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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group V. Moreno 3 Internet-Draft Cisco Systems 4 Intended status: Experimental D. Farinacci 5 Expires: January 21, 2018 lispers.net 6 July 20, 2017 8 Signal-Free LISP Multicast 9 draft-ietf-lisp-signal-free-multicast-05 11 Abstract 13 When multicast sources and receivers are active at LISP sites, the 14 core network is required to use native multicast so packets can be 15 delivered from sources to group members. When multicast is not 16 available to connect the multicast sites together, a signal-free 17 mechanism can be used to allow traffic to flow between sites. The 18 mechanism within here uses unicast replication and encapsulation over 19 the core network for the data-plane and uses the LISP mapping 20 database system so encapsulators at the source LISP multicast site 21 can find decapsulators at the receiver LISP multicast sites. 23 Requirements Language 25 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 26 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 27 document are to be interpreted as described in [RFC2119]. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at http://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on January 21, 2018. 46 Copyright Notice 48 Copyright (c) 2017 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 4 65 3. Reference Model . . . . . . . . . . . . . . . . . . . . . . . 5 66 4. General Procedures . . . . . . . . . . . . . . . . . . . . . 7 67 4.1. General Receiver-Site Procedures . . . . . . . . . . . . 8 68 4.1.1. Multicast Receiver Detection . . . . . . . . . . . . 8 69 4.1.2. Receiver-Site Registration . . . . . . . . . . . . . 8 70 4.1.3. Consolidation of the Replication-List . . . . . . . . 9 71 4.2. General Source-Site Procedures . . . . . . . . . . . . . 10 72 4.2.1. Multicast Tree Building at the Source-Site . . . . . 10 73 4.2.2. Multicast Destination Resolution . . . . . . . . . . 10 74 4.3. General LISP Notification Procedures . . . . . . . . . . 11 75 5. Source Specific Multicast Trees . . . . . . . . . . . . . . . 11 76 5.1. Source Directly Connected to Source-ITRs . . . . . . . . 12 77 5.2. Source not Directly Connected to Source-ITRs . . . . . . 12 78 6. Multi-Homing Considerations . . . . . . . . . . . . . . . . . 12 79 6.1. Multiple ITRs at a Source-Site . . . . . . . . . . . . . 12 80 6.2. Multiple ETRs at a Receiver-Site . . . . . . . . . . . . 13 81 6.3. Multiple RLOCs for an ETR at a Receiver-Site . . . . . . 13 82 6.4. Multicast RLOCs for an ETR at a Receiver-Site . . . . . . 14 83 7. PIM Any Source Multicast Trees . . . . . . . . . . . . . . . 14 84 8. Signal-Free Multicast for Replication Engineering . . . . . . 15 85 9. Security Considerations . . . . . . . . . . . . . . . . . . . 18 86 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 87 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19 88 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 89 12.1. Normative References . . . . . . . . . . . . . . . . . . 19 90 12.2. Informative References . . . . . . . . . . . . . . . . . 20 91 Appendix A. Document Change Log . . . . . . . . . . . . . . . . 21 92 A.1. Changes to draft-ietf-lisp-signal-free-multicast-05 . . . 21 93 A.2. Changes to draft-ietf-lisp-signal-free-multicast-04 . . . 21 94 A.3. Changes to draft-ietf-lisp-signal-free-multicast-03 . . . 21 95 A.4. Changes to draft-ietf-lisp-signal-free-multicast-02 . . . 21 96 A.5. Changes to draft-ietf-lisp-signal-free-multicast-01 . . . 22 97 A.6. Changes to draft-ietf-lisp-signal-free-multicast-00 . . . 22 98 A.7. Changes to draft-farinacci-lisp-signal-free-multicast-04 22 99 A.8. Changes to draft-farinacci-lisp-signal-free-multicast-03 22 100 A.9. Changes to draft-farinacci-lisp-signal-free-multicast-02 22 101 A.10. Changes to draft-farinacci-lisp-signal-free-multicast-01 22 102 A.11. Changes to draft-farinacci-lisp-signal-free-multicast-00 23 103 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 105 1. Introduction 107 When multicast sources and receivers are active at LISP sites, and 108 the core network between the sites does not provide multicast 109 support, a signal-free mechanism can be used to create an overlay 110 that will allow multicast traffic to flow between sites and connect 111 the multicast trees at the different sites. 113 The signal-free mechanism here proposed does not extend PIM over the 114 overlay as proposed in [RFC6831], nor does the mechanism utilize 115 direct signaling between the Receiver-ETRs and Sender-ITRs as 116 described in [I-D.farinacci-lisp-mr-signaling]. The signal-free 117 mechanism proposed reduces the amount of signaling required between 118 sites to a minimum and is centered around the registration of 119 Receiver-sites for a particular multicast-group or multicast-channel 120 with the LISP Mapping System. 122 Registrations from the different receiver-sites will be merged at the 123 Mapping System to assemble a multicast-replication-list inclusive of 124 all RLOCs that lead to receivers for a particular multicast-group or 125 multicast-channel. The replication-list for each specific multicast- 126 entry is maintained as a LISP database mapping entry in the Mapping 127 Database. 