BIER WG Quan Xiong Internet-Draft Greg Mirsky Intended status: Informational ZTE Corporation Expires: September 7, 2019 Fangwei Hu Individual March 6, 2019 The Resilience for BIER draft-xiong-bier-resilience-02.txt Abstract Bit Index Explicit Replication (BIER) is an architecture for the forwarding of multicast data packets. In some scenarios, the resilience should be provided to guarantee the multicast data is protected by a given backup resource and forwarded successfully to the receivers in BIER-specific network. This document discusses the resilience use cases, requirements and proposes solutions for BIER, including the protection and restoration mechanisms and detection methods. 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 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. BIER Resilience Use Cases . . . . . . . . . . . . . . . . . . 3 2.1. BIER End-to-End 1+1 Protection . . . . . . . . . . . . . 3 2.2. BIER End-to-End Restoration . . . . . . . . . . . . . . . 4 2.3. BIER Link Protection . . . . . . . . . . . . . . . . . . 5 3. Management and Control Considerations . . . . . . . . . . . . 6 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. Normative References . . . . . . . . . . . . . . . . . . 6 7.2. Informational References . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction [RFC8279] defined Bit Index Explicit Replication (BIER) architecture as a solution for the forwarding of multicast data packets. The routers which support BIER are known as Bit-Forwarding Router (BFR) and the multicast data packet enters a BIER domain at a Bit- Forwarding Ingress Router (BFIR) and leaves at one or more Bit- Forwarding Egress Routers (BFERs). [I-D.eckert-bier-te-frr] provides some protection mechanisms for traffic engineering in a BIER domain. However, there is no mechanism to protect multicast traffic against BIER-specific network failures. In some scenarios, the resilience should be provided to guarantee the multicast data is protected by a given backup resource and forwarded successfully to the receivers in BIER-specific network. This document describes the resilience use cases and requirements for BIER-specific network and discusses the protection and restoration mechanisms and detection methods. Quan Xiong, et al. Expires September 7, 2019 [Page 2] Internet-Draft The Resilience for BIER March 2019 1.1. 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 [RFC2119]. 1.2. Terminology The terminology is defined as [RFC8279]. 2. BIER Resilience Use Cases The resilience use cases for a BIER-specific network should be considered including end-to-end and link protection scenarios. The protection, restoration, and related detection mechanisms MUST be provided for BIER resilience against a failure of a link or a node. 2.1. BIER End-to-End 1+1 Protection The end-to-end protection mechanisms for a BIER-specific network should be considered in some scenarios like shown in Figure 1. It includes end-to-end 1+1 protection and restoration use cases. Two disjoint end-to-end multicast paths that are available for 1+1 protection or restoration from BFIR to BFERs should be provided. One path could be BFIR->BFR1->BFR2->BFR3->BFER1 and BFIR->BFR1->BFR2->BFR3->BFER2; and the alternative path is BFIR->BFR6->BFR5->BFR4->BFER1 and BFIR->BFR6->BFR5->BFR4->BFER2. +----+ +----+ +----+ +-----+ |BFR1|----|BFR2|-----|BFR3|--------|BFER1| +----+ +----+ +----+ +-----+ / \ / / \ / +----+ \ / |BFIR| \/ +----+ /\ \ / \ \ / \ +----+ +----+ +----+ +-----+ |BFR6|----|BFR5|------|BFR4|------|BFER2| +----+ +----+ +----+ +-----+ Figure 1: BIER End-to-End Protection and Restoration For a 1+1 protection scenario, it is referred to as live-live, the BFIR sends two flows of multicast traffic to all BFERs through the Quan Xiong, et al. Expires September 7, 2019 [Page 3] Internet-Draft The Resilience for BIER March 2019 disjiont multipoint paths. BFERs need to merge the two flows when no failure happens. The BFERs MUST monitor and detect multicast failures and switch from one flow to another when a failure of a flow is detected. For example, in a Deterministic Networking (DetNet) service, Packet Replication Function (PRF) is used in combination with Packet Elimination Function (PEF) and usually referred to as PREF. PREF is used in DetNet to lower the packet loss metric and it can be viewed as an example of live-live terminated within BIER domain. PRF replicates packets into multiple DetNet member flows and sends them along multiple different paths to the destinations and PEF eliminates the duplication based on the failure detection. The failure detection mechanism for the end-to-end 1+1 protection scenario MUST be able to monitor and detect multicast failures in each working path. P2MP BFD [I-D.ietf-bfd-multipoint] MAY be used to verify multipoint connectivity between a BFIR and a set of BFERs. [I-D.hu-bier-bfd] describes the use of p2mp BFD in a BIER domain. End-to-end 1+1 protection provides fast switch but low resource utilization. All BFERs MAY receive two copies from two paths in the no-failure scenario and the receivers MUST be able to choose one of them and eliminate the duplication. 