Network Working Group S. Chen Internet-Draft F. Duan Intended status: Standards Track Huawei Technologies Expires: 8 May 2024 5 November 2023 BIER Anycast MPLS Label draft-chen-bier-anycast-label-00 Abstract This document provides a method to reduce packet loss when failures occur at BIER transit or egress nodes or link. Requirements Language 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. 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 8 May 2024. Copyright Notice Copyright (c) 2023 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 Chen & Duan Expires 8 May 2024 [Page 1] Internet-Draft BIER Anycast MPLS Label November 2023 and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. Egress Protection . . . . . . . . . . . . . . . . . . . . . . 3 3.1. Anycast and Bypass MPLS Label . . . . . . . . . . . . . . 3 3.2. Advertisement of MPLS Label . . . . . . . . . . . . . . . 4 3.3. Establishment of BIER Forwarding Table . . . . . . . . . 4 3.4. Fast Recovery . . . . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 7. Normative References . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction When failures occur at transit or egress BIER node, there is no fast recovery or protecting mechanism currently. The recovery duration depends on how fast the unicast algorithm can re-calculate the new path. The new available path can only be generated in this way called 'hard convergence'. In this document, a fast failover method is designed for BIER to generate an alternative path for flow in advance by allocating and transmitting additional BIER MPLS label. In [RFC8279], BIER MPLS label was assigned locally to identify different set of [Sub-domain, SI, BSL] and therefore can identify different instances of BIER Forwarding Table. In this document, a BFR node will be assigned two MPLS Labels called 'Anycast' and 'Bypass' MPLS Label. Anycast MPLS Label will be used to represent the site, while bypass MPLS label will only be used within each site to ensure the forwarding function. The BIER Forwarding Table will also be modified to record two different out interfaces for single target BFR-id. 2. Terminology The terminology used in this document is the terminology defined in[RFC8279], [RFC8296] and [RFC8556]. For convenience of description, the abbreviations used in this document is listed below. Chen & Duan Expires 8 May 2024 [Page 2] Internet-Draft BIER Anycast MPLS Label November 2023 BIER: Bit Index Explicit Replication BGP: Border Gateway Protocol IGP: Interior gateway protocol BFR: Bit-Forwarding Router BFR-ID: Bit-Forwarding Router ID BFR-Prefix: Bit-Forwarding Router Prefix BFR-NBR: Bit-Forwarding Router Neighbor BIRT: Bit index routing table BIFT: Bit index forwarding table F-BM: Forwarding Bit Mask MPLS: Multiprotocol Label Switching 3. Egress Protection 3.1. Anycast and Bypass MPLS Label As shown in the following figure, one customer device is multihomed to two BFERs in order to perform egress protection. Two BFERs are deployed in the same egress site. Different BFR-ids and BFR-prefixes are configured. However, they are assigned with same Anycast MPLS label and different Bypass MPLS labels. The same Anycast label can be used to specify the egress site. The Bypass MPLS label works as the traditional MPLS label to ensure the normal behavior of BIER forwarding function within the site. They are advertised by BIER- Info Sub-Tlv in BIER prefix. BIER prefix carrying Anycast MPLS label is called Anycast BIER Prefix. After receiving BIER prefix, BIER MPLS Label will be contained in BIER Forwarding Table to instruct forwarding data packet. ( BFIR-A ) ------ ( BFR-B ) ------ ( BFER-C ) ---- ( CE ) 1 (0:001) \ 2 (0:010) / \ | / \ | / \ | / \ | / ( BFER-D ) 3 (0:100) Chen & Duan Expires 8 May 2024 [Page 3] Internet-Draft BIER Anycast MPLS Label November 2023 Figure 1: BIER Egress Site Deployment 3.2. Advertisement of MPLS Label [RFC8401] defines BIER Info Sub-TLV to advertise BIER parameters such as BFR-id, subdomain-id. The key field of the Sub-TLV is BIER prefix. Within the Sub-TLV, sub-sub-TLV is contained and it carries MAX-SI, BSL and MPLS Label. The sub-sub-TLV is modified in this document so that both MPLS Labels can be advertised. 