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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: October 14, 2017 lispers.net 6 April 12, 2017 8 Signal-Free LISP Multicast 9 draft-ietf-lisp-signal-free-multicast-03 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 de-capsulators 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 October 14, 2017. 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 . . . . . . . . . . . . . 9 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 . . . . . . . . . . 10 75 5. Source Specific Multicast Trees . . . . . . . . . . . . . . . 11 76 5.1. Source Directly Connected to Source-ITRs . . . . . . . . 11 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 . . . . . . . . . . . . 12 81 6.3. Multiple RLOCs for an ETR at a Receiver-Site . . . . . . 13 82 7. PIM Any Source Multicast Trees . . . . . . . . . . . . . . . 14 83 8. Signal-Free Multicast for Replication Engineering . . . . . . 15 84 9. Security Considerations . . . . . . . . . . . . . . . . . . . 17 85 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 86 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 87 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 88 12.1. Normative References . . . . . . . . . . . . . . . . . . 18 89 12.2. Informative References . . . . . . . . . . . . . . . . . 19 90 Appendix A. Document Change Log . . . . . . . . . . . . . . . . 20 91 A.1. Changes to draft-ietf-lisp-signal-free-multicast-03 . . . 20 92 A.2. Changes to draft-ietf-lisp-signal-free-multicast-02 . . . 20 93 A.3. Changes to draft-ietf-lisp-signal-free-multicast-01 . . . 20 94 A.4. Changes to draft-ietf-lisp-signal-free-multicast-00 . . . 20 95 A.5. Changes to draft-farinacci-lisp-signal-free-multicast-04 20 96 A.6. Changes to draft-farinacci-lisp-signal-free-multicast-03 21 97 A.7. Changes to draft-farinacci-lisp-signal-free-multicast-02 21 98 A.8. Changes to draft-farinacci-lisp-signal-free-multicast-01 21 99 A.9. Changes to draft-farinacci-lisp-signal-free-multicast-00 21 100 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 102 1. Introduction 104 When multicast sources and receivers are active at LISP sites, and 105 the core network between the sites does not provide multicast 106 support, a signal-free mechanism can be used to create an overlay 107 that will allow multicast traffic to flow between sites and connect 108 the multicast trees at the different sites. 110 The signal-free mechanism here proposed does not extend PIM over the 111 overlay as proposed in [RFC6831], nor does the mechanism utilize 112 direct signaling between the Receiver-ETRs and Sender-ITRs as 113 described in [I-D.farinacci-lisp-mr-signaling]. The signal-free 114 mechanism proposed reduces the amount of signaling required between 115 sites to a minimum and is centered around the registration of 116 Receiver-sites for a particular multicast-group or multicast-channel 117 with the LISP Mapping System. 119 Registrations from the different receiver-sites will be merged at the 120 Mapping System to assemble a multicast-replication-list inclusive of 121 all RLOCs that lead to receivers for a particular multicast-group or 122 multicast-channel. The replication-list for each specific multicast- 123 entry is maintained as a LISP database mapping entry in the Mapping 124 Database. 126 When the ITR at the source-site receives multicast traffic from 127 sources at its site, the ITR can query the mapping system by issuing 128 Map-Request messages for the (S,G) source and destination addresses 129 in the packets received. The Mapping System will return the RLOC 130 replication-list to the ITR, which the ITR will cache as per standard 131 LISP procedure. Since the core is assumed to not support multicast, 132 the ITR will replicate the multicast traffic for each RLOC on the 133 replication-list and will unicast encapsulate the traffic to each 134 RLOC. The combined function or replicating and encapsulating the 135 traffic to the RLOCs in the replication-list is referred to as "rep- 136 encapsulation" in this document. 138 The document describes the General Procedures and information 139 encoding that are required at the Receiver-sites and Source-sites to 140 achieve signal-free multicast interconnectivity. The General 141 Procedures for Mapping System Notifications to different sites are 142 also described. A section dedicated to the specific case of SSM 143 trees discusses the implications to the General Procedures for SSM 144 multicast trees over different topological scenarios. A section on 145 ASM support is included to identify the constraints that come along 146 with supporting it using LISP Signal-Free multicast. 