentication phase     PANA-PAA-Discover(0,0)[Session-Id]
         <-----     PANA-Auth-Request(x+1,y)[EAP]     PANA-Auth-Request(p,q)[Session-Id, EAP, MAC]
         ----->     PANA-Auth-Answer(y+1,x+1)[EAP]     PANA-Auth-Answer(q+1,p)[Session-Id, EAP, MAC]
         <-----     PANA-Auth-Request(x+2,y+1)[EAP]     PANA-Auth-Request(p+1,q+1)[Session-Id, EAP, MAC]
         ----->     PANA-Auth-Answer(y+2,x+2)[EAP]     PANA-Auth-Answer(q+2,p+1)[Session-Id, EAP, MAC]
         <-----     PANA-Bind-Request(x+3,y+2)
                      [EAP{Success},     PANA-Bind-Request(p+2,q+2)
                       [Session-Id, EAP{Success}, Device-Id, Key-Id,
                        Lifetime, Protection-Cap., PPAC, MAC]
         ----->     PANA-Bind-Answer(y+3,x+3)[Device-Id,     PANA-Bind-Answer(q+3,p+2)
                       [Session-Id, Device-Id, Key-Id, PPAC, MAC]

      // Re-authentication
         <-----     PANA-Reauth-Request (x+4,y+3)[MAC]
         ----->     PANA-Reauth-Answer (y+4,x+4)[MAC]

      // Termination phase
         ----->     PANA-Termination-Request(y+5,x+4)[MAC]
         <-----     PANA-Termination-Answer (x+5,y+5)[MAC]

  Figure 8: A Complete Message 6: Example Sequence

   Another PANA message sequence is illustrated in Figure 9. The example
   assumes the following scenario:

   o for EAP-based re-authentication initiated
                                 by PaC multicasts PANA-PAA-Discover message

   o

   The ISNs used by second type of re-authentication is based on a single protected
   message exchange without entering the PAA authentication phase.
   PANA-Reauth-Request and PANA-Reauth-Answer messages are used for this
   purpose.  If there is an established PANA session, both the PaC are x and y, respectively.

   o
   the PAA offers NAP and ISP separate authentication, as well as are allowed to send a
      choice PANA-Reauth-Request message to the
   communicating peer whenever they need to make sure the availability
   of ISP from "ISP1" and "ISP2".  PaC accepts the offer from
      PAA, with choosing "ISP1" as session on the ISP.

   o  An EAP sequence for NAP authentication peer and an EAP sequence for ISP
      authentication is performed in this order in authentication phase.

   o  An EAP authentication method expect the peer to return a
   PANA-Reauth-Answer message.  Both PANA-Reauth-Request and
   PANA-Reauth-Answer messages MUST be protected with a single round trip MAC AVP when a
   PANA SA is used in available.

   Implementations MUST limit the EAP sequence.

   o rate of performing re-authentication
   for both types of re-authentication.  The EAP authentication methods derive keys.  Once the two EAP
      authenticatioins are successful, the PANA_MAC_KEY is derived from PaC and the two AAA-Keys.

   o  After PANA SA PAA can handle
   rate limitation on their own, they do not have to perform any
   coordination with each other.  There is established, all messages are integrity no negotiation of timers for
   this purpose.

   Figure 7 and
      replay protected with the MAC AVP.

   o  Re-authentication Figure 8 show re-authentication procedures based on the PANA-Reauth-Request/ PANA-Reauth-
      Answer
   PANA-Reauth exchange is performed.

   o  Re-authentication initiated by a PaC and termination phase are not shown. a PAA, respectively.

      PaC      PAA     Message(tseq,rseq)[AVPs]
      -----------------------------------------------------
      // Discovery and initial handshake phase
      ------------------------------------------------------
         ----->    PANA-PAA-Discover (0,0)        PANA-Reauth-Request(q,p)[Session-Id, MAC]
         <-----     PANA-Start-Request (x,0)            // S-flag set
                    [Cookie, ISP-Information("ISP1"),
                     ISP-Information("ISP2"),
                     NAP-Information("MyNAP")]
         ----->     PANA-Start-Request-Answer (y,x)     // S-flag set
                    [Cookie, ISP-Information("ISP1")]   //        PANA-Reauth-Answer(p+1,q)[Session-Id, MAC]

        Figure 7: Example Sequence for PaC-initiated second type
                           Re-authentication

      PaC chooses "ISP1"

      // Authentication phase
         <-----     PANA-Auth-Request(x+1,y)[EAP]       // NAP authentication
                                                        // S- and N-flags set
         ----->     PANA-Auth-Answer(y+1,x+1)[EAP]      // S- and N-flags set      PAA     Message(tseq,rseq)[AVPs]
      ------------------------------------------------------
         <-----     PANA-Auth-Request(x+2,y+1)[EAP]     // S- and N-flags set        PANA-Reauth-Request(p,q)[Session-Id, MAC]
         ----->     PANA-Auth-Answer(y+2,x+2)[EAP]      // S-        PANA-Reauth-Answer(q+1,p)[Session-Id, MAC]

        Figure 8: Example Sequence for PAA-initiated second type
                           Re-authentication

4.5  Termination Phase

   A procedure for explicitly terminating a PANA session can be
   initiated either from PaC (i.e., disconnect indication) or from PAA
   (i.e., session revocation).  The PANA-Termination-Request and N-flags set
         <-----     PANA-FirstAuth-End-Request(x+3,y+2) // S- the
   PANA-Termination-Answer message exchanges are used for disconnect
   indication and N-flags set
                      [EAP{Success}, Key-Id, MAC]
         ----->     PANA-FirstAuth-End-Answer(y+3,x+3)  // S- session revocation procedures.

   The reason for termination is indicated in the Termination-Cause AVP.
   When there is an established PANA SA established between the PaC and N-flags set
                      [Key-Id, MAC]
         <-----     PANA-Auth-Request(x+3,y+4)[EAP, MAC]// ISP authentication
                                                        // S-flag set
         ----->     PANA-Auth-Answer(y+4,x+4)[EAP, MAC] // S-flag set
         <-----     PANA-Auth-Request(x+4,y+5)[EAP, MAC]// S-flag set
   the PAA, all messages exchanged during the termination phase MUST be
   protected with a MAC AVP.  When the sender of the
   PANA-Termination-Request receives a valid acknowledgment, all states
   maintained for the PANA session MUST be deleted immediately.

      PaC      PAA     Message(tseq,rseq)[AVPs]
      ------------------------------------------------------
         ----->     PANA-Auth-Answer(y+5,x+5)[EAP,        PANA-Termination-Request(q,p)[Session-Id, MAC] // S-flag set
         <-----     PANA-Bind-Request(x+5,y+6)          // S-flag set
                      [EAP{Success}, Device-Id, Key-Id,
                       Lifetime, Protection-Cap., PPAC, MAC]
         ----->     PANA-Bind-Answer(y+6,x+5)           // S-flag set
                      [Device-Id, Key-Id, PPAC,        PANA-Termination-Answer(p+1,q)[Session-Id, MAC]

           Figure 9: A Complete Message Example Sequence for Session Termination

4.6  Example Sequence for NAP and ISP Separate Authentications

4.7 Device ID Choice

   A PANA message sequence where NAP and ISP separate authentications
   occur is illustrated in Figure 10.  The device identifiers example assumes the following
   scenario:

   o  The PaC multicasts PANA-PAA-Discover message.

   o  The ISNs used in by the context of PANA can be an IP
   address, PAA and the PaC are x and y, respectively.

   o  The PAA offers NAP and ISP separate authentications, as well as a MAC address, or
      choice of ISP from "ISP1" and "ISP2".  The PaC accepts the offer
      from PAA, with choosing "ISP1" as the ISP.

   o  An EAP sequence for NAP authentication and an identifier that EAP sequence for ISP
      authentication is not carried on data
   packets but has local significance performed in identifying this order in authentication phase.

   o  An EAP authentication method with a connected host
   (e.g., circuit ID).  The last type of identifiers are commonly single round trip is used in physically secured point-to-point links where MAC addresses
      each EAP sequence.

   o  Two AAA-Keys are
   not available.

   It is assumed that PAA knows derived from the link type EAP authentication methods,
      i.e., AAA-Key1 and AAA-Key2.  The PANA_MAC_KEY is first derived
      from 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, AAA-Key1 upon the PAA can decide
   what type completion of device ID will be used when running PANA with the
   client.  When IPsec-based mechanism [I-D.ietf-pana-ipsec] first EAP, and then
      it is updated so that it is derived from both AAA-Key1 and
      AAA-Key2 upon the
   choice completion of access control, PAA SHOULD provide an IP address as device
   ID, and expect the second EAP.

   o  After a PANA SA is established, all messages are integrity and
      replay protected with MAC AVPs.

   o  Re-authentication based on the PANA-Reauth exchange is performed.

   o  Re-authentication and termination phase are not shown.

   o  Session-Id AVP is not shown.

