RFC 3817 (rfc3817) - Page 1 of 17

Layer 2 Tunneling Protocol (L2TP) Active Discovery Relay for PPP over Ethernet (PPPoE)

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Network Working Group                                        W. Townsley
Request for Comments: 3817                                 cisco Systems
Category: Informational                                      R. da Silva
                                                         AOL Time Warner
                                                               June 2004


        Layer 2 Tunneling Protocol (L2TP) Active Discovery Relay
                     for PPP over Ethernet (PPPoE)

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2004).

Abstract

   The Point-to-Point Protocol (PPP) provides a standard method for
   transporting multi-protocol datagrams over point-to-point links.
   Layer Two Tunneling Protocol (L2TP), facilitates the tunneling of PPP
   packets across an intervening packet-switched network.  And yet a
   third protocol, PPP over Ethernet (PPPoE) describes how to build PPP
   sessions and to encapsulate PPP packets over Ethernet.

   L2TP Active Discovery Relay for PPPoE describes a method to relay
   Active Discovery and Service Selection functionality from PPPoE over
   the reliable control channel within L2TP.  Two new L2TP control
   message types and associated PPPoE-specific Attribute Value Pairs
   (AVPs) for L2TP are defined.  This relay mechanism provides enhanced
   integration of a specific feature in the PPPoE tunneling protocol
   with L2TP.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Protocol Operation . . . . . . . . . . . . . . . . . . . . . .  2
       2.1.  PPPoE Active Discovery Stage . . . . . . . . . . . . . .  3
       2.2.  Session Establishment and Teardown . . . . . . . . . . .  4
       2.3.  PPPoE PAD Message Exchange Coherency . . . . . . . . . .  6
       2.4.  PPPoE Service Relay Capabilities Negotiation . . . . . .  8
             2.4.1.  PPPoE Service Relay Response Capability AVP. . .  8
             2.4.2.  PPPoE Service Relay Forward Capability AVP . . .  9
   3.  L2TP Service Relay Messages. . . . . . . . . . . . . . . . . .  9



Townsley & da Silva          Informational
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