148 There is a section dedicated to Replication Engineering. A mechanism 149 to reduce the impact of head-end replication. The mapping system, 150 via LISP Signal-Free mechanisms, can be used to build a layer of 151 RTRs. 153 2. Definition of Terms 155 LISP related terms, notably Map-Request, Map-Reply, Ingress Tunnel 156 Router (ITR), Egress Tunnel Router (ETR), Map-Server (MS) and Map- 157 Resolver (MR) are defined in the LISP specification [RFC6830]. 159 Extensions to the definitions in [RFC6830] for their application to 160 multicast routing are documented in [RFC6831]. 162 Terms defining interactions with the LISP Mapping System are defined 163 in [RFC6833]. 165 The following terms are consistent with the definitions in [RFC6830] 166 and [RFC6831]. The terms are specific cases of the general terms and 167 are here defined to facilitate the descriptions and discussions 168 within this particular document. 170 Source: Multicast source end-point. Host originating multicast 171 packets. 173 Receiver: Multicast group member end-point. Host joins multicast 174 group as a receiver of multicast packets sent to the group. 176 Receiver-site: LISP site where multicast receivers are located. 178 Source-site: LISP site where multicast sources are located. 180 RP-site: LISP site where an ASM PIM Rendezvous Point is located. The 181 RP-site and the Source-site may be the same in some situations. 183 Receiver-ETR: LISP xTR at the Receiver-site. This is a multicast 184 ETR. 186 Source-ITR: LISP xTR at the Source-site. This is a multicast ITR. 188 RP-xTR: LISP xTR at the RP-site. This is typically a multicast ITR. 190 Replication-list: Mapping-entry containing the list of RLOCs that 191 have registered Receivers for a particular multicast-entry. 193 Multicast-entry: A tuple identifying a multicast tree. Multicast- 194 entries are in the form of (S-prefix, G-prefix). 196 Rep-encapsulation: The process of replicating and then encapsulating 197 traffic to multiple RLOCs. 199 Re-encapsulating Tunnel Router (RTR): An RTR is a router that 200 implements the re-encapsulating tunnel function detailed in Section 8 201 of the main LISP specification [RFC6830]. A LISP RTR performs packet 202 re-routing by chaining ETR and ITR functions, whereby it first 203 removes the LISP header of an ingress packet and then prepends a new 204 LISP header to an egress packet. 206 RTR Level: An RTR level is encoded in a Replication-List-Entry (RLE) 207 LCAF Type detailed in [RFC8060]. Each entry in the replication list 208 contains an address of an xTR and a level value. Level values are 209 used to create a replication hierarchy so that ITRs at source LISP 210 sites replicate to the lowest (smaller value) level number RTRs in a 211 RLE entry. And then RTRs at a given level replicate to the next 212 higher level of RTRs. The number of RTRs at each level are 213 engineered to control the fan-out or replication factor so a tradeoff 214 between the width of the level versus the number of levels can be 215 selected. 217 3. Reference Model 219 The reference model that will be used for the discussion of the 220 Signal-Free multicast tree interconnection is illustrated in 221 Figure 1. 223 MS/MR 224 +---+ 225 | | 226 +---+ +---+ +---+ +---+ +---+ 227 Src-1 ----| R1|-----|ITR| | |ETR|------| R2|------ Rcv-2 228 +---+ +---+ | +---+ +---+ 229 \ | / 230 Source-site-1 \ | / Receiver-site-2 231 \ | / 232 \ | / 233 \ | / 234 Core 235 / \ 236 / \ 237 / \ 238 / \ 239 / \ 240 +---+ +---+ 241 Src-3 --------------|ITR| |ETR|----------------- Rcv-4 242 +---+ +---+ 244 Source-site-3 Receiver-site-4 246 Figure 1: LISP Multicast Generic Reference Model 248 Sites 1 and 3 are Source-sites. 250 Source-site-3 presents a Source (Src-3) that is directly connected to 251 the Source-ITR 253 Source-site-1 presents a Source (Src-1) that is one hop or more away 254 from the Source-ITR 256 Receiver-site-2 and 4 are receiver sites with not-directly connected 257 and directly connected Receiver end-points respectively 259 R1 is a router in Source-site-1. 