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: 2019-Feb-15
Document File: 29 page(s) / 38K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

A. Valencia: AUTHOR [+2]

Related Documents

10.17487/RFC2341: DOI

Abstract

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. This memo describes a historic protocol for the Internet community. It does not specify an Internet standard of any kind.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 11% 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

Valencia, et. al. Historic [Page 1]

RFC 2341 Cisco L2F May 1998

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 13 4.2.9 Packet Checksum 13 4.2.10 Payload Offset 14 4.2.11 Packet Key 14 4.2.12 Packet priority 14 4.3 L2F Tunnel Establishment 14 4.3.1 Normal Tunnel Negotiation Sequence 15 4.3.2 Normal Client Negotiation Sequence 17 4.4 L2F management message types 18 4.4.1 L2F message type: Invalid 18 4.4.2 L2F_CONF 19 4.4.3 L2F_OPEN, tunnel establishment 20 4.4.4 L2F_OPEN, client establishment 20 4.4.5 L2F_CLOSE 22 4.4.6 L2F_ECHO 22 4.4.7 L2F_ECHO_RESP 23 4.5 L2F Message Delivery 23 4.5.1 Sequenced Delivery 23 4.5.2 Flow Control 23 4.5.3 Tunnel State Table 24 4.5.4 Client State Table 25 5.0 Protocol Considerations 26 5.1 PPP Features 26 5.2 Termination 26 5.3 Extended Authentication 26 5.4 MNP4 and Apple Remote Access Protocol 27 5.5 Operation over IP/UDP 27 6.0 Acknowledgments 27 7.0 References 27 8.0 Security Considerations 28 9.0 Authors’ Addresses 28 10.0 Full Copyright Statement 29

Valencia, et. al. Historic [Page 2]

RFC 2341 Cisco L2F May 1998

1.0 Introduction

The traditional dial-up network service on the Internet is for registered IP addresses only. A new class of virtual dial-up application which allows multiple protocols and unregistered IP addresses is also desired on the Internet. Examples of...

Processing...
Loading...