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Farinacci 5 Expires: June 1, 2018 lispers.net 6 November 28, 2017 8 Signal-Free LISP Multicast 9 draft-ietf-lisp-signal-free-multicast-07 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 https://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 June 1, 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 (https://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-07 . . . 21 93 A.2. Changes to draft-ietf-lisp-signal-free-multicast-06 . . . 21 94 A.3. Changes to draft-ietf-lisp-signal-free-multicast-05 . . . 21 95 A.4. Changes to draft-ietf-lisp-signal-free-multicast-04 . . . 21 96 A.5. Changes to draft-ietf-lisp-signal-free-multicast-03 . . . 22 97 A.6. Changes to draft-ietf-lisp-signal-free-multicast-02 . . . 22 98 A.7. Changes to draft-ietf-lisp-signal-free-multicast-01 . . . 22 99 A.8. Changes to draft-ietf-lisp-signal-free-multicast-00 . . . 22 100 A.9. Changes to draft-farinacci-lisp-signal-free-multicast-04 22 101 A.10. Changes to draft-farinacci-lisp-signal-free-multicast-03 23 102 A.11. Changes to draft-farinacci-lisp-signal-free-multicast-02 23 103 A.12. Changes to draft-farinacci-lisp-signal-free-multicast-01 23 104 A.13. Changes to draft-farinacci-lisp-signal-free-multicast-00 23 105 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 107 1. Introduction 109 When multicast sources and receivers are active at LISP sites, and 110 the core network between the sites does not provide multicast 111 support, a signal-free mechanism can be used to create an overlay 112 that will allow multicast traffic to flow between sites and connect 113 the multicast trees at the different sites. 115 The signal-free mechanism here proposed does not extend PIM [RFC7761] 116 over the overlay as proposed in [RFC6831], nor does the mechanism 117 utilize direct signaling between the Receiver-ETRs and Sender-ITRs as 118 described in [I-D.farinacci-lisp-mr-signaling]. The signal-free 119 mechanism proposed reduces the amount of signaling required between 120 sites to a minimum and is centered around the registration of 121 Receiver-sites for a particular multicast-group or multicast-channel 122 with the LISP Mapping System. 124 Registrations from the different receiver-sites will be merged at the 125 Mapping System to assemble a multicast-replication-list inclusive of 126 all RLOCs that lead to receivers for a particular multicast-group or 127 multicast-channel. The replication-list for each specific multicast- 128 entry is maintained as a database mapping entry in the LISP Mapping 129 System. 131 When the ITR at the source-site receives multicast traffic from 132 sources at its site, the ITR can query the mapping system by issuing 133 Map-Request messages for the (S,G) source and destination addresses 134 in the packets received. The Mapping System will return the RLOC 135 replication-list to the ITR, which the ITR will cache as per standard 136 LISP procedure. Since the core is assumed to not support multicast, 137 the ITR will replicate the multicast traffic for each RLOC on the 138 replication-list and will unicast encapsulate the traffic to each 139 RLOC. The combined function or replicating and encapsulating the 140 traffic to the RLOCs in the replication-list is referred to as "rep- 141 encapsulation" in this document. 143 The document describes the General Procedures (Section 4) and 144 information encoding that are required at the Receiver-sites and 145 Source-sites to achieve signal-free multicast interconnectivity. The 146 General Procedures for Mapping System Notifications to different 147 sites are also described. A section dedicated to the specific case 148 of SSM trees discusses the implications to the General Procedures for 149 SSM multicast trees over different topological scenarios. A section 150 on ASM support is included to identify the constraints that come 151 along with supporting it using LISP Signal-Free multicast. 153 There is a section dedicated to Replication Engineering. A mechanism 154 to reduce the impact of head-end replication. The mapping system, 155 via LISP Signal-Free mechanisms, can be used to build a layer of 156 RTRs. 158 2. Definition of Terms 160 LISP related terms, notably Map-Request, Map-Reply, Ingress Tunnel 161 Router (ITR), Egress Tunnel Router (ETR), Map-Server (MS) and Map- 162 Resolver (MR) are defined in the LISP specification [RFC6830]. 164 Extensions to the definitions in [RFC6830] for their application to 165 multicast routing are documented in [RFC6831]. 167 Terms defining interactions with the LISP Mapping System are defined 168 in [RFC6833]. 170 The following terms are consistent with the definitions in [RFC6830] 171 and [RFC6831]. The terms are specific cases of the general terms and 172 are here defined to facilitate the descriptions and discussions 173 within this particular document. 175 Source: Multicast source end-point. Host originating multicast 176 packets. 178 Receiver: Multicast group member end-point. Host joins multicast 179 group as a receiver of multicast packets sent to the group. 