Segment Routing Path MTU in BGP
draft-ietf-idr-sr-policy-path-mtu-01
Interdomain Routing Working Group C. Li
Internet-Draft Huawei Technologies
Intended status: Standards Track Y. Zhu
Expires: October 30, 2020 China Telecom
A. Sawaf
Saudi Telecom Company
Z. Li
Huawei Technologies
April 28, 2020
Segment Routing Path MTU in BGP
draft-ietf-idr-sr-policy-path-mtu-01
Abstract
Segment Routing is a source routing paradigm that explicitly
indicates the forwarding path for packets at the ingress node. An SR
policy is a set of candidate SR paths consisting of one or more
segment lists with necessary path attributes. However, the path
maximum transmission unit (MTU) information for SR path is not
available in the SR policy since the SR does not require signaling.
This document defines extensions to BGP to distribute path MTU
information within SR policies.
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document authors. All rights reserved.
Li, et al. Expires October 30, 2020 [Page 1]
Internet-Draft SR Path MTU in BGP April 2020
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. SR Policy for Path MTU . . . . . . . . . . . . . . . . . . . 3
3.1. Path MTU Sub-TLV . . . . . . . . . . . . . . . . . . . . 4
4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Implementation Status . . . . . . . . . . . . . . . . . . . . 6
5.1. Huawei's Commercial Delivery . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
10.1. Normative References . . . . . . . . . . . . . . . . . . 7
10.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Segment routing (SR) [RFC8402] is a source routing paradigm that
explicitly indicates the forwarding path for packets at the ingress
node. The ingress node steers packets into a specific path according
to the Segment Routing Policy ( SR Policy) as defined in
[I-D.ietf-spring-segment-routing-policy]. In order to distribute SR
policies to the headend, [I-D.ietf-idr-segment-routing-te-policy]
specifies a mechanism by using BGP.
The maximum transmission unit (MTU) is the largest size packet or
frame, in bytes, that can be sent in a network. An MTU that is too
large might cause retransmissions. Too small an MTU might cause the
router to send and handle relatively more header overhead and
acknowledgments.
When an LSP is created across a set of links with different MTU
sizes, the ingress router needs to know what the smallest MTU is on
the LSP path. If this MTU is larger than the MTU of one of the
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