129 When the ITR at the source-site receives multicast traffic from 130 sources at its site, the ITR can query the mapping system by issuing 131 Map-Request messages for the (S,G) source and destination addresses 132 in the packets received. The Mapping System will return the RLOC 133 replication-list to the ITR, which the ITR will cache as per standard 134 LISP procedure. Since the core is assumed to not support multicast, 135 the ITR will replicate the multicast traffic for each RLOC on the 136 replication-list and will unicast encapsulate the traffic to each 137 RLOC. The combined function or replicating and encapsulating the 138 traffic to the RLOCs in the replication-list is referred to as "rep- 139 encapsulation" in this document. 141 The document describes the General Procedures and information 142 encoding that are required at the Receiver-sites and Source-sites to 143 achieve signal-free multicast interconnectivity. The General 144 Procedures for Mapping System Notifications to different sites are 145 also described. A section dedicated to the specific case of SSM 146 trees discusses the implications to the General Procedures for SSM 147 multicast trees over different topological scenarios. A section on 148 ASM support is included to identify the constraints that come along 149 with supporting it using LISP Signal-Free multicast. 151 There is a section dedicated to Replication Engineering. A mechanism 152 to reduce the impact of head-end replication. The mapping system, 153 via LISP Signal-Free mechanisms, can be used to build a layer of 154 RTRs. 156 2. Definition of Terms 158 LISP related terms, notably Map-Request, Map-Reply, Ingress Tunnel 159 Router (ITR), Egress Tunnel Router (ETR), Map-Server (MS) and Map- 160 Resolver (MR) are defined in the LISP specification [RFC6830]. 162 Extensions to the definitions in [RFC6830] for their application to 163 multicast routing are documented in [RFC6831]. 165 Terms defining interactions with the LISP Mapping System are defined 166 in [RFC6833]. 168 The following terms are consistent with the definitions in [RFC6830] 169 and [RFC6831]. The terms are specific cases of the general terms and 170 are here defined to facilitate the descriptions and discussions 171 within this particular document. 173 Source: Multicast source end-point. Host originating multicast 174 packets. 176 Receiver: Multicast group member end-point. Host joins multicast 177 group as a receiver of multicast packets sent to the group. 179 Receiver-site: LISP site where multicast receivers are located. 181 Source-site: LISP site where multicast sources are located. 183 RP-site: LISP site where an ASM PIM Rendezvous Point is located. The 184 RP-site and the Source-site may be the same in some situations. 186 Receiver-ETR: LISP xTR at the Receiver-site. This is a multicast 187 ETR. 189 Source-ITR: LISP xTR at the Source-site. This is a multicast ITR. 191 RP-xTR: LISP xTR at the RP-site. This is typically a multicast ITR. 193 Replication-list: Mapping-entry containing the list of RLOCs that 194 have registered Receivers for a particular multicast-entry. 196 Multicast-entry: A tuple identifying a multicast tree. Multicast- 197 entries are in the form of (S-prefix, G-prefix). 199 Rep-encapsulation: The process of replicating and then encapsulating 200 traffic to multiple RLOCs. 202 Re-encapsulating Tunnel Router (RTR): An RTR is a router that 203 implements the re-encapsulating tunnel function detailed in Section 8 204 of the main LISP specification [RFC6830]. A LISP RTR performs packet 205 re-routing by chaining ETR and ITR functions, whereby it first 206 removes the LISP header of an ingress packet and then prepends a new 207 LISP header to an egress packet. 209 RTR Level: An RTR level is encoded in a Replication-List-Entry (RLE) 210 LCAF Type detailed in [RFC8060]. Each entry in the replication list 211 contains an address of an xTR and a level value. Level values are 212 used to create a replication hierarchy so that ITRs at source LISP 213 sites replicate to the lowest (smaller value) level number RTRs in a 214 RLE entry. And then RTRs at a given level replicate to the next 215 higher level of RTRs. The number of RTRs at each level are 216 engineered to control the fan-out or replication factor so a tradeoff 217 between the width of the level versus the number of levels can be 218 selected. 220 3. Reference Model 222 The reference model that will be used for the discussion of the 223 Signal-Free multicast tree interconnection is illustrated in 224 Figure 1. 226 MS/MR 227 +---+ 228 | | 229 +---+ +---+ +---+ +---+ +---+ 230 Src-1 ----| R1|-----|ITR| | |ETR|------| R2|------ Rcv-2 231 +---+ +---+ | +---+ +---+ 232 \ | / 233 Source-site-1 \ | / Receiver-site-2 234 \ | / 235 \ | / 236 \ | / 237 Core 238 / \ 239 / \ 240 / \ 241 / \ 242 / \ 243 +---+ +---+ 244 Src-3 --------------|ITR| |ETR|----------------- Rcv-4 245 +---+ +---+ 247 Source-site-3 Receiver-site-4 249 Figure 1: LISP Multicast Generic Reference Model 251 Sites 1 and 3 are Source-sites. 