181 Receiver-site: LISP site where multicast receivers are located. 183 Source-site: LISP site where multicast sources are located. 185 RP-site: LISP site where an ASM PIM Rendezvous Point [RFC7761] is 186 located. The RP-site and the Source-site MAY be the same in some 187 situations. 189 Receiver-ETR: LISP decapsulating xTR at the Receiver-site. This is a 190 multicast ETR. 192 Source-ITR: LISP encapsulating xTR at the Source-site. This is a 193 multicast ITR. 195 RP-xTR: LISP xTR at the RP-site. This is typically a multicast ITR. 197 Replication-list: Mapping-entry containing the list of RLOCs that 198 have registered Receivers for a particular multicast-entry. 200 Multicast-entry: A tuple identifying a multicast tree. Multicast- 201 entries are in the form of (S-prefix, G-prefix). 203 Rep-encapsulation: The process of replicating and then encapsulating 204 traffic to multiple RLOCs. 206 Re-encapsulating Tunnel Router (RTR): An RTR is a router that 207 implements the re-encapsulating tunnel function detailed in Section 8 208 of the main LISP specification [RFC6830]. A LISP RTR performs packet 209 re-routing by chaining ETR and ITR functions, whereby it first 210 removes the LISP header of an ingress packet and then prepends a new 211 LISP header to an egress packet. 213 RTR Level: An RTR level is encoded in a Replication-List-Entry (RLE) 214 LCAF Type detailed in [RFC8060]. Each entry in the replication list 215 contains an address of an xTR and a level value. Level values are 216 used to create a replication hierarchy so that ITRs at source LISP 217 sites replicate to the lowest (smaller value) level number RTRs in a 218 RLE entry. And then RTRs at a given level replicate to the next 219 higher level of RTRs. The number of RTRs at each level are 220 engineered to control the fan-out or replication factor so a tradeoff 221 between the width of the level versus the number of levels can be 222 selected. 224 ASM: Any-Source Multicast as defined in [RFC3569] and [RFC7761] where 225 multicast distribution trees are built with a Rendezvous Point. 227 SSM: Single-Source Multicast as defined in [RFC3569] where multicast 228 distribution trees are built and rooted at the multicast router(s) 229 directly connected to the multicast source. 231 3. Reference Model 233 The reference model that will be used for the discussion of the 234 Signal-Free multicast tree interconnection is illustrated in 235 Figure 1. 237 MS/MR 238 +---+ 239 | | 240 +---+ +---+ +---+ +---+ +---+ 241 Src-1 ----| R1|-----|ITR| | |ETR|------| R2|------ Rcv-2 242 +---+ +---+ | +---+ +---+ 243 \ | / 244 Source-site-1 \ | / Receiver-site-2 245 \ | / 246 \ | / 247 \ | / 248 Core 249 / \ 250 / \ 251 / \ 252 / \ 253 / \ 254 +---+ +---+ 255 Src-3 --------------|ITR| |ETR|----------------- Rcv-4 256 +---+ +---+ 258 Source-site-3 Receiver-site-4 260 Figure 1: LISP Multicast Generic Reference Model 262 Sites 1 and 3 are Source-sites. 264 Source-site-3 presents a Source (Src-3) that is directly connected to 265 the Source-ITR 267 Source-site-1 presents a Source (Src-1) that is one hop or more away 268 from the Source-ITR 270 Receiver-site-2 and 4 are receiver sites with not-directly connected 271 and directly connected Receiver end-points respectively 273 R1 is a multicast router in Source-site-1. 275 R2 is a multicast router at the Receiver-site. 277 The Map-Servers and Resolvers are reachable in the RLOC space in the 278 Core, only one is shown for illustration purposes, but these can be 279 many or even part of a Distributed Mapping System, such as a DDT 280 Tree. 282 The procedures for interconnecting multicast Trees over an overlay 283 can be broken down into three functional areas: 285 o Receiver-site procedures 287 o Source-site procedures 289 o LISP notification procedures 291 The receiver site procedures will be common for most tree types and 292 topologies. 294 The procedures at the source site can vary depending on the type of 295 trees being interconnected as well as based on the topological 296 relation between sources and source-site xTRs. For ASM trees, a 297 special case of the Source-site is the RP-site for which a variation 298 of the Source-site procedures MAY be necessary if ASM trees are to be 299 supported in future specifications of LISP Signal-Free multicast. 301 The LISP notification procedures between sites are normalized for the 302 different possible scenarios. Certain scenarios MAY benefit from a 303 simplified notification mechanism or no notification requirement at 304 all. 306 4. General Procedures 308 The interconnection of multicast trees across different LISP sites 309 involves the following procedures to build the necessary multicast 310 distribution trees across sites. 312 1. The presence of multicast Receiver end-points is detected by the 313 Receiver-ETRs at the Receiver-sites. 315 2. Receiver-ETRs register their RLOCs as part of the replication- 316 list for the multicast-entry the detected Receivers subscribe to. 318 3. The Mapping-system merges all receiver-ETR or delivery-group 319 RLOCs to build a comprehensive replication-list inclusive of all 320 Receiver-sites for each multicast-entry. 