Preferred Path Loop-Free Alternate (pLFA)
draft-bryant-rtgwg-plfa-01
Routing Area Working Group S. Bryant
Internet-Draft S. Bryant
Intended status: Informational U. Chunduri
Expires: June 25, 2021 T. Eckert
Futurewei Technologies Inc
December 22, 2020
Preferred Path Loop-Free Alternate (pLFA)
draft-bryant-rtgwg-plfa-01
Abstract
Fast re-route (FRR) is a technique that allows productive forwarding
to continue in a network after a failure has occurred, but before the
network has has time to re-converge. This is achieved by forwarding
a packet on an alternate path that will not result in the packet
looping. Preferred Path Routing (PPR) provides a method of injecting
explicit paths into the routing protocol. The use of PPR to support
FRR has a number of advantages. This document describes the
advantages of using PPR to provide a loop-free alternate FRR path,
and provides a framework for its use in this application.
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Bryant, et al. Expires June 25, 2021 [Page 1]
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. A Note on the term IPFRR . . . . . . . . . . . . . . . . 3
2. PPR Overview . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Preferred Path LFA (pLFA) Deployment Advantages . . . . . . . 4
4. Simple Repair Using pLFA . . . . . . . . . . . . . . . . . . 6
4.1. Link Repair . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Node Repair . . . . . . . . . . . . . . . . . . . . . . . 7
4.3. Shared Risk Link Groups . . . . . . . . . . . . . . . . . 8
4.4. Local Area Networks . . . . . . . . . . . . . . . . . . . 9
4.5. Multiple Independent Failures . . . . . . . . . . . . . . 9
4.6. Multi-homed Prefixes . . . . . . . . . . . . . . . . . . 9
4.7. ECMP . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5. Repair To A Traffic Engineered Alternate Path . . . . . . . . 10
6. Use of a Repair Graph . . . . . . . . . . . . . . . . . . . . 11
6.1. Single Repair Graph . . . . . . . . . . . . . . . . . . . 11
6.2. Multiple Disjoint Graphs . . . . . . . . . . . . . . . . 11
7. Centralized and Decentralized Approaches . . . . . . . . . . 13
8. Independence of operation . . . . . . . . . . . . . . . . . . 14
9. Data-plane Considerations . . . . . . . . . . . . . . . . . . 14
9.1. Traditional IP . . . . . . . . . . . . . . . . . . . . . 15
9.2. Segment Routing over an IPv6 Data Plane (SRv6) . . . . . 15
9.3. MPLS . . . . . . . . . . . . . . . . . . . . . . . . . . 15
10. Loop Free Convergence . . . . . . . . . . . . . . . . . . . . 16
11. OAM Considerations . . . . . . . . . . . . . . . . . . . . . 16
12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 16
13. Security Considerations . . . . . . . . . . . . . . . . . . . 17
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
15.1. Normative References . . . . . . . . . . . . . . . . . . 17
15.2. Informative References . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
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