Restart Signaling for IS-IS
RFC 8706
Document | Type |
RFC - Proposed Standard
(February 2020; No errata)
Obsoletes RFC 5306
|
|
---|---|---|---|
Authors | Les Ginsberg , Paul Wells | ||
Last updated | 2020-02-23 | ||
Replaces | draft-ginsberg-isis-rfc5306bis | ||
Stream | IETF | ||
Formats | plain text html xml pdf htmlized bibtex | ||
Reviews | |||
Stream | WG state | Submitted to IESG for Publication | |
Document shepherd | Uma Chunduri | ||
Shepherd write-up | Show (last changed 2019-06-04) | ||
IESG | IESG state | RFC 8706 (Proposed Standard) | |
Consensus Boilerplate | Yes | ||
Telechat date | |||
Responsible AD | Alvaro Retana | ||
Send notices to | Uma Chunduri <umac.ietf@gmail.com>, aretana.ietf@gmail.com | ||
IANA | IANA review state | Version Changed - Review Needed | |
IANA action state | RFC-Ed-Ack |
Internet Engineering Task Force (IETF) L. Ginsberg Request for Comments: 8706 P. Wells Obsoletes: 5306 Cisco Systems, Inc. Category: Standards Track February 2020 ISSN: 2070-1721 Restart Signaling for IS-IS Abstract This document describes a mechanism for a restarting router to signal to its neighbors that it is restarting, allowing them to reestablish their adjacencies without cycling through the DOWN state while still correctly initiating database synchronization. This document additionally describes a mechanism for a router to signal its neighbors that it is preparing to initiate a restart while maintaining forwarding-plane state. This allows the neighbors to maintain their adjacencies until the router has restarted but also allows the neighbors to bring the adjacencies down in the event of other topology changes. This document additionally describes a mechanism for a restarting router to determine when it has achieved Link State Protocol Data Unit (LSP) database synchronization with its neighbors and a mechanism to optimize LSP database synchronization while minimizing transient routing disruption when a router starts. This document obsoletes RFC 5306. Status of This Memo This is an Internet Standards Track document. 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). Further information on Internet Standards is available in Section 2 of RFC 7841. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8706. Copyright Notice Copyright (c) 2020 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 (https://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. Table of Contents 1. Overview 2. Conventions Used in This Document 2.1. Requirements Language 3. Approach 3.1. Timers 3.2. Restart TLV 3.2.1. Use of RR and RA Bits 3.2.2. Use of the SA Bit 3.2.3. Use of PR and PA Bits 3.3. Adjacency (Re)Acquisition 3.3.1. Adjacency Reacquisition during Restart 3.3.2. Adjacency Acquisition during Start 3.3.3. Multiple Levels 3.4. Database Synchronization 3.4.1. LSP Generation and Flooding and SPF Computation 4. State Tables 4.1. Running Router 4.2. Restarting Router 4.3. Starting Router 5. IANA Considerations 6. Security Considerations 7. Manageability Considerations 8. Normative References Appendix A. Summary of Changes from RFC 5306 Acknowledgements Authors' Addresses 1. Overview The Intermediate System to Intermediate System (IS-IS) routing protocol [RFC1195] [ISO10589] is a link state intra-domain routing protocol. Normally, when an IS-IS router is restarted, temporary disruption of routing occurs due to events in both the restarting router and the neighbors of the restarting router. The router that has been restarted computes its own routes before achieving database synchronization with its neighbors. The results of this computation are likely to be non-convergent with the routes computed by other routers in the area/domain. Neighbors of the restarting router detect the restart event and cycle their adjacencies with the restarting router through the DOWN state. The cycling of the adjacency state causes the neighbors to regenerate their LSPs describing the adjacency concerned. This in turn causes a temporary disruption of routes passing through the restarting router. In certain scenarios, the temporary disruption of the routes is highly undesirable. This document describes mechanisms to avoid or minimize the disruption due to both of these causes. When an adjacency is reinitialized as a result of a neighbor restarting, a router does three things: 1. It causes its own LSP(s) to be regenerated, thus triggering Shortest Path First (SPF) runs throughout the area (or in the case of Level 2, throughout the domain). 2. It sets SRMflags on its own LSP database on the adjacencyShow full document text