Enhanced Topology Independent Loop-free Alternate Fast Re-route
draft-li-rtgwg-enhanced-ti-lfa-01
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RTGWG Working Group C. Li
Internet-Draft Z. Hu
Intended status: Standards Track Huawei Technologies
Expires: July 14, 2020 January 11, 2020
Enhanced Topology Independent Loop-free Alternate Fast Re-route
draft-li-rtgwg-enhanced-ti-lfa-01
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.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 14, 2020.
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
Li & Hu Expires July 14, 2020 [Page 1]
Internet-Draft Enhanced TI-LFA January 2020
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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described in the Simplified BSD License.
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 . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
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
major improvment compared to LFA [RFC5286], and remote LFA [RFC7490]
which cannot be applicable in some topologies [RFC6571].
However, the TI-LFA path may skip the node that the active SID points
to when protecting [Adjacency, Node] segment lists. For instance,
the node that a adjacency SID points to is a very important node and
can not be skipped, such as a firewall node. When the link between
the local repair node and firewall node fails, the packets should be
steered back to the firewall and then forwarding. But in TI-LFA, if
the next SID in the SID list is a node SID, the TI-LFA FRR path MAY
bypass the node that the active segment points to. Also, if the
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