322 4. LISP Map-Notify messages MUST be sent to the Source-ITR informing 323 of any changes in the replication-list. 325 5. Multicast-tree building at the Source-site is initiated when the 326 Source-ITR receives the LISP Notification. 328 Once the multicast distribution trees are built, the following 329 forwarding procedures may take place: 331 1. The Source sends multicast packets to the multicast group 332 destination address. 334 2. Multicast traffic follows the multicast tree built at the Source- 335 site and makes its way to the Source-ITRs. 337 3. The Source-ITR will issue a map-request to resolve the 338 replication-list for the multicast-entry. 340 4. The Mapping System responds to the Source-ITR with a map-reply 341 containing the replication-list for the multicast group 342 requested. 344 5. The Source-ITR caches the replication-list received in the map- 345 reply for the multicast-entry. 347 6. Multicast traffic is rep-encapsulated. That is, the packet is 348 replicated for each RLOC in the replication-list and then 349 encapsulated to each one. 351 4.1. General Receiver-Site Procedures 353 4.1.1. Multicast Receiver Detection 355 When the Receiver-ETRs are directly connected to the Receivers (e.g. 356 Receiver-site-4 in Figure 1), the Receiver-ETRs will receive IGMP 357 Reports from the Receivers indicating which group the Receivers wish 358 to subscribe to. Based on these IGMP Reports, the receiver-ETR is 359 made aware of the presence of Receivers as well as which group they 360 are interested in. 362 When the Receiver-ETRs are several hops away from the Receivers (e.g. 363 Receiver-site-2 in Figure 1), the Receiver-ETRs will receive PIM join 364 messages which will allow the Receiver-ETR to know that there are 365 multicast Receivers at the site and also learn which multicast group 366 the Receivers are for. 368 4.1.2. Receiver-Site Registration 370 Once the Receiver-ETRs detect the presence of Receivers at the 371 Receiver-site, the Receiver-ETRs MUST issue Map-Register messages to 372 include the Receiver-ETR RLOCs in the replication-list for the 373 multicast-entry the Receivers joined. 375 The Map-Register message MUST use the multicast-entry (Source, Group) 376 tuple as its EID record type with the Receiver-ETR RLOCs conforming 377 the locator set. 379 The EID in the Map-Register message MUST be encoded using the 380 Multicast Information LCAF type defined in [RFC8060]. 382 The RLOC in the Map-Register message MUST be encoded using the 383 Replication List Entry (RLE) LCAF type defined in [RFC8060] with the 384 Level Value fields for all entries set to 128 (decimal). 386 The encoding described above MUST be used consistently for Map- 387 Register messages, entries in the Mapping System, Map-reply messages 388 as well as the map-cache at the Source-ITRs. 390 The Map-Register messages [RFC6830] sent by the receiver-ETRs MUST 391 have the following bits set as here specified: 393 1. merge-request-bit set to 1. The Map-Register messages are sent 394 with "Merge Semantics". The Map-Server will receive 395 registrations from a multitude of Receiver-ETRs. The Map-Server 396 will merge the registrations for common EIDs and maintain a 397 consolidated replication-list for each multicast-entry. 399 2. want-map-notify-bit (M) set to 0. This tells the Mapping System 400 that the receiver-ETR does not expect to receive Map-Notify 401 messages as it does not need to be notified of all changes to the 402 replication-list. 404 3. proxy-reply-bit (P) set to 1. The merged replication-list is 405 kept in the Map-Servers. By setting the proxy-reply bit, the 406 receiver-ETRs instruct the Mapping-system to proxy reply to map- 407 requests issued for the multicast entries. 409 Map-Register messages for a particular multicast-entry MAY be sent 410 for every receiver detected, even if previous receivers have been 411 detected for the particular multicast-entry. This allows the 412 replication-list to remain up to date. 414 Receiver-ETRs MUST be configured to know what Map-Servers Map- 415 Register messages are sent to. The configuration is likely to be 416 associated with an S-prefix that multiple (S,G) entries match to and 417 are more specific for. Therefore, the S-prefix determines the Map- 418 Server set in the least number of configuration statements. 420 4.1.3. Consolidation of the Replication-List 422 The Map-Server will receive registrations from a multitude of 423 Receiver-ETRs. The Map-Server will merge the registrations for 424 common EIDs and consolidate a replication-list for each multicast- 425 entry. 