--- 1/draft-ietf-idr-bgp-ls-segment-routing-msd-06.txt 2019-09-11 16:13:21.241166898 -0700 +++ 2/draft-ietf-idr-bgp-ls-segment-routing-msd-07.txt 2019-09-11 16:13:21.349169653 -0700 @@ -1,26 +1,26 @@ IDR Working Group J. Tantsura Internet-Draft Apstra, Inc. Intended status: Standards Track U. Chunduri -Expires: March 8, 2020 Futurewei Technologies +Expires: March 14, 2020 Futurewei Technologies K. Talaulikar Cisco Systems G. Mirsky ZTE Corp. N. Triantafillis Apstra, Inc. - September 5, 2019 + September 11, 2019 Signaling MSD (Maximum SID Depth) using Border Gateway Protocol Link- State - draft-ietf-idr-bgp-ls-segment-routing-msd-06 + draft-ietf-idr-bgp-ls-segment-routing-msd-07 Abstract This document defines a way for a Border Gateway Protocol Link-State (BGP-LS) speaker 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 Segment Identifier (SID) stack can be supported in a given network. @@ -33,21 +33,21 @@ 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 March 8, 2020. + This Internet-Draft will expire on March 14, 2020. Copyright Notice Copyright (c) 2019 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 @@ -62,26 +62,26 @@ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Conventions used in this document . . . . . . . . . . . . 3 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 4 2. Advertisement of MSD via BGP-LS . . . . . . . . . . . . . . . 4 3. Node MSD TLV . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Link MSD TLV . . . . . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. Manageability 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 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction When Segment Routing (SR) [RFC8402] paths are computed by a centralized controller, it is critical that the controller learns the Maximum SID Depth (MSD) that can be imposed at each node/link on a given SR path. This ensures that the Segment Identifier (SID) stack depth of a computed path doesn't exceed the number of SIDs the node is capable of imposing. @@ -146,32 +146,32 @@ 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 . 2. Advertisement of MSD via BGP-LS This document describes extensions that enable BGP-LS speakers to - signal the MSD capabilities of nodes and their links in a network to - a BGP-LS consumer of network topology such as a centralized - controller. The centralized controller can leverage this information - in computation of SR paths and their instantiation on network nodes - based on their MSD capabilities. When a BGP-LS speaker is - originating the topology learnt via link-state routing protocols like - OSPF or IS-IS, the MSD information for the nodes and their links is - sourced from the underlying extensions as defined in [RFC8476] and - [RFC8491] respectively. The BGP-LS speaker may also advertise the - MSD information for the local node and its links when not running any - link-state IGP protocol e.g. when running BGP as the only routing - protocol. + signal the MSD capabilities (described in [RFC8491] ) of nodes and + their links in a network to a BGP-LS consumer of network topology + such as a centralized controller. The centralized controller can + leverage this information in computation of SR paths and their + instantiation on network nodes based on their MSD capabilities. When + a BGP-LS speaker is originating the topology learnt via link-state + routing protocols like OSPF or IS-IS, the MSD information for the + nodes and their links is sourced from the underlying extensions as + defined in [RFC8476] and [RFC8491] respectively. The BGP-LS speaker + may also advertise the MSD information for the local node and its + links when not running any link-state IGP protocol e.g. when running + BGP as the only routing protocol. The extensions introduced in this document allow for advertisement of different MSD-Types. This document does not define these MSD-Types but leverages the definition, guidelines and the code-point registry specified in [RFC8491]. This enables sharing of MSD-Types that may be defined in the future by the IGPs in BGP-LS. 3. Node MSD TLV Node MSD is encoded in a new Node Attribute TLV [RFC7752] using the @@ -284,37 +284,49 @@ PCE to perform path computations taking into consideration the size of SID Stack that the specific headend node may be able to impose. Errors in the encoding or decoding of the MSD information may result in the unavailability of