IDR Working Group G. Van de Velde, Ed. Internet-Draft W. Henderickx Intended status: Standards Track M. Bocci Expires:December 20, 2019February 21, 2020 Nokia K. Patel ArrcusJune 18,August 20, 2019 Signalling ERLD using BGP-LSdraft-ietf-idr-bgp-ls-segment-routing-rld-04draft-ietf-idr-bgp-ls-segment-routing-rld-05 Abstract This document defines the attribute encoding to use for BGP-LS to expose ERLD "Entropy capable Readable Label Depth" from a node to a centralised controller (PCE/SDN). Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [1]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. 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Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions used in this document . . . . . . . . . . . . . .32 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 4.OriginationAdvertising of ERLD in BGP-LS . . . . . . . . . . . . . . . . 3 5.ERLD support by a node . . . . . . . . . . . . . . . . . . . 4 6.Security Considerations . . . . . . . . . . . . . . . . . . . 47.6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 48.7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 49.8. References . . . . . . . . . . . . . . . . . . . . . . . . .5 9.1.4 8.1. Normative References . . . . . . . . . . . . . . . . . .5 9.2.4 8.2. Informative References . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction When Segment Routing tunnels are computed by a centralised controller, it is beneficial that the controller knows the ERLD (EntropycapableReadable Label Depth) of each node or link a tunnel traverses. A network node signalling an ERLD MUST support the ability to read the signalled number of labels before any action is done upon the packet and SHOULD support entropy awareness found within the signalled ERLD depth. ERLD awareness of each node will allow a network SDN controller to influence the path used for each tunnel. The SDN controller may for example only create tunnels with a label stack smaller or equal as the ERLD of each node on the path. This will allow the network to behave accordingly (e.g. make use of Entropy Labels to improve ECMP) upon the imposed Segment Routing label stack on each packet. This document describes how to use BGP-LS to expose the ERLD of a node. 2. Conventions used in this document 2.1. Terminology BGP-LS: Distribution of Link-State and TE Information using Border Gateway Protocol ERLD: Entropy capable Readable Label DepthPCC: Path Computation Client PCE: Path Computation Element PCEP: Path Computation Element ProtocolELC: Entropy Label Capability MSD: Maximum SID Depth SID: Segment IdentifierSR: Segment routing3. Problem StatementIn existingFor Segment Routing technology both ISIS[4][7] and OSPF[3][6] have proposed extensions to signal theRLD (ReadableERLD (Entropy Readable Label Depth) and ELC (Entropy Label Capability) of a node. However, if a network SDN controller is connected to the network through a BGP-LS session and not through either ISIS or OSPF technology, then bothRLDERLD and ELC needs to be signalled using BGP-LS encoding. This document describes the extension BGP-LS requires totransport the combined RLD and ELC into an ERLD (Entropy capable Readable Label Depth) attribute.signal ERLD. A network SDN controller having awareness of the ERLD can for example use it as a constraint on path computation to make sure that high bandwidth LSPs are not placed on LAG (Link Aggregation Group), containing links with smaller member bandwidth, if they know theEntropy Labelentropy label cannot be processed by the node at the ingress to the link. 4.OriginationAdvertising of ERLD in BGP-LS Both ISIS[4][7] and OSPF[3][6] have proposed extensions to signal theRLD (ReadableERLD (Entropy Readable Label Depth) and ELC (Entropy Label Capability)forusing new MSD-type of the Node MSD sub-Type TLV RFC8491 [4] or RFC8476 [3]. This document defines anode.new node BGP MSD sub-type TLV from draft- ietf-idr-bgp-ls-segment-routing-msd [5] to signal the ERLD. A BGP-LS router exporting the IGP LSDB, MUST NOT encode the IGPRLDERLD value in an BGP-LS ERLD attribute, if the associatednodeELC is not signalled.5. ERLD support by a node Node ERLD is encoded in a new Node Attribute TLV, as defined in RFC7752 [2].0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |LengthMSD-Type=TBD |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ERLDERLD-Value |+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1Type : A 2-octet field specifying code-point of the new TLV type. Code-point: TBA fromThe BGP-LSNode Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs registry Length: A 2-octet field that indicates the length of the value portion ERLD: NodeERLD is encoded as anumbernode MSD sub-type defined in the IANA registry titled "IGP MSD-Types" under the "Interior Gateway Protocol (IGP) Parameters" registry created by RFC8491 [4]. The ERLD-Value field in the rangeof 0-254.between 0 to 255 is set to the BGP- LS imported IGP ERLD. The value of 0 represents lack of ability to read a label stack of any depth, any other value represents the readable label depth of the node.6.5. Security Considerations This document does not introduce security issues beyond those discussed in RFC7752 [2]7.6. Acknowledgements Thanks to discussions with Acee Lindem, Jeff Tantsura, Stephane Litkowski, Bruno Decraene, Kireeti Kompella, John E. Drake and Carlos Pignataro to bring the concept of combining ELC and RLD into a single ERLD signalled parameter more suitable for SDN controller based networks.8.7. IANA Considerations This document requests assigninganew BGP MSD sub-TLV code-pointsfrom the BGP-LS Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs registryasspecifieddescribed in section5.4. Note: placeholder IANA requestRequest Node ERLD codepoint BGP-LS TLV Code Point: TBD1 ISIS TLV 242/TBD2 Note: There is nothing in IANA from draft draft-ietf-isis-mpls-elc Note: Draft talks only about ELC/RLD and that is mismatch with ERLD OSPF RI TLV TBD5 OSPF ELC in Non-OSPF functionality Capability Bits (TBD6) 9.8. References9.1.8.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997, <http://xml.resource.org/public/rfc/html/rfc2119.html>. [2] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and S. Ray, "North-Bound Distribution of Link-State and Traffic Engineering (TE) Information Using BGP", RFC 7752, DOI 10.17487/RFC7752, March 2016, <https://www.rfc-editor.org/info/rfc7752>.9.2.[3] Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak, "Signaling Maximum SID Depth (MSD) Using OSPF", RFC 8476, DOI 10.17487/RFC8476, December 2018, <https://www.rfc-editor.org/info/rfc8476>. [4] 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, <https://www.rfc-editor.org/info/rfc8491>. [5] Tantsura, J., Chunduri, U., Talaulikar, K., Mirsky, G., and N. Triantafillis, "draft-ietf-idr-bgp-ls-segment- routing-msd", June 2019. 8.2. Informative References[3][6] Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. Litkowski, "draft-ietf-ospf-mpls-elc",January 2018. [4]May 2019. [7] Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. Litkowski, "draft-ietf-isis-mpls-elc",January 2018.May 2019. Authors' Addresses Gunter Van de Velde (editor) Nokia Antwerp BE Email: gunter.van_de_velde@nokia.com Wim Henderickx Nokia Belgium Email: wim.henderickx@nokia.com Matthew Bocci Nokia Shoppenhangers Road Maidenhead, Berks UK Email: matthew.bocci@nokia.com Keyur Patel Arrcus USA Email: keyur@arrcus.com