427 When an ETR sends an RLE RLOC-record in a Map-Register and the RLE 428 entry already exists in the Map-Server's RLE merged list, the Map- 429 Server will replace the single RLE entry with the information from 430 the Map-Register RLOC-record. The Map-Server MUST NOT merge 431 duplicate RLOCs in the consolidated replication-list. 433 4.2. General Source-Site Procedures 435 Source-ITRs MUST register the unicast EIDs of any Sources or 436 Rendezvous Points that may be present on the Source-site. In other 437 words, it is assumed that the Sources and RPs are LISP EIDs. 439 The registration of the unicast EIDs for the Sources or Rendezvous 440 Points allows the Map-Server to know where to send Map-Notify 441 messages to. Therefore, the Source-ITR MUST register the unicast 442 S-prefix EID with the want-map-notify-bit set in order to receive 443 Map-Notify messages whenever there is a change in the replication- 444 list. 446 4.2.1. Multicast Tree Building at the Source-Site 448 When the source site receives the Map-Notify messages from the 449 mapping system as described in Section 4.3, it will initiate the 450 process of building a multicast distribution tree that will allow the 451 multicast packets from the Source to reach the Source-ITR. 453 The Source-ITR MUST issue a PIM join for the multicast-entry for 454 which it received the Map-Notify message. The join will be issued in 455 the direction of the source or in the direction of the RP for the SSM 456 and ASM cases respectively. 458 4.2.2. Multicast Destination Resolution 460 On reception of multicast packets, the source-ITR obtains the 461 replication-list for the (S,G) addresses in the packets. 463 In order to obtain the replication-list, the Source-ITR MUST issue a 464 Map-Request message in which the EID is the (S,G) multicast tuple 465 which is encoded using the Multicast Info LCAF type defined in 466 [RFC8060]. 468 The Mapping System (most likely the Map-Server) will Map-reply with 469 the merged replication-list maintained in the Mapping System. The 470 Map-reply message MUST follow the format defined in [RFC6830], its 471 EID is encoded using the Multicast Info LCAF type and the 472 corresponding RLOC-records are encoded using the RLE LCAF type. Both 473 LCAF types defined in [RFC8060]. 475 4.3. General LISP Notification Procedures 477 The Map-Server will issue LISP Map-Notify messages to inform the 478 Source-site of the presence of receivers for a particular multicast 479 group over the overlay. 481 Updated Map-Notify messages SHOULD be issued every time a new 482 registration is received from a Receiver-site. This guarantees that 483 the source-sites are aware of any potential changes in the multicast- 484 distribution-list membership. 486 The Map-Notify messages carry (S,G) multicast EIDs encoded using the 487 Multicast Info LCAF type defined in [RFC8060]. 489 Map-Notify messages will be sent by the Map-Server to the RLOCs with 490 which the unicast S-prefix EID was registered. In the case when 491 sources are discovered dynamically [I-D.ietf-lisp-eid-mobility], xTRs 492 MUST register sources explicitly with the want-map-notify-bit set. 493 This is so the ITR in the site the source has moved to can get the 494 most current replication list. 496 When both the Receiver-sites and the Source-sites register to the 497 same Map-Server, the Map-Server has all the necessary information to 498 send the Map-Notify messages to the Source-site. 500 When the Map-Servers are distributed (when using LISP-DDT [RFC8111]), 501 the Receiver-sites MAY register to one Map-Server while the Source- 502 site registers to a different Map-Server. In this scenario, the Map- 503 Server for the receiver sites MUST resolve the unicast S-prefix EID 504 across a distributed mapping transport system, per standard LISP 505 lookup procedures and obtain the necessary information to send the 506 Map-Notify messages to the Source-site. The Map-Notify messages are 507 sent with an authentication length of 0 as they would not be 508 authenticated. 510 When the Map-Servers are distributed, different Receiver-sites MAY 511 register to different Map-Servers. However, this is not supported 512 with the currently defined mechanisms. 514 5. Source Specific Multicast Trees 516 The interconnection of Source Specific Multicast (SSM) Trees across 517 sites will follow the General Receiver-site Procedures described in 518 Section 4.1 on the Receiver-sites. 520 The Source-site Procedures will vary depending on the topological 521 location of the Source within the Source-site as described in 522 Section 5.1 and Section 5.2 . 524 5.1. Source Directly Connected to Source-ITRs 526 When the Source is directly connected to the source-ITR, it is not 527 necessary to trigger signaling to build a local multicast tree at the 528 Source-site. Therefore Map-Notify messages are not required to 529 initiate building of the multicast tree at the Source-site. 531 Map-Notify messages are still required to ensure that any changes to 532 the replication-list are communicated to the Source-site so that the 533 map-cache at the Source-ITRs is kept updated. 535 5.2. Source not Directly Connected to Source-ITRs 537 The General LISP Notification Procedures described in Section 4.3 538 MUST be followed when the Source is not directly connected to the 539 source-ITR. On reception of Map-Notify messages, local multicast 540 signaling MUST be initiated at the Source-site per the General Source 541 Site Procedures for Multicast Tree building described in 542 Section 4.2.1. 