such information to the SR PCE or incorrect information being made available to it. This may result in the headend node not being able to instantiate the desired SR path in its forwarding and provide the SR based optimization functionality. The handling of such errors by applications like SR PCE may be implementation specific and out of scope of this document. - The extensions, specified in this document, do not introduce any new - configuration or monitoring aspects in BGP or BGP-LS other than as - discussed in [RFC7752]. The manageability aspects of the MSD - features are covered by [I-D.ietf-spring-sr-yang]. + The extensions specified in this document, do not specify any new + configuration or monitoring aspects in BGP or BGP-LS. The + specification of BGP models BGP and BGP-LS models is an ongoing work + based on the [I-D.ietf-idr-bgp-model]. The management of the MSD + features within an ietf segment-routing stack is also an ongoing work + based on the [I-D.ietf-spring-sr-yang]. Management of the segment + routing in IGPs is ongoing work for ISIS [I-D.ietf-isis-sr-yang] , + and OSPF [I-D.ietf-ospf-sr-yang]. 7. Security Considerations The advertisement of an incorrect MSD value may have negative consequences. If the value is smaller than supported, path computation may fail to compute a viable path. If the value is larger than supported, an attempt to instantiate a path that can't be supported by the head-end (the node performing the SID imposition) may occur. The presence of this information may also inform an attacker of how to induce any of the aforementioned conditions. - This document does not introduce security issues beyond those - discussed in [RFC7752], [RFC8476] and [RFC8491] + The document does not introduce additional security issues beyond + discussed in [RFC7752], [RFC8476] and [RFC8491]. However, [RFC7752] + is being revised in [I-D.ietf-idr-rfc7752bis] to provide additional + clarification in several portions of the specification after + receiving feedback from implementers. One of the places that is + being clarified is the error handling and security. It is expected + that after [I-D.ietf-idr-rfc7752bis] is released that implementers + will update all BGP-LS base implementations improving the error + handling for protocol work (including this document) that depend on + this function. 8. Contributors Siva Sivabalan Cisco Systems Inc. Canada Email: msiva@cisco.com 9. Acknowledgements @@ -346,31 +358,53 @@ DOI 10.17487/RFC8476, December 2018, . [RFC8491] Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg, "Signaling Maximum SID Depth (MSD) Using IS-IS", RFC 8491, DOI 10.17487/RFC8491, November 2018, . 10.2. Informative References + [I-D.ietf-idr-bgp-model] + Jethanandani, M., Patel, K., and S. Hares, "BGP YANG Model + for Service Provider Networks", draft-ietf-idr-bgp- + model-06 (work in progress), June 2019. + + [I-D.ietf-idr-rfc7752bis] + Talaulikar, K., Gredler, H., Medved, J., Previdi, S., + Farrel, A., and S. Ray, "Distribution of Link-State and + Traffic Engineering Information Using BGP", draft-ietf- + idr-rfc7752bis-00 (work in progress), September 2019. + [I-D.ietf-isis-mpls-elc] Xu, X., Kini, S., Psenak, P., Filsfils, C., and S. Litkowski, "Signaling Entropy Label Capability and Entropy Readable Label Depth Using IS-IS", draft-ietf-isis-mpls- elc-08 (work in progress), September 2019. + [I-D.ietf-isis-sr-yang] + Litkowski, S., Qu, Y., Sarkar, P., Chen, I., and J. + Tantsura, "YANG Data Model for IS-IS Segment Routing", + draft-ietf-isis-sr-yang-06 (work in progress), July 2019. + [I-D.ietf-ospf-mpls-elc] Xu, X., Kini, S., Psenak, P., Filsfils, C., and S. Litkowski, "Signaling Entropy Label Capability and Entropy Readable Label-stack Depth Using OSPF", draft-ietf-ospf- - mpls-elc-08 (work in progress), May 2019. + mpls-elc-09 (work in progress), September 2019. + + [I-D.ietf-ospf-sr-yang] + Yeung, D., Qu, Y., Zhang, Z., Chen, I., and A. Lindem, + "YANG Data Model for OSPF SR (Segment Routing) Protocol", + draft-ietf-ospf-sr-yang-10 (work in progress), August + 2019. [I-D.ietf-pce-segment-routing] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., and J. Hardwick, "PCEP Extensions for Segment Routing", draft-ietf-pce-segment-routing-16 (work in progress), March 2019. [I-D.ietf-spring-sr-yang] Litkowski, S., Qu, Y., Lindem, A., Sarkar, P., and J. Tantsura, "YANG Data Model for Segment Routing", draft-