253 Source-site-3 presents a Source (Src-3) that is directly connected to 254 the Source-ITR 256 Source-site-1 presents a Source (Src-1) that is one hop or more away 257 from the Source-ITR 259 Receiver-site-2 and 4 are receiver sites with not-directly connected 260 and directly connected Receiver end-points respectively 262 R1 is a router in Source-site-1. 264 R2 is a PIM router at the Receiver-site. 266 The Map-Servers and Resolvers are reachable in the RLOC space in the 267 Core, only one is shown for illustration purposes, but these can be 268 many or even part of a DDT tree. 270 The procedures for interconnecting multicast Trees over an overlay 271 can be broken down into three functional areas: 273 o Receiver-site procedures 275 o Source-site procedures 277 o LISP notification procedures 279 The receiver site procedures will be common for most tree types and 280 topologies. 282 The procedures at the source site can vary depending on the type of 283 trees being interconnected as well as based on the topological 284 relation between sources and source-site xTRs. For ASM trees, a 285 special case of the Source-site is the RP-site for which a variation 286 of the Source-site procedures may be necessary if ASM trees are to be 287 supported in future specifications of LISP Signal-Free multicast. 289 The LISP notification procedures between sites are normalized for the 290 different possible scenarios. Certain scenarios may benefit from a 291 simplified notification mechanism or no notification requirement at 292 all. 294 4. General Procedures 296 The interconnection of multicast trees across different LISP sites 297 involves the following procedures to build the necessary multicast 298 distribution trees across sites. 300 1. The presence of multicast Receiver end-points is detected by the 301 Receiver-ETRs at the Receiver-sites. 303 2. Receiver-ETRs register their RLOCs as part of the replication- 304 list for the multicast-entry the detected Receivers subscribe to. 306 3. The Mapping-system merges all receiver-ETR or delivery-group 307 RLOCs to build a comprehensive replication-list inclusive of all 308 Receiver-sites for each multicast-entry. 310 4. LISP Map-Notify messages should be sent to the Source-ITR 311 informing of any changes in the replication-list. 313 5. Multicast-tree building at the Source-site is initiated when the 314 Source-ITR receives the LISP Notification. 316 Once the multicast distribution trees are built, the following 317 forwarding procedures may take place: 319 1. The Source sends multicast packets to the multicast group 320 destination address. 322 2. Multicast traffic follows the multicast tree built at the Source- 323 site and makes its way to the Source-ITRs. 325 3. The Source-ITR will issue a map-request to resolve the 326 replication-list for the multicast-entry. 328 4. The Mapping System responds to the Source-ITR with a map-reply 329 containing the replication-list for the multicast group 330 requested. 332 5. The Source-ITR caches the replication-list received in the map- 333 reply for the multicast-entry. 335 6. Multicast traffic is rep-encapsulated. That is, the packet is 336 replicated for each RLOC in the replication-list and then 337 encapsulated to each one. 339 4.1. General Receiver-Site Procedures 341 4.1.1. Multicast Receiver Detection 343 When the Receiver-ETRs are directly connected to the Receivers (e.g. 344 Receiver-site-4 in Figure 1), the Receiver-ETRs will receive IGMP 345 Reports from the Receivers indicating which group the Receivers wish 346 to subscribe to. Based on these IGMP Reports, the receiver-ETR is 347 made aware of the presence of Receivers as well as which group they 348 are interested in. 350 When the Receiver-ETRs are several hops away from the Receivers (e.g. 351 Receiver-site-2 in Figure 1), the Receiver-ETRs will receive PIM join 352 messages which will allow the Receiver-ETR to know that there are 353 multicast Receivers at the site and also learn which multicast group 354 the Receivers are for. 356 4.1.2. Receiver-Site Registration 358 Once the Receiver-ETRs detect the presence of Receivers at the 359 Receiver-site, the Receiver-ETRs will issue Map-Register messages to 360 include the Receiver-ETR RLOCs in the replication-list for the 361 multicast-entry the Receivers joined. 363 The Map-Register message will use the multicast-entry (Source, Group) 364 tuple as its EID record type with the Receiver-ETR RLOCs conforming 365 the locator set. 367 The EID in the Map-Register message must be encoded using the 368 Multicast Information LCAF type defined in [RFC8060]. 370 The RLOC in the Map-Register message must be encoded using the 371 Replication List Entry (RLE) LCAF type defined in [RFC8060] with the 372 Level Value fields for all entries set to 128 (decimal). 374 The encoding described above must be used consistently for Map- 375 Register messages, entries in the Mapping Database, Map-reply 376 messages as well as the map-cache at the Source-ITRs. 378 The Map-Register messages [RFC6830] sent by the receiver-ETRs should 379 have the following bits set as here specified: 381 1. merge-request-bit set to 1. The Map-Register messages must be 382 sent with "Merge Semantics". The Map-Server will receive 383 registrations from a multitude of Receiver-ETRs. The Map-Server 384 will merge the registrations for common EIDs and maintain a 385 consolidated replication-list for each multicast-entry. 