261 R2 is a PIM router at the Receiver-site. 263 The Map-Servers and Resolvers are reachable in the RLOC space in the 264 Core, only one is shown for illustration purposes, but these can be 265 many or even part of a DDT tree. 267 The procedures for interconnecting multicast Trees over an overlay 268 can be broken down into three functional areas: 270 o Receiver-site procedures 272 o Source-site procedures 274 o LISP notification procedures 276 The receiver site procedures will be common for most tree types and 277 topologies. 279 The procedures at the source site can vary depending on the type of 280 trees being interconnected as well as based on the topological 281 relation between sources and source-site xTRs. For ASM trees, a 282 special case of the Source-site is the RP-site for which a variation 283 of the Source-site procedures may be necessary if ASM trees are to be 284 supported in future specifications of LISP Signal-Free multicast. 286 The LISP notification procedures between sites are normalized for the 287 different possible scenarios. Certain scenarios may benefit from a 288 simplified notification mechanism or no notification requirement at 289 all. 291 4. General Procedures 293 The interconnection of multicast trees across different LISP sites 294 involves the following procedures to build the necessary multicast 295 distribution trees across sites. 297 1. The presence of multicast Receiver end-points is detected by the 298 Receiver-ETRs at the Receiver-sites. 300 2. Receiver-ETRs register their RLOCs as part of the replication- 301 list for the multicast-entry the detected Receivers subscribe to. 303 3. The Mapping-system merges all receiver-ETR or delivery-group 304 RLOCs to build a comprehensive replication-list inclusive of all 305 Receiver-sites for each multicast-entry. 307 4. LISP Map-Notify messages should be sent to the Source-ITR 308 informing of any changes in the replication-list. 310 5. Multicast-tree building at the Source-site is initiated when the 311 Source-ITR receives the LISP Notification. 313 Once the multicast distribution trees are built, the following 314 forwarding procedures may take place: 316 1. The Source sends multicast packets to the multicast group 317 destination address. 319 2. Multicast traffic follows the multicast tree built at the Source- 320 site and makes its way to the Source-ITRs. 322 3. The Source-ITR will issue a map-request to resolve the 323 replication-list for the multicast-entry. 325 4. The Mapping System responds to the Source-ITR with a map-reply 326 containing the replication-list for the multicast group 327 requested. 329 5. The Source-ITR caches the replication-list received in the map- 330 reply for the multicast-entry. 332 6. Multicast traffic is rep-encapsulated. That is, the packet is 333 replicated for each RLOC in the replication-list and then 334 encapsulated to each one. 336 4.1. General Receiver-Site Procedures 338 4.1.1. Multicast Receiver Detection 340 When the Receiver-ETRs are directly connected to the Receivers (e.g. 341 Receiver-site-4 in Figure 1), the Receiver-ETRs will receive IGMP 342 Reports from the Receivers indicating which group the Receivers wish 343 to subscribe to. Based on these IGMP Reports, the receiver-ETR is 344 made aware of the presence of Receivers as well as which group they 345 are interested in. 347 When the Receiver-ETRs are several hops away from the Receivers (e.g. 348 Receiver-site-2 in Figure 1), the Receiver-ETRs will receive PIM join 349 messages which will allow the Receiver-ETR to know that there are 350 multicast Receivers at the site and also learn which multicast group 351 the Receivers are for. 353 4.1.2. Receiver-Site Registration 355 Once the Receiver-ETRs detect the presence of Receivers at the 356 Receiver-site, the Receiver-ETRs will issue Map-Register messages to 357 include the Receiver-ETR RLOCs in the replication-list for the 358 multicast-entry the Receivers joined. 360 The Map-Register message will use the multicast-entry (Source, Group) 361 tuple as its EID record type with the Receiver-ETR RLOCs conforming 362 the locator set. 364 The EID in the Map-Register message must be encoded using the 365 Multicast Information LCAF type defined in [RFC8060]. 367 The RLOC in the Map-Register message must be encoded using the 368 Replication List Entry (RLE) LCAF type defined in [RFC8060] with the 369 Level Value fields for all entries set to 128 (decimal). 