Simple PANA PAA Discovery Protocol
draft-fajardo-pana-paa-discovery-00.txt

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Abstract

The PANA Base protocol defines a method for carrying EAP message exchanges over UDP/IP. This means that the PANA Client (PaC) is required to know the IP address of the PANA Authentication Agent (PAA). In many cases, this is not convinient or practical. This document proposes a simple PAA discovery scheme that allows the PaC to determine the PAA IP address without any modification to the base protocol messages or exchange sequence.

Table of Contents

1.  Introduction
2.  Terminology
3.  PAA Discovery Details
4.  Message Formats
    4.1.  PANA-Agent-Discover-Request
    4.2.  PANA-Agent-Discover-Answer
5.  IANA Considerations
6.  Security Considerations
7.  Acknowledgments
§  Author's Address
§  Intellectual Property and Copyright Statements

1.  Introduction

The PANA Base protocol specifies that all messages are carried over unicast UDP/IP packet. This means that the PANA Client (PaC) needs to know the PANA Authentication Agent (PAA) IP address before initiating a PANA conversation. Like many other protocols, it is not practical nor convinient to configure client devices (PaC) with PAA IP address before using it. In general, statically configuring parameters on every device for their currently attached subnet or network does not scale as the number of devices grow.

This document proposes a simple method of dynamically discovering the PAA. A simple and independent discovery protocol can be installed on the PaC and PAA devices that will allow PaC to pro-actively discover the PAA by sending a link local multicast message, PANA-Agent-Discover-Request (PDR). In this case, the PAA listening on that multicast address, can issue a corresponding answer sent unicast to the PaC. The PaC determines the PAA IP address from the source IP of the answer to the PDR message.

2.  Terminology

This document reuses the terminology used in PANA.

3.  PAA Discovery Details

A PaC device wishing to actively discover a PAA can immediately send a PDR message. The PDR is sent as a PANA message with a source IP address set to the PaC IP address and the destination IP address set to a well known multicast address 224.0.0.[TBD]. The PDR MUST be sent to the well known PANA port [TBD] and the PaC device MUST be prepared to accept message on the source port it sets in the PDRs UDP header.

A PAA device which supports the PAA discovery protocol MUST be prepared to accept messages at the well known PANA port and multicast address. If a PDR message is received, the PAA device MUST issue a unicast PANA-Agent-Discover-Answer (PDA) message with the source IP address set to the PAA IP address and destination IP address set to the PaC IP address learned from the PDR message. It MUST also set the destination port of the PDA to the source port of the PDR. A PAA device which reponds to a PDR MAY initiate the PANA session since it has knowledge of the PaC IP address, See Section 4.1 of PANA.

When a PaC device receives a PDA, it SHOULD use the source IP address as the IP address of the PAA in the subsequent PANA exchanges. If the PaC device receives multiple PDA from different PAAs, it can make a local policy decision on which PAA IP address to use.

4.  Message Formats

All message formats are taken from Sec 6 and 7 of the PANA base protocol document. Message types are allocated using rules in Sec 10.2.1 of the PANA base protocol document. As of this writing, there are no AVPs associated with any of the discovery protocol messages. All messages MUST set both the session identifier and the sequence numbers in the PANA header to zero(0).

4.1.  PANA-Agent-Discover-Request

The PANA-Agent-Discover-Request (PDR) message is sent by the PaC device. The message MUST have the 'R' (Request) bit set in the PANA message header.

Message Format

PANA-Agent-Discover-Request ::= < PANA-Header: 5,REQ >
                                *[ AVP ]

4.2.  PANA-Agent-Discover-Answer

The PANA-Agent-Discover-Answer (PDA) message is sent by the PAA device in response to a PANA-Agent-Discover-Request. The message MUST NOT have the 'R' (Request) bit set in the PANA message header.

Message Format

PANA-Agent-Discover-Answer ::= < PANA-Header: 5 >
                               * [ AVP ]

5.  IANA Considerations

This document does not require actions by IANA.

6.  Security Considerations

This document does describes a companion protocol to PANA for discovery PAA IP addresses. It does not define nor address security related protocols or schemes.

7.  Acknowledgments

[TBD].

Author's Address

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