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Layer Two Tunneling Protocol "L2TP" (RFC2661)

IP.com Disclosure Number: IPCOM000003251D
Original Publication Date: 1999-Aug-01
Included in the Prior Art Database: 2019-Feb-11
Document File: 80 page(s) / 96K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

W. Townsley: AUTHOR [+5]

Related Documents

10.17487/RFC2661: DOI

Abstract

This document describes the Layer Two Tunneling Protocol (L2TP). [STANDARDS-TRACK]

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 3% of the total text.

Network Working Group W. Townsley Request for Comments: 2661 A. Valencia Category: Standards Track cisco Systems A. Rubens Ascend Communications G. Pall G. Zorn Microsoft Corporation B. Palter Redback Networks August 1999

Layer Two 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 (1999). All Rights Reserved.

Abstract

This document describes the Layer Two Tunneling Protocol (L2TP). STD 51, RFC 1661 specifies multi-protocol access via PPP [RFC1661]. L2TP facilitates the tunneling of PPP packets across an intervening network in a way that is as transparent as possible to both end-users and applications.

Table of Contents

1.0 Introduction.......................................... 3 1.1 Specification of Requirements......................... 4 1.2 Terminology........................................... 4 2.0 Topology.............................................. 8 3.0 Protocol Overview..................................... 9 3.1 L2TP Header Format.................................... 9 3.2 Control Message Types................................. 11 4.0 Control Message Attribute Value Pairs................. 12 4.1 AVP Format............................................ 13 4.2 Mandatory AVPs........................................ 14 4.3 Hiding of AVP Attribute Values........................ 14

Townsley, et al. Standards Track [Page 1]

RFC 2661 L2TP August 1999

4.4 AVP Summary........................................... 17 4.4.1 AVPs Applicable To All Control Messages.......... 17 4.4.2 Result and Error Codes........................... 18 4.4.3 Control Connection Management AVPs............... 20 4.4.4 Call Management AVPs............................. 27 4.4.5 Proxy LCP and Authentication AVPs................ 34 4.4.6 Call Status AVPs................................. 39 5.0 Protocol Operation.................................... 41 5.1 Control Connection Establishment...................... 41 5.1.1 Tunnel Authentication............................ 42 5.2 Session Establishment................................. 42 5.2.1 Incoming Call Establishment...................... 42 5.2.2 Outgoing Call Establishment...................... 43 5.3 Forwarding PPP Frames................................. 43 5.4 Using Sequence Numbers on the Data Channel............ 44 5.5 Keepalive (Hello)..................................... 44 5.6 Session Teardown...................................... 45 5.7 Control Connection Teardown........................... 45 5.8 Reliable Delivery of Control Messages................. 46 6.0 Control Connection Protocol Specification............. 48 6.1 Start-Control-Connection...

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