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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group V. Kamath 3 Internet-Draft VMware 4 Intended status: Standards Track R. Chokkanathapuram Sundaram 5 Expires: November 14, 2021 Cisco Systems, Inc. 6 R. Banthia 7 Apstra 8 A. Gopal 9 Cisco Systems, Inc. 10 May 13, 2021 12 PIM Null-Register packing 13 draft-ietf-pim-null-register-packing-09 15 Abstract 17 In PIM-SM networks PIM Null-Register messages are sent by the 18 Designated Router (DR) to the Rendezvous Point (RP) to signal the 19 presence of Multicast sources in the network. There are periodic PIM 20 Null-Registers sent from the DR to the RP to keep the state alive at 21 the RP as long as the source is active. The PIM Null-Register 22 message carries information about a single Multicast source and 23 group. 25 This document defines a standard to send multiple multicast source 26 and group information in a single PIM Null-Register message, in a 27 packed format. We will refer to this packed format as the PIM Packed 28 Null-Register format throughout the document. This document also 29 discusses the interoperability between the PIM routers which do not 30 understand the packed message format with multiple multicast source 31 and group details. 33 Status of This Memo 35 This Internet-Draft is submitted in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF). Note that other groups may also distribute 40 working documents as Internet-Drafts. The list of current Internet- 41 Drafts is at https://datatracker.ietf.org/drafts/current/. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on November 14, 2021. 50 Copyright Notice 52 Copyright (c) 2021 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (https://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 68 1.1. Conventions used in this document . . . . . . . . . . . . 3 69 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 70 2. Packed Null-Register Capability . . . . . . . . . . . . . . . 3 71 3. PIM Packed Null-Register message . . . . . . . . . . . . . . 4 72 4. PIM Packed Register-Stop message format . . . . . . . . . . . 5 73 5. Protocol operation . . . . . . . . . . . . . . . . . . . . . 6 74 6. PIM Anycast RP considerations . . . . . . . . . . . . . . . . 7 75 7. PIM RP router version downgrade . . . . . . . . . . . . . . . 7 76 8. Fragmentation consideration . . . . . . . . . . . . . . . . . 7 77 9. Security Considerations . . . . . . . . . . . . . . . . . . . 7 78 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 79 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 80 12. Normative References . . . . . . . . . . . . . . . . . . . . 8 81 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 83 1. Introduction 85 PIM Null-Registers are sent by the DR periodically for Multicast 86 streams to keep the states active on the RP, as long as the multicast 87 source is alive. As the number of multicast sources increases, the 88 number of PIM Null-Register messages that are sent also increases. 89 This results in more PIM packet processing at the RP and the DR. 91 The control plane policing (COPP), monitors the packets that are 92 processed by the control plane. The high rate at which Null- 93 Registers are received at the RP can lead to COPP drops of Multicast 94 PIM Null-Register messages. This draft proposes a method to 95 efficiently pack multiple PIM Null-Registers [[RFC7761] 96 (Section 4.4)] and Register-Stops [[RFC7761] (Section 3.2)] into a 97 single message as these packets anyway do not contain encapsulated 98 data. 100 The draft also discusses interoperability with PIM routers that do 101 not understand the new packet format. 103 1.1. Conventions used in this document 105 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 106 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 107 "OPTIONAL" in this document are to be interpreted as described in BCP 108 14 [RFC2119] when, and only when, they appear in all capitals, as 109 shown here. 111 1.2. Terminology 113 RP: Rendezvous Point 115 DR: Designated Router 117 2. Packed Null-Register Capability 119 A router (DR) can decide to pack multiple Null-Register messages 120 based on the capability received from the RP as part of the PIM 121 Register-Stop. This ensures compatibility with routers that do not 122 support processing of the new format. The capability information can 123 be indicated by the RP via the PIM Register-Stop message sent to the 124 DR. Thus a DR will switch to the new format only when it learns that 125 the RP is capable of handling the PIM Packed Null-Register messages. 127 Conversely, a DR that does not support the packed format can continue 128 generating the PIM Null-Register as defined in [[RFC7761] 129 (Section 4.4)]. To exchange the capability information in the 130 Register-Stop message, the "Reserved" field can be used to indicate 131 this capability in those Register-Stop messages. One bit of the 132 Reserved field is used to indicate the "packing" capability (P bit). 