Browse Prior Art Database

Cisco Layer Two Forwarding (Protocol) "L2F" (RFC2341)

IP.com Disclosure Number: IPCOM000002910D
Original Publication Date: 1998-May-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 24 page(s) / 62K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

A. Valencia: AUTHOR [+3]

Abstract

Virtual dial-up allows many separate and autonomous protocol domains to share common access infrastructure including modems, Access Servers, and ISDN routers. Previous RFCs have specified protocols for supporting IP dial-up via SLIP [1] and multiprotocol dial-up via PPP [2]. This document describes the Layer Two Forwarding protocol (L2F) which permits the tunneling of the link layer (i.e., HDLC, async HDLC, or SLIP frames) of higher level protocols. Using such tunnels, it is possible to divorce the location of the initial dial- up server from the location at which the dial-up protocol connection is terminated and access to the network provided.

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 5% of the total text.

Network Working Group A. Valencia

Request for Comments: 2341 M. Littlewood

Category: Historic T. Kolar

Cisco Systems

May 1998

Cisco Layer Two Forwarding (Protocol) "L2F"

Status of Memo

This memo describes a historic protocol 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 (1998). All Rights Reserved.

Abstract

Virtual dial-up allows many separate and autonomous protocol domains

to share common access infrastructure including modems, Access

Servers, and ISDN routers. Previous RFCs have specified protocols

for supporting IP dial-up via SLIP [1] and multiprotocol dial-up via

PPP [2]. This document describes the Layer Two Forwarding protocol

(L2F) which permits the tunneling of the link layer (i.e., HDLC,

async HDLC, or SLIP frames) of higher level protocols. Using such

tunnels, it is possible to divorce the location of the initial dial-

up server from the location at which the dial-up protocol connection

is terminated and access to the network provided.

Table of Contents

1.0 Introduction 3

1.1 Conventions 3

2.0 Problem Space Overview 3

2.1 Initial Assumptions 3

2.2 Topology 4

2.3 Virtual dial-up Service - a walk-though 5

3.0 Service Model Issues 7

3.1 Security 7

3.2 Address allocation 8

3.3 Authentication 8

3.4 Accounting 8

4.0 Protocol Definition 9

4.1 Encapsulation within L2F 10

4.1.1 Encapsulation of PPP within L2F 10

4.1.2 Encapsulation of SLIP within L2F 10

4.2 L2F Packet Format 10

4.2.1 Overall Packet Format 10

4.2.2 Packet Header 11

4.2.3 Version field 11

4.2.4 Protocol field 11

4.2.5 Sequence Number 12

4.2.6 Packet Multiplex ID 12

4.2.7 Client ID 13

4.2.8 Length ...