544 In the SSM case, the IP address of the Source is known and it is also 545 registered with the LISP mapping system. Thus, the mapping system 546 MAY resolve the mapping for the Source address in order to send Map- 547 Notify messages to the correct source-ITR. 549 6. Multi-Homing Considerations 551 6.1. Multiple ITRs at a Source-Site 553 When multiple ITRs exist at a source multicast site, care MUST be 554 taken that more than one ITR does not head-end replicate packets else 555 receiver multicast sites will receive duplicate packets. The 556 following procedures will be used for each topology scenarios: 558 o When more than one ITR is directly connected to the source host, 559 either the PIM DR or the IGMP querier (when PIM is not enabled on 560 the ITRs) is responsible for packet replication. All other ITRs 561 silently drop the packet. In the IGMP querier case, one or more 562 ITRs on the source LAN MUST be IGMP querier candidates. 563 Therefore, it is required they are configured as such. 565 o When more than one ITR is multiple hops away from the source host 566 and one of the ITRs is the PIM Rendezvous Point, then the PIM RP 567 is responsible for packet replication. 569 o When more than one ITR is multiple hops away from the source host 570 and the PIM Rendezvous Point is not one of the ITRs, then one of 571 the ITRs MUST join to the RP. When a Map-Notify is received from 572 the Map-Server by an ITR, only the highest RLOC addressed ITR will 573 join toward the PIM RP or toward the source. 575 6.2. Multiple ETRs at a Receiver-Site 577 When multiple ETRs exist in a receiver multicast site, and each 578 create multicast join state, they each Map-Register their RLOC 579 addresses to the mapping system. In this scenario, the replication 580 happens on the overlay causing multiple ETR entry points to replicate 581 to all receivers versus a single ETR entry point replicating to all 582 receivers. If an ETR does not create join state, because it has not 583 received PIM joins or IGMP reports, it will not Map-Register its RLOC 584 addresses to the mapping system. The same procedures in Section 4.1 585 are followed. 587 When multiple ETRs exist on the same LAN as a receiver host, then the 588 PIM DR, when PIM is enabled, or the IGMP querier is responsible for 589 sending a Map-Register for its RLOC. In the IGMP case, one or more 590 ETRs on LAN MUST be IGMP querier candidates. Therefore, it is 591 required they are configured as such. 593 6.3. Multiple RLOCs for an ETR at a Receiver-Site 595 It MAY be desirable to have multiple underlay paths to an ETR for 596 multicast packet delivery. This can be done by having multiple RLOCs 597 assigned to an ETR and having the ETR send Map-Registers for all its 598 RLOCs. By doing this, an ITR can choose a specific path based on 599 underlay performance and/or RLOC reachability. 601 It is recommended that an ETR sends a Map-Register with a single 602 RLOC-record that uses the ELP LCAF type [RFC8060] that is nested 603 inside RLE entry LCAF. For example say ETR1 has assigned RLOC1 and 604 RLOC2 for a LISP receiver site. And there is ETR2 in another LISP 605 receiver site, that has RLOC3. The two receiver sites have the same 606 (S,G) being joined. Here is how the RLOC-record is encoded on each 607 ETR: 609 ETR1: EID-record: (S,G) 610 RLOC-record: RLE[ ELP{ (RLOC1,s,p), (RLOC2,s,p) } ] 612 ETR2: EID-record: (S,G) 613 RLOC-record: RLE[ RLOC3 ] 615 And here is how the entry is merged and stored on the Map-Server 616 since the Map-Registers have an RLE encoded RLOC-record: 618 MS: EID-record: (S,G) 619 RLOC-record: RLE[ RLOC3, ELP{ (RLOC1,s,p), (RLOC2,s,p) } ] 621 When the ITR receives a packet from a multicast source S for group G, 622 it uses the merged RLOC-record, returned from the Map-Server. The 623 ITR replicates the packet to (RLOC3 and RLOC1) or (RLOC3 and RLOC2). 624 Since it is required for the s-bit to be set for RLOC1, the ITR MUST 625 replicate to RLOC1 if it is reachable. When the required p-bit is 626 also set, the RLOC-reachability mechanisms from [RFC6830] are 627 followed. If the ITR determines that RLOC1 is unreachable, it uses 628 RLOC2, as long as RLOC2 is reachable. 630 6.4. Multicast RLOCs for an ETR at a Receiver-Site 632 This specification is focused on underlays without multicast support, 633 but does not preclude the use of multicast RLOCs in RLE entries. 634 ETRs MAY register multicast EID entries using multicast RLOCs. In 635 such cases the ETRs will get joined to underlay multicast 636 distribution trees by using IGMP as a multicast host using mechanisms 637 in [RFC2236] and [RFC3376]. 639 7. PIM Any Source Multicast Trees 641 LISP signal-free multicast can support ASM Trees in limited but 642 acceptable topologies. It is suggested for the simplification of 643 building ASM trees across the LISP overlay to have PIM-ASM run 644 independently in each LISP site. What this means, is that a PIM 645 Rendezvous Point (RP) is configured in each LISP site so PIM Register 646 procedures and (*,G) state maintenance is contained within the LISP 647 site. 649 The following procedure will be used to support ASM in each LISP 650 site: 652 1. In a Receiver-site, the RP is colocated with the ETR. RPs for 653 different groups can be spread across each ETR, but is not 654 required. 