LDP IGP Synchronization for Broadcast Networks
RFC 6138
Document | Type |
RFC - Informational
(February 2011; No errata)
Updates RFC 5443
|
|
---|---|---|---|
Authors | Wenhu Lu , Sriganesh Kini | ||
Last updated | 2015-10-14 | ||
Replaces | draft-lu-ldp-igp-sync-bcast | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | WG Document | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 6138 (Informational) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Adrian Farrel | ||
Send notices to | martin.vigoureux@alcatel-lucent.com |
Internet Engineering Task Force (IETF) S. Kini, Ed. Request for Comments: 6138 W. Lu, Ed. Updates: 5443 Ericsson Category: Informational February 2011 ISSN: 2070-1721 LDP IGP Synchronization for Broadcast Networks Abstract RFC 5443 describes a mechanism to achieve LDP IGP synchronization to prevent black-holing traffic (e.g., VPN) when an Interior Gateway Protocol (IGP) is operational on a link but Label Distribution Protocol (LDP) is not. If this mechanism is applied to broadcast links that have more than one LDP peer, the metric increase procedure can only be applied to the link as a whole but not to an individual peer. When a new LDP peer comes up on a broadcast network, this can result in loss of traffic through other established peers on that network. This document describes a mechanism to address that use- case without dropping traffic. The mechanism does not introduce any protocol message changes. Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6138. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents Kini & Lu Informational [Page 1] RFC 6138 LDP IGP Sync for Broadcast Networks February 2011 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction ....................................................2 2. Conventions Used in This Document ...............................2 3. Problem Statement ...............................................2 4. Solution ........................................................4 5. Scope ...........................................................5 6. Applicability ...................................................5 7. Security Considerations .........................................6 8. Conclusions .....................................................6 9. References ......................................................7 9.1. Normative References .......................................7 9.2. Informative References .....................................7 Acknowledgments ....................................................7 Appendix A. Computation of "Cut-Edge" ..............................8 Appendix B. Sync without Support at One End ........................8 1. Introduction In RFC 5443 [LDP-IGP-SYNC], when [LDP] is not fully operational on a link, the IGP advertises the link with maximum cost to avoid any transit traffic on the link if possible. When LDP becomes operational, i.e., all the label bindings have been exchanged, the link is advertised with its correct cost. This tries to ensure that the LDP Label Switch Path (LSP) is available all along the IGP shortest path. The mechanisms in [LDP-IGP-SYNC] have limitations when applied to a broadcast link. These are described in Section 3. A solution is defined in Section 4. 2. Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 3. Problem Statement On broadcast networks, a router's Link State Advertisement (LSA) contains a single cost to the broadcast network rather than a separate cost to each peer on the broadcast network. The operation of the mechanism in [LDP-IGP-SYNC] is analyzed using the sample topology in Figure 1, where routers A, B, C, and E are attached to a Kini & Lu Informational [Page 2] RFC 6138 LDP IGP Sync for Broadcast Networks February 2011Show full document text