      PaC      PAA  Message(tseq,rseq)[AVPs]
      -----------------------------------------------------
      // Discovery and initial handshake phase
         ----->     PANA-PAA-Discover(0,0)
         <-----     PANA-Start-Request(x,0)                 // S-flag set
                    [Nonce, Cookie, ISP-Information("ISP1"),
                     ISP-Information("ISP2"),
                     NAP-Information("MyNAP")]
         ----->     PANA-Start-Request-Answer(y,x)       // S-flag set
                    [Nonce, Cookie, ISP-Information("ISP1")]// PaC chooses "ISP1"

      // Authentication phase
         <-----     PANA-Auth-Request(x+1,y)[EAP]       // NAP authentication
                                                           // S- and N-flags set
         ----->     PANA-Auth-Answer(y+1,x+1)[EAP]      // S- and N-flags set
         <-----     PANA-Auth-Request(x+2,y+1)[EAP]     // S- and N-flags set
         ----->     PANA-Auth-Answer(y+2,x+2)[EAP]      // S- and N-flags set
         <-----     PANA-FirstAuth-End-Request(x+3,y+2) // S- and N-flags set
                      [EAP{Success}, Key-Id, MAC]
         ----->     PANA-FirstAuth-End-Answer(y+3,x+3)  // S- and N-flags set
                      [Key-Id, MAC]
         <-----     PANA-Auth-Request(x+3,y+4)[EAP, MAC]// ISP authentication
                                                           // S-flag set
         ----->     PANA-Auth-Answer(y+4,x+4)[EAP, MAC] // S-flag set
         <-----     PANA-Auth-Request(x+4,y+5)[EAP, MAC]// S-flag set
         ----->     PANA-Auth-Answer(y+5,x+5)[EAP, MAC] // S-flag set
         <-----     PANA-Bind-Request(x+5,y+6)          // S-flag set
                      [EAP{Success}, Device-Id, Key-Id,
                       Lifetime, Protection-Cap., PPAC, MAC]
         ----->     PANA-Bind-Answer(y+6,x+5)           // S-flag set
                      [Device-Id, Key-Id, PPAC, MAC]

    Figure 10: A Complete Message Sequence for NAP and ISP Separate
                            Authentications

4.7  Responding to Duplicate Requests

   Since PANA is designed over UDP, an answer as well as a request can
   be lost.  In order to provide robustness against possible loss of
   synchronization between a PaC and a PAA, the responder MAY send a
   duplicate answer to a request that it had just answered.  The only
   difference between two consecutive duplicate requests are the
   sequence numbers and the content of MAC AVP (when present).

   o  When a PaC receives a duplicate PANA-Start-Request message for
      which it has already answered, it SHOULD send a duplicate
      PANA-Start-Answer message until it receives a valid
      PANA-Auth-Request message.

   o  When a PaC receives a duplicate PANA-FirstAuth-End-Request message
      for which it has already answered, it SHOULD send a duplicate
      PANA-FirstAuth-End-Answer message until it receives a valid
      PANA-Auth-Request message for the second EAP authentication.

   o  When a PaC receives a duplicate PANA-Bind-Request message for
      which it has already answered, it SHOULD send a duplicate
      PANA-Bind-Answer message until it receives some hint provided
      outside the PANA protocol (e.g., receipt of a secure association
      protocol message from an EP or receipt of data traffic) indicating
      that the PAA has received a PANA-Bind-Answer message.

   o  When a PaC or a PAA receives a duplicate PANA-Termination-Request
      message for which it has already answered, it MAY send a duplicate
      PANA-Termination-Answer message in accordance with the timers
      described in Section 7.

4.8  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 host
   (e.g., circuit ID).  The last type of identifiers are commonly used
   in physically secured point-to-point links where MAC addresses are
   not available.

   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 device ID will be used 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 an IP address as
   device ID, and expect the PaC to provide its IP address in return.
   In case IPsec is not used, MAC addresses are used as device IDs when
   available.  If non-IPsec access control is enabled, and a MAC address
   is not available, device ID exchange does not occur within PANA.
   Instead, peers rely on lower-layers to provide locally-significant
   identifiers along with received PANA packets.

4.8

4.9  Updating PaC' 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), and the PaC and PAA create host routes to each other
   in order to maintain on-link communication based on the POPA.  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 message MUST carry the
   new PaC address in an IP-Address AVP.  If the address contained in
   the request is invalid, the PAA MUST send a PANA-Error message with
   the result code PANA_INVALID_IP_ADDRESS.  Otherwise, the PAA MUST
   update the PANA session with the new PaC 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.

4.10  Session Lifetime

   The authentication 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
   PaC about the valid lifetime of the PANA session.  It MUST be ignored
   when included in other PANA messages.  When there are multiple EAP
   authentication taking place, this AVP SHOULD be included after the
   final authentication.

   The lifetime is a non-negotiable parameter that can be used by PaC to
   manage PANA-related state.  PaC does not have to perform any actions
   when the lifetime expires, other than optionally purging local state.
   PAA SHOULD initiate EAP authentication before the current session
   lifetime expires.

   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.  PANA peer can use PANA-Reauth-Request message to
   verify the disconnection before taking an action.

   The session lifetime parameter is not related to the transmission of
   PANA-Reauth-Request messages.  These messages can be used for
   asynchronously verifying the liveness of the peer and enabling
   mobility optimizations.  The decision to send PANA-Reauth-Request PANA-Reauth-Request
   message is taken locally and does not require coordination between
   the peers.

   When separate EAP authentications are performed for ISP and NAP in a
   single PANA session, it is possible that different authorization
   lifetime values are associated with the two authentications.  In this
   case, the smaller authorization lifetime value MUST be used for
   calculating the PANA Session-Lifetime value.  As a result, when
   EAP-based re-authentication occurs, both NAP and ISP authentications
   will be performed in the same re-authentication procedure.

4.11  Retransmission of Duplicate Answers

   Since PANA is designed over UDP, an answer as well as a request can
   be lost.  In order to improve robustness against possible loss of
   synchronization between a PaC and a PAA, the responder of a request
   MAY send a duplicate answer to a duplicate request for which already
   answered (as well as a fresh answer to a new request if any).  In
   PANA, a duplicate PANA-Start-Request or PANA-Start-Answer message has
   the same contents as the original request or answer, respectively.  A
   duplicate request other than PANA-Start-Request has the same contents
   as the original request except for the transmission sequence number
   and a MAC AVP (if any).  Also, a duplicate answer other than
   PANA-Start-Answer has the same contents as the original answer except
   for the transmission and receiving sequence numbers and a MAC AVP (if
   any).  Retransmission of a duplicate answer in response to a
   duplicate request occurs in the following ways.

   o  When a PaC receives a duplicate PANA-Start-Request message for
      which it has already answered, it MAY send a duplicate
      PANA-Start-Answer message until it receives a valid
      PANA-Auth-Request message.

   o  When a PaC receives a duplicate PANA-FirstAuth-End-Request message
      for which it has already answered, it MAY send a duplicate
      PANA-FirstAuth-End-Answer message is taken locally and does not require coordination between until it receives a valid
      PANA-Auth-Request message for the peers.

   When separate second EAP authentications are performed authentication.

   o  When a PaC receives a duplicate PANA-Bind-Request message for ISP and NAP in
      which it has already answered, it MAY send a
   single PANA session, duplicate
      PANA-Bind-Answer message until it is possible that different authorization
   lifetime values are associated with receives some hint provided
      outside the two authentications.  In this
   case, PANA protocol (e.g., receipt of a secure association
      protocol message from an EP or receipt of data traffic) indicating
      that the smaller authorization lifetime value MUST be used PAA has received a PANA-Bind-Answer message.

   o  When a PaC or a PAA receives a duplicate PANA-Termination-Request
      message for
   calculating which it has already answered, it MAY send a duplicate
      PANA-Termination-Answer message for a while before deleting the
      PANA Session-Lifetime value.  As a result, when
   EAP-based re-authentication occurs, both NAP and ISP authentications
   will session.  The period to send duplicate
      PANA-Termination-Answer messages may be performed in the same re-authentication procedure.

4.9 a configurable parameter.

4.12  Mobility Handling

   A mobile PaC's AAA network access authentication performance can be
   enhanced by deploying a context-transfer-based mechanism, where some
   session attributes are transferred from the previous PAA to the current new
   one in order to avoid performing a full EAP authentication (reactive
   approach).  Additional mechanisms that are based on the proactive AAA
   state establishment at one or more candidate PAAs may be developed in
   the future [I-D.irtf-aaaarch-handoff].  The details of a
   context-transfer-based mechanism is provided in this section.

   Upon changing its point of attachment, a PaC that wants to quickly
   resume its ongoing PANA session without running EAP MAY send its
   unexpired PANA session identifier in its PANA-Start-Answer message.
   Along with the Session-Id AVP, a MAC and Nonce AVPs AVP MUST be included in this
   message.  Nonce AVP carries a randomly chosen value (PaC_Nonce),
   and  The MAC AVP is computed by using the PANA_MAC_Key PANA_MAC_KEY shared
   between the PaC and its previous PAA that has an unexpired PANA
   session with the PaC.  This action signals PaC's desire to perform
   the mobility optimization.  In the absence of a Session-Id AVP in
   this message, the PANA session takes its usual course (i.e.,
   EAP-based authentication is performed).

   If a PAA receives a session identifier in the PANA-Start-Answer
   message, and it is configured to enable this optimization, it SHOULD
   retrieve the PANA session attributes from the previous PAA.  Current
   PAA determines the identity of the previous PAA by looking at the
   DiameterIdentity part of the PANA session identifier.  The MAC AVP
   can only be verified by the previous PAA, therefore a copy of the
   PANA message SHOULD be provided to the previous PAA.  The mechanism
   required to send a copy of the PANA-Start-Answer message from current
   PAA to the previous PAA, and retrieve the session attributes is
   outside the scope of PANA protocol.  Seamoby Context Transfer
   Protocol [I-D.ietf-seamoby-ctp] might be useful for this purpose.

   When the previous or current PAA is not configured to enable this
   optimization, the current PAA can not retrieve the PANA session
   attributes, or the PANA session has already expired (i.e., session
   lifetime is zero), the PAA MUST send the PANA-Auth-Request message
   with a new session identifier and let the PANA exchange take its
   usual course.  This action will engage EAP-based authentication and
   create a fresh PANA session from scratch.

   In case the current PAA can retrieve the on-going PANA session
   attributes from the previous PAA, the PANA session continues with a
   PANA-Bind exchange.

