draft-ietf-isis-segment-routing-msd-11.txt   draft-ietf-isis-segment-routing-msd-12.txt 
IS-IS Working Group J. Tantsura IS-IS Working Group J. Tantsura
Internet-Draft Nuage Networks Internet-Draft Nuage Networks
Intended status: Standards Track U. Chunduri Intended status: Standards Track U. Chunduri
Expires: November 11, 2018 Huawei Technologies Expires: November 17, 2018 Huawei Technologies
S. Aldrin S. Aldrin
Google, Inc Google, Inc
L. Ginsberg L. Ginsberg
Cisco Systems Cisco Systems
May 10, 2018 May 16, 2018
Signaling MSD (Maximum SID Depth) using IS-IS Signaling MSD (Maximum SID Depth) using IS-IS
draft-ietf-isis-segment-routing-msd-11 draft-ietf-isis-segment-routing-msd-12
Abstract Abstract
This document defines a way for an IS-IS Router to advertise multiple This document defines a way for an IS-IS Router to advertise multiple
types of supported Maximum SID Depths (MSDs) at node and/or link types of supported Maximum SID Depths (MSDs) at node and/or link
granularity. Such advertisements allow entities (e.g., centralized granularity. Such advertisements allow entities (e.g., centralized
controllers) to determine whether a particular SID stack can be controllers) to determine whether a particular SID stack can be
supported in a given network. This document only defines one type of supported in a given network. This document only defines one type of
MSD maximum label imposition, but defines an encoding that can MSD maximum label imposition, but defines an encoding that can
support other MSD types. support other MSD types.
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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-
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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 November 11, 2018. This Internet-Draft will expire on November 17, 2018.
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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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3 1.1. Conventions used in this document . . . . . . . . . . . . 3
1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4 2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4
3. Link MSD Advertisement . . . . . . . . . . . . . . . . . . . 4 3. Link MSD Advertisement . . . . . . . . . . . . . . . . . . . 5
4. Using Node and Link MSD Advertisements . . . . . . . . . . . 5 4. Using Node and Link MSD Advertisements . . . . . . . . . . . 6
5. Base MPLS Imposition MSD . . . . . . . . . . . . . . . . . . 6 5. Base MPLS Imposition MSD . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . 8 10.1. Normative References . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . 8 10.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
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
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| MSD-Type | MSD Value | | MSD-Type | MSD Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Node MSD Sub-TLV Figure 1: Node MSD Sub-TLV
Type: 23 (allocated by IANA via the early assignment process) Type: 23 (allocated by IANA via the early assignment process)
Length: variable (minimum of 2, multiple of 2 octets) and represents Length: variable (minimum of 2, multiple of 2 octets) and represents
the total length of value field. the total length of value field.
Value: field consists of one or more pairs of a 1 octet MSD-Type Value: field consists of one or more pairs of a 1 octet MSD-Type and
(IANA Registry) and 1 octet Value. 1 octet MSD-Value.
Node MSD value is a number in the range of 0-255. 0 represents lack MSD-Type is one of the values defined in the MSD Types registry
of the ability to support SID stack of any depth; any other value created by the IANA Section of this document.
represents that of the node. This value MUST represent the lowest
value supported by any link configured for use by the advertising IS- MSD-Value is a number in the range of 0-255. For all MSD-Types, 0
IS instance. represents lack of the ability to support SID stack of any depth; any
other value represents that of the node. This value MUST represent
the lowest value supported by any link configured for use by the
advertising IS-IS instance.
This sub-TLV is optional. The scope of the advertisement is specific This sub-TLV is optional. The scope of the advertisement is specific
to the deployment. to the deployment.
If there exist multiple Node MSD advertisements for the same MSD-Type
originated by the same router, the procedures defined in [RFC7981]
apply.
3. Link MSD Advertisement 3. Link MSD Advertisement
The link MSD sub-TLV is defined for TLVs 22, 23, 25, 141, 222, and The link MSD sub-TLV is defined for TLVs 22, 23, 25, 141, 222, and
223 to carry the MSD of the interface associated with the link. MSD 223 to carry the MSD of the interface associated with the link. MSD
values may be learned via a hardware API or may be provisioned. values may be learned via a hardware API or may be provisioned.
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| MSD-Type | MSD Value | | MSD-Type | MSD Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Link MSD Sub-TLV Figure 2: Link MSD Sub-TLV
Type: 15 (allocated by IANA via the early assignment process) Type: 15 (allocated by IANA via the early assignment process)
Length: variable (minimum of 2, multiple of 2 octets) and represents Length: variable (minimum of 2, multiple of 2 octets) and represents
the total length of value field. the total length of value field.
Value: consists of one or more pairs of a 1 octet MSD-Type (IANA Value: consists of one or more pairs of a 1 octet MSD-Type and 1
Registry) and 1 octet Value. octet Value.
Link MSD value is a number in the range of 0-255. 0 represents lack MSD-Type is one of the values defined in the MSD Types registry
of the ability to support SID stack of any depth; any other value created by the IANA Section of this document.
represents that of the link when used as an outgoing link.
MSD-Value is a number in the range of 0-255. For all MSD-Types, 0
represents lack of the ability to support SID stack of any depth; any
other value represents that of the link when used as an outgoing
link.
This sub-TLV is optional. The scope of the advertisement is specific This sub-TLV is optional. The scope of the advertisement is specific
to the deployment. to the deployment.
If multiple Link MSD advertisements for the same MSD Type and the
same link are received, the procedure used to select which copy is
used is undefined.
4. Using Node and Link MSD Advertisements 4. Using Node and Link MSD Advertisements
When Link MSD is present for a given MSD type, the value of the Link When Link MSD is present for a given MSD type, the value of the Link
MSD MUST take preference over the Node MSD. When a Link MSD type is MSD MUST take preference over the Node MSD. When a Link MSD type is
not signalled but the Node MSD type is, then the Node MSD type value not signalled but the Node MSD type is, then the Node MSD type value
MUST be considered as the MSD value for that link. MUST be considered as the MSD value for that link.
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.
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