387 2. want-map-notify-bit (M) set to 0. This tells the Mapping System 388 that the receiver-ETR does not expect to receive Map-Notify 389 messages as it does not need to be notified of all changes to the 390 replication-list. 392 3. proxy-reply-bit (P) set to 1. The merged replication-list is 393 kept in the Map-Servers. By setting the proxy-reply bit, the 394 receiver-ETRs instruct the Mapping-system to proxy reply to map- 395 requests issued for the multicast entries. 397 Map-Register messages for a particular multicast-entry should be sent 398 for every receiver detected, even if previous receivers have been 399 detected for the particular multicast-entry. This allows the 400 replication-list to remain up to date. 402 Receiver-ETRs must be configured to know what Map-Servers Map- 403 Register messages are sent to. The configuration is likely to be 404 associated with an S-prefix that multiple (S,G) entries match to and 405 are more specific for. Therefore, the S-prefix determines the Map- 406 Server set in the least number of configuration statements. 408 4.1.3. Consolidation of the Replication-List 410 The Map-Server will receive registrations from a multitude of 411 Receiver-ETRs. The Map-Server will merge the registrations for 412 common EIDs and consolidate a replication-list for each multicast- 413 entry. 415 When an ETR sends an RLE RLOC-record in a Map-Register and the RLE 416 entry already exists in the Map-Server's RLE merged list, the Map- 417 Server will replace the single RLE entry with the information from 418 the Map-Register RLOC-record. The Map-Server MUST never merge 419 duplicate RLOCs in the consolidated replication-list. 421 4.2. General Source-Site Procedures 423 Source-ITRs must register the unicast EIDs of any Sources or 424 Rendezvous Points that may be present on the Source-site. In other 425 words, it is assumed that the Sources and RPs are LISP EIDs. 427 The registration of the unicast EIDs for the Sources or Rendezvous 428 Points allows the map-server to know where to send Map-Notify 429 messages to. Therefore, the Source-ITR must register the unicast 430 S-prefix EID with the want-map-notify-bit set in order to receive 431 Map-Notify messages whenever there is a change in the replication- 432 list. 434 4.2.1. Multicast Tree Building at the Source-Site 436 When the source site receives the Map-Notify messages from the 437 mapping system as described in Section 4.3, it will initiate the 438 process of building a multicast distribution tree that will allow the 439 multicast packets from the Source to reach the Source-ITR. 441 The Source-ITR will issue a PIM join for the multicast-entry for 442 which it received the Map-Notify message. The join will be issued in 443 the direction of the source or in the direction of the RP for the SSM 444 and ASM cases respectively. 446 4.2.2. Multicast Destination Resolution 448 On reception of multicast packets, the source-ITR must obtain the 449 replication-list for the (S,G) addresses in the packets. 451 In order to obtain the replication-list, the Source-ITR must issue a 452 Map-Request message in which the EID is the (S,G) multicast tuple 453 which is encoded using the Multicast Info LCAF type defined in 454 [RFC8060]. 456 The Mapping System (most likely the Map-Server) will Map-reply with 457 the merged replication-list maintained in the Mapping System. The 458 Map-reply message must follow the format defined in [RFC6830], its 459 EID must be encoded using the Multicast Info LCAF type and the 460 corresponding RLOC-records must be encoded using the RLE LCAF type. 461 Both LCAF types defined in [RFC8060]. 463 4.3. General LISP Notification Procedures 465 The Map-Server will issue LISP Map-Notify messages to inform the 466 Source-site of the presence of receivers for a particular multicast 467 group over the overlay. 469 Updated Map-Notify messages should be issued every time a new 470 registration is received from a Receiver-site. This guarantees that 471 the source-sites are aware of any potential changes in the multicast- 472 distribution-list membership. 474 The Map-Notify messages carry (S,G) multicast EIDs encoded using the 475 Multicast Info LCAF type defined in [RFC8060]. 477 Map-Notify messages will be sent by the Map-Server to the RLOCs with 478 which the unicast S-prefix EID was registered. In the case when 479 sources are discovered dynamically [I-D.ietf-lisp-eid-mobility], xTRs 480 must register sources explicitly with the want-map-notify-bit set. 481 This is so the ITR in the site the source has moved to can get the 482 most current replication list. 484 When both the Receiver-sites and the Source-sites register to the 485 same Map-Server, the Map-Server has all the necessary information to 486 send the Map-Notify messages to the Source-site. 488 When the Map-Servers are distributed in a DDT, the Receiver-sites may 489 register to one Map-Server while the Source-site registers to a 490 different Map-Server. In this scenario, the Map-Server for the 491 receiver sites must resolve the unicast S-prefix EID in the DDT per 492 standard LISP lookup procedures and obtain the necessary information 493 to send the Map-Notify messages to the Source-site. The Map-Notify 494 messages must be sent with an authentication length of 0 as they 495 would not be authenticated. 