   As part of the context transfer, an intermediate AAA-Key material is
   provided by the previous PAA to the current PAA.

      AAA-Key-int = The first N bits of
                    HMAC-SHA1(AAA-Key, DiameterIdentity | Session-ID)

   In case there are two AAA-Keys generated from a NAP-ISP
   authentication, the AAA-Key-int computation is:

      AAA-Key-int = The first N bits of
                    HMAC-SHA1(AAA-Key1 | AAA-Key2, DiameterIdentity |
                              Session-ID)
   The value of N depends on the integrity protection algorithm in use,
   i.e., N=160 for HMAC-SHA1.  DiameterIdentity is the identifier of the
   current PAA.  Session-ID is the identifier of the PaC's PANA session
   with the previous PAA.

   The current PAA and PaC compute the new AAA-Key by using the nonce
   values and the AAA-Key-int.  PAA_Nonce is the randomly chosen value
   that MUST be carried in a Nonce AVP in the PANA-Bind-Request message.

      AAA-Key-new = The first N bits of
                    HMAC-SHA1(AAA-Key-int, PaC_nonce | PAA_nonce)

   New PANA_MAC_Key PANA_MAC_KEY is computed based on the algorithm described in
   Section 4.1.5, by using the new AAA-Key and the new Session-ID
   assigned by the current PAA.  The MAC AVP contained in the
   PANA-Bind-Request and PANA-Bind-Answer messages MUST be generated and
   verified by using the new PANA_MAC_Key. PANA_MAC_KEY.  The Session-ID AVP MUST
   include a new session identifier assigned by the current PAA.  A new
   PANA session is created upon successful completion of this exchange.

   Note that correct operation of this optimization relies on many
   factors, including applicability of authorization state from one
   network attachment to another.  [I-D.ietf-eap-keying] identifies this
   operation as "fast handoff" and provides deployment considerations.
   Operators are recommended to take those guidelines into account when
   using this optimization in their networks.

4.10

4.13  Support for Separate EP

   PANA allows the PAA and the EP to be separate entities.  In this
   case, if data traffic protection needs to be initiated after
   successful PANA authentication phase, the PaC needs to know the
   device identifier of EP(s) so that it is able to establish a security
   association with each EP to protect data traffic.

   To this end, when a Protection-Capability AVP with either
   L2_PROTECTION or IPSEC_PROTECTION in the AVP payload is carried in a
   PANA-Bind-Request message and if there is an EP that has a different
   device identifier than that of the PAA, one or more EP-Device-Id AVPs
   MUST also be carried in the PANA-Bind-Request message.  In this case,
   if one EP has the same device identifier as the PAA, an EP-Device-Id
   AVP that contains the device identifier of the EP (i.e., the PAA)
   MUST also be included in the PANA-Bind-Request.

   Aside from provisioning the EP, the same PAA-to-EP protocol MAY be
   used for triggering the PAA upon detecting the need to authenticate a
   new client.

5.  PANA Security Association Establishment

   When PANA is used over an already established secure channel, such as
   physically secured wires or ciphered link-layers, we can reasonably
   assume that man-in-the-middle attack attacks or service theft is not possible
   [I-D.ietf-pana-threats-eval].

   Anywhere else
   possible.  See [I-D.ietf-pana-threats-eval] for a detailed
   discussion.

   In environments where there is no secure channel prior to PANA, the
   protocol PANA execution
   is available, PANA needs to protect itself against such a number of
   attacks.  The device identifier that is used during the
   authentication needs to be verified at the end of the authentication
   to prevent service theft and DoS attacks.  Additionally, a free
   loader should be prevented from spoofing data packets by using the
   device identifier of an already authorized legitimate client.  Both
   of these requirements necessitate generation of a security
   association between the PaC and the PAA at the end of the
   authentication.  This can only be done when the authentication method
   used can generate cryptographic session keys.  Use of secret session keys can prevent
   attacks which would otherwise be very easy to launch by eavesdropping
   on and spoofing traffic over an insecure link.

   PANA relies on EAP and the

   The EAP methods to provide a method provided session key in
   order to establish a PANA security association.  An example of such a
   method is EAP-TLS [RFC2716], whereas EAP-MD5
   [I-D.ietf-eap-rfc2284bis] transported to the PAA (if
   necessary) and is an example of a method that cannot
   create such keying material. The choice subsequently input to the creation of EAP method becomes
   important, as discussed in the next section.

   This keying material is already used within PANA SA.
   Applying the PANA SA to the messages exchanged during the final
   handshake.  This PANA
   handshake ensures that the device identifier that is
   bound provides implicit key confirmation to both the PaC at the end of the authentication process is not
   coming from a man-in-the-middle, but from PAA and the legitimate
   PaC.
   Knowledge of  Implicit key confirmation shows both, the same keying material on both PaC and the PAA helps
   prove this.  The PAA, that
   they possess the unique and fresh session key.

   Protecting the final PANA handshake also ensures that the device
   identifier (and other use information) cannot be modified by an
   adversary.  Further usage of the keying material is discussed in
   [I-D.ietf-pana-framework].

6.  Message Formats

   This section defines message formats for PANA protocol.

6.1  IP and UDP Headers

   The Hop Limit (or TTL) field of the IP header MUST be set to 255.
   When a PANA-PAA-Discover message is multicast, IP destination address
   of the message is set to a well-known link-local multicast address
   (TBD).  A PANA-PAA-Discover message MAY be unicast in some cases as
   specified in Section 4.2.  Any other PANA packet is unicasted 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 packet is sent in response to a request, the UDP source
   and destination ports of the response packet MUST be copied from the
   destination and source ports of the request packet, respectively.
   The destination port of an unsolicited PANA packet MUST be set to an
   assigned value (TBD), and the source port MUST be set to a value
   chosen by the sender.

6.2  PANA Header

   A summary of the PANA header format is shown below.  The fields are
   transmitted in network byte order.

       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    |                 Message Length                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Flags      |                 Message Type                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Transmitted Sequence Number                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Received Sequence Number                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  AVPs ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-

   Version
      This Version field MUST be set to 1 to indicate PANA Version 1.

   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 eight bits.  The following bits are assigned:

       0 1 2 3 4 5 6 7
      +-+-+-+-+-+-+-+-+
      |R r r r S N r r|
      +-+-+-+-+-+-+-+-+

      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 EAP
         authentications for NAP and ISP.  When the S-flag is set in a
         PANA-Start-Answer message it indicates that PaC accepts on
         performing separate EAP authentications for NAP and ISP.  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 authentications are being
         performed in the authentication phase.

      N(AP authentication)

         When the N-flag is set in a PANA-Auth-Request message, it
         indicates that PAA is performing NAP authentication.  When the
         N-flag is unset in a PANA-Auth-Request message, it indicates
         that PAA is performing ISP authentication.  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.

   Message Type

      The Message Type field is three octets, and is used in order to
      communicate the message type with the message.  The 24-bit address
      space is managed by IANA [ianaweb].  PANA uses its own address
      space for this field.

   Transmitted Sequence Number

      The Transmitted Sequence Number field contains the monotonically
      increasing 32 bit sequence number that the message sender
      increments every time a new PANA message is sent.

   Received Sequence Number

      The Received Sequence Number field contains the 32 bit transmitted
      sequence number that the message sender has last received from its
      peer.

   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 MUST be 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                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Vendor-Id (opt)                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Data ...
      +-+-+-+-+-+-+-+-+
   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 eight bits.  The following bits are
      assigned:

       0 1 2 3 4 5 6 7
      +-+-+-+-+-+-+-+-+
      |V M r r r r r r|
      +-+-+-+-+-+-+-+-+

      M(andatory)

         The 'M' Bit, known as the Mandatory bit, indicates whether
         support of the AVP is required.

      V(endor)

         The 'V' bit, known as the Vendor-Specific bit, indicates
         whether the optional Vendor-Id field is present in the AVP
         header.

      r(eserved)

         these flag bits are reserved for future use, and MUST be set to
         zero, and ignored by the receiver.

   AVP Length

      The AVP Length field is three octets, and indicates the number of
      octets in this AVP including the AVP Code, AVP Length, AVP Flags,
      and the AVP data

   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
      uniquely
      IANA assigned id "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.

   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.

6.4  PANA Messages

   Figure 10 11 lists all PANA messages defined in this document

                 Message          Direction: PaC---PAA
                 ----------------------------------------
                 PANA-PAA-Discover           -------->

                 PANA-Start-Request          <--------
                 PANA-Start-Answer           -------->

                 PANA-Auth-Request           <--------
                 PANA-Auth-Answer            -------->

                 PANA-FirstAuth-End-Request  <--------
                 PANA-FirstAuth-End-Answer   -------->

                 PANA-Bind-Request           <--------
                 PANA-Bind-Answer            -------->

                 PANA-Reauth-Request         <------->
                 PANA-Reauth-Answer          <------->

                 PANA-Termination-Request    <------->
                 PANA-Termination-Answer     <------->

                 PANA-Update-Request         -------->
                 PANA-Update-Answer          <--------

                 PANA-Error                  <------->

                    Figure 10: 11: PANA Message Overview

6.4.1  Message Specifications

   Every PANA message MUST include a corresponding ABNF [RFC2234]
   specification found in [RFC3588].  Note that PANA messages have a
   different header format compared to Diameter.

   Example:

      message ::= < PANA-Header: <Message type>, [REQ] [SEP] >
                * [ AVP ]

6.4.2  PANA-PAA-Discover (PDI)

   The PANA-PAA-Discover (PDI) message is used to discover the address
   of PAA(s).  Both sequence numbers in this message are set to zero
   (0).

         PANA-PAA-Discover ::= < PANA-Header: 1 >
                   0*1 < Session-Id >
                    *  [ AVP ]

6.4.3  PANA-Start-Request (PSR)

   PANA-Start-Request (PSR) is sent by the PAA to the PaC.  The PAA sets
   the transmission sequence number to an initial random value.  The
   received sequence number is set to zero (0).