133 The rest of the bits in the "Reserved" field will be retained for 134 future use. 136 0 1 2 3 137 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 1 138 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 139 |PIM Ver| Type |P| Reserved | Checksum | 140 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 141 | Group Address (Encoded-Group format) | 142 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 143 | Source Address (Encoded-Unicast format) | 144 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 145 Figure 1: PIM Register-Stop message with capability option 147 PIM Version, Type, Checksum, Group Address, Source Address: 149 Same as [RFC7761] (Section 4.9.4) 151 P: 153 Capability bit (flag bit 7) used to indicate support for the 154 Packed Null-Register Capability 156 3. PIM Packed Null-Register message 158 PIM Packed Null-Register message format includes a count to indicate 159 the number of Null-Register records in the message. 161 0 1 2 3 162 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 1 163 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 164 |PIM Ver| Type |Subtype| FB | Checksum | 165 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 166 | Count | Reserved | 167 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 168 | Group Address[1] (Encoded-Group format) | 169 | Source Address[1] (Encoded-Unicast format) | 170 . . 171 . . 172 . . 173 . . 174 . Group Address[N] . 175 | Source Address[N] | 176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 177 Figure 2: PIM Packed Null-Register message format 179 PIM Version, Reserved, Checksum: 181 Same as [RFC7761] (Section 4.9.3) 183 Type, SubType: 185 The new packed Null-Register Type and SubType values TBD. 186 [RFC8736] 188 Count: 190 The number of packed Null-Register records. A record consists of 191 a Group Address and Source Address pair. 193 Group Address, Source Address: 195 Same as [RFC7761] (Section 4.9.4) 197 4. PIM Packed Register-Stop message format 199 The PIM Packed Register-Stop message includes a count to indicate the 200 number of records that are present in the message. 202 0 1 2 3 203 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 1 204 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 205 |PIM Ver| Type |Subtype| FB | Checksum | 206 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 207 | Count | Reserved | 208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 209 | Group Address[1] (Encoded-Group format) | 210 | Source Address[1] (Encoded-Unicast format) | 211 . . 212 . . 213 . . 214 . . 215 . Group Address[N] . 216 | Source Address[N] | 217 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 219 Figure 3: PIM Packed Register-Stop message format 221 PIM Version, Reserved, Checksum: 223 Same as [RFC7761] (Section 4.9.4) 225 Type: 227 The new Register Stop Type and SubType values TBD 229 Count: 231 The number of PIM packed Register-Stop records. A record consists 232 of a Group Address and Source Address pair. 234 Group Address, Source Address: 236 Same as [RFC7761] (Section 4.9.4) 238 5. Protocol operation 240 The following combinations exist - 242 1. DR and RP both support the PIM Packed Null-Register and PIM 243 Packed Register-Stop formats: 245 * As specified in [[RFC7761]], the DR sends PIM Null-Register 246 messages towards the RP when a new source is detected. 248 * An RP supporting this specification MUST set the P-bit in the 249 corresponding Register-Stop messages. 251 * When a Register-Stop message with the P-bit set is received, 252 the DR MAY send PIM Packed Null-Register messages (Section 3) 253 to the RP instead of multiple Register messages with the N-bit 254 set ([[RFC7761]]). 256 * The RP, after receiving a PIM Packed Null-Register message MAY 257 start sending PIM Packed Register-Stop messages (Section 4) to 258 the corresponding DR instead of individual Register-Stop 259 messages. 261 2. DR supports but RP does not support the PIM Packed Null-Register 262 and PIM Packed Register-Stop formats: 264 * As specified in [[RFC7761]], DR sends PIM Null-Registers 265 towards the RP. 267 * RP sends a normal Register-Stop without any capability 268 information. 270 * DR then sends PIM Null-Registers in the unpacked format. 271 [[RFC7761]] 273 3. RP supports but DR does not support the PIM Packed Null-Register 274 and PIM Packed Register-Stop formats: 276 * As specified in [[RFC7761]], DR sends the PIM Null-Register 277 towards the RP. 279 * RP sends a PIM Packed Register-Stop towards the DR that 280 includes capability information. 