497 When the Map-Servers are distributed in a DDT, different Receiver- 498 sites may register to different Map-Servers. This is an unsupported 499 scenario with the currently defined mechanisms. 501 5. Source Specific Multicast Trees 503 The interconnection of Source Specific Multicast (SSM) Trees across 504 sites will follow the General Receiver-site Procedures described in 505 Section 4.1 on the Receiver-sites. 507 The Source-site Procedures will vary depending on the topological 508 location of the Source within the Source-site as described in 509 Section 5.1 and Section 5.2 . 511 5.1. Source Directly Connected to Source-ITRs 513 When the Source is directly connected to the source-ITR, it is not 514 necessary to trigger signaling to build a local multicast tree at the 515 Source-site. Therefore Map-Notify messages may not be required to 516 initiate building of the multicast tree at the Source-site. 518 Map-Notify messages are still required to ensure that any changes to 519 the replication-list are communicated to the Source-site so that the 520 map-cache at the Source-ITRs is kept updated. 522 5.2. Source not Directly Connected to Source-ITRs 524 The General LISP Notification Procedures described in Section 4.3 525 must be followed when the Source is not directly connected to the 526 source-ITR. On reception of Map-Notify messages, local multicast 527 signaling must be initiated at the Source-site per the General Source 528 Site Procedures for Multicast Tree building described in 529 Section 4.2.1. 531 In the SSM case, the IP address of the Source is known and it is also 532 registered with the LISP mapping system. Thus, the mapping system 533 may resolve the mapping for the Source address in order to send Map- 534 Notify messages to the correct source-ITR. 536 6. Multi-Homing Considerations 538 6.1. Multiple ITRs at a Source-Site 540 When multiple ITRs exist at a source multicast site, care should be 541 taken that more than one ITR does not head-end replicate packets else 542 receiver multicast sites will receive duplicate packets. The 543 following procedures will be used for each topology scenarios: 545 o When more than one ITR is directly connected to the source host, 546 either the PIM DR or the IGMP querier (when PIM is not enabled on 547 the ITRs) is responsible for packet replication. All other ITRs 548 silently drop the packet. In the IGMP querier case, it is 549 required to configure the source LAN to have one of the ITRs be 550 the IGMP querier. 552 o When more than one ITR is multiple hops away from the source host 553 and one of the ITRs is the PIM Rendezvous Point, then the PIM RP 554 is responsible for packet replication. 556 o When more than one ITR is multiple hops away from the source host 557 and the PIM Rendezvous Point is not one of the ITRs, then one of 558 the ITRs must join to the RP. When a Map-Notify is received from 559 the Map-Server by an ITR, only the highest RLOC addressed ITR will 560 join toward the PIM RP or toward the source. 562 6.2. Multiple ETRs at a Receiver-Site 564 When multiple ETRs exist in a receiver multicast site, and each 565 create multicast join state, they each Map-Register their RLOC 566 addresses to the mapping system. In this scenario, the replication 567 happens on the overlay causing multiple ETR entry points to replicate 568 to all receivers versus a single ETR entry point replicating to all 569 receivers. If an ETR does not create join state, because it has not 570 received PIM joins or IGMP reports, it will not Map-Register its RLOC 571 addresses to the mapping system. The same procedures in Section 4.1 572 should be followed. 574 When multiple ETRs exist on the same LAN as a receiver host, then the 575 PIM DR, when PIM is enabled, or the IGMP querier is responsible for 576 sending a Map-Register for its RLOC. In the IGMP case, it is 577 required that the LAN is configured with one of the ETRs as IGMP 578 querier. 580 6.3. Multiple RLOCs for an ETR at a Receiver-Site 582 It may be desirable to have multiple underlay paths to an ETR for 583 multicast packet delivery. This can be done by having multiple RLOCs 584 assigned to an ETR and having the ETR send Map-Registers for all its 585 RLOCs. By doing this, an ITR can choose a specific path based on 586 underlay performance and/or RLOC reachability. 588 It is suggested that an ETR sends a Map-Register with a single RLOC- 589 record that uses the ELP LCAF type [RFC8060] that is nested inside 590 RLE entry LCAF. For example say ETR1 has assigned RLOC1 and RLOC2 591 for a LISP receiver site. And there is ETR2 in another LISP receiver 592 site, that has RLOC3. The two receiver sites have the same (S,G) 593 being joined. Here is how the RLOC-record is encoded on each ETR: 595 ETR1: EID-record: (S,G) 596 RLOC-record: RLE[ ELP{ (RLOC1,s,p), (RLOC2,s,p) } ] 598 ETR2: EID-record: (S,G) 599 RLOC-record: RLE[ RLOC3 ] 601 And here is how the entry is merged and stored on the Map-Server 602 since the Map-Registers have an RLE encoded RLOC-record: 604 MS: EID-record: (S,G) 605 RLOC-record: RLE[ RLOC3, ELP{ (RLOC1,s,p), (RLOC2,s,p) } ] 607 When the ITR receives a packet from a multicast source S for group G, 608 it uses the merged RLOC-record, returned from the Map-Server. The 609 ITR replicates the packet to (RLOC3 and RLOC1) or (RLOC3 and RLOC2). 