IDR Working Group Yao. Liu Internet-Draft Shaofu. Peng Intended status: Standards Track ZTE Corp. Expires: February 22, 2021 August 21, 2020 BGP Extension for SR-MPLS Entropy Label Position draft-zhou-idr-bgp-srmpls-elp-01 Abstract This document proposed an extension for BGP to configure the entropy label position for SR-MPLS networks. 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. 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 February 22, 2021. Copyright Notice Copyright (c) 2020 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 carefully, as they describe your rights and restrictions with respect to this document. 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. Liu & Peng Expires February 22, 2021 [Page 1] Internet-DrafBGP Extension for SR-MPLS Entropy Label Positio August 2020 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Entropy Labels in SR-MPLS Scenario with a Controller . . . . 2 3. BGP Extensions . . . . . . . . . . . . . . . . . . . . . . . 3 4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 3 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. Normative References . . . . . . . . . . . . . . . . . . . . 4 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction Entropy Label(EL) [RFC6790]is a technology that can be used for load- balancing in Segment Routing (SR) MPLS. [RFC8662] proposes to use entropy labels for SR-MPLS networks and mutiple < ELI, EL> pairs SHOULD be inserted in the SR-MPLS label stack. The ingress node may decide the number and position of the ELI/ELs which need to be inserted into the label stack, that is termed as ELP (Entropy Label Position). In some cases, the controller is used to perform the TE path computation for intra or inter-domain scenarios, thus it is also the responsibility of the controller to calculate ELP and inform it to the headend of the SR-TE path. [I-D.ietf-idr-segment-routing-te-policy] defines the specific process of how the controller in the SR network passes the path calculation result of the SR-TE policy to the headend of the network through BGP. In this document, the ELP information is transmitted by extending the flags of Segment List Sub-TLV in the BGP. 2. Entropy Labels in SR-MPLS Scenario with a Controller [RFC8662] proposes to use entropy labels for SR-MPLS networks. The Entropy Readable Label Depth (ERLD) is defined as the number of labels which means that the router will perform load-balancing using the ELI/EL. An appropriate algorithm should consider the following criteria: o a limited number of < ELI, EL> pairs SHOULD be inserted in the SR- MPLS label stack; o the inserted positions SHOULD be whithin the ERLD of a maximize number of transit LSRs; o a minimum number of < ELI, EL> pairs SHOULD be inserted while satisfying the above criteria. Liu & Peng Expires February 22, 2021 [Page 2] Internet-DrafBGP Extension for SR-MPLS Entropy Label Positio August 2020 As shown in Figure 1 , in SR-MPLS inter-domain scenario, the controller may perform the computation of the end-to-end path as well as the the Entropy Label Position (ELP) including the number and the position of the ELI/ELs. The controller has the capability to get the ERLD information of all nodes in inter-domain scenarios. .................... .................... ..................... . . . . . . .+---+ +---+ . . +---+ +---+ . .+---+ +----+ . .| A |-------| B |------ | C |------| X |-------| Y |------| Z | . .+---+ +---+ . . +---+ +---+ . .+---+ +----+ . . domain 1 . . domain 2 . . domain 3 . .................... .................... ..................... Figure 1: Entropy Labels in SR-MPLS Inter-Domain Scenario 3. BGP Extensions The Segment Flags is defined in Section 2.4.3.2.12 of [I-D.ietf-idr-segment-routing-te-policy]. 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |V|A|E| | +-+-+-+-+-+-+-+-+ E-Flag: This flag indicates that presence of < ELI, EL> label pairs are inserted after this segment. It is applicable to all SR-MPLS Segment Types. 4. Operations Supposed the head end had received a SR-TE path from the controller with multiple Segment List Sub-TLVs, for example, , especially S3 and S6 with E-flag. It indicates that two < ELI, EL> pairs SHOULD be inserted into the label stack of the SR-TE forwarding entry, respectively after the Label for S3 and Label for S6. With EL information, the label stack for SR-MPLS would be . Note that the value of EL is supplemented by headend, according to load-balancing function of the appropriate keys extracted from a given packet. Liu & Peng Expires February 22, 2021 [Page 3] Internet-DrafBGP Extension for SR-MPLS Entropy Label Positio August 2020 5. IANA Considerations This document requests bit 2 for Entropy Label Flag. Bit Description Reference ------------------------------------------------------------------ 2 Entropy Label Position Flag(E-Flag) This document 6. Normative References [I-D.ietf-idr-segment-routing-te-policy] Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., Rosen, E., Jain, D., and S. Lin, "Advertising Segment Routing Policies in BGP", draft-ietf-idr-segment-routing- te-policy-09 (work in progress), May 2020. [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and L. Yong, "The Use of Entropy Labels in MPLS Forwarding", RFC 6790, DOI 10.17487/RFC6790, November 2012, . [RFC8662] Kini, S., Kompella, K., Sivabalan, S., Litkowski, S., Shakir, R., and J. Tantsura, "Entropy Label for Source Packet Routing in Networking (SPRING) Tunnels", RFC 8662, DOI 10.17487/RFC8662, December 2019, . Authors' Addresses Liu Yao ZTE Corp. Email: liu.yao71@zte.com.cn Peng Shaofu ZTE Corp. Email: peng.shaofu@zte.com.cn Liu & Peng Expires February 22, 2021 [Page 4]