draft-ietf-isis-segment-routing-msd-14.txt   draft-ietf-isis-segment-routing-msd-15.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: February 20, 2019 Huawei Technologies Expires: March 2, 2019 Huawei Technologies
S. Aldrin S. Aldrin
Google, Inc Google, Inc
L. Ginsberg L. Ginsberg
Cisco Systems Cisco Systems
August 19, 2018 August 29, 2018
Signaling MSD (Maximum SID Depth) using IS-IS Signaling MSD (Maximum SID Depth) using IS-IS
draft-ietf-isis-segment-routing-msd-14 draft-ietf-isis-segment-routing-msd-15
Abstract Abstract
This document defines a way for an Intermediate System to This document defines a way for an Intermediate System to
Intermediate System (IS-IS) Router to advertise multiple types of Intermediate System (IS-IS) Router to advertise multiple types of
supported Maximum SID Depths (MSDs) at node and/or link granularity. supported Maximum SID Depths (MSDs) at node and/or link granularity.
Such advertisements allow entities (e.g., centralized controllers) to Such 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 only defines one type of MSD maximum label network. This document only defines one type of MSD maximum label
imposition, but defines an encoding that can support other MSD types. imposition, but defines an encoding that can 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-
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 February 20, 2019. This Internet-Draft will expire on March 2, 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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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. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 3 2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 3
3. Link MSD Advertisement . . . . . . . . . . . . . . . . . . . 4 3. Link MSD Advertisement . . . . . . . . . . . . . . . . . . . 4
4. Using Node and Link MSD Advertisements . . . . . . . . . . . 5 4. Procedures for using Node and Link MSD Advertisements . . . . 5
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 . . . . . . . . . . . . . . . . . . . . . . . . 7
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
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represents lack of the ability to support SID stack of any depth; any represents lack of the ability to support SID stack of any depth; any
other value represents that of the node. This value MUST represent other value represents that of the node. This value MUST represent
the lowest value supported by any link configured for use by the the lowest value supported by any link configured for use by the
advertising IS-IS instance. 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 If there exist multiple Node MSD advertisements for the same MSD-Type
originated by the same router, the procedures defined in [RFC7981] originated by the same router, the procedures defined in [RFC7981]
apply. apply. These procedures may result in different MSD values being
used by (for example) different controllers - but this does not
create any interoperability issue.
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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represents lack of the ability to support SID stack of any depth; any 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 other value represents that of the link when used as an outgoing
link. link.
This sub-TLV is optional. This sub-TLV is optional.
If multiple Link MSD advertisements for the same MSD-Type and the If multiple Link MSD advertisements for the same MSD-Type and the
same link are received, the procedure used to select which copy is same link are received, the procedure used to select which copy is
used is undefined. used is undefined.
4. Using Node and Link MSD Advertisements 4. Procedures for 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 signaled but the Node MSD type is, then the Node MSD type value not signaled 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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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.
5. Base MPLS Imposition MSD 5. Base MPLS Imposition MSD
Base MPLS Imposition MSD (BMI-MSD) signals the total number of MPLS Base MPLS Imposition MSD (BMI-MSD) signals the total number of MPLS
labels a node is capable of imposing, including all labels which can be imposed, including all service/transport/special
service/transport/special labels. labels.
Absence of BMI-MSD advertisements indicates solely that the Absence of BMI-MSD advertisements indicates solely that the
advertising node does not support advertisement of this capability. advertising node does not support advertisement of this capability.
6. IANA Considerations 6. IANA Considerations
This document requests IANA to allocate a sub-TLV type for the new This document requests IANA to allocate a sub-TLV type for the new
sub TLV proposed in Section 2 of this document from IS-IS Router sub TLV proposed in Section 2 of this document from IS-IS Router
Capability TLV Registry as defined by [RFC7981]. Capability TLV Registry as defined by [RFC7981].
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Value Name Reference Value Name Reference
----- --------------------- ------------- ----- --------------------- -------------
0 Reserved This document 0 Reserved This document
1 Base MPLS Imposition MSD This document 1 Base MPLS Imposition MSD This document
2-250 Unassigned This document 2-250 Unassigned This document
251-254 Experimental This document 251-254 Experimental This document
255 Reserved This document 255 Reserved This document
Figure 6: MSD Types Codepoints Registry Figure 6: MSD Types Codepoints Registry
Guidance for the Designated Experts is as defined in [RFC7370] General guidance for the Designated Experts is as defined in
[RFC7370]
7. Security Considerations 7. Security Considerations
Security considerations as specified by [RFC7981] are applicable to Security considerations as specified by [RFC7981] are applicable to
this document. this document.
Advertisement of the additional information defined in this document Advertisement of the additional information defined in this document
that is false, e.g., an MSD that is incorrect, may result in a path that is false, e.g., an MSD that is incorrect, may result in a path
computation failing, having a service unavailable, or instantiation computation failing, having a service unavailable, or instantiation
of a path that can't be supported by the head-end (the node of a path that can't be supported by the head-end (the node
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