PIM Working Group G. Mirsky Internet-Draft ZTE Corp. Updates: 7761 (if approved) J. Xiaoli Intended status: Standards Track ZTE Corporation Expires: August 19, 2018 February 15, 2018 Bidirectional Forwarding Detection (BFD) for Multi-point Networks and Protocol Independent Multicast - Sparse Mode (PIM-SM) Use Case draft-mirsky-pim-bfd-p2mp-use-case-00 Abstract This document discusses use of Bidirectional Forwarding Detection (BFD) for multi-point networks to provide nodes that participate in Protocol Independent Multicast - Sparse Mode (PIM-SM) over shared- media segment with sub-second convergence of the Designated Router and defines the extension to bootstrap point-to-multipoint BFD session. Optional extension to PIM-SM Hello, as defined in RFC 7761, also defined in this document. 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 August 19, 2018. Copyright Notice Copyright (c) 2018 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 Mirsky & Xiaoli Expires August 19, 2018 [Page 1] Internet-Draft BFD P2MP Use in PIM-SM February 2018 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Conventions used in this document . . . . . . . . . . . . 3 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 3. Applicability of p2mp BFD . . . . . . . . . . . . . . . . . . 3 3.1. Multipoint BFD Encapsulation . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 7. Normative References . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction [RFC7761] is the current specification of the Protocol Independent Multicast - Sparse Mode (PIM-SM) for IPv4 and IPv6 networks. Confirming implementation of PIM-SM elects a Designated Router (DR) on each PIM-SM interface. When a group of PIM-SM nodes are connected to shared-media segment, e.g. Ethernet, the one elected as DR is to act on behalf of directly connected hosts in context of the PIM-SM protocol. Failure of the DR impacts quality of the multicast services it provides to directly connected hosts because the default failure detection interval for PIM-SM routers is 105 seconds. Introduction of Backup DR (BDR), proposed in [I-D.ietf-pim-dr-improvement] improves convergence time in the PIM-SM over shared-media segment but still depends on long failure detection interval. Bidirectional Forwarding Detection (BFD) [RFC5880] had been originally defined to detect failure of point-to-point (p2p) paths - single-hop [RFC5881], multihop [RFC5883]. [I-D.ietf-bfd-multipoint] extends [RFC5880] for multipoint and multicast networks, which precisely characterizes deployment scenarios for PIM-SM over LAN segment. This document demonstrates how point-to-multipoint (p2mp) BFD can enable faster detection of PIM-SM DR and BDR failure and thus minimize multicast service disruption. The document also defines the extension to PIM-SM [RFC7761] to bootstrap a PIM-SM router to join in p2mp BFD session over shared-media link. Mirsky & Xiaoli Expires August 19, 2018 [Page 2] Internet-Draft BFD P2MP Use in PIM-SM February 2018 1.1. Conventions used in this document 1.1.1. Terminology BFD: Bidirectional Forwarding Detection BDR: Backup Designated Router DR: Designated Router p2mp: Pont-to-Multipoint PIM-SM: Protocol Independent Multicast - Sparse Mode 1.1.2. 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. 2. Problem Statement Several PIM-SM routers may be connected over shared-media link, e.g. Ethernet. [RFC7761] does not provide method for fast, e.g. sub- second, DR failure detection by other PIM-SM routers on the same Ethernet link. BFD already has many implementations based on HW that are capable to support multiple sub-second session concurrently. [Editor's note: monitoring of PIM-SM BDR liveliness will be addressed in the next update of the draft.] 