371 The encoding described above must be used consistently for Map- 372 Register messages, entries in the Mapping Database, Map-reply 373 messages as well as the map-cache at the Source-ITRs. 375 The Map-Register messages [RFC6830] sent by the receiver-ETRs should 376 have the following bits set as here specified: 378 1. merge-request-bit set to 1. The Map-Register messages must be 379 sent with "Merge Semantics". The Map-Server will receive 380 registrations from a multitude of Receiver-ETRs. The Map-Server 381 will merge the registrations for common EIDs and maintain a 382 consolidated replication-list for each multicast-entry. 384 2. want-map-notify-bit (M) set to 0. This tells the Mapping System 385 that the receiver-ETR does not expect to receive Map-Notify 386 messages as it does not need to be notified of all changes to the 387 replication-list. 389 3. proxy-reply-bit (P) set to 1. The merged replication-list is 390 kept in the Map-Servers. By setting the proxy-reply bit, the 391 receiver-ETRs instruct the Mapping-system to proxy reply to map- 392 requests issued for the multicast entries. 394 Map-Register messages for a particular multicast-entry should be sent 395 for every receiver detected, even if previous receivers have been 396 detected for the particular multicast-entry. This allows the 397 replication-list to remain up to date. 399 4.1.3. Consolidation of the Replication-List 401 The Map-Server will receive registrations from a multitude of 402 Receiver-ETRs. The Map-Server will merge the registrations for 403 common EIDs and consolidate a replication-list for each multicast- 404 entry. 406 4.2. General Source-Site Procedures 408 Source-ITRs must register the unicast EIDs of any Sources or 409 Rendezvous Points that may be present on the Source-site. In other 410 words, it is assumed that the Sources and RPs are LISP EIDs. 412 The registration of the unicast EIDs for the Sources or Rendezvous 413 Points allows the map-server to know where to send Map-Notify 414 messages to. Therefore, the Source-ITR must register the unicast 415 S-prefix EID with the want-map-notify-bit set in order to receive 416 Map-Notify messages whenever there is a change in the replication- 417 list. 419 4.2.1. Multicast Tree Building at the Source-Site 421 When the source site receives the Map-Notify messages from the 422 mapping system as described in Section 4.3, it will initiate the 423 process of building a multicast distribution tree that will allow the 424 multicast packets from the Source to reach the Source-ITR. 426 The Source-ITR will issue a PIM join for the multicast-entry for 427 which it received the Map-Notify message. The join will be issued in 428 the direction of the source or in the direction of the RP for the SSM 429 and ASM cases respectively. 431 4.2.2. Multicast Destination Resolution 433 On reception of multicast packets, the source-ITR must obtain the 434 replication-list for the (S,G) addresses in the packets. 436 In order to obtain the replication-list, the Source-ITR must issue a 437 Map-Request message in which the EID is the (S,G) multicast tuple 438 which is encoded using the Multicast Info LCAF type defined in 439 [RFC8060]. 441 The Mapping System (most likely the Map-Server) will Map-reply with 442 the merged replication-list maintained in the Mapping System. The 443 Map-reply message must follow the format defined in [RFC6830], its 444 EID must be encoded using the Multicast Info LCAF type and the 445 corresponding RLOC-records must be encoded using the RLE LCAF type. 446 Both LCAF types defined in [RFC8060]. 448 4.3. General LISP Notification Procedures 450 The Map-Server will issue LISP Map-Notify messages to inform the 451 Source-site of the presence of receivers for a particular multicast 452 group over the overlay. 454 Updated Map-Notify messages should be issued every time a new 455 registration is received from a Receiver-site. This guarantees that 456 the source-sites are aware of any potential changes in the multicast- 457 distribution-list membership. 459 The Map-Notify messages carry (S,G) multicast EIDs encoded using the 460 Multicast Info LCAF type defined in [RFC8060]. 