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MPLS Label Stack Encoding (RFC3032)

IP.com Disclosure Number: IPCOM000005224D
Original Publication Date: 2001-Jan-01
Included in the Prior Art Database: 2001-Aug-17
Document File: 24 page(s) / 48K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

E. Rosen: AUTHOR [+7]

Abstract

"Multi-Protocol Label Switching (MPLS)" [1] requires a set of procedures for augmenting network layer packets with "label stacks", thereby turning them into "labeled packets". Routers which support MPLS are known as "Label Switching Routers", or "LSRs". In order to transmit a labeled packet on a particular data link, an LSR must support an encoding technique which, given a label stack and a network layer packet, produces a labeled packet. This document specifies the encoding to be used by an LSR in order to transmit labeled packets on Point-to-Point Protocol (PPP) data links, on LAN data links, and possibly on other data links as well. On some data links, the label at the top of the stack may be encoded in a different manner, but the techniques described here MUST be used to encode the remainder of the label stack. This document also specifies rules and procedures for processing the various fields of the label stack encoding.

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Network Working Group E. Rosen Request for Comments: 3032 D. Tappan Category: Standards Track G. Fedorkow Cisco Systems, Inc.

Y. Rekhter Juniper Networks D. Farinacci

T. Li Procket Networks, Inc.

A. Conta TranSwitch Corporation

January 2001

MPLS Label Stack Encoding

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 (2001). All Rights Reserved.

Abstract

"Multi-Protocol Label Switching (MPLS)" [1] requires a set of procedures for augmenting network layer packets with "label stacks", thereby turning them into "labeled packets". Routers which support MPLS are known as "Label Switching Routers", or "LSRs". In order to transmit a labeled packet on a particular data link, an LSR must support an encoding technique which, given a label stack and a network layer packet, produces a labeled packet. This document specifies the encoding to be used by an LSR in order to transmit labeled packets on Point-to-Point Protocol (PPP) data links, on LAN data links, and possibly on other data links as well. On some data links, the label at the top of the stack may be encoded in a different manner, but the techniques described here MUST be used to encode the remainder of the label stack. This document also specifies rules and procedures for processing the various fields of the label stack encoding.

Rosen, et al. Standards Track [Page 1]

RFC 3032 MPLS Label Stack Encoding January 2001

Table of Contents

1 Introduction ........................................... 2 1.1 Specification of Requirements .......................... 3 2 The Label Stack ........................................ 3 2.1 Encoding the Label Stack ............................... 3 2.2 Determining the Network Layer Protocol ................. 5 2.3 Generating ICMP Messages for Labeled IP Packets ........ 6 2.3.1 Tunneling through a Transit Routing Domain ............. 7 2.3.2 Tunneling Private Addresses through a Public Backbone .. 7 2.4 Processing the Time to Live Field ...................... 8 2.4.1 Definitions ............................................ 8 2.4.2 Protocol-independent rules ............................. 8 2.4.3 IP-dependent rules ..................................... 9 2.4.4 Translating Between Different Encapsulations ........... 9 3 Fragmentation and Path MTU Discovery ................... 10 3.1 Terminology ............................................ 11 3.2 Maximum Initially Labeled IP Datagram Size ............. 12 3.3 When are Labeled IP Datagrams Too Big? ................. 13 3.4 Processing Labeled IPv4 Dat...