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Mirsky 3 Internet-Draft ZTE Corp. 4 Updates: 7761 (if approved) J. Xiaoli 5 Intended status: Standards Track ZTE Corporation 6 Expires: April 25, 2019 October 22, 2018 8 Bidirectional Forwarding Detection (BFD) for Multi-point Networks and 9 Protocol Independent Multicast - Sparse Mode (PIM-SM) Use Case 10 draft-ietf-pim-bfd-p2mp-use-case-00 12 Abstract 14 This document discusses the use of Bidirectional Forwarding Detection 15 (BFD) for multi-point networks to provide nodes that participate in 16 Protocol Independent Multicast - Sparse Mode (PIM-SM) with the sub- 17 second convergence. Optional extension to PIM-SM Hello, as specified 18 in RFC 7761, to bootstrap point-to-multipoint BFD session. also 19 defined in this document. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at https://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on April 25, 2019. 38 Copyright Notice 40 Copyright (c) 2018 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (https://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 56 1.1. Conventions used in this document . . . . . . . . . . . . 3 57 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 58 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3 59 2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 60 3. Applicability of p2mp BFD . . . . . . . . . . . . . . . . . . 3 61 3.1. Multipoint BFD Encapsulation . . . . . . . . . . . . . . 4 62 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 63 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 64 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 65 7. Normative References . . . . . . . . . . . . . . . . . . . . 5 66 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 68 1. Introduction 70 Faster convergence in the control plane, in general, is beneficial 71 and allows minimizing periods of traffic blackholing, transient 72 routing loops and other scenarios that may negatively affect service 73 data flow. That equally applies to unicast and multicast routing 74 protocols. 76 [RFC7761] is the current specification of the Protocol Independent 77 Multicast - Sparse Mode (PIM-SM) for IPv4 and IPv6 networks. 78 Confirming implementation of PIM-SM elects a Designated Router (DR) 79 on each PIM-SM interface. When a group of PIM-SM nodes is connected 80 to shared-media segment, e.g. Ethernet, the one elected as DR is to 81 act on behalf of directly connected hosts in context of the PIM-SM 82 protocol. Failure of the DR impacts the quality of the multicast 83 services it provides to directly connected hosts because the default 84 failure detection interval for PIM-SM routers is 105 seconds. 85 Introduction of Backup DR (BDR), proposed in 86 [I-D.ietf-pim-dr-improvement] improves convergence time in the PIM-SM 87 over shared-media segment but still depends on long failure detection 88 interval. 90 Bidirectional Forwarding Detection (BFD) [RFC5880] had been 91 originally defined to detect failure of point-to-point (p2p) paths - 92 single-hop [RFC5881], multihop [RFC5883]. [I-D.ietf-bfd-multipoint] 93 extends the BFD base specification [RFC5880] for multipoint and 94 multicast networks, which precisely characterizes deployment 95 scenarios for PIM-SM over LAN segment. This document demonstrates 96 how point-to-multipoint (p2mp) BFD can enable faster detection of 97 PIM-SM router ailure and thus minimize multicast service disruption. 98 The document also defines the extension to PIM-SM [RFC7761] to 99 bootstrap a PIM-SM router to join in p2mp BFD session over shared- 100 media link. 102 1.1. Conventions used in this document 104 1.1.1. Terminology 106 BFD: Bidirectional Forwarding Detection 108 BDR: Backup Designated Router 110 DR: Designated Router 112 p2mp: Pont-to-Multipoint 114 PIM-SM: Protocol Independent Multicast - Sparse Mode 116 1.1.2. Requirements Language 118 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 119 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 120 "OPTIONAL" in this document are to be interpreted as described in BCP 121 14 [RFC2119] [RFC8174] when, and only when, they appear in all 122 capitals, as shown here. 124 2. Problem Statement 126 [RFC7761] does not provide a method for fast, e.g. sub-second, 127 failure detection of a neighbor PIM-SM router. BFD already has many 128 implementations based on HW that are capable to support multiple sub- 129 second session concurrently. 131 3. Applicability of p2mp BFD 133 [I-D.ietf-bfd-multipoint] may provide the efficient and scalable 134 solution for the fast-converging environment that has head-tails 135 relationships. Each such group presents itself as p2mp BFD session 136 with its head being the root and other routers being tails of the 137 p2mp BFD session. Figure 1 displays the new BFD Discriminator TLV 138 [RFC7761] to bootstrap tail of the p2mp BFD session. 