         PANA-Start-Request ::= < PANA-Header: 2, REQ [SEP] >
                       { Nonce }
                       [ Cookie ]
                       [ EAP-Payload ]
                       [ NAP-Information ]
                    *  [ ISP-Information ]
                       [ Protection-Capability]
                       [ PPAC ]
                    *  [ AVP ]

6.4.4  PANA-Start-Answer (PSA)

   PANA-Start-Answer (PSA) is sent by the PaC to the PAA in response to
   a PANA-Start-Request message.  The PANA_start message transmission
   sequence number field is copied to the received sequence number
   field.  The transmission sequence number is set to initial random
   value.

         PANA-Start-Answer ::= < PANA-Header: 2 [SEP] >
                       { Nonce }
                       [ Session-Id ]
                       [ Cookie ]
                       [ Nonce ]
                       [ EAP-Payload ]
                       [ ISP-Information ]
                    *  [ AVP ]
                   0*1 < MAC >

6.4.5  PANA-Auth-Request (PAR)

   PANA-Auth-Request (PAR) is sent by the PAA to the PaC.

         PANA-Auth-Request ::= < PANA-Header: 3, REQ [SEP] [NAP] >
                       < Session-Id >
                       < EAP-Payload >
                    *  [ AVP ]
                   0*1 < MAC >

   (Both NAP-Information and ISP-Information MUST NOT be included at the
   same time)

6.4.6  PANA-Auth-Answer (PAN)

   PANA-Auth-Answer (PAN) is sent by the PaC to the PAA in response to a
   PANA-Auth-Request message.

         PANA-Auth-Answer ::= < PANA-Header: 3 [SEP] [NAP] >
                       < Session-Id >
                       < EAP-Payload >
                    *  [ AVP ]
                   0*1 < MAC >

6.4.7  PANA-Bind-Request (PBR)

   PANA-Bind-Request (PBR) is sent by the PAA to the PaC.

         PANA-Bind-Request ::= < PANA-Header: 4, REQ [SEP] [NAP] >
                       < Session-Id >
                       { Result-Code }
                       { PPAC }
                       [ EAP-Payload ]
                       [ Device-Id ]
                       [ Session-Lifetime ]
                       [ Protection-Capability ]
                       [ Key-Id ]
                       [ Nonce ]
                    *  [ EP-Device-Id ]
                    *  [ AVP ]
                   0*1 < MAC >

6.4.8  PANA-Bind-Answer (PBA)

   PANA-Bind-Answer (PBA) is sent by the PaC to the PAA in response to a
   PANA-Result-Request message.

         PANA-Bind-Answer ::= < PANA-Header: 4 [,SEP] [NAP] >
                       < Session-Id >
                       { Result-Code }
                       [ PPAC ]
                       [ Device-Id ]
                       [ Key-Id ]
                    *  [ AVP ]
                   0*1 < MAC >

6.4.9  PANA-Reauth-Request (PRAR)

   PANA-Reauth-Request (PRAR) is either sent by the PaC or the PAA.

         PANA-Reauth-Request ::= < PANA-Header: 5, REQ >
                       < Session-Id >
                       [ Device-Id ]
                    *  [ AVP ]
                   0*1 < MAC >

6.4.10  PANA-Reauth-Answer (PRAA)

   PANA-Reauth-Answer (PRAA) is sent in response to a
   PANA-Reauth-Request.

         PANA-Reauth-Answer ::= < PANA-Header: 5 >
                       < Session-Id >
                       [ Device-Id ]
                    *  [ AVP ]
                   0*1 < MAC >

6.4.11  PANA-Termination-Request (PTR)

   PANA-Termination-Request (PTR) is sent either by the PaC or the PAA.

         PANA-Termination-Request ::= < PANA-Header: 6, REQ >
                       < Session-Id >
                       < Termination-Cause >
                    *  [ AVP ]
                   0*1 < MAC >

6.4.12  PANA-Termination-Answer (PTA)

   PANA-Termination-Answer (PTA) is sent either by the PaC or the PAA in
   response to PANA-Termination-Request.

         PANA-Termination-Answer ::= < PANA-Header: 6 >
                       < Session-Id >
                    *  [ AVP ]
                   0*1 < MAC >

6.4.13  PANA-Error (PER)

   PANA-Error is sent either by the PaC or the PAA.

         PANA-Error ::= < PANA-Header: 7 >
                        < Session-Id >
                        < Result-Code >
                        { Failed-AVP }
                     *  [ AVP ]
                    0*1 < MAC >

6.4.14  PANA-FirstAuth-End-Request (PFER)

   PANA-FirstAuth-End-Request (PFER) is sent by the PAA to the PaC.

         PANA-FirstAuth-End-Request ::= < PANA-Header: 8, REQ [SEP] [NAP] >
                       < Session-Id >
                       < Device-Id >
                       { EAP-Payload }
                       { Result-Code }
                       [ Key-Id ]
                    *  [ AVP ]
                   0*1 < MAC >

6.4.15 PANA-FirstAuth-End-Answer (PFEA)

   PANA-FirstAuth-End-Answer (PFEA)

6.4.15  PANA-FirstAuth-End-Answer (PFEA)

   PANA-FirstAuth-End-Answer (PFEA) is sent by the PaC to the PAA in
   response to a PANA-FirstAuth-End-Request message.

         PANA-FirstAuth-End-Answer ::= < PANA-Header: 8, REQ [SEP] [NAP] >
                       < Session-Id >
                       < Device-Id >
                       [ Key-Id ]
                    *  [ AVP ]
                   0*1 < MAC >

6.4.16  PANA-Update-Request (PUR)

   PANA-Update-Request (PUR) is sent by the PaC to the PAA.

         PANA-Update-Request ::= < PANA-Header: 9, REQ >
                       < Session-Id >
                       < IP-Address >
                    *  [ AVP ]
                   0*1 < MAC >

6.4.17  PANA-Update-Answer (PUA)

   PANA-Update-Answer (PUA) is sent by the PaC PAA to the PAA PaC in response to
   a PANA-FirstAuth-End-Request message.

         PANA-FirstAuth-End-Answer PANA-Update-Request.

         PANA-Update-Answer ::= < PANA-Header: 8, REQ [SEP] [NAP] 9 >
                       < Session-Id >
                       < Device-Id >
                       [ Key-Id ]
                    *  [ AVP ]
                   0*1 < MAC >

6.5  AVPs in PANA

   Some of the used AVPs are defined in this document and some of them
   are defined in other documents like [RFC3588].  PANA proposes to use
   the same name space with [RFC3588].  For temporary allocation, PANA
   uses AVP type numbers starting from 1024.

6.5.1  MAC AVP

   The first octet (8 bits) of the MAC (Code 1024) AVP data contains the
   MAC algorithm type.  Rest of the AVP data payload contains the MAC
   encoded in network byte order.  The Algorithm 8 bit 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...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Algorithm

   		1              HMAC-SHA1 (20 bytes)
   MAC
      The Message Authentication Code is encoded in network byte order.

6.5.2  Device-Id AVP

   The Device-Id AVP (Code 1025) 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.

6.5.3  Session-Id AVP

   All messages pertaining to a specific PANA session MUST include a
   Session-Id AVP (Code 1026) which carries a PAA-assigned fix value
   throughout the lifetime of a session.  When present, the Session-Id
   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].

6.5.4  Cookie AVP

   The Cookie AVP (Code 1027) is of type OctetString.  The data is
   opaque and the exact content is outside the scope of this protocol.

6.5.5  Protection-Capability AVP

   The Protection-Capability AVP (Code 1028) is of type Unsigned32.  The
   AVP data indicates the cryptographic data protection capability
   supported by the EPs.  Below is a list of specified data protection
   capabilities:

         0          L2_PROTECTION
         1          IPSEC_PROTECTION

6.5.6  Termination-Cause AVP

   The Termination-Cause AVP (Code 1029) is of type of type Enumerated,
   and is used to indicate the reason why a session was terminated on
   the access device.  The AVP data is used as a collection of flags The
   following Termination-Cause AVP defined in [RFC3588] are used for
   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, such as the receipt of a
      Abort-Session-Request message.

   SESSION_TIMEOUT          8  (PAA -> PaC)

      The session has timed out, and service has been terminated.

6.5.7  Result-Code AVP

   The Result-Code AVP (AVP Code 1030) 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.

6.5.7.1  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 that
   corresponds to the one detected first is returned.

   PANA_SUCCESS                            2001

      Both the authentication and authorization processes are
      successful.

   PANA_AUTHENTICATION_REJECTED            4001

      The authentication process failed.  When this error is returned,
      the authorization process also fails.

   PANA_AUTHORIZATION_REJECTED             5003

      The authorization process failed.  This error could occur when
      authorization is rejected by a AAA proxy or rejected locally by a
      PAA, even if the authentication procedure succeeds.

6.5.7.2  Protocol Error Result Codes

   Protocol error result code values.

   PANA_MESSAGE_UNSUPPORTED                3001

      Error code from PAA to PaC or from PaC to PAA.  Message type not
      recognized or supported.

   PANA_UNABLE_TO_DELIVER                  3002

      Error code from PAA to PaC.  PAA was unable to deliver the EAP
      payload to the authentication server.

   PANA_INVALID_HDR_BITS                   3008

      Error code from PAA to PaC or from PaC to PAA.  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's definition.

   PANA_INVALID_AVP_BITS                   3009

      Error code from PAA to PaC or from PaC to PAA.  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

      Error code from PAA to PaC or from PaC to PAA.  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

      Error code from PAA to PaC or from PaC to PAA.  The message
      contained an unknown Session-Id.  PAA MUST NOT send this error
      result code value to PaC if PaC sent an unknown Session-Id in the
      PANA-Start-Answer message (session resumption).

