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LDP Applicability (RFC3037)

IP.com Disclosure Number: IPCOM000005229D
Original Publication Date: 2001-Jan-01
Included in the Prior Art Database: 2001-Aug-17
Document File: 8 page(s) / 14K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

B. Thomas: AUTHOR [+2]

Abstract

Multiprotocol Label Switching (MPLS) is a method for forwarding packets that uses short, fixed-length values carried by packets, called labels, to determine packet nexthops. A fundamental concept in MPLS is that two Label Switching Routers (LSRs) must agree on the meaning of the labels used to forward traffic between and through them. This common understanding is achieved by using a set of procedures, called a label distribution protocol, by which one LSR informs another of label bindings it has made. This document describes the applicability of a set of such procedures called LDP (for Label Distribution Protocol) by which LSRs distribute labels to support MPLS forwarding along normally routed paths.

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Network Working Group B. Thomas Request for Comments: 3037 Cisco Systems, Inc. Category: Informational E. Gray Zaffire, Inc.

January 2001

LDP Applicability

Status of this Memo

This memo provides information 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 (2001). All Rights Reserved.

Abstract

Multiprotocol Label Switching (MPLS) is a method for forwarding packets that uses short, fixed-length values carried by packets, called labels, to determine packet nexthops. A fundamental concept in MPLS is that two Label Switching Routers (LSRs) must agree on the meaning of the labels used to forward traffic between and through them. This common understanding is achieved by using a set of procedures, called a label distribution protocol, by which one LSR informs another of label bindings it has made. This document describes the applicability of a set of such procedures called LDP (for Label Distribution Protocol) by which LSRs distribute labels to support MPLS forwarding along normally routed paths.

1. LDP Applicability

A label distribution protocol is a set of procedures by which one Label Switching Router (LSR) informs another of the meaning of labels used to forward traffic between and through them.

The MPLS architecture allows for the possibility of more than a single method for distributing labels, and a number of different label distribution protocols are being standardized. Existing protocols have been extended so that label distribution can be piggybacked on them, and new protocols have been defined for the explicit purpose of distributing labels.

Thomas Gray Informational [Page 1]

RFC 3037 LDP Applicability January 2001

This document describes the applicability of the Label Distribution Protocol (LDP), a new protocol for label distribution designed to support label distribution for MPLS forwarding along normally routed paths as determined by destination-based routing protocols. This is sometimes called MPLS hop-by-hop forwarding.

LDP, together with an IP routing plane and software to program ATM switch or Frame Relay switch cross-connect tables, can implement IP in a network of ATM and/or Frame Relay switches without requiring an overlay or the use of ATM-specific or Frame Relay-specific addressing or routing.

LDP is also useful in situations that require efficient hop-by-hop routed tunnels, such as MPLS-based VPN architectures [RFC2574] and tunneling between BGP border routers.

In addition, LDP includes a mechanism that makes it possible to extend it to support MPLS features that go beyond best effort hop- by-hop forwarding.

As a stand-alone protocol for distributing labels LDP does not rely on the presence of specific routing protocols at every hop along an LSP path in order to ...