656 2. When (*,G) state is created in an ETR, the procedures in 657 Section 4.1.2 are followed. In addition, the ETR registers 658 (S-prefix,G), where S-prefix is 0/0 (the respective unicast 659 default route for the address-family) to the mapping system. 661 3. In a Source-site, the RP is colocated with the ITR. RPs for 662 different groups can be spread across each ITR, but is not 663 required. 665 4. When a multicast source sends a packet, a PIM Register message is 666 delivered to the ITR and the procedures in Section 4.2 are 667 followed. 669 5. When the the ITR sends a Map-Request for (S,G) and no Receiver- 670 site has registered for (S,G), the mapping system will return the 671 (0/0,G) entry to the ITR so it has a replication list of all the 672 ETRs that have received (*,G) state. 674 6. The ITR stores the replication-list in its map-cache for (S,G). 675 It replicates packets to all ETRs in the list. 677 7. ETRs decapsulate packets and forward based on (*,G) state in 678 their site. 680 8. When last-hop PIM routers join the newly discovered (S,G), the 681 ETR will store the state and follow the procedures in 682 Section 4.1.2. 684 8. Signal-Free Multicast for Replication Engineering 686 The mechanisms in this draft can be applied to the LISP Replication- 687 Engineering [I-D.coras-lisp-re] design. Rather than having the 688 layered LISP-RE RTR hierarchy use signaling mechanisms, the RTRs can 689 register their availability for multicast tree replication via the 690 mapping database system. 692 As stated in [I-D.coras-lisp-re], the RTR layered hierarchy is used 693 to avoid head-end replication in replicating nodes closest to a 694 multicast source. Rather than have multicast ITRs replicate to each 695 ETR in an RLE entry of a (S,G) mapping database entry, it could 696 replicate to one or more layer-0 RTRs in the LISP-RE hierarchy. 698 This draft documents how the RTR hierarchy is determined but not what 699 are the optimal layers of RTRs to use. Methods for determining 700 optimal paths or RTR topological closeness are out of scope for his 701 document. 703 There are two formats an (S,G) mapping database entry could have. 704 One format is a 'complete-format' and the other is a 'filtered- 705 format'. A 'complete-format' entails an (S,G) entry having multiple 706 RLOC records which contain both ETRs that have registered as well as 707 the RTRs at the first level of the LISP-RE hierarchy for the ITR to 708 replicate to. When using 'complete-format', the ITR has the ability 709 to select if it replicates to RTRs or to the registered ETRs at the 710 receiver sites. A 'filtered-format' (S,G) entry is one where the 711 Map-Server returns the RLOC-records that it decides the ITR SHOULD 712 use. So replication policy is shifted from the ITRs to the mapping 713 system. The Map-Servers can also decide for a given ITR, if it uses 714 a different set of replication targets per (S,G) entry for which the 715 ITR is replicating for. 717 The procedure for the LISP-RE RTRs to make themselves available for 718 replication can occur before or after any receivers join an (S,G) 719 entry or any sources send for a particular (S,G) entry. Therefore, 720 newly configured RTR state will be used to create new (S,G) state and 721 inherited into existing (S,G) state. A set of RTRs can register 722 themselves to the mapping system or a third-party can do so on their 723 behalf. When RTR registration occurs, it is done with an (S-prefix, 724 G-prefix) entry so it can advertise its replication services for a 725 wide-range of source/group combinations. 727 When a Map-Server receives (S,G) registrations from ETRs and 728 (S-prefix, G-prefix) registrations from RTRs, it has the option of 729 merging the RTR RLOC-records for each (S,G) that is more-specific for 730 the (S-prefix, G-prefix) entry or keep them separate. When merging, 731 a Map-Server is ready to return a 'complete-format' Map-Reply. When 732 keeping the entries separate, the Map-Server can decide what to 733 include in a Map-Reply when a Map-Request is received. It can 734 include a combination of RLOC-records from each entry or decide to 735 use one or the other depending on policy configured. 