462 Map-Notify messages will be sent by the Map-Server to the RLOCs with 463 which the unicast S-prefix EID was registered. In the case when 464 sources are discovered dynamically [I-D.portoles-lisp-eid-mobility], 465 xTRs must register sources explicitly with the want-map-notify-bit 466 set. This is so the ITR in the site the source has moved to can get 467 the most current replication list. 469 When both the Receiver-sites and the Source-sites register to the 470 same Map-Server, the Map-Server has all the necessary information to 471 send the Map-Notify messages to the Source-site. 473 When the Map-Servers are distributed in a DDT, the Receiver-sites may 474 register to one Map-Server while the Source-site registers to a 475 different Map-Server. In this scenario, the Map-Server for the 476 receiver sites must resolve the unicast S-prefix EID in the DDT per 477 standard LISP lookup procedures and obtain the necessary information 478 to send the Map-Notify messages to the Source-site. The Map-Notify 479 messages must be sent with an authentication length of 0 as they 480 would not be authenticated. 482 When the Map-Servers are distributed in a DDT, different Receiver- 483 sites may register to different Map-Servers. This is an unsupported 484 scenario with the currently defined mechanisms. 486 5. Source Specific Multicast Trees 488 The interconnection of Source Specific Multicast (SSM) Trees across 489 sites will follow the General Receiver-site Procedures described in 490 Section 4.1 on the Receiver-sites. 492 The Source-site Procedures will vary depending on the topological 493 location of the Source within the Source-site as described in 494 Section 5.1 and Section 5.2 . 496 5.1. Source Directly Connected to Source-ITRs 498 When the Source is directly connected to the source-ITR, it is not 499 necessary to trigger signaling to build a local multicast tree at the 500 Source-site. Therefore Map-Notify messages may not be required to 501 initiate building of the multicast tree at the Source-site. 503 Map-Notify messages are still required to ensure that any changes to 504 the replication-list are communicated to the Source-site so that the 505 map-cache at the Source-ITRs is kept updated. 507 5.2. Source not Directly Connected to Source-ITRs 509 The General LISP Notification Procedures described in Section 4.3 510 must be followed when the Source is not directly connected to the 511 source-ITR. On reception of Map-Notify messages, local multicast 512 signaling must be initiated at the Source-site per the General Source 513 Site Procedures for Multicast Tree building described in 514 Section 4.2.1. 516 In the SSM case, the IP address of the Source is known and it is also 517 registered with the LISP mapping system. Thus, the mapping system 518 may resolve the mapping for the Source address in order to send Map- 519 Notify messages to the correct source-ITR. 521 6. Multi-Homing Considerations 523 6.1. Multiple ITRs at a Source-Site 525 When multiple ITRs exist at a source multicast site, care should be 526 taken that more than one ITR does not head-end replicate packets else 527 receiver multicast sites will receive duplicate packets. The 528 following procedures will be used for each topology scenarios: 530 o When more than one ITR is directly connected to the source host, 531 either the PIM DR or the IGMP querier (when PIM is not enabled on 532 the ITRs) is responsible for packet replication. All other ITRs 533 silently drop the packet. In the IGMP querier case, it is 534 required to configure the source LAN to have one of the ITRs be 535 the IGMP querier. 537 o When more than one ITR is multiple hops away from the source host 538 and one of the ITRs is the PIM Rendezvous Point, then the PIM RP 539 is responsible for packet replication. 541 o When more than one ITR is multiple hops away from the source host 542 and the PIM Rendezvous Point is not one of the ITRs, then one of 543 the ITRs must join to the RP. When a Map-Notify is received from 544 the Map-Server by an ITR, only the highest RLOC addressed ITR will 545 join toward the PIM RP or toward the source. 547 6.2. Multiple ETRs at a Receiver-Site 549 When multiple ETRs exist in a receiver multicast site, and each 550 create multicast join state, they each Map-Register their RLOC 551 addresses to the mapping system. In this scenario, the replication 552 happens on the overlay causing multiple ETR entry points to replicate 553 to all receivers versus a single ETR entry point replicating to all 554 receivers. If an ETR does not create join state, because it has not 555 received PIM joins or IGMP reports, it will not Map-Register its RLOC 556 addresses to the mapping system. The same procedures in Section 4.1 557 should be followed. 559 When multiple ETRs exist on the same LAN as a receiver host, then the 560 PIM DR, when PIM is enabled, or the IGMP querier is responsible for 561 sending a Map-Register for its RLOC. In the IGMP case, it is 562 required that the LAN is configured with one of the ETRs as IGMP 563 querier. 