draft-ietf-ospf-segment-routing-msd-22.txt   draft-ietf-ospf-segment-routing-msd-23.txt 
OSPF Working Group J. Tantsura OSPF Working Group J. Tantsura
Internet-Draft Apstra, Inc. Internet-Draft Apstra, Inc.
Intended status: Standards Track U. Chunduri Intended status: Standards Track U. Chunduri
Expires: April 14, 2019 Huawei Technologies Expires: April 15, 2019 Huawei Technologies
S. Aldrin S. Aldrin
Google, Inc Google, Inc
P. Psenak P. Psenak
Cisco Systems Cisco Systems
October 11, 2018 October 12, 2018
Signaling MSD (Maximum SID Depth) using OSPF Signaling MSD (Maximum SID Depth) using OSPF
draft-ietf-ospf-segment-routing-msd-22 draft-ietf-ospf-segment-routing-msd-23
Abstract Abstract
This document defines a way for an Open Shortest Path First (OSPF) This document defines a way for an Open Shortest Path First (OSPF)
Router to advertise multiple types of supported Maximum SID(Segment Router to advertise multiple types of supported Maximum SID(Segment
Identifier) Depths (MSDs) at node and/or link granularity. Such Identifier) Depths (MSDs) at node and/or link granularity. Such
advertisements allow entities (e.g., centralized controllers) to advertisements allow entities (e.g., centralized controllers) to
determine whether a particular SID stack can be supported in a given determine whether a particular SID stack can be supported in a given
network. This document defines only one type of MSD, but defines an network. This document defines only one type of MSD, but defines an
encoding that can support other MSD types. Here the term OSPF means encoding that can support other MSD types. Here the term OSPF means
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 14, 2019. This Internet-Draft will expire on April 15, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4 2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4
3. Link MSD sub-TLV . . . . . . . . . . . . . . . . . . . . . . 5 3. Link MSD sub-TLV . . . . . . . . . . . . . . . . . . . . . . 5
4. Procedures for Defining and Using Node and Link MSD 4. Procedures for Defining and Using Node and Link MSD
Advertisements . . . . . . . . . . . . . . . . . . . . . . . 6 Advertisements . . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8 7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . 8 9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 9 9.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction 1. Introduction
When Segment Routing (SR) paths are computed by a centralized When Segment Routing (SR) paths are computed by a centralized
controller, it is critical that the controller learns the Maximum SID controller, it is critical that the controller learns the Maximum SID
(Segment Identifier) Depth (MSD) that can be imposed at each node/ (Segment Identifier) Depth (MSD) that can be imposed at each node/
link on a given SR path to ensure that the Segment Identifier (SID) link on a given SR path to ensure that the Segment Identifier (SID)
stack depth of a computed path doesn't exceed the number of SIDs the stack depth of a computed path doesn't exceed the number of SIDs the
node is capable of imposing. node is capable of imposing.
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In order to increase flooding efficiency, it is RECOMMENDED that In order to increase flooding efficiency, it is RECOMMENDED that
routers with homogenous link MSD values advertise just the Node MSD routers with homogenous link MSD values advertise just the Node MSD
value. value.
The meaning of the absence of both Node and Link MSD advertisements The meaning of the absence of both Node and Link MSD advertisements
for a given MSD-type is specific to the MSD-type. Generally it can for a given MSD-type is specific to the MSD-type. Generally it can
only be inferred that the advertising node does not support only be inferred that the advertising node does not support
advertisement of that MSD-type. However, in some cases the lack of advertisement of that MSD-type. However, in some cases the lack of
advertisement might imply that the functionality associated with the advertisement might imply that the functionality associated with the
MSD-type is not supported. The correct interpretation MUST be MSD-type is not supported. The correct interpretation MUST be
specified when an MSD-type is defined. specified when an MSD-type is defined in
[I-D.ietf-isis-segment-routing-msd].
5. IANA Considerations 5. IANA Considerations
This document requests IANA to allocate TLV type (TBD1) from the OSPF This document requests IANA to allocate TLV type (TBD1) from the OSPF
Router Information (RI) TLVs Registry as defined by [RFC7770]. IANA Router Information (RI) TLVs Registry as defined by [RFC7770]. IANA
has allocated the value 12 through the early assignment process. has allocated the value 12 through the early assignment process.
Value Description Reference Value Description Reference
----- --------------- ------------- ----- --------------- -------------
12 Node MSD This document 12 Node MSD This document
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