737 +---+ +----+ 738 Src-1 --------------|ITR| |ETR1|---------------- Rcv-1 739 +---+ +----+ 740 \ / 741 Source-site-1 \ / Receiver-site-1 742 \ / 743 \ / 744 +----+ \ / +----+ 745 |RTR1| \ / |RTR2| Level-0 746 +----+ \ / +----+ 747 \ <^^^^^^^^^^^^^^> / 748 \ < > / 749 < Core-Network > 750 < > 751 752 / / \ \ 753 / / \ \ 754 +----+ / / \ \ +----+ 755 |RTR3| / \ |RTR4| Level-1 756 +----+ / \ +----+ 757 / \ 758 / \ 759 +----+ +----+ 760 Rcv-2 --------------|ETR2| |ETR3|---------------- Rcv-3 761 +----+ +----+ 763 Receiver-site-2 Receiver-site-3 765 Figure 2: LISP-RE Reference Model 767 Here is a specific example, illustrated in Figure 2, of (S,G) and 768 (S-prefix, G-prefix) mapping database entries when a source S is 769 behind an ITR and there are receiver sites joined to (S,G) via ETR1, 770 ETR2, and ETR3. And there exists a LISP-RE hierarchy of RTR1 and 771 RTR2 at level-0 and RTR3 and RTR4 at level-1: 773 EID-record: (S,G) 774 RLOC-record: RLE: (ETR1, ETR2, ETR3), p1 775 EID-record: (S-prefix, G-prefix) 776 RLOC-record: RLE: (RTR1(L0), RTR2(L0), RTR3(L1), RTR4(L1)), p1 778 The above entries are in the form of how they were registered and 779 stored in a Map-Server. When a Map-Server uses 'complete-format', a 780 Map-Reply it originates has the mapping record encoded as: 782 EID-record: (S,G) 783 RLOC-record: RLE: (RTR1(L0), RTR3(L1)), p1 784 RLOC-record: RLE: (ETR1, ETR2, ETR3), p1 786 The above Map-Reply allows the ITR to decide if it replicates to the 787 ETRs or if it SHOULD replicate only to level-0 RTR1. This decision 788 is left to the ITR since both RLOC-records have priority 1. If the 789 Map-Server wanted to force the ITR to replicate to RTR1, it would set 790 the ETRs RLOC-record to priority greater than 1. 792 When a Map_server uses "filtered-format', a Map-Reply it originates 793 has the mapping record encoded as: 795 EID-record: (S,G) 796 RLOC-record: RLE: (RTR1(L0), RTR3(L1)), p1 798 An (S,G) entry can contain alternate RTRs. So rather than 799 replicating to multiple RTRs, one of a RTR set MAY be used based on 800 the RTR reachability status. An ITR can test reachability status to 801 any layer-0 RTR using RLOC-probing so it can choose one RTR from a 802 set to replicate to. When this is done the RTRs are encoded in 803 different RLOC-records versus together in one RLE RLOC-record. This 804 moves the replication load off the ITRs at the source site to the 805 RTRs inside the network infrastructure. This mechanism can also be 806 used by level-n RTRs to level-n+1 RTRs. 808 The following mapping would be encoded in a Map-Reply sent by a Map- 809 Server and stored in the ITR. The ITR would use RTR1 until it went 810 unreachable and then switch to use RTR2: 812 EID-record: (S,G) 813 RLOC-record: RTR1, p1 814 RLOC-record: RTR2, p2 816 9. Security Considerations 818 [I-D.ietf-lisp-sec] defines a set of security mechanisms that provide 819 origin authentication, integrity and anti-replay protection to LISP's 820 EID-to-RLOC mapping data conveyed via mapping lookup process. LISP- 821 SEC also enables verification of authorization on EID-prefix claims 822 in Map-Reply messages. 824 Additional security mechanisms to protect the LISP Map-Register 825 messages are defined in [RFC6833]. 827 The security of the Mapping System Infrastructure depends on the 828 particular mapping database used. The [RFC8111] specification, as an 829 example, defines a public-key based mechanism that provides origin 830 authentication and integrity protection to the LISP DDT protocol. 832 Map-Replies received by the source-ITR can be signed (by the Map- 833 Server) so the ITR knows the replication-list is from a legit source. 835 Data-plane encryption can be used when doing unicast rep- 836 encapsulation as described in [RFC8061]. 838 10. IANA Considerations 840 This document has no IANA implications 842 11. Acknowledgements 844 The authors want to thank Greg Shepherd, Joel Halpern and Sharon 845 Barkai for their insightful contribution to shaping the ideas in this 846 document. A special thanks to Luigi Iannone, LISP WG co-chair, for 847 shepherding this working group document. Thanks also goes to Jimmy 848 Kyriannis, Paul Vinciguerra, Florin Coras, and Yan Filyurin for 849 testing an implementation of this draft. 851 12. References 853 12.1. Normative References 855 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 856 Requirement Levels", BCP 14, RFC 2119, 857 DOI 10.17487/RFC2119, March 1997, 858 . 860 [RFC2236] Fenner, W., "Internet Group Management Protocol, Version 861 2", RFC 2236, DOI 10.17487/RFC2236, November 1997, 862 . 864 [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. 865 Thyagarajan, "Internet Group Management Protocol, Version 866 3", RFC 3376, DOI 10.17487/RFC3376, October 2002, 867 . 869 [RFC3569] Bhattacharyya, S., Ed., "An Overview of Source-Specific 870 Multicast (SSM)", RFC 3569, DOI 10.17487/RFC3569, July 871 2003, . 873 [RFC5698] Kunz, T., Okunick, S., and U. Pordesch, "Data Structure 874 for the Security Suitability of Cryptographic Algorithms 875 (DSSC)", RFC 5698, DOI 10.17487/RFC5698, November 2009, 876 . 878 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 879 Locator/ID Separation Protocol (LISP)", RFC 6830, 880 DOI 10.17487/RFC6830, January 2013, 881 . 883 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 884 Locator/ID Separation Protocol (LISP) for Multicast 885 Environments", RFC 6831, DOI 10.17487/RFC6831, January 886 2013, . 888 [RFC6833] Fuller, V. and D. Farinacci, "Locator/ID Separation 889 Protocol (LISP) Map-Server Interface", RFC 6833, 890 DOI 10.17487/RFC6833, January 2013, 891 . 