565 6.3. Multiple RLOCs for an ETR at a Receiver-Site 567 It may be desirable to have multiple underlay paths to an ETR for 568 multicast packet delivery. This can be done by having multiple RLOCs 569 assigned to an ETR and having the ETR send Map-Registers for all its 570 RLOCs. By doing this, an ITR can choose a specific path based on 571 underlay performance and/or RLOC reachability. 573 It is suggested that an ETR sends a Map-Register with a single RLOC- 574 record that uses the ELP LCAF type [RFC8060] that is nested inside 575 RLE entry LCAF. For example say ETR1 has assigned RLOC1 and RLOC2 576 for a LISP receiver site. And there is ETR2 in another LISP receiver 577 site, that has RLOC3. The two receiver sites have the same (S,G) 578 being joined. Here is how the RLOC-record is encoded on each ETR: 580 ETR1: EID-record: (S,G) 581 RLOC-record: RLE[ ELP{ (RLOC1,s,p), (RLOC2,s,p) } ] 583 ETR2: EID-record: (S,G) 584 RLOC-record: RLE[ RLOC3 ] 586 And here is how the entry is merged and stored on the Map-Server 587 since the Map-Registers have an RLE encoded RLOC-record: 589 MS: EID-record: (S,G) 590 RLOC-record: RLE[ RLOC3, ELP{ (RLOC1,s,p), (RLOC2,s,p) } ] 592 When the ITR receives a packet from a multicast source S for group G, 593 it uses the merged RLOC-record, returned from the Map-Server. The 594 ITR replicates the packet to (RLOC3 and RLOC1) or (RLOC3 and RLOC2). 595 Since it is required for the s-bit to be set for RLOC1, the ITR must 596 replicate to RLOC1 if it is reachable. When the required p-bit is 597 also set, the RLOC-reachability mechanisms from [RFC6830] are 598 followed. If the ITR determines that RLOC1 is unreachable, it uses 599 RLOC2, as long as RLOC2 is reachable. 601 7. PIM Any Source Multicast Trees 603 LISP signal-free multicast can support ASM Trees in limited but 604 acceptable topologies. It is suggested for the simplification of 605 building ASM trees across the LISP overlay to have PIM-ASM run 606 independently in each LISP site. What this means, is that a PIM 607 Rendezvous Point (RP) is configured in each LISP site so PIM Register 608 procedures and (*,G) state maintenance is contained within the LISP 609 site. 611 The following procedure will be used to support ASM in each LISP 612 site: 614 1. In a Receiver-site, the RP is colocated with the ETR. RPs for 615 different groups can be spread across each ETR, but is not 616 required. 618 2. When (*,G) state is created in an ETR, the procedures in 619 Section 4.1.2 are followed. In addition, the ETR registers 620 (S-prefix,G), where S-prefix is 0/0 (the respective unicast 621 default route for the address-family) to the mapping system. 623 3. In a Source-site, the RP is colocated with the ITR. RPs for 624 different groups can be spread across each ITR, but is not 625 required. 627 4. When a multicast source sends a packet, a PIM Register message is 628 delivered to the ITR and the procedures in Section 4.2 are 629 followed. 631 5. When the the ITR sends a Map-Request for (S,G) and no Receiver- 632 site has registered for (S,G), the mapping system will return the 633 (0/0,G) entry to the ITR so it has a replication list of all the 634 ETRs that have received (*,G) state. 636 6. The ITR stores the replication-list in its map-cache for (S,G). 637 It replicates packets to all ETRs in the list. 639 7. ETRs decapsulate packets and forward based on (*,G) state in 640 their site. 642 8. When last-hop PIM routers join the newly discovered (S,G), the 643 ETR will store the state and follow the procedures in 644 Section 4.1.2. 646 8. Signal-Free Multicast for Replication Engineering 648 The mechanisms in this draft can be applied to the LISP Replication- 649 Engineering [I-D.coras-lisp-re] design. Rather than having the 650 layered LISP-RE RTR hierarchy use signaling mechanisms, the RTRs can 651 register their availability for multicast tree replication via the 652 mapping database system. As stated in [I-D.coras-lisp-re], the RTR 653 layered hierarchy is used to avoid head-end replication in 654 replicating nodes closest to a multicast source. Rather than have 655 multicast ITRs replicate to each ETR in an RLE entry of a (S,G) 656 mapping database entry, it could replicate to one or more layer-0 657 RTRs in the LISP-RE hierarchy. 