   PANA_INVALID_AVP_VALUE                  5004
      Error code from PAA to PaC or from PaC to PAA.  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.

   PANA_MISSING_AVP                        5005

      Error code from PAA to PaC or from PaC to PAA.  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

      Error code from PAA to PaC.  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.

   PANA_CONTRADICTING_AVPS                 5007

      Error code from PAA to PaC.  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.

   PANA_AVP_NOT_ALLOWED                    5008

      Error code from PAA to PaC or from PaC to PAA.  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

      Error code from PAA to PaC or from PaC to PAA.  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.

   PANA_UNSUPPORTED_VERSION                5011
      Error code from PAA to PaC or from PaC to PAA.  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
      PANA-Error message.

   PANA_INVALID_AVP_LENGTH                 5014

      Error code from PAA to PaC or from PaC to PAA.  The message
      contained an AVP with an invalid length.  The PANA-Error message
      indicating this error MUST include the offending AVPs within a
      Failed-AVP AVP.

   PANA_INVALID_MESSAGE_LENGTH             5015

      Error code from PAA to PaC or from PaC to PAA.  This error is
      returned when a message is received with an invalid message
      length.

   PANA_PROTECTION_CAPABILITY_UNSUPPORTED  5016

      Error code from PaC to PAA.  This error is returned when the PaC
      receives a PANA-Bind-Request is received with an
      Protection-Capability AVP and a valid MAC AVP but does not support
      the protection capability specified in the Protection-Capability
      AVP.

   PANA_PPAC_CAPABILITY_UNSUPPORTED  5017

      Error code from PaC to PAA.  This error is returned in a
      PANA-Bind-Answer message when there is no match between the list
      of PPAC methods offered by the PAA and the ones available on the
      PaC.

   PANA_INVALID_IP_ADDRESS  5018

      Error code from PAA to PaC.  This error is returned in a
      PANA-Error message when the IP-Address AVP in the received
      PANA-Update-Request message is invalid (e.g., a non-unicast
      address).

6.5.8  EAP-Payload AVP

   The EAP-Payload AVP (AVP Code 1031) is of type OctetString and is
   used to encapsulate the actual EAP packet that is being exchanged
   between the EAP peer and the EAP authenticator.

6.5.9  Session-Lifetime AVP

   The Session-Lifetime AVP (Code 1032) data is of type Unsigned32.  It
   contains the number of seconds remaining before the current session
   is considered expired.

6.5.10  Failed-AVP AVP

   The Failed-AVP AVP (AVP Code 1033) is of type Grouped and provides
   debugging information in cases where a request is rejected or not
   fully processed due to erroneous information in a specific AVP.  The
   format of the Failed-AVP AVP is defined in [RFC3588].

6.5.11  NAP-Information AVP

   The NAP-Information AVP (AVP Code: 1034) is of type Grouped, and
   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.  Its Data field has the following ABNF grammar:

         NAP-Information ::= < AVP Header: 1034 >
                    0*1 { Provider-Identifier }
                        { Provider-Name }
                     *  [ AVP ]

6.5.12  ISP-Information AVP

   The ISP-Information AVP (AVP Code: 1035) is of type Grouped, and
   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.  Its Data field has the following ABNF grammar:

         ISP-Information ::= < AVP Header: 1035 >
                    0*1 { Provider-Identifier }
                        { Provider-Name }
                     *  [ AVP ]

6.5.13  Provider-Identifier AVP

   The Provider-Identifier AVP (AVP Code: 1036) is of type Unsigned32,
   and contains an IANA assigned "SMI Network Management Private
   Enterprise Codes" [ianaweb] value, encoded in network byte order.

6.5.14  Provider-Name AVP

   The Provider-Name AVP (AVP Code: 1037) is of type UTF8String, and
   contains the UTF8-encoded name of the provider.

6.5.15  EP-Device-Id AVP

   The EP-Device-Id AVP (AVP Code: 1038) contains the device identifier
   of an EP.  The payload format of the EP-Device-Id AVP is the same as
   that of the Device-Id AVP (see See section Section 6.5.2).

6.5.16  Key-Id AVP

   The Key-Id AVP (AVP Code: 1039) 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.

6.5.17  Post-PANA-Address-Configuration (PPAC) AVP

   The data field of PPAC AVP (Code 1040) is of type Unsigned32.  The
   AVP data is used to carry a set of flags which maps to various IP
   address configuration methods.  When sent by the PAA, the AVP MUST
   have at least one of the flags set, and MAY have more than one set.
   When sent by the PaC, only one of the flags MUST be set.

   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.

      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.

6.5.18  Nonce AVP

   The Nonce AVP (Code 1041) is of type OctetString.  The data contains
   a randomly generated value in opaque format.  The data length MUST be
   between 8 and 256 bytes inclusive.

6.5.19  IP-Address AVP

   The IP-Address (AVP Code: 1042) contains an IP address of a PaC.  The
   payload format of the IP-Address AVP is the same as that of the
   Device-Id AVP (see See section Section 6.5.2).  Address families for
   IPv4 or IPv6 MUST be used for this AVP.

6.6  AVP Occurrence Table

   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.

   1+    At least one instance of the AVP MUST be present in the
         message.

                          +-----------------------------------------+
                          |        Message                          |
                          |          Type                           |
                          +-----+-----+-----+-----+-----+-----+-----+
      Attribute Name      | PSR | PSA | PAR | PAN | PBR | PBA | PDI |
      --------------------+-----+-----+-----+-----+-----+-----+-----+
      Result-Code         |  0  |  0  |  0  |  0  |  1  |  1  |  0  |
      Session-Id          |  0  | 0-1 |  1  |  1  |  1  |  1  | 0-1 |
      Termination-Cause   |  0  |  0  |  0  |  0  |  0  |  0  |  0  |
      EAP-Payload         | 0-1 | 0-1 |  1  |  1  | 0-1 |  0  |  0  |
      MAC                 |  0  | 0-1 | 0-1 | 0-1 | 0-1 | 0-1 |  0  |
      Nonce               |  0  1  | 0-1  1  |  0  |  0  | 0-1  0  |  0  |  0  |
      Device-Id           |  0  |  0  |  0  |  0  | 0-1 | 0-1 |  0  |
      Cookie              | 0-1 | 0-1 |  0  |  0  |  0  |  0  |  0  |
      Protection-Cap.     | 0-1 |  0  |  0  |  0  | 0-1 |  0  |  0  |
      PPAC                | 0-1 |  0  |  0  |  0  |  1  | 0-1 |  0  |
      Session-Lifetime    |  0  |  0  |  0  |  0  | 0-1 |  0  |  0  |
      Failed-AVP          |  0  |  0  |  0  |  0  |  0  |  0  |  0  |
      ISP-Information     |  0+ | 0-1 |  0  |  0  |  0  |  0  |  0  |
      NAP-Information     | 0-1 |  0  |  0  |  0  |  0  |  0  |  0  |
      EP-Device-Id        |  0  |  0  |  0  |  0  |  0+ |  0  |  0  |
      Key-Id              |  0  |  0  |  0  |  0  | 0-1 | 0-1 |  0  |
      IP-Address          |  0  |  0  |  0  |  0  |  0  |  0  |  0  |
      --------------------+-----+-----+-----+-----+-----+-----+-----+

                 Figure 11: 12: AVP Occurrence Table (1/2) (1/3)
                          +---------------------------------------------+
                          |      Message                                |
                          |       Type                                  |
                          +------+------+-----+-----+-----+------+------+
      Attribute Name      | PRAR | PRAA | PTR | PTA | PER | PFER | PFEA |
      --------------------+------+------+-----+-----+-----+------+------+
      Result-Code         |  0   |  0   |  0  |  0  |  1  |  1   |  0   |
      Session-Id          |  1   |  1   |  1  |  1  |  1  |  1   |  1   |
      Termination-Cause   |  0   |  0   |  1  |  0  |  0  |  0   |  0   |
      EAP-Payload         |  0   |  0   |  0  |  0  |  0  |  1   |  0   |
      MAC                 | 0-1  | 0-1  | 0-1 | 0-1 | 0-1 | 0-1  | 0-1  |
      Nonce               |  0   |  0   |  0  |  0  |  0  |  0   |  0   |
      Device-Id           | 0-1  0   | 0-1  0   |  0  |  0  |  0  |  0   |  0   |
      Cookie              |  0   |  0   |  0  |  0  |  0  |  0   |  0   |
      Protection-Cap.     |  0   |  0   |  0  |  0  |  0  |  0   |  0   |
      PPAC                |  0   |  0   |  0  |  0  |  0  |  0   |  0   |
      Session-Lifetime    |  0   |  0   |  0  |  0  |  0  |  0   |  0   |
      Failed-AVP          |  0   |  0  0   |  0  |  0  |  1  |  0   |  0   |
      ISP-Information     |  0   |  0   |  0  |  0  |  0  |  0   |  0   |
      NAP-Information     |  0   |  0   |  0  |  0  |  0  |  0   |  0   |
      EP-Device-Id        |  0   |  0   |  0  |  0  |  0  |  0   |  0   |
      Key-Id              |  0   |  0   |  0  |  0  |  0  | 0-1  | 0-1  |
      IP-Address          |  0   |  0   |  0  |  0  |  0  |  0   |  0   |
      --------------------+------+------+-----+-----+-----+------+------+

