--- 1/draft-ietf-isis-segment-routing-msd-11.txt 2018-05-16 09:13:28.567149736 -0700 +++ 2/draft-ietf-isis-segment-routing-msd-12.txt 2018-05-16 09:13:28.611150787 -0700 @@ -1,23 +1,23 @@ IS-IS Working Group J. Tantsura Internet-Draft Nuage Networks Intended status: Standards Track U. Chunduri -Expires: November 11, 2018 Huawei Technologies +Expires: November 17, 2018 Huawei Technologies S. Aldrin Google, Inc L. Ginsberg Cisco Systems - May 10, 2018 + May 16, 2018 Signaling MSD (Maximum SID Depth) using IS-IS - draft-ietf-isis-segment-routing-msd-11 + draft-ietf-isis-segment-routing-msd-12 Abstract 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 granularity. Such advertisements allow entities (e.g., centralized controllers) to determine whether a particular SID stack can be supported in a given network. This document only defines one type of MSD maximum label imposition, but defines an encoding that can support other MSD types. @@ -30,21 +30,21 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any 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 November 11, 2018. + This Internet-Draft will expire on November 17, 2018. Copyright Notice Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -54,26 +54,26 @@ the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Conventions used in this document . . . . . . . . . . . . 3 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Node MSD Advertisement . . . . . . . . . . . . . . . . . . . 4 - 3. Link MSD Advertisement . . . . . . . . . . . . . . . . . . . 4 - 4. Using Node and Link MSD Advertisements . . . . . . . . . . . 5 + 3. Link MSD Advertisement . . . . . . . . . . . . . . . . . . . 5 + 4. Using Node and Link MSD Advertisements . . . . . . . . . . . 6 5. Base MPLS Imposition MSD . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 - 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 7 + 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 10.1. Normative References . . . . . . . . . . . . . . . . . . 8 10.2. Informative References . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction When Segment Routing(SR) paths are computed by a centralized controller, it is critical that the controller learns the Maximum SID @@ -166,32 +166,39 @@ | MSD-Type | MSD Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Node MSD Sub-TLV Type: 23 (allocated by IANA via the early assignment process) Length: variable (minimum of 2, multiple of 2 octets) and represents the total length of value field. - Value: field consists of one or more pairs of a 1 octet MSD-Type - (IANA Registry) and 1 octet Value. + Value: field consists of one or more pairs of a 1 octet MSD-Type and + 1 octet MSD-Value. - Node MSD value is a number in the range of 0-255. 0 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. + MSD-Type is one of the values defined in the MSD Types registry + created by the IANA Section of this document. + + 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 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 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 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 values may be learned via a hardware API or may be provisioned. 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ @@ -204,30 +211,38 @@ | MSD-Type | MSD Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Link MSD Sub-TLV Type: 15 (allocated by IANA via the early assignment process) Length: variable (minimum of 2, multiple of 2 octets) and represents the total length of value field. - Value: consists of one or more pairs of a 1 octet MSD-Type (IANA - Registry) and 1 octet Value. + Value: consists of one or more pairs of a 1 octet MSD-Type and 1 + octet Value. - Link MSD value is a number in the range of 0-255. 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. + MSD-Type is one of the values defined in the MSD Types registry + created by the IANA Section of this document. + + 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 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 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 not signalled but the Node MSD type is, then the Node MSD type value MUST be considered as the MSD value for that link. In order to increase flooding efficiency, it is RECOMMENDED that routers with homogenous link MSD values advertise just the Node MSD value.