Segment Routing with MPLS data plane
draft-ietf-spring-segment-routing-mpls-12
Network Working Group A. Bashandy, Ed.
Internet Draft C. Filsfils, Ed.
Intended status: Standards Track S. Previdi,
Expires: August 2018 Cisco Systems, Inc.
B. Decraene
S. Litkowski
Orange
R. Shakir
Google
February 23, 2018
Segment Routing with MPLS data plane
draft-ietf-spring-segment-routing-mpls-12
Abstract
Segment Routing (SR) leverages the source routing paradigm. A node
steers a packet through a controlled set of instructions, called
segments, by prepending the packet with an SR header. In the MPLS
dataplane, the SR header is instantiated through a label stack. This
document specifies the forwarding behavior to allow instantiating SR
over the MPLS dataplane.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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
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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
Filsfils, et al. Expires August 23, 2018 [Page 1]
Internet-Draft Segment Routing with MPLS February 2018
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 August 23, 2018.
Copyright Notice
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Table of Contents
1. Introduction...................................................3
2. MPLS Instantiation of Segment Routing..........................3
2.1. Supporting Multiple Forwarding Behaviors for the Same Prefix
...............................................................4
2.2. SID Representation in the MPLS Forwarding Plane...........4
2.3. Segment Routing Global Block and Local Block..............5
2.4. Mapping a SID Index to an MPLS label......................6
2.5. Incoming Label Collision..................................6
2.5.1. Tie-breaking Rules...................................8
2.5.2. Redistribution between Routing Protocol Instances...11
2.5.2.1. Illustration...................................11
2.6. Outgoing Label Collision.................................11
2.7. PUSH, CONTINUE, and NEXT.................................12
2.7.1. PUSH................................................12
2.7.2. CONTINUE............................................12
2.7.3. NEXT................................................12
2.8. MPLS Label downloaded to FIB corresponding to Global and
Local SIDs....................................................13
2.9. Active Segment...........................................13
2.10. Forwarding behavior for Global SIDs.....................13
2.10.1. Forwarding Behavior for PUSH and CONTINUE Operation for
Global SIDs................................................13
2.10.2. Forwarding Behavior for NEXT Operation for Global SIDs
...........................................................15
Filsfils, et al. Expires August 23, 2018 [Page 2]
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