                 Figure 13: AVP Occurrence Table (2/3)
                          +-----------+
                          |  Message  |
                          |   Type    |
                          +-----+-----+
      Attribute Name      | PUR | PUA |
      --------------------+-----+-----+
      Result-Code         |  0  |  0  |
      Session-Id          |  1  |  1  |
      Termination-Cause   |  0  |  0  |
      EAP-Payload         |  0  |  0  |
      MAC                 | 0-1 | 0-1 |
      Nonce               |  0  |  0  |  1
      Device-Id           |  0  |  0  |
      ISP-Information
      Cookie              |  0  |  0  |  0
      Protection-Cap.     |  0  |  0  |  0
      PPAC                |  0  |
      NAP-Information     |  0  |  0
      Session-Lifetime    |  0  |  0  |  0
      Failed-AVP          |  0  |  0  |
      EP-Device-Id
      ISP-Information     |  0  |  0  |  0
      NAP-Information     |  0  |  0  |
      EP-Device-Id        |  0  |  0  |
      Key-Id              |  0  |  0  |  0
      IP-Address          |  0  1  |  0  | 0-1  | 0-1  |
      --------------------+------+------+-----+-----+-----+------+------+
      --------------------+-----+-----+

                 Figure 12: 14: AVP Occurrence Table (2/2) (3/3)

7.  PANA Protocol Message Retransmissions

   The PANA protocol provides retransmissions for all the message
   exchanges except PANA-Auth-Request/Answer.  PANA-Auth-Request
   messages carry EAP requests which are retransmitted by the EAP
   protocol entities when needed.  The messages that need PANA-level
   retransmissions are listed below:

         PANA-PAA-Discover (PDI)
         PANA-Start-Request (PSR)*
         PANA-Start-Answer (PSA)**
         PANA-Bind-Request (PBR)
         PANA-FirstAuth-End-Request (PFER)
         PANA-Reauth-Request (PRAR)
         PANA-Termination-Request (PTR)
         PANA-Update-Request (PUR)

         *)  PSR that carries a Cookie AVP is not retransmitted.
         **) PSA that does not carry a Cookie AVP is not retransmitted.

   The PDI and PSA messages are always sent by the PaC.  PBR is sent by
   PAA.  The last two messages, PRAR and PTR are sent either by PaC or
   PAA.

   The rule is that the sender of the request message retransmits the
   request if the corresponding answer is not received in time.  Answer
   messages are sent as answers to the request messages, not based on a
   timer.  Exception to this rule is the PSA message.  Because of the
   stateless nature of the PAA in the beginning PaC provides
   retransmission also for the PSA message.  PANA-Error messages MUST
   not
   NOT be retransmitted.  See Section 4.1.8 for more details of PANA
   error handling.

   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 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

   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.

7.1  Transmission and +0.1.  The randomization factor is included Retransmission Parameters

   This section presents a table of values used to
   minimize synchronization describe the message
   retransmission behavior of messages. request and PANA-Start-Answer messages
   marked with REQ_*.  PANA-PAA-Discover message retransmission values
   are marked with PDI_*.  The algorithm 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 choosing a random number does not need to be
   cryptographically sound.  The algorithm SHOULD produce a different
   sequence of random numbers from each invocation. example the first RT for the first PBR message transmission is based on calculated using
   REQ_IRT as the IRT:

           RT = IRT REQ_IRT + RAND*IRT

   RT for each subsequent message transmission is based on RAND*REQ_IRT

8.  IANA Considerations

   This section provides guidance to the previous
   value Internet Assigned Numbers
   Authority (IANA) regarding registration of RT:

         RT = 2*RTprev + RAND*RTprev

   MRT specifies an upper bound on 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 value of RT (disregarding responsible IESG area director should appoint the
   randomization added by
   Designated Expert.  For Designated Expert with Specification
   Required, the use of RAND). If MRT has a value of 0,
   there request is no upper limit on posted to the value of RT.  Otherwise: PANA WG mailing list (or, if (RT > MRT)
            RT = MRT + RAND*MRT

   MRC specifies an upper bound on
   it has been disbanded, a successor designated by the number of times Area Director)
   for comment and review, and MUST include a sender may
   retransmit pointer to a message.  Unless MRC is zero, public
   specification.  Before a period of 30 days has passed, the message exchange fails
   once Designated
   Expert will either approve or deny the sender has transmitted registration request and
   publish a notice of the message MRC times.

   MRD specifies decision to the PANA WG mailing list or its
   successor.  A denial notice must be justified by an upper bound on explanation and,
   in the length of time a sender may
   retransmit a message.  Unless MRD cases where it is zero, possible, concrete suggestions on how the message exchange fails
   once MRD seconds have elapsed since
   request can be modified so as to become acceptable.

8.1  PANA UDP Port Number

   PANA uses one well-known UDP port number (Section 4.1.2, Section 4.2
   and Section 6.1, which needs to be assigned by the client first transmitted IANA.

8.2  PANA Multicast Address

   PANA uses one well-known IPv4 multicast address for which the
   message.

   If both MRC and MRD are non-zero, scope
   is limited to be link-local by setting the message exchange fails whenever
   either of TTL field to 255, and one
   well-known IPv6 link-local scoped multicast address (Section 4.2 and
   Section 6.1), which need to be assigned by the conditions specified IANA.

8.3  PANA Header

   As defined in Section 6.2, the previous PANA header contains two paragraphs are
   met.

   If both MRC and MRD are zero, the client continues to transmit fields that
   requires IANA namespace management; the
   message until it receives a response.

7.1 Transmission Message Type and Retransmission Parameters

   This section presents a table of values Flags field.

8.3.1  Message Type

   The Message Type namespace is used to describe the identify PANA messages.  Values
   0-16,777,213 are for permanent, standard message
   retransmission behavior types, allocated by
   IETF Consensus [IANA].  This document defines the Message Types 1-8.
   See Section 6.4.1 for the assignment of request the namespace in this
   specification.

   The values 16,777,214 and PANA-Start-Answer messages
   marked with REQ_*. PANA-PAA-Discover message retransmission 16,777,215 (hexadecimal values 0xfffffe -
   0xffffff) are marked with 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 reserved for example the first RT experimental messages.  As these codes are
   only for the PBR message experimental and testing purposes, no guarantee is calculated made for
   interoperability between communicating PaC and PAA using
   REQ_IRT experimental
   commands, as outlined in [IANA-EXP].

8.3.2  Flags

   There are eight bits in the IRT:

           RT = REQ_IRT + RAND*REQ_IRT

8. IANA Considerations

   This section provides guidance to the Internet Assigned Numbers
   Authority (IANA) regarding registration Flags field of values related to the
   Diameter protocol, in accordance with BCP 26 PANA header.  This
   document assigns bit 0 ('R'equest), bit 4 ('S'eparate) and bit 5
   ('N'AP Authentication).  The remaining bits MUST only be assigned via
   a Standards Action [IANA].  The following
   policies are used here with the meanings

8.4  AVP Header

   As defined in BCP 26: "Private
   Use", "First Come First Served", "Expert Review", "Specification
   Required", "IETF Consensus", "Standards Action".

   This section explains Section 6.3, the criteria 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.

8.4.1  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 used 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
   1024-1041.  See Section 6.5 for the assignment of numbers within namespaces defined within the namespace in
   this document.

   For registration requests where a Designated Expert should specification.

   AVPs may be
   consulted, the responsible IESG area director should appoint the
   Designated Expert.  For allocated following Designated Expert with Specification
   Required,
   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 request Vendor-Id field in the AVP header is posted set to the PANA WG mailing list (or, if
   it has been disbanded, a successor designated by the Area Director) non-zero value.
   Vendor-Specific AVPs codes are for comment and review, Private Use and MUST include a pointer 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 public
   specification.  Before a period Vendor-Specific AVP is
   implemented by more than one vendor, allocation of 30 days has passed, global AVPs should
   be encouraged instead.

8.4.2  Flags

   There are 8 bits in the Designated
   Expert will either approve or deny AVP Flags field of the registration request AVP header, defined in
   Section 6.3.  This document assigns bit 0 ('V'endor Specific) and
   publish bit
   1 ('M'andatory).  The remaining bits should only be assigned via a notice
   Standards Action .

8.5  AVP Values

   Certain AVPs in PANA define a list of the decision values with various meanings.
   For attributes other than those specified in this section, adding
   additional values to the PANA WG mailing list or its
   successor.  A denial notice must can be justified done on a First Come, First
   Served basis by an explanation and, IANA [IANA].

8.5.1  Algorithm Values of MAC AVP

   As defined in Section 6.5.1, the cases where it is possible, concrete suggestions on how the
   request can be modified so as to become acceptable.

8.1 PANA UDP Port Number

   TBD.

8.2 PANA Multicast Address

   TBD.

8.3 PANA Header

8.3.1 Message Type

   TBD.

8.3.2 Flags

   TBD.

8.4 AVP Header

8.4.1 AVP Code

   TBD.

8.4.2 Flags

   TBD.

8.4.3 Vendor Id

   TBD.

8.5 AVP Values

8.5.1 Algorithm field of MAC AVP Values

   TBD. (AVP Code
   1024) defines the value of 1 (one) for HMAC-SHA1.

   All remaining values are available for assignment via IETF Consensus
   [IANA].

8.5.2 Device-Id  Protection-Capability AVP Values

   TBD.

8.5.3

   As defined in Section 6.5.5, the Protection-Capability AVP (AVP Code
   1028) defines the values 0 and 1.

   All remaining values are available for assignment via a Standards
   Action [IANA].

8.5.3  Termination-Cause AVP Values

   TBD.

   As defined in Section 6.5.6, the Termination-Cause AVP (AVP Code
   1029) defines the values 1, 4 and 8.

   All remaining values are available for assignment via IETF Consensus
   [IANA].

8.5.4  Result-Code AVP Values

   TBD.

8.5.5 Termination-Cause

   As defined in Section 6.5.7, the Result-Code AVP Values

   TBD.