140 0 1 2 3 141 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 1 142 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 143 | OptionType | OptionLength | 144 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 145 | My Discriminator | 146 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 148 Figure 1: BFD Discriminator TLV to Bootstrap P2MP BFD session 150 where new fields are interpreted as: 152 OptionType is a value (TBA1) assigned by IANA Section 4 that 153 identifies the TLV as BFD Discriminator TLV; 155 OptionLength value is always 4 157 My Discriminator - My Discriminator value allocated by the root of 158 the p2mp BFD session. 160 If PIM-SM routers, that support this specification, are configured to 161 use p2mp BFD for faster convergence, then the router to be monitored, 162 referred to as 'head', MUST create BFD session MultipointHead, as 163 defined in [I-D.ietf-bfd-multipoint]. The head MUST include BFD TLV 164 in its PIM-Hello message and periodically transmit BFD control 165 packets. Source IP address of the BFD control packet MUST be the 166 same as the source IP address of the PIM-Hello with BFD TLV messages 167 being transmitted by the head. The values of My Discriminator in the 168 BFD control packet and My Discriminator field of the BFD TLV in PIM- 169 Hello, transmitted by the head MUST be the same. When a PIM-SM 170 router configured to monitor the head, referred to as 'tail', via 171 p2mp BFD receives PIM-Hello packet with BFD TLV it MAY create p2mp 172 BFD session as MultipointTail, as defined in 173 [I-D.ietf-bfd-multipoint], and demultiplex p2mp BFD test session 174 based on head's source IP address the My Discriminator value it 175 learned from BFD Discriminator TLV. If the head ceased to include 176 BFD TLV in its PIM-Hello message, tails MUST close the corresponding 177 MultipointTail BFD session. If the tail detects MultipointHead 178 failure it MUST remove the neighbor. If the failed head node was 179 PIM-SM DR or BDR the tail MAY start DR Election process as specified 180 in Section 4.3.2 [RFC7761] or in Section 4.1 181 [I-D.ietf-pim-dr-improvement] respectively. 183 3.1. Multipoint BFD Encapsulation 185 The MultipointHead of p2mp BFD session when transmitting BFD control 186 packet: 188 MUST set TTL value to 1; 190 SHOULD use group address ALL-PIM-ROUTERS ('224.0.0.13' for IPv4 191 and 'ff02::d' for IPv6) as destination IP address 193 MAY use network broadcast address for IPv4 or link-local all nodes 194 multicast group for IPv6 as the destination IP address; 196 MUST set destination UDP port value to 3784 when transmitting BFD 197 control packets, as defined in [I-D.ietf-bfd-multipoint]. 199 4. IANA Considerations 201 IANA is requested to allocate a new OptionType value from PIM Hello 202 Options registry according to: 204 +-------------+----------------+-------------------+---------------+ 205 | Value Name | Length Number | Name Protocol | Reference | 206 +-------------+----------------+-------------------+---------------+ 207 | TBA | 4 | BFD Discriminator | This document | 208 +-------------+----------------+-------------------+---------------+ 210 Table 1: BFD Discriminator option type 212 5. Security Considerations 214 Security considerations discussed in [RFC7761], [RFC5880], and 215 [I-D.ietf-bfd-multipoint], apply to this document. 217 6. Acknowledgments 219 Authors cannot say enough to express their appreciation of comments 220 and suggestions we received from Stig Venaas. 222 7. Normative References 224 [I-D.ietf-bfd-multipoint] 225 Katz, D., Ward, D., Networks, J., and G. Mirsky, "BFD for 226 Multipoint Networks", draft-ietf-bfd-multipoint-18 (work 227 in progress), June 2018. 229 [I-D.ietf-pim-dr-improvement] 230 Zhang, Z., hu, f., Xu, B., and m. mishra, "PIM DR 231 Improvement", draft-ietf-pim-dr-improvement-05 (work in 232 progress), June 2018. 234 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 235 Requirement Levels", BCP 14, RFC 2119, 236 DOI 10.17487/RFC2119, March 1997, 237 . 239 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 240 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 241 . 243 [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 244 (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, 245 DOI 10.17487/RFC5881, June 2010, 246 . 248 [RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 249 (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883, 250 June 2010, . 252 [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I., 253 Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent 254 Multicast - Sparse Mode (PIM-SM): Protocol Specification 255 (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March 256 2016, . 258 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 259 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 260 May 2017, . 262 Authors' Addresses 264 Greg Mirsky 265 ZTE Corp. 267 Email: gregimirsky@gmail.com 269 Ji Xiaoli 270 ZTE Corporation 271 No.50 Software Avenue, Yuhuatai District 272 Nanjing 273 China 275 Email: ji.xiaoli@zte.com.cn