RFC 2661 (rfc2661) - Page 1 of 80
Layer Two Tunneling Protocol "L2TP"
Alternative Format: Original Text Document
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 [RFC 1661]. 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