8.5.6 Provider-Identifier (AVP Code 1030)
   defines the values 2001, 3001-3002, 3008-3009, 4001, 5001-5009 and
   5011-5019.

   All remaining values are available for assignment via IETF Consensus
   [IANA].

8.5.5  Post-PANA-Address-Configuration AVP Values

   TBD.

8.5.7

   As defined in Section 6.5.17, the Post-PANA-Address-Configuration AVP Values

   TBD.
   (AVP Code 1040) 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.  Security Considerations

   The PANA protocol provides ordered delivery for EAP messages.  If an
   EAP method that provides session keys is used, a PANA SA is created.
   The EAP Success/Failure message is one of the signaling messages
   which is integrity protected with this PANA SA.  The PANA protocol
   does not provide security protection for the initial EAP message
   exchange.  Integrity protection can only be provided after the PANA
   SA has been established.  Thus, PANA re-authentication, revocation
   and disconnect notifications can be authenticated, integrity and
   replay protected.  In certain environments (e.g., on a shared link)
   the EAP method selection is an important issue.

   The PANA framework described in this document covers the discussion
   of different protocols which are of interest for a protocol between
   the PaC and the PAA (typically referred as the PANA protocol).

   The PANA itself consists of a sequence of steps which are executed to
   complete the network access authentication procedure.  Some of these
   steps are optional.

   The following execution steps have been identified as being relevant
   for PANA.  They security considerations will be discussed in detail
   subsequently.

   a) Discovery message exchange

   In general it is difficult to prevent a vulnerabilities of the
   discovery protocol since the initial discovery are unsecured.  To
   prevent very basic attacks an adversary should not be able to cause
   state creation with discovery messages at the PAA.  This is prevented
   by re-using a cookie concept (see [RFC2522] which allows the
   responder to be stateless in the first message exchange.  Because of
   the architectural assumptions made in PANA (i.e., the PAA is the on
   the same link as the PaC) the return-routability concept does not
   provide additional protection.  Hence it is difficult to prevent this
   threat entirely.  Furthermore it is not possible to shift heavy
   cryptographic operations to the PaC at the first few messages since
   the computational effort depends on the EAP method.  The usage of
   client-puzzles as introduced by [jb99] is under investigation.

   Resistance against blind DoS attacks (i.e., attacks by off-path
   adversaries) is achieved with sequence numbers and cookies.

   Since PAA and PaC are supposed to be one IP hop away, a simple TTL
   check can prevent off-link attacks.  Furthermore, additional
   filtering can be enabled on the EPs.  An EP may be able to filter
   unauthorized PAA advertisements when they are received on the access
   side of the network where only PaCs are connected.

   In networks where lower-layers are not secured prior to running PANA,
   the capability discovery enabled through inclusion of
   Protection-Capability and Post-PANA-Address-Configuration AVPs in
   PANA-Start-Request message is susceptible to spoofing.  Therefore,
   usage of these AVPs during the discovery phase in such insecure
   networks is NOT RECOMMENDED.  The same AVPs are delivered via an
   integrity-protected PANA-Bind-Request upon successful authentication.

   b) EAP over PANA message exchange

   The EAP derived session key is used to create a PANA security
   association.  Since the execution of an EAP method might require a
   large number of roundtrips and no other session key is available it
   is not possible to secure the EAP message exchange itself.  Hence an
   adversary can both eavesdrop the EAP messages and is also able to
   inject arbitrary messages which might confuse both the EAP peer on
   PaC and the EAP authenticator or authentication server on the PAA.
   The threats caused by this ability heavily depend on the EAP state
   machine.  Since especially the PAA is not allowed to discard packets
   and packets have to be stored or forwarded to an AAA infrastructure
   some risk of DoS attacks exists.

   Eavesdropping EAP packets might cause problems when (a) 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 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
   usage environment an EAP authentication has to be used for example
   which supports user identity confidentiality, protection against
   dictionary attacks and session key establishment.  It is therefore
   the responsibility of the network operators and end users to choose
   the proper EAP method.

   PANA does not protect the EAP method exchange, but provides ordered
   delivery with sequence numbers.  Sequence numbers and cookies provide
   resistance against blind DoS attacks.

   c) PANA SA establishment

   Once the EAP message authentication is finished a fresh and unique
   session key is available to the PaC and the PAA.  This assumes that
   the EAP method allows session key derivation and that the generated
   session key has a good quality.  For further discussion about the
   importance of the session key generation refer to the next subsection
   (d) about compound authentication.  The session key available for the
   PaC is established as part of the authentication and key exchange
   procedure of the selected EAP method.  The PAA obtains the session
   key via the AAA infrastructure (if used).  Security issues raised
   with this session key transport are described in
   [I-D.ietf-eap-keying].

   The establishment of a PANA SA is required in environments where no
   physical or link layer security is available.  The PANA SA allows
   subsequently exchanged messages to experience cryptographic
   protection.  For the current version of the document an integrity
   object (MAC AVP) is defined which supports data-origin
   authentication, replay protection based on sequence numbers and
   integrity protection based on a keyed message digest.
   Confidentiality protection is not provided.  The session keys used
   for this object have to be provided by the EAP method.  For this
   version of the document it is assumed that no negotiation of
   algorithms and parameters takes place.  Instead HMAC-SHA1 is used by
   default.  A different algorithm may be chosen by default in a future
   version of the PANA protocol specification.  The used algorithm is
   indicated in the header of the Integrity object.  To select the
   security association for signaling message protection the Session ID
   is conveyed.  The keyed message digest included in the Integrity
   object will include all fields of the PANA signaling message
   including the sequence number field fields of the packet.

   The protection of subsequent signaling messages prevents an adversary
   from acting as a man-in-the-middle adversary, from injecting packets,
   from replaying messages and from modifying the content of the
   exchanged packets.  This prevents subsequently described threats.

   If an entity (PAA or PaC) loses its state (especially the current
   sequence number) then the entire PANA protocol has to be restarted.
   No re-synchronization procedure is provided.

   The lifetime of the PANA SA has to be bound to the AAA-authorized
   session lifetime with an additional tolerance period.  Unless PANA
   state is updated by executing another EAP authentication, PANA SA is
   removed when the current session expires.  The lifetime of the PANA
   SA has to be bound to the AAA-authorized session lifetime with an
   additional tolerance period.  Unless PANA state is updated by
   executing another EAP authentication, PANA SA is removed when the
   current session expires.

   d) Enabling weak legacy authentication methods in insecure networks
   Some of the authentication methods are not strong enough to be used
   in insecure networks where attackers can easily eavesdrop and spoof
   on the link.  They may not be able to produce much needed keying
   material either.  An example would be using EAP-MD5 over wireless
   links.  Use of such legacy methods can be enabled by carrying them
   over a secure channel.  There are EAP methods which are specifically
   designed for this purpose, such as EAP-TTLS
   [I-D.ietf-pppext-eap-ttls],PEAP [I-D.josefsson-pppext-eap-tls-eap] or
   EAP-IKEv2 [I-D.tschofenig-eap-ikev2].  PANA can carry these EAP
   tunneling methods which can carry the legacy methods.  PANA does not
   do anything special for this case.  The EAP tunneling method will
   have to produce keying material for PANA SA when needed.  There are
   certain MitM vulnerabilities with tunneling EAP methods [mitm].
   Solving these problems is outside the scope of PANA.  The compound
   authentication problem described in [I-D.puthenkulam-eap-binding] is
   likely to be solved in EAP itself rather than in PANA.

   e) Device Identifier exchange

   As part of the authorization procedure a Device Identifier has to be
   installed at the EP by the PAA.  The PaC provides the Device
   Identifier information to the PAA secured with the PANA SA.  Section
   6.2.4 of [I-D.ietf-pana-threats-eval] describes a threat where an
   adversary modifies the Device Identifier to gain unauthorized access
   to the network.

   The installation of the Device Identifier at the EP (independently
   whether the EP is co-located with the PAA or not) has to be
   accomplished in a secure manner.  These threats are, however, not
   part of the PANA protocol itself since the protocol is not PANA
   specific.

   f) Triggering a data protection protocol

   Recent activities in the EAP working group try to create a common
   framework for key derivation which is described in
   [I-D.ietf-eap-keying].  This framework is also relevant for PANA in
   various ways.  First, a PANA security association needs to be
   created.  Additionally it might be necessary to trigger a protocol
   which allows link layer and network layer data protection to be
   established.  As an example see Section 1 of [I-D.ietf-eap-keying]
   with [802.11i] and [802.11] as an example.  Furthermore, a derived
   session key might help to create the pre-requisites for network-layer
   protection (for example IPsec [I-D.ietf-pana-ipsec]).

   As motivated in Section 6.4 of [I-D.ietf-pana-threats-eval] it might
   be necessary to establish either a link layer or a network layer
   protection to prevent certain thefts in certain scenarios.

   Threats specific to the establishment of a link layer or a network
   layer security association are outside the scope of PANA.  The
   interested reader should refer to the relevant working groups such as
   IPsec or Midcom.

   g) Liveness test

   Network access authentication is done for a very specific purpose and
   often charging procedures are involved which allow restricting
   network resource usage based on some policies.  In mobile
   environments it is always possible that an end host suddenly
   disconnects without transmitting a disconnect message.  Operators are
   generally motivated to detect a disconnected end host as soon as
   possible in order to release resources (i.e., garbage collection).
   The PAA can remove per-session state information including installed
   security association, packet filters, etc.

   Different procedures can be used for disconnect indication.  PANA
   cannot assume link-layer disconnect indication.  Hence this
   functionality has to be provided at a higher layer.  With this
   version of the draft we suggest to apply the soft-state principle
   found at other protocols (such as RSVP).  Soft-state means that
   session state is kept alive as long as refresh messages refresh the
   state.  If no new refresh messages are provided then the state
   automatically times out and resources are released.  This process
   includes stopping accounting procedures.