282 * Since DR does not support the new format, it sends PIM Null- 283 Registers in the unpacked format. [[RFC7761]] 285 6. PIM Anycast RP considerations 287 The PIM Packed Null-Register format should be enabled only if it is 288 supported by all PIM Anycast RP [[RFC4610]] members in the RP set for 289 the RP address. This consideration applies to PIM Anycast RP with 290 MSDP [[RFC3446]] as well. 292 7. PIM RP router version downgrade 294 Consider a PIM RP router that supports PIM Packed Null-Registers and 295 PIM Packed Register-Stops. When this router downgrades to a software 296 version which does not support PIM Packed Null-Registers and PIM 297 Packed Register-Stops, the DR that sends the PIM Packed Null-Register 298 message will not get a PIM Register-Stop message back from the RP. 299 In such scenarios the DR can send an unpacked PIM Null-Register and 300 check the PIM Register-Stop to see if the capability bit (P-bit) for 301 PIM Packed Null-Register is set or not. If it is not set then the DR 302 will continue sending unpacked PIM Null-Register messages. 304 8. Fragmentation consideration 306 When building a PIM Packed Null-Register message or PIM Packed 307 Register-Stop message, a router should include as many records as 308 possible based on the path MTU towards RP, if path MTU discovery is 309 done. Otherwise, the number of records should be limited by the MTU 310 of the outgoing interface. 312 9. Security Considerations 314 General Register messages security considerations from RFC7761 apply. 315 As mentioned in RFC7761, PIM Null-Register messages and Register-Stop 316 messages are forwarded by intermediate routers to their destination 317 using normal IP forwarding. Without data origin authentication, an 318 attacker who is located anywhere in the network may be able to forge 319 a Null-Register or Register-Stop message. We next consider the 320 effect of a forgery of each of these messages. By forging a Register 321 message, an attacker can cause the RP to inject forged traffic onto 322 the shared multicast tree. 324 By forging a Register-Stop message, an attacker can prevent a 325 legitimate DR from registering packets to the RP. This can prevent 326 local hosts on that LAN from sending multicast packets. The above 327 two PIM messages are not changed by intermediate routers and need 328 only be examined by the intended receiver. Thus, these messages can 329 be authenticated end-to-end. Attacks on Register and Register-Stop 330 messages do not apply to a PIM-SSM-only implementation, as these 331 messages are not used in PIM-SSM. 333 There is another case where a spoofed Register-Stop can be sent to 334 make it appear that is from the RP, and that the RP supports this new 335 packed capability when it does not. This can cause Null-Registers to 336 be sent to an RP that doesnt support this packed format. But 337 standard methods to prevent spoofing should take care of this case. 338 For example, uRPF can be used to filter out packets coming from the 339 outside from addresses that belong to routers inside. 341 10. IANA Considerations 343 This document requires the assignment of Capability bit (P-bit), 344 flag bit 7 in the PIM Register-Stop message. 346 This document requires the assignment of 2 new PIM message types 347 for the PIM Packed Null-Register and PIM Packed Register-Stop. 349 11. Acknowledgments 351 The authors would like to thank Stig Venaas, Anish Peter, Zheng Zhang 352 and Umesh Dudani for their helpful comments on the draft. 354 12. Normative References 356 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 357 Requirement Levels", BCP 14, RFC 2119, 358 DOI 10.17487/RFC2119, March 1997, 359 . 361 [RFC3446] Kim, D., Meyer, D., Kilmer, H., and D. Farinacci, "Anycast 362 Rendevous Point (RP) mechanism using Protocol Independent 363 Multicast (PIM) and Multicast Source Discovery Protocol 364 (MSDP)", RFC 3446, DOI 10.17487/RFC3446, January 2003, 365 . 367 [RFC4610] Farinacci, D. and Y. Cai, "Anycast-RP Using Protocol 368 Independent Multicast (PIM)", RFC 4610, 369 DOI 10.17487/RFC4610, August 2006, 370 . 372 [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I., 373 Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent 374 Multicast - Sparse Mode (PIM-SM): Protocol Specification 375 (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March 376 2016, . 378 [RFC8736] Venaas, S. and A. Retana, "PIM Message Type Space 379 Extension and Reserved Bits", RFC 8736, 380 DOI 10.17487/RFC8736, February 2020, 381 . 383 Authors' Addresses 385 Vikas Ramesh Kamath 386 VMware 387 3401 Hillview Ave 388 Palo Alto CA 94304 389 USA 391 Email: vkamath@vmware.com 393 Ramakrishnan Chokkanathapuram Sundaram 394 Cisco Systems, Inc. 395 Tasman Drive 396 San Jose CA 95134 397 USA 399 Email: ramaksun@cisco.com 401 Raunak Banthia 402 Apstra 403 333 Middlefield Rd STE 200 404 Menlo Park CA 94025 405 USA 407 Email: rbanthia@apstra.com 409 Ananya Gopal 410 Cisco Systems, Inc. 411 Tasman Drive 412 San Jose CA 95134 413 USA 415 Email: ananygop@cisco.com