3. Applicability of p2mp BFD [I-D.ietf-bfd-multipoint] may provide the efficient and scalable solution for fast-converging environment that has head-tails relationships. Each such group presents itself as p2mp BFD session with its head being the root and other routers being tails of the p2mp BFD session. Figure 1 displays the new BFD Discriminator TLV [RFC7761] to bootstrap tail of the p2mp BFD session. Mirsky & Xiaoli Expires August 19, 2018 [Page 3] Internet-Draft BFD P2MP Use in PIM-SM February 2018 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OptionType | OptionLength | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | My Discriminator | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: BFD Discriminator TLV to Bootstrap P2MP BFD session where new fields are interpreted as: OptionType is value (TBA1) assigned by IANA Section 4 that identifies the TLV as BFD Discriminator TLV; OptionLength value is always 4 My Discriminator - My Discriminator value allocated by the root of the p2mp BFD session. If PIM-SM routers, that support this specification, are configured to use p2mp BFD for faster convergence, then the DR MUST create BFD session MultipointHead, as defined in [I-D.ietf-bfd-multipoint]. PIM-SM DR MUST include BFD TLV in its PIM-Hello message. PIM-SM DR periodically transmits BFD control packets. Source IP address of the BFD control packet MUST be the same as the source IP address of the PIM-Hello with BFD TLV messages being transmitted by the DR. The values of My Discriminator in the BFD control packet and My Discriminator field of the BFD TLV in PIM-Hello, transmitted by the PIM-SM DR, MUST be the same. When non-DR PIM-SM router receives PIM- Hello packet from DR with BFD TLV it MAY create p2mp BFD session as MultipointTail, as defined in [I-D.ietf-bfd-multipoint], and demultiplex p2mp BFD test session based on DR source IP address the My Discriminator value value it learned from BFD Discriminator TLV. If DR ceased to include BFD TLV in its PIM-Hello message, other PIM- SM nodes MUST close corresponding MultipointTail BFD session. 3.1. Multipoint BFD Encapsulation The MultipointHead of p2mp BFD session when transmitting BFD control packet: MUST set TTL value to 1; SHOULD use group address ALL-PIM-ROUTERS ('224.0.0.13' for IPv4 and 'ff02::d' for IPv6) as destination IP address Mirsky & Xiaoli Expires August 19, 2018 [Page 4] Internet-Draft BFD P2MP Use in PIM-SM February 2018 MAY use network broadcast address for IPv4 or link-local all nodes multicast group for IPv6 as destination IP address; MUST set destination UDP port value to 3784 when transmitting BFD control packets, as defined in [I-D.ietf-bfd-multipoint]. 4. IANA Considerations IANA is requested to allocate new OptionType value from PIM Hello Options registry according to: +-------------+----------------+-------------------+---------------+ | Value Name | Length Number | Name Protocol | Reference | +-------------+----------------+-------------------+---------------+ | TBA | 4 | BFD Discriminator | This document | +-------------+----------------+-------------------+---------------+ Table 1: BFD Discriminator option type 5. Security Considerations Security considerations discussed in [RFC7761], [RFC5880], and [I-D.ietf-bfd-multipoint], apply to this document. 6. Acknowledgements TBD 7. Normative References [I-D.ietf-bfd-multipoint] Katz, D., Ward, D., Networks, J., and G. Mirsky, "BFD for Multipoint Networks", draft-ietf-bfd-multipoint-13 (work in progress), January 2018. [I-D.ietf-pim-dr-improvement] Zhang, Z., hu, f., Xu, B., and m. mishra, "PIM DR Improvement", draft-ietf-pim-dr-improvement-04 (work in progress), December 2017. [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, . Mirsky & Xiaoli Expires August 19, 2018 [Page 5] Internet-Draft BFD P2MP Use in PIM-SM February 2018 [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, DOI 10.17487/RFC5881, June 2010, . [RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883, June 2010, . [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I., Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March 2016, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Authors' Addresses Greg Mirsky ZTE Corp. Email: gregimirsky@gmail.com Ji Xiaoli ZTE Corporation No.50 Software Avenue, Yuhuatai District Nanjing China Email: ji.xiaoli@zte.com.cn Mirsky & Xiaoli Expires August 19, 2018 [Page 6]