   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 lifetime expires.  A
   disconnect may also be detected earlier by using PANA
   reauthentication 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 discontinuation of data traffic).  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 PANA SA is available in order to
   prevent threats associated with the abuse of this functionality.

   h) Tear-Down message

   The PANA protocol supports the ability for both the PaC and the PAA
   to transmit a tear-down message.  This message causes state removal,
   a stop of the accounting procedure and removes the installed packet
   filters.

   It is obvious that such a message must be protected to prevent an
   adversary from deleting state information and thereby causing denial
   of service attacks.

   i) Mobility optimization

   The mobility optimization described in Section 4.9 4.12 involves the
   previous PAA providing a AAA-Key to the current PAA of the PaC.
   There are security risks stemming from potential compromise of PAAs.
   Compromise of the current PAA does not yield compromise of the
   previous PAA, as AAA-Key cannot be computed from a compromised
   AAA-Key-new.  But a compromised previous PAA along with the
   intercepted nonce values leads to the compromise of AAA-Key-new.
   Operators should be aware of the potential risk of using this
   optimization.  An operator can reduce the risk exposure by forcing
   the PaC to perform an EAP-based authentication immediately after the
   optimized PANA execution.

   j) Updating PaC's address

   An attacker can generate a PANA-Update-Request with an IP-Address
   AVP.  There are several threats:
   o  An attacker spoofs an address and registers itself with the
      address.  If the registered address is not assigned to any PaC,
      subsequent PANA messages sent from the PAA to the attacker will
      not reach any node and this is not a significant harm.  If the
      registered address is assigned to some PaC, subsequent PANA
      messages sent from the PAA to the attacker will reach the PaC, but
      will be silently discarded because the Session-Id is different.
   o  An attacker registers other PaC with any address.  As a result,
      subsequent PANA messages sent from the PAA to the PaC will not
      reach the PaC.

   To avoid all those attacks against an address update, an additional
   mechanism may be defined outside the PANA protocol for the PAA to
   validate ownership of the address.

10.  Open Issues and Change History

   A list of open issues is maintained at [2].

   Issues incorporated in PANA-01 June 2003: 1, 3, 10, 5, 6, 7 and 11.

   Issues incorporated in PANA-02 October 2003: 8, 17, 18, 19, 20, 21,
   22, 23, 24, 25, 26, 30, 31, 32 and 33.

   Issues incorporated in PANA-03 February 2004: 2, 16, 34, 35, 36, 38,
   39, 40, 42, 43, 44, 50, 51 and 60.

   Issues incorporated in PANA-04 May 2004: 28, 52, 53, 56, 57, 58, 59,
   61, 62, 63, 64, 65, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80 and 83.

   Issues incorporated in PANA-05 July 2004: 84, 85, 91, 92, 93, 96, 97,
   98, 99, 100, 103 and 107.

11.  Acknowledgments

   We would like to thank Jari Arkko, Mohan Parthasarathy, Julien
   Bournelle, Rafael Marin Lopez Lopez, Pasi Eronen, Randy Turner, Erik
   Nordmark and all members of the PANA working group for their valuable
   comments to this document.

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.

   [RFC1982]  Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
              August 1996.

   [RFC2988]  Paxson, V. and M. Allman, "Computing TCP's Retransmission
              Timer", RFC 2988, November 2000.

   [I-D.ietf-eap-rfc2284bis]
              Blunk, L., "Extensible Authentication Protocol (EAP)",
              draft-ietf-eap-rfc2284bis-09 (work in progress), February
              2004.

   [RFC2716]  Aboba, B. and D. Simon, "PPP EAP TLS Authentication
              Protocol", RFC 2716, October 1999.

   [RFC2234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 2234, November 1997.

   [RFC3588]  Calhoun, P., Loughney, J., Guttman, E., Zorn, G. and J.
              Arkko, "Diameter Base Protocol", RFC 3588, September 2003.

   [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.

   [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", (DHCPv4) Configuration of
              IPsec Tunnel Mode", RFC 3456, January 2003.

   [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J. and H.
              Levkowetz, "Extensible Authentication Protocol (EAP)", RFC 3456, January 2003.
              3748, June 2004.

   [I-D.ietf-eap-keying]
              Aboba, B., "EAP "Extensible Authentication Protocol (EAP) Key
              Management Framework",
              draft-ietf-eap-keying-01 draft-ietf-eap-keying-02 (work in
              progress), October 2003. June 2004.

   [IANA]     Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs",  BCP 26, RFC 2434,
              October 1998.

12.2  Informative References

   [I-D.ietf-pana-requirements]
              Yegin, A. and Y. Ohba, "Protocol for Carrying
              Authentication for Network Access (PANA)Requirements",
              draft-ietf-pana-requirements-07
              draft-ietf-pana-requirements-08 (work in progress), June
              2003.
              2004.

   [I-D.ietf-aaa-eap]
              Eronen, P., Hiller, T. and G. Zorn, "Diameter Extensible
              Authentication Protocol (EAP) Application",
              draft-ietf-aaa-eap-05
              draft-ietf-aaa-eap-08 (work in progress), April June 2004.

   [I-D.puthenkulam-eap-binding]
              Puthenkulam, J., "The Compound Authentication Binding
              Problem", draft-puthenkulam-eap-binding-04 (work in
              progress), October 2003.

   [RFC2522]  Karn, P. and W. Simpson, "Photuris: Session-Key Management
              Protocol", RFC 2522, March 1999.

   [I-D.ietf-pana-usage-scenarios]
              Ohba, Y., "Problem Statement and Usage Scenarios for
              PANA", draft-ietf-pana-usage-scenarios-06 (work in
              progress), April 2003.

   [I-D.ietf-pana-threats-eval]
              Parthasarathy, M., "PANA "Protocol for Carrying Authentication
              and Network Access Threat Analysis and security
              requirements", draft-ietf-pana-threats-eval-04  Security
              Requirements", draft-ietf-pana-threats-eval-06 (work in
              progress), May 2003. June 2004.

   [I-D.ietf-pana-ipsec]
              Parthasarathy, M., "PANA enabling IPsec based Access
              Control", draft-ietf-pana-ipsec-03 (work in progress), May
              2004.

   [I-D.ietf-pana-framework]
              Jayaraman, P., "PANA Framework",
              draft-ietf-pana-framework-00 (work in progress), May 2004.

   [I-D.ietf-pana-snmp]
              Mghazli, Y., Ohba, Y. and J. Bournelle, "SNMP usage for
              PAA-2-EP interface", draft-ietf-pana-snmp-00 (work in
              progress), April 2004.

   [I-D.irtf-aaaarch-handoff]
              Arbaugh, W. and B. Aboba, "Experimental Handoff Extension
              to RADIUS", draft-irtf-aaaarch-handoff-04 (work in
              progress), November 2003.

   [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-03 (work in progress), March
              2004.

   [I-D.ietf-seamoby-ctp]
              Loughney, J., "Context Transfer Protocol",
              draft-ietf-seamoby-ctp-08
              draft-ietf-seamoby-ctp-10 (work in progress), January June 2004.

   [RFC2716]  Aboba, B. and D. Simon, "PPP EAP TLS Authentication
              Protocol", RFC 2716, October 1999.

   [I-D.ietf-ipsec-ikev2]
              Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
              draft-ietf-ipsec-ikev2-13
              draft-ietf-ipsec-ikev2-14 (work in progress), March June 2004.

   [I-D.josefsson-pppext-eap-tls-eap]
              Josefsson, S., Palekar, A., Simon, D. and G. Zorn,
              "Protected EAP Protocol (PEAP)",
              draft-josefsson-pppext-eap-tls-eap-07 (work in progress),
              October 2003.

   [I-D.ietf-pppext-eap-ttls]
              Funk, P. and S. Blake-Wilson, "EAP Tunneled TLS
              Authentication Protocol (EAP-TTLS)",
              draft-ietf-pppext-eap-ttls-04 (work in progress), April
              2004.

   [I-D.tschofenig-eap-ikev2]
              Tschofenig, H. and D. Kroeselberg, "EAP IKEv2 Method
              (EAP-IKEv2)", draft-tschofenig-eap-ikev2-03 (work in
              progress), February 2004.

   [ianaweb]  IANA, "Number assignment",  http://www.iana.org.

   [jb99]     Juels, A. and J. Brainard, "Client Puzzles: A
              Cryptographic Defense Against Connection Depletion
              Attacks",  Proceedings of NDSS '99 (Networks and
              Distributed Security Systems), pages 151-165, 1999.

   [mitm]     Asokan, N., Niemi, V. and K. Nyberg, "Man-in-the-middle in
              tunnelled authentication",  In the Proceedings of the 11th
              International Workshop on Security Protocols, Cambridge,
              UK, April 2003.

   [802.11i]  Institute of Electrical and Electronics Engineers, "Draft
              supplement to standard for telecommunications and
              information exchange between systems - lan/man specific
              requirements - part 11: Wireless medium access control
              (mac) and physical layer (phy) specifications:
              Specification for enhanced security", IEEE 802.11i/D10.0,
              2004.

   [802.11]   Institute of Electrical and Electronics Engineers,
              "Information technology - telecommunications and
              information exchange between systems - local and
              metropolitan area networks - specific requirements part
              11: Wireless lan medium access control (mac) and physical
              layer (phy) specifications", IEEE Standard 802.11,
              1999(R2003).

   [IANA-EXP]
              Narten, T., "Assigning Experimental and Testing Numbers
              Considered Useful",  BCP 82, RFC 3692, January 2004.

URIs

   [1]  <http://www.toshiba.com/tari/pana/sequence-number.txt>

   [2]  <http://danforsberg.info:8080/pana-issues/>

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

   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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