610 Since it is required for the s-bit to be set for RLOC1, the ITR must 611 replicate to RLOC1 if it is reachable. When the required p-bit is 612 also set, the RLOC-reachability mechanisms from [RFC6830] are 613 followed. If the ITR determines that RLOC1 is unreachable, it uses 614 RLOC2, as long as RLOC2 is reachable. 616 6.4. Multicast RLOCs for an ETR at a Receiver-Site 618 This specification is focused on underlays without multicast support, 619 but does not preclude the use of multicast RLOCs in RLE entries. 620 ETRs MAY register multicast EID entries using multicast RLOCs. In 621 such cases the ETRs will join underlay multicast trees following the 622 procedures specified in [RFC6831]. 624 7. PIM Any Source Multicast Trees 626 LISP signal-free multicast can support ASM Trees in limited but 627 acceptable topologies. It is suggested for the simplification of 628 building ASM trees across the LISP overlay to have PIM-ASM run 629 independently in each LISP site. What this means, is that a PIM 630 Rendezvous Point (RP) is configured in each LISP site so PIM Register 631 procedures and (*,G) state maintenance is contained within the LISP 632 site. 634 The following procedure will be used to support ASM in each LISP 635 site: 637 1. In a Receiver-site, the RP is colocated with the ETR. RPs for 638 different groups can be spread across each ETR, but is not 639 required. 641 2. When (*,G) state is created in an ETR, the procedures in 642 Section 4.1.2 are followed. In addition, the ETR registers 643 (S-prefix,G), where S-prefix is 0/0 (the respective unicast 644 default route for the address-family) to the mapping system. 646 3. In a Source-site, the RP is colocated with the ITR. RPs for 647 different groups can be spread across each ITR, but is not 648 required. 650 4. When a multicast source sends a packet, a PIM Register message is 651 delivered to the ITR and the procedures in Section 4.2 are 652 followed. 654 5. When the the ITR sends a Map-Request for (S,G) and no Receiver- 655 site has registered for (S,G), the mapping system will return the 656 (0/0,G) entry to the ITR so it has a replication list of all the 657 ETRs that have received (*,G) state. 659 6. The ITR stores the replication-list in its map-cache for (S,G). 660 It replicates packets to all ETRs in the list. 662 7. ETRs decapsulate packets and forward based on (*,G) state in 663 their site. 665 8. When last-hop PIM routers join the newly discovered (S,G), the 666 ETR will store the state and follow the procedures in 667 Section 4.1.2. 669 8. Signal-Free Multicast for Replication Engineering 671 The mechanisms in this draft can be applied to the LISP Replication- 672 Engineering [I-D.coras-lisp-re] design. Rather than having the 673 layered LISP-RE RTR hierarchy use signaling mechanisms, the RTRs can 674 register their availability for multicast tree replication via the 675 mapping database system. 677 As stated in [I-D.coras-lisp-re], the RTR layered hierarchy is used 678 to avoid head-end replication in replicating nodes closest to a 679 multicast source. Rather than have multicast ITRs replicate to each 680 ETR in an RLE entry of a (S,G) mapping database entry, it could 681 replicate to one or more layer-0 RTRs in the LISP-RE hierarchy. 683 This draft documents how the RTR hierarchy is determined but not what 684 are the optimal layers of RTRs to use. Methods for determining 685 optimal paths or RTR topological closeness are out of scope for his 686 document. 688 There are two formats an (S,G) mapping database entry could have. 689 One format is a 'complete-format' and the other is a 'filtered- 690 format'. A 'complete-format' entails an (S,G) entry having multiple 691 RLOC records which contain both ETRs that have registered as well as 692 the RTRs at the first level of the LISP-RE hierarchy for the ITR to 693 replicate to. When using 'complete-format', the ITR has the ability 694 to select if it replicates to RTRs or to the registered ETRs at the 695 receiver sites. A 'filtered-format' (S,G) entry is one where the 696 Map-Server returns the RLOC-records that it decides the ITR should 697 use. So replication policy is shifted from the ITRs to the mapping 698 system. The Map-Servers can also decide for a given ITR, if it uses 699 a different set of replication targets per (S,G) entry for which the 700 ITR is replicating for. 702 The procedure for the LISP-RE RTRs to make themselves available for 703 replication can occur before or after any receivers join an (S,G) 704 entry or any sources send for a particular (S,G) entry. Therefore, 705 newly configured RTR state will be used to create new (S,G) state and 706 inherited into existing (S,G) state. A set of RTRs can register 707 themselves to the mapping system or a third-party can do so on their 708 behalf. When RTR registration occurs, it is done with an (S-prefix, 709 G-prefix) entry so it can advertise its replication services for a 710 wide-range of source/group combinations. 