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Max SI | BSL | (Bypass) Label | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Max SI | BSL | Anycast Label | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: New BIER Sub-sub-TLV 3.3. Establishment of BIER Forwarding Table After receiving BIER Info Sub-TLV, BFR will parse Bypass MPLS Label and Anycast MPLS Label. The relationship of [BFR-id, Anycast Label, Bypass Label] will be maintained by each BFR. As shown in the figure below, BFR will receive BIER Info Sub-TLVs from BFER-C and BFER-D. The Anycast Label of two BFERs are different with BFR's, but they are same with each other. BFR will combine BFR-id of BFER-C and BFER-D as the one entry in the Bit Index Forwarding Table. Both BFER-C and BFER-D may receive packet. Site1 Site2 ------ BFER-C ------ CE | | | BFR-B ---- BFER-D -------- Figure 3: BIER Egress Site Deployment Chen & Duan Expires 8 May 2024 [Page 4] Internet-Draft BIER Anycast MPLS Label November 2023 BFR-B BIFT -------------------------------------- | F-BM | BFR-NBR | NBR-Label | ===================================== | 001 | A | Label-1 | ------------------------------------- | 011 | C | AnycastLabel-2 | ------------------------------------- | D | AnycastLabel-2 | ------------------------------------- Figure 4: BFR-B BIFT When BFR receives BIER data packet, it will locate the BIFT according to the BIFT-id encapsulted in BIER header. If the packet needs to be forwarded to BFR-id 3, it will modify the BIFT-id field as AnycastLabel-2 and then forward it. When BFER-D receives this packet, the packet will be finnaly sent to CE. BFERs will also advertise their BIER Info Sub-Tlv to each other. When BFER-C receives BFER-D's Sub-sub-TLV, it finds BFER-D has same anycast label and different bypass label, it will encode bypass label into its BIFT as shown below. BFR-C BIFT -------------------------------------- | F-BM | BFR-NBR | NBR-Label | ===================================== | 001 | B | Label-3 | ------------------------------------- | 100 | D | BypassLabel-13 | ------------------------------------- Figure 5: BFR-C BIFT 3.4. Fast Recovery When link between BFR-B and BFER-D goes down due to certain reason, BFR-B will detect it and forward packet to BFER-C immediately according to BIFT entry. AnycastLabel-2 will be encapsulated. When BFER-C receives this packet, it will firstly use anycast label to locate corresponding BIFT table. Then it will use BFR-id 3 to look for F-BM and find its neighbor is BFER-D. The bypass label of BFER-D will be encapsulated into data packet header. Then BFER-D will finally receive the packet. No packet will be dropped because the backup out interface has been generated when the anycast and bypass MPLS Labels have been advertised and utilized. Chen & Duan Expires 8 May 2024 [Page 5] Internet-Draft BIER Anycast MPLS Label November 2023 4. Security Considerations //TODO 5. IANA Considerations //TODO 6. Acknowledgements //TODO 7. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., Przygienda, T., and S. Aldrin, "Multicast Using Bit Index Explicit Replication (BIER)", RFC 8279, DOI 10.17487/RFC8279, November 2017, . [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation for Bit Index Explicit Replication (BIER) in MPLS and Non- MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 2018, . [RFC8401] Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z. Zhang, "Bit Index Explicit Replication (BIER) Support via IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018, . [RFC8556] Rosen, E., Ed., Sivakumar, M., Przygienda, T., Aldrin, S., and A. Dolganow, "Multicast VPN Using Bit Index Explicit Replication (BIER)", RFC 8556, DOI 10.17487/RFC8556, April 2019, . Chen & Duan Expires 8 May 2024 [Page 6] Internet-Draft BIER Anycast MPLS Label November 2023 Authors' Addresses Siyu Chen Huawei Technologies Email: chensiyu27@huawei.com Fanghong Duan Huawei Technologies Email: duanfanghong@huawei.com Chen & Duan Expires 8 May 2024 [Page 7]