Framework for Loop-Free Convergence Using the Ordered Forwarding Information Base (oFIB) Approach
RFC 6976
Document | Type | RFC - Informational (July 2013; No errata) | |
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Authors | Mike Shand , Stewart Bryant , Stefano Previdi , Clarence Filsfils , Pierre Francois , Olivier Bonaventure | ||
Last updated | 2018-12-20 | ||
Stream | Internet Engineering Task Force (IETF) | ||
Formats | plain text html pdf htmlized (tools) htmlized bibtex | ||
Reviews | |||
Stream | WG state | Submitted to IESG for Publication | |
Document shepherd | Alvaro Retana | ||
Shepherd write-up | Show (last changed 2013-01-15) | ||
IESG | IESG state | RFC 6976 (Informational) | |
Action Holders |
(None)
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Consensus Boilerplate | Yes | ||
Telechat date | |||
Responsible AD | Adrian Farrel | ||
IESG note | Alvaro Retana (aretana@cisco.com) is the Document Shepherd. | ||
Send notices to | (None) |
Internet Engineering Task Force (IETF) M. Shand Request for Comments: 6976 Individual Contributor Category: Informational S. Bryant ISSN: 2070-1721 S. Previdi C. Filsfils Cisco Systems P. Francois Institute IMDEA Networks O. Bonaventure Universite catholique de Louvain July 2013 Framework for Loop-Free Convergence Using the Ordered Forwarding Information Base (oFIB) Approach Abstract This document describes an illustrative framework of a mechanism for use in conjunction with link-state routing protocols that prevents the transient loops that would otherwise occur during topology changes. It does this by correctly sequencing the forwarding information base (FIB) updates on the routers. This mechanism can be used in the case of non-urgent (management action) link or node shutdowns and restarts or link metric changes. It can also be used in conjunction with a fast reroute mechanism that converts a sudden link or node failure into a non-urgent topology change. This is possible where a complete repair path is provided for all affected destinations. After a non-urgent topology change, each router computes a rank that defines the time at which it can safely update its FIB. A method for accelerating this loop-free convergence process by the use of completion messages is also described. The technology described in this document has been subject to extensive simulation using pathological convergence behavior and real network topologies and costs. However, the mechanisms described in this document are purely illustrative of the general approach and do not constitute a protocol specification. This document represents a snapshot of the work of the Routing Area Working Group at the time of publication and is published as a document of record. Further work is needed before implementation or deployment. Shand, et al. Informational [Page 1] RFC 6976 Loop-Free Convergence Using oFIB July 2013 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/rfc6976. Copyright Notice Copyright (c) 2013 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 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. Shand, et al. Informational [Page 2] RFC 6976 Loop-Free Convergence Using oFIB July 2013 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. The Purpose of This Document . . . . . . . . . . . . . . 4 1.2. Overview . . . . . . . . . . . . . . . . . . . . . . . . 4 2. The Required FIB Update Order . . . . . . . . . . . . . . . . 6 2.1. Single Link Events . . . . . . . . . . . . . . . . . . . 6 2.1.1. Link Down / Metric Increase . . . . . . . . . . . . . 6 2.1.2. Link Up / Metric Decrease . . . . . . . . . . . . . . 7 2.2. Multi-Link Events . . . . . . . . . . . . . . . . . . . . 8 2.2.1. Router Down Events . . . . . . . . . . . . . . . . . 8 2.2.2. Router Up Events . . . . . . . . . . . . . . . . . . 8 2.2.3. Line-Card Failure/Restoration Events . . . . . . . . 8 3. Applying Ordered FIB Updates . . . . . . . . . . . . . . . . 9Show full document text