712 When a Map-Server receives (S,G) registrations from ETRs and 713 (S-prefix, G-prefix) registrations from RTRs, it has the option of 714 merging the RTR RLOC-records for each (S,G) that is more-specific for 715 the (S-prefix, G-prefix) entry or keep them separate. When merging, 716 a Map-Server is ready to return a 'complete-format' Map-Reply. When 717 keeping the entries separate, the Map-Server can decide what to 718 include in a Map-Reply when a Map-Request is received. It can 719 include a combination of RLOC-records from each entry or decide to 720 use one or the other depending on policy configured. 722 +---+ +----+ 723 Src-1 --------------|ITR| |ETR1|----------------- Rcv-1 724 +---+ +----+ 725 \ / 726 Source-site-1 \ / Receiver-site-1 727 \ / 728 \ / 729 +----+ \ / +----+ 730 |RTR1| \ / |RTR2| Level-0 731 +----+ \ / +----+ 732 \ <^^^^^^^^^^^^^^> / 733 \ < > / 734 < Core-Network > 735 < > 736 737 / / \ \ 738 / / \ \ 739 +----+ / / \ \ +----+ 740 |RTR3| / \ |RTR4| Level-1 741 +----+ / \ +----+ 742 / \ 743 / \ 744 +----+ +----+ 745 Rcv-2 --------------|ETR2| |ETR3|----------------- Rcv-3 746 +----+ +----+ 748 Receiver-site-2 Receiver-site-3 750 Figure 2: LISP-RE Reference Model 752 Here is a specific example, illustrated in Figure 2, of (S,G) and 753 (S-prefix, G-prefix) mapping database entries when a source S is 754 behind an ITR and there are receiver sites joined to (S,G) via ETR1, 755 ETR2, and ETR3. And there exists a LISP-RE hierarchy of RTR1 and 756 RTR2 at level-0 and RTR3 and RTR4 at level-1: 758 EID-record: (S,G) 759 RLOC-record: RLE: (ETR1, ETR2, ETR3), p1 760 EID-record: (S-prefix, G-prefix) 761 RLOC-record: RLE: (RTR1(L0), RTR2(L0), RTR3(L1), RTR4(L1)), p1 763 The above entries are in the form of how they were registered and 764 stored in a Map-Server. When a Map-Server uses 'complete-format', a 765 Map-Reply it originates has the mapping record encoded as: 767 EID-record: (S,G) 768 RLOC-record: RLE: (RTR1(L0), RTR3(L1)), p1 769 RLOC-record: RLE: (ETR1, ETR2, ETR3), p1 771 The above Map-Reply allows the ITR to decide if it replicates to the 772 ETRs or if it should replicate only to level-0 RTR1. This decision 773 is left to the ITR since both RLOC-records have priority 1. If the 774 Map-Server wanted to force the ITR to replicate to RTR1, it would set 775 the ETRs RLOC-record to priority greater than 1. 777 When a Map_server uses "filtered-format', a Map-Reply it originates 778 has the mapping record encoded as: 780 EID-record: (S,G) 781 RLOC-record: RLE: (RTR1(L0), RTR3(L1)), p1 783 An (S,G) entry can contain alternate RTRs. So rather than 784 replicating to multiple RTRs, one of a RTR set may be used based on 785 the RTR reachability status. An ITR can test reachability status to 786 any layer-0 RTR using RLOC-probing so it can choose one RTR from a 787 set to replicate to. When this is done the RTRs are encoded in 788 different RLOC-records versus together in one RLE RLOC-record. This 789 moves the replication load off the ITRs at the source site to the 790 RTRs inside the network infrastructure. This mechanism can also be 791 used by level-n RTRs to level-n+1 RTRs. 793 The following mapping would be encoded in a Map-Reply sent by a Map- 794 Server and stored in the ITR. The ITR would use RTR1 until it went 795 unreachable and then switch to use RTR2: 797 EID-record: (S,G) 798 RLOC-record: RTR1, p1 799 RLOC-record: RTR2, p2 801 9. Security Considerations 803 [I-D.ietf-lisp-sec] defines a set of security mechanisms that provide 804 origin authentication, integrity and anti-replay protection to LISP's 805 EID-to-RLOC mapping data conveyed via mapping lookup process. LISP- 806 SEC also enables verification of authorization on EID-prefix claims 807 in Map-Reply messages. 809 Additional security mechanisms to protect the LISP Map-Register 810 messages are defined in [RFC6833]. 812 The security of the Mapping System Infrastructure depends on the 813 particular mapping database used. The [I-D.ietf-lisp-ddt] 814 specification, as an example, defines a public-key based mechanism 815 that provides origin authentication and integrity protection to the 816 LISP DDT protocol. 818 Map-Replies received by the source-ITR can be signed (by the Map- 819 Server) so the ITR knows the replication-list is from a legit source. 821 Data-plane encryption can be used when doing unicast rep- 822 encapsulation as described in [RFC8061]. For further study we will 823 look how to do multicast rep-encapsulation. 825 10. IANA Considerations 827 This document has no IANA implications 829 11. Acknowledgements 831 The authors want to thank Greg Shepherd, Joel Halpern and Sharon 832 Barkai for their insightful contribution to shaping the ideas in this 833 document. Thanks also goes to Jimmy Kyriannis, Paul Vinciguerra, 834 Florin Coras, and Yan Filyurin for testing an implementation of this 835 draft. 837 12. References 839 12.1. Normative References 841 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 842 Requirement Levels", BCP 14, RFC 2119, 843 DOI 10.17487/RFC2119, March 1997, 844 . 846 [RFC3618] Fenner, B., Ed. and D. Meyer, Ed., "Multicast Source 847 Discovery Protocol (MSDP)", RFC 3618, 848 DOI 10.17487/RFC3618, October 2003, 849 . 