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Layer 2 Virtual Private Network (L2VPN) Extensions for Layer 2 Tunneling Protocol (L2TP)
RFC 4667

Document type: RFC - Proposed Standard (September 2006; No errata)
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 4667 (Proposed Standard)
Responsible AD: Mark Townsley
Send notices to: rdasilva@va.rr.com, igoyret@lucent.com, luo@cisco.com, cpignata@cisco.com

Network Working Group                                             W. Luo
Request for Comments: 4667                           Cisco Systems, Inc.
Category: Standards Track                                 September 2006

          Layer 2 Virtual Private Network (L2VPN) Extensions
                 for Layer 2 Tunneling Protocol (L2TP)

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   The Layer 2 Tunneling Protocol (L2TP) provides a standard method for
   setting up and managing L2TP sessions to tunnel a variety of L2
   protocols.  One of the reference models supported by L2TP describes
   the use of an L2TP session to connect two Layer 2 circuits attached
   to a pair of peering L2TP Access Concentrators (LACs), which is a
   basic form of Layer 2 Virtual Private Network (L2VPN).  This document
   defines the protocol extensions for L2TP to set up different types of
   L2VPNs in a unified fashion.

Table of Contents

   1. Introduction ....................................................2
      1.1. Specification of Requirements ..............................2
   2. Network Reference Model .........................................2
   3. Forwarder Identifier ............................................3
   4. Protocol Components .............................................4
      4.1. Control Messages ...........................................4
      4.2. Existing AVPs for L2VPN ....................................4
      4.3. New AVPs for L2VPN .........................................5
      4.4. AVP Interoperability .......................................7
   5. Signaling Procedures ............................................7
      5.1. Overview ...................................................7
      5.2. Pseudowire Tie Detection ...................................8
      5.3. Generic Algorithm ..........................................9
   6. IANA Considerations ............................................12

Luo                         Standards Track                     [Page 1]
RFC 4667               L2VPN Extensions for L2TP          September 2006

   7. Security Considerations ........................................12
   8. Acknowledgement ................................................13
   9. References .....................................................13
      9.1. Normative References ......................................13
      9.2. Informative References ....................................13

1.  Introduction

   [RFC3931] defines a dynamic tunneling mechanism to carry multiple
   Layer 2 protocols besides Point-to-Point Protocol (PPP), the only
   protocol supported in [RFC2661], over a packet-based network.  The
   baseline protocol supports various types of applications, which have
   been highlighted in the different Layer 2 Tunneling Protocol (L2TP)
   reference models in [RFC3931].  An L2TP Access Concentrator (LAC) is
   an L2TP Control Connection Endpoint (LCCE) that cross-connects
   attachment circuits and L2TP sessions.  Layer 2 Virtual Private
   Network (L2VPN) applications are typically in the scope of the LAC-
   LAC reference model.

   This document discusses the commonalities and differences among L2VPN
   applications with respect to using L2TPv3 as the signaling protocol.
   In this document, the acronym "L2TP" refers to L2TPv3 or L2TP in
   general.

1.1.  Specification of Requirements

   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.  Network Reference Model

   In the LAC-LAC reference model, a LAC serves as a cross-connect
   between attachment circuits and L2TP sessions.  Each L2TP session
   acts as an emulated circuit, also known as pseudowire.  A pseudowire
   is used to bind two "forwarders" together.  For different L2VPN
   applications, different types of forwarders are defined.

   In the L2VPN framework [L2VPNFW], a LAC is a Provider Edge (PE)
   device.  LAC and PE are interchangeable terms in the context of this
   document.  Remote systems in the LAC-LAC reference model are Customer
   Edge (CE) devices.

Luo                         Standards Track                     [Page 2]

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