Enhanced Topology Independent Loop-free Alternate Fast Re-route
draft-li-rtgwg-enhanced-ti-lfa-03
RTGWG Working Group C. Li
Internet-Draft Z. Hu
Intended status: Standards Track Huawei Technologies
Expires: May 5, 2021 Y. Zhu
China Telecom
S. Hegde
Juniper Networks Inc.
November 1, 2020
Enhanced Topology Independent Loop-free Alternate Fast Re-route
draft-li-rtgwg-enhanced-ti-lfa-03
Abstract
Topology Independent Loop-free Alternate Fast Re-route (TI-LFA) aims
at providing protection of node and adjacency segments within the
Segment Routing (SR) framework. A key aspect of TI-LFA is the FRR
path selection approach establishing protection over the expected
post-convergence paths from the point of local repair. However, the
TI-LFA FRR path may skip the node even if it is specified in the SID
list to be traveled.
This document defines Enhanced TI-LFA(TI-LFA+) by adding a No-bypass
indicator for segments to ensure that the FRR route will not bypass
the specific node, such as firewall. Also, this document defines No-
bypass flag and No-FRR flag in SRH to indicate not to bypass nodes
and not to perform FRR on all the nodes along the SRv6 path,
respectively.
Status of This Memo
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 5, 2021.
Li, et al. Expires May 5, 2021 [Page 1]
Internet-Draft Enhanced TI-LFA November 2020
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. Overview of Enhanced TI-LFA . . . . . . . . . . . . . . . . . 3
4. IGP Protocol Extensions . . . . . . . . . . . . . . . . . . . 4
4.1. IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.2. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Flags in SRH . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1. No-bypass Flag in SRH . . . . . . . . . . . . . . . . . . 8
5.2. No-FRR Flag in SRH . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Segment Routing [RFC8402] enables to steer packets by explicitly
encoding instructions in the data packets at the source node to
support services like traffic engineer. Relying on SR,
[I-D.ietf-rtgwg-segment-routing-ti-lfa] defines Topology Independent
Loop-free Alternate Fast Re-route (TI-LFA), a local repair mechanism
for IGP shortest path that capable of restoring end-to-end
connectivity in the case of a sudden directly connected failure of a
network component.
TI-LFA supports to establish a loop free backup path over the
expected post-convergence paths from the point of local repair
irrespective of the topologies used in the network, which provides a
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