893 [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I., 894 Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent 895 Multicast - Sparse Mode (PIM-SM): Protocol Specification 896 (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March 897 2016, . 899 [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 900 Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, 901 February 2017, . 903 [RFC8111] Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A. 904 Smirnov, "Locator/ID Separation Protocol Delegated 905 Database Tree (LISP-DDT)", RFC 8111, DOI 10.17487/RFC8111, 906 May 2017, . 908 12.2. Informative References 910 [I-D.coras-lisp-re] 911 Coras, F., Cabellos-Aparicio, A., Domingo-Pascual, J., 912 Maino, F., and D. Farinacci, "LISP Replication 913 Engineering", draft-coras-lisp-re-08 (work in progress), 914 November 2015. 916 [I-D.farinacci-lisp-mr-signaling] 917 Farinacci, D. and M. Napierala, "LISP Control-Plane 918 Multicast Signaling", draft-farinacci-lisp-mr-signaling-06 919 (work in progress), February 2015. 921 [I-D.ietf-lisp-eid-mobility] 922 Portoles-Comeras, M., Ashtaputre, V., Moreno, V., Maino, 923 F., and D. Farinacci, "LISP L2/L3 EID Mobility Using a 924 Unified Control Plane", draft-ietf-lisp-eid-mobility-01 925 (work in progress), November 2017. 927 [I-D.ietf-lisp-sec] 928 Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D. 929 Saucez, "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-14 930 (work in progress), October 2017. 932 [RFC8061] Farinacci, D. and B. Weis, "Locator/ID Separation Protocol 933 (LISP) Data-Plane Confidentiality", RFC 8061, 934 DOI 10.17487/RFC8061, February 2017, 935 . 937 Appendix A. Document Change Log 939 A.1. Changes to draft-ietf-lisp-signal-free-multicast-07 941 o Posted November 2017. 943 o Changes after shepherd review and RFC1918 terminology compliant. 945 A.2. Changes to draft-ietf-lisp-signal-free-multicast-06 947 o Posted July 2017. 949 o Stig made a comment about referencing RFC6831 when an RLOC is a 950 multicast address. It opens up a lot of assumptions on what parts 951 of RFC6831 is performed and which parts should not be performed. 952 In the case of signal-free-multicast, join the underlay trees as a 953 multicast host by using IGMP. 955 A.3. Changes to draft-ietf-lisp-signal-free-multicast-05 957 o Posted July 2017. 959 o Make it clear that when a RLE is sent by an ETR and it is already 960 in the merged RLE list on the Map-Server, that the Map-Server 961 replaces the RLE entry (versus adding a duplicate RLE entry to the 962 list). 964 o Make it clear that an RLOC can be a unicast or multicast address. 965 Then make a reference to RFC6831 about mechanisms to support 966 multicast RLOCs. 968 o Fix some typos. 970 A.4. Changes to draft-ietf-lisp-signal-free-multicast-04 972 o Posted May 2017. 974 o Make it clear that recieiver-ETRs need configuraiton information 975 for what Map-Servers (S,G) entries are registered to. 977 o Make it clear this document indicates what RTR layered hierarchy 978 to use and not if its the best hierarchy to use. 980 A.5. Changes to draft-ietf-lisp-signal-free-multicast-03 982 o Posted April 2017. 984 o Add "Multi-Homing Considerations" section to describe the case 985 where a source LISP site has multiple ITRs and the multicast 986 distribution tree at the source site branches to more than one 987 ITR. And at receiver sites where there are multiple ETRs and 988 multiple RLOCs per ETR. 990 A.6. Changes to draft-ietf-lisp-signal-free-multicast-02 992 o Posted October 2016. 994 o Updated document expiration timer. 996 A.7. Changes to draft-ietf-lisp-signal-free-multicast-01 998 o Posted April 2016. 1000 o Add text to define RTRs and indicate how RTR level number is used 1001 for LISP-RE. 1003 o Draw figure 2 that shows a LISP-RE topology. 1005 o Indicate that PIM-ASM or (*,G) trees can be supported in LISP 1006 Signal-Free Multicast. 1008 A.8. Changes to draft-ietf-lisp-signal-free-multicast-00 1010 o Posted late December 2015. 1012 o Converted draft-farinacci-lisp-signal-free-multicast-04 into LISP 1013 working group draft. 1015 A.9. Changes to draft-farinacci-lisp-signal-free-multicast-04 1017 o Posted early December 2015. 1019 o Update references and document timer. 1021 A.10. Changes to draft-farinacci-lisp-signal-free-multicast-03 1023 o Posted June 2015. 1025 o Update references and document timer. 1027 A.11. Changes to draft-farinacci-lisp-signal-free-multicast-02 1029 o Posted December 2014. 1031 o Added section about how LISP-RE can use the mechanisms from 1032 signal-free-multicast so we can avoid head-end replication and 1033 avoid signalling across a layered RE topology. 1035 A.12. Changes to draft-farinacci-lisp-signal-free-multicast-01 1037 o Posted June 2014. 1039 o Changes based on implementation experience of this draft. 1041 A.13. Changes to draft-farinacci-lisp-signal-free-multicast-00 1043 o Posted initial draft February 2014. 1045 Authors' Addresses 1047 Victor Moreno 1048 Cisco Systems 1049 170 Tasman Drive 1050 San Jose, California 95134 1051 USA 1053 Email: vimoreno@cisco.com 1055 Dino Farinacci 1056 lispers.net 1057 San Jose, CA 95120 1058 USA 1060 Email: farinacci@gmail.com