851 [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, 852 "Protocol Independent Multicast - Sparse Mode (PIM-SM): 853 Protocol Specification (Revised)", RFC 4601, 854 DOI 10.17487/RFC4601, August 2006, 855 . 857 [RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for 858 IP", RFC 4607, DOI 10.17487/RFC4607, August 2006, 859 . 861 12.2. Informative References 863 [I-D.coras-lisp-re] 864 Coras, F., Cabellos-Aparicio, A., Domingo-Pascual, J., 865 Maino, F., and D. Farinacci, "LISP Replication 866 Engineering", draft-coras-lisp-re-08 (work in progress), 867 November 2015. 869 [I-D.farinacci-lisp-mr-signaling] 870 Farinacci, D. and M. Napierala, "LISP Control-Plane 871 Multicast Signaling", draft-farinacci-lisp-mr-signaling-06 872 (work in progress), February 2015. 874 [I-D.ietf-lisp-ddt] 875 Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A. 876 Smirnov, "LISP Delegated Database Tree", draft-ietf-lisp- 877 ddt-09 (work in progress), January 2017. 879 [I-D.ietf-lisp-eid-mobility] 880 Portoles-Comeras, M., Ashtaputre, V., Moreno, V., Maino, 881 F., and D. Farinacci, "LISP L2/L3 EID Mobility Using a 882 Unified Control Plane", draft-ietf-lisp-eid-mobility-00 883 (work in progress), May 2017. 885 [I-D.ietf-lisp-sec] 886 Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D. 887 Saucez, "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-12 888 (work in progress), November 2016. 890 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 891 Locator/ID Separation Protocol (LISP)", RFC 6830, 892 DOI 10.17487/RFC6830, January 2013, 893 . 895 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 896 Locator/ID Separation Protocol (LISP) for Multicast 897 Environments", RFC 6831, DOI 10.17487/RFC6831, January 898 2013, . 900 [RFC6833] Fuller, V. and D. Farinacci, "Locator/ID Separation 901 Protocol (LISP) Map-Server Interface", RFC 6833, 902 DOI 10.17487/RFC6833, January 2013, 903 . 905 [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 906 Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, 907 February 2017, . 909 [RFC8061] Farinacci, D. and B. Weis, "Locator/ID Separation Protocol 910 (LISP) Data-Plane Confidentiality", RFC 8061, 911 DOI 10.17487/RFC8061, February 2017, 912 . 914 Appendix A. Document Change Log 916 A.1. Changes to draft-ietf-lisp-signal-free-multicast-05 918 o Posted July 2017. 920 o Make it clear that when a RLE is sent by an ETR and it is already 921 in the merged RLE list on the Map-Server, that the Map-Server 922 replaces the RLE entry (versus adding a duplicate RLE entry to the 923 list). 925 o Make it clear that an RLOC can be a unicast or multicast address. 926 Then make a reference to RFC6831 about mechanisms to support 927 multicast RLOCs. 929 o Fix some typos. 931 A.2. Changes to draft-ietf-lisp-signal-free-multicast-04 933 o Posted May 2017. 935 o Make it clear that recieiver-ETRs need configuraiton information 936 for what Map-Servers (S,G) entries are registered to. 938 o Make it clear this document indicates what RTR layered hierarchy 939 to use and not if its the best hierarchy to use. 941 A.3. Changes to draft-ietf-lisp-signal-free-multicast-03 943 o Posted April 2017. 945 o Add "Multi-Homing Considerations" section to describe the case 946 where a source LISP site has multiple ITRs and the multicast 947 distribution tree at the source site branches to more than one 948 ITR. And at receiver sites where there are multiple ETRs and 949 multiple RLOCs per ETR. 951 A.4. Changes to draft-ietf-lisp-signal-free-multicast-02 953 o Posted October 2016. 955 o Updated document expiration timer. 957 A.5. Changes to draft-ietf-lisp-signal-free-multicast-01 959 o Posted April 2016. 961 o Add text to define RTRs and indicate how RTR level number is used 962 for LISP-RE. 964 o Draw figure 2 that shows a LISP-RE topology. 966 o Indicate that PIM-ASM or (*,G) trees can be supported in LISP 967 Signal-Free Multicast. 969 A.6. Changes to draft-ietf-lisp-signal-free-multicast-00 971 o Posted late December 2015. 973 o Converted draft-farinacci-lisp-signal-free-multicast-04 into LISP 974 working group draft. 976 A.7. Changes to draft-farinacci-lisp-signal-free-multicast-04 978 o Posted early December 2015. 980 o Update references and document timer. 982 A.8. Changes to draft-farinacci-lisp-signal-free-multicast-03 984 o Posted June 2015. 986 o Update references and document timer. 988 A.9. Changes to draft-farinacci-lisp-signal-free-multicast-02 990 o Posted December 2014. 992 o Added section about how LISP-RE can use the mechanisms from 993 signal-free-multicast so we can avoid head-end replication and 994 avoid signalling across a layered RE topology. 996 A.10. Changes to draft-farinacci-lisp-signal-free-multicast-01 998 o Posted June 2014. 1000 o Changes based on implementation experience of this draft. 1002 A.11. Changes to draft-farinacci-lisp-signal-free-multicast-00 1004 o Posted initial draft February 2014. 1006 Authors' Addresses 1008 Victor Moreno 1009 Cisco Systems 1010 170 Tasman Drive 1011 San Jose, California 95134 1012 USA 1014 Email: vimoreno@cisco.com 1016 Dino Farinacci 1017 lispers.net 1018 San Jose, CA 95120 1019 USA 1021 Email: farinacci@gmail.com