Segment Routing Policy Architecture
draft-ietf-spring-segment-routing-policy-09
SPRING Working Group C. Filsfils
Internet-Draft K. Talaulikar, Ed.
Intended status: Standards Track Cisco Systems, Inc.
Expires: May 5, 2021 D. Voyer
Bell Canada
A. Bogdanov
Google, Inc.
P. Mattes
Microsoft
November 1, 2020
Segment Routing Policy Architecture
draft-ietf-spring-segment-routing-policy-09
Abstract
Segment Routing (SR) allows a headend node to steer a packet flow
along any path. Intermediate per-flow states are eliminated thanks
to source routing. The headend node steers a flow into an SR Policy.
The header of a packet steered in an SR Policy is augmented with an
ordered list of segments associated with that SR Policy. This
document details the concepts of SR Policy and steering into an SR
Policy.
Status of This Memo
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Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
Filsfils, et al. Expires May 5, 2021 [Page 1]
Internet-Draft SR Policy Architecture November 2020
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. SR Policy . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Identification of an SR Policy . . . . . . . . . . . . . 4
2.2. Candidate Path and Segment List . . . . . . . . . . . . . 5
2.3. Protocol-Origin of a Candidate Path . . . . . . . . . . . 6
2.4. Originator of a Candidate Path . . . . . . . . . . . . . 6
2.5. Discriminator of a Candidate Path . . . . . . . . . . . . 7
2.6. Identification of a Candidate Path . . . . . . . . . . . 7
2.7. Preference of a Candidate Path . . . . . . . . . . . . . 8
2.8. Validity of a Candidate Path . . . . . . . . . . . . . . 8
2.9. Active Candidate Path . . . . . . . . . . . . . . . . . . 8
2.10. Validity of an SR Policy . . . . . . . . . . . . . . . . 9
2.11. Instantiation of an SR Policy in the Forwarding Plane . . 9
2.12. Priority of an SR Policy . . . . . . . . . . . . . . . . 10
2.13. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 10
3. Segment Routing Database . . . . . . . . . . . . . . . . . . 11
4. Segment Types . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1. Explicit Null . . . . . . . . . . . . . . . . . . . . . . 16
5. Validity of a Candidate Path . . . . . . . . . . . . . . . . 16
5.1. Explicit Candidate Path . . . . . . . . . . . . . . . . . 16
5.2. Dynamic Candidate Path . . . . . . . . . . . . . . . . . 18
5.3. Composite Candidate Path . . . . . . . . . . . . . . . . 18
6. Binding SID . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.1. BSID of a candidate path . . . . . . . . . . . . . . . . 19
6.2. BSID of an SR Policy . . . . . . . . . . . . . . . . . . 19
6.3. Forwarding Plane . . . . . . . . . . . . . . . . . . . . 20
6.4. Non-SR usage of Binding SID . . . . . . . . . . . . . . . 21
7. SR Policy State . . . . . . . . . . . . . . . . . . . . . . . 21
8. Steering into an SR Policy . . . . . . . . . . . . . . . . . 21
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