2.2. BIER End-to-End Restoration This section discusses the end-to-end restoration for BIER. If duplicate transmission is not desirable for some networks, the restoration mechanism may be taken into consideration where only one copy is sent to each receiver. The BFIR will send multicast flows onto the original path. If the BFIR detects a failure in the multicast path, the BFIR MAY create and new multicast tree and switch the multicast flow accordingly. The failure detection mechanism for end-to-end restoration use case MUST be enable receivers (tails) to monitor and detect multicast failures in the multicast tree and notify the head node. BIER- specific extensions MAY be proposed based on [I-D.ietf-bfd-multipoint-active-tail]. The P2MP active tail detection method extends the mechanism defined in [I-D.ietf-bfd-multipoint]. It allows tails to notify the head of the failure of the multicast path and can be used in multipoint and multicast networks, e.g., in BIER domain as described in [I-D.hu-bier-bfd]. If P2MP BFD uses the active tail mode, then when one of the BFERs detects the failure, it will send a message to the BFIR. The BFIR Quan Xiong, et al. Expires September 7, 2019 [Page 4] Internet-Draft The Resilience for BIER March 2019 will create a new multicast path to restore the service and notify BFERs of switchover and start forwarding the multicast flows over the restoration path. 2.3. BIER Link Protection Local protection, i.e., link or node protection, MAY be considered for BIER domain as an alternative to end-to-end protection. The nodes which are the BFRs in BIER network and they exchange the information needed for them to forward packets to each other using BIER. The node protection MAY be provided by using mechanisms already existing in the underlay network, for example, described in [I-D.eckert-bier-te-frr]. A BFR MAY send BIER packets to directly connected BIER neighbors through a BIER link without requiring a routing underlay. Link protection SHOULD be considered in BIER domain. The detection of link failure MAY use the Point-to-Point BFD detection defined in [RFC5880]. A set of extension for BIER-specific P2P BFD SHOULD be proposed in further discussion. As shown in Figure 2, the BIER path from BFIR to BFERs is BFIR->BFR4->BFR3 ->BFR2->BFER1 and BFIR->BFR4->BFR3->BFER2. If the BIER link from BFR4 to BFR3 fails, the failure can be protected by the backup paths over BFR4->BFR1->BFR2 ->BFR3. +-----+ +-----+ +--+--+ |BFR1 +--------+BFR2 +-------+BFER1| +--+--+ +--+--+ +--+--+ | | | | +--+--+ +--+--+ +--+--+ +--+--+ |BFIR +--------+BFR4 +--------+BFR3 +-------+BFER2| +--+--+ +-----+ +-----+ +-----+ Figure 2: BIER Link Protection As discussed in [I-D.eckert-bier-te-frr], the BIER link protection MAY use the existing RSVP-TE/P2MP or SR tunnel bypass. When a node detects a failure on a link, it MAY be assumed that the link has failed and the traffic is switched onto the pre-established backup path to get packets to the downstream node. Also, as discussed in [RFC7490], the Topology Independent Loop-free Alternate Fast Re-route (TI-LFA) Fast Reroute (FRR) approach that achieves guaranteed coverage against link or node failure in the Quan Xiong, et al. Expires September 7, 2019 [Page 5] Internet-Draft The Resilience for BIER March 2019 Interior Gateway Protocol (IGP) network MAY be applied in BIER network. 3. Management and Control Considerations BIER protection or restoration configuration, including BIER end-to- end protection, restoration, link/node protection and related information, MAY be defined and controlled from a centralized controller or a network management system. A failure detection and notification mechanism MUST be supported. The fast protection switching MUST be supported to minimize the loss of BIER packets due to BIER network failure. 4. Security Considerations Security aspects of protection in BIER domain may be considered in relation to the data plane, and handling the dedicated OAM packets used to detect, signal a failure, coordinate the state in the BIER protection domain. 5. IANA Considerations TBD 6. Acknowledgements Authors would like to thank the comments and suggestions from Jeffrey (Zhaohui) Zhang. 7. References 7.1. Normative References [I-D.hu-bier-bfd] Xiong, Q., Mirsky, G., hu, f., and C. Liu, "BIER BFD", draft-hu-bier-bfd-03 (work in progress), February 2019. [I-D.ietf-bfd-multipoint] Katz, D., Ward, D., Networks, J., and G. Mirsky, "BFD for Multipoint Networks", draft-ietf-bfd-multipoint-19 (work in progress), December 2018. [I-D.ietf-bfd-multipoint-active-tail] Katz, D., Ward, D., Networks, J., and G. Mirsky, "BFD Multipoint Active Tails.", draft-ietf-bfd-multipoint- active-tail-10 (work in progress), November 2018. Quan Xiong, et al. Expires September 7, 2019 [Page 6] Internet-Draft The Resilience for BIER March 2019 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, . [RFC7490] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N. So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)", RFC 7490, DOI 10.17487/RFC7490, April 2015, . [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, . 7.2. Informational References [I-D.eckert-bier-te-frr] Eckert, T., Cauchie, G., Braun, W., and M. Menth, "Protection Methods for BIER-TE", draft-eckert-bier-te- frr-03 (work in progress), March 2018. Authors' Addresses Quan Xiong ZTE Corporation No.6 Huashi Park Rd Wuhan, Hubei 430223 China Phone: +86 27 83531060 Email: xiong.quan@zte.com.cn Greg Mirsky ZTE Corporation USA Email: gregimirsky@gmail.com Quan Xiong, et al. Expires September 7, 2019 [Page 7] Internet-Draft The Resilience for BIER March 2019 Fangwei Hu Individual China Email: hufwei@gmail.com Quan Xiong, et al. Expires September 7, 2019 [Page 8]