659 There are two formats an (S,G) mapping database entry could have. 660 One format is a 'complete-format' and the other is a 'filtered- 661 format'. A 'complete-format' entails an (S,G) entry having multiple 662 RLOC records which contain both ETRs that have registered as well as 663 the RTRs at the first level of the LISP-RE hierarchy for the ITR to 664 replicate to. When using 'complete-format', the ITR has the ability 665 to select if it replicates to RTRs or to the registered ETRs at the 666 receiver sites. A 'filtered-format' (S,G) entry is one where the 667 Map-Server returns the RLOC-records that it decides the ITR should 668 use. So replication policy is shifted from the ITRs to the mapping 669 system. The Map-Servers can also decide for a given ITR, if it uses 670 a different set of replication targets per (S,G) entry for which the 671 ITR is replicating for. 673 The procedure for the LISP-RE RTRs to make themselves available for 674 replication can occur before or after any receivers join an (S,G) 675 entry or any sources send for a particular (S,G) entry. Therefore, 676 newly configured RTR state will be used to create new (S,G) state and 677 inherited into existing (S,G) state. A set of RTRs can register 678 themselves to the mapping system or a third-party can do so on their 679 behalf. When RTR registration occurs, it is done with an (S-prefix, 680 G-prefix) entry so it can advertise its replication services for a 681 wide-range of source/group combinations. 683 When a Map-Server receives (S,G) registrations from ETRs and 684 (S-prefix, G-prefix) registrations from RTRs, it has the option of 685 merging the RTR RLOC-records for each (S,G) that is more-specific for 686 the (S-prefix, G-prefix) entry or keep them separate. When merging, 687 a Map-Server is ready to return a 'complete-format' Map-Reply. When 688 keeping the entries separate, the Map-Server can decide what to 689 include in a Map-Reply when a Map-Request is received. It can 690 include a combination of RLOC-records from each entry or decide to 691 use one or the other depending on policy configured. 693 +---+ +----+ 694 Src-1 --------------|ITR| |ETR1|----------------- Rcv-1 695 +---+ +----+ 696 \ / 697 Source-site-1 \ / Receiver-site-1 698 \ / 699 \ / 700 +----+ \ / +----+ 701 |RTR1| \ / |RTR2| Level-0 702 +----+ \ / +----+ 703 \ <^^^^^^^^^^^^^^> / 704 \ < > / 705 < Core-Network > 706 < > 707 708 / / \ \ 709 / / \ \ 710 +----+ / / \ \ +----+ 711 |RTR3| / \ |RTR4| Level-1 712 +----+ / \ +----+ 713 / \ 714 / \ 715 +----+ +----+ 716 Rcv-2 --------------|ETR2| |ETR3|----------------- Rcv-3 717 +----+ +----+ 719 Receiver-site-2 Receiver-site-3 721 Figure 2: LISP-RE Reference Model 723 Here is a specific example, illustrated in Figure 2, of (S,G) and 724 (S-prefix, G-prefix) mapping database entries when a source S is 725 behind an ITR and there are receiver sites joined to (S,G) via ETR1, 726 ETR2, and ETR3. And there exists a LISP-RE hierarchy of RTR1 and 727 RTR2 at level-0 and RTR3 and RTR4 at level-1: 729 EID-record: (S,G) 730 RLOC-record: RLE: (ETR1, ETR2, ETR3), p1 731 EID-record: (S-prefix, G-prefix) 732 RLOC-record: RLE: (RTR1(L0), RTR2(L0), RTR3(L1), RTR4(L1)), p1 734 The above entries are in the form of how they were registered and 735 stored in a Map-Server. When a Map-Server uses 'complete-format', a 736 Map-Reply it originates has the mapping record encoded as: 738 EID-record: (S,G) 739 RLOC-record: RLE: (RTR1(L0), RTR3(L1)), p1 740 RLOC-record: RLE: (ETR1, ETR2, ETR3), p1 742 The above Map-Reply allows the ITR to decide if it replicates to the 743 ETRs or if it should replicate only to level-0 RTR1. This decision 744 is left to the ITR since both RLOC-records have priority 1. If the 745 Map-Server wanted to force the ITR to replicate to RTR1, it would set 746 the ETRs RLOC-record to priority greater than 1. 748 When a Map_server uses "filtered-format', a Map-Reply it originates 749 has the mapping record encoded as: 751 EID-record: (S,G) 752 RLOC-record: RLE: (RTR1(L0), RTR3(L1)), p1 754 An (S,G) entry can contain alternate RTRs. So rather than 755 replicating to multiple RTRs, one of a RTR set may be used based on 756 the RTR reachability status. An ITR can test reachability status to 757 any layer-0 RTR using RLOC-probing so it can choose one RTR from a 758 set to replicate to. When this is done the RTRs are encoded in 759 different RLOC-records versus together in one RLE RLOC-record. This 760 moves the replication load off the ITRs at the source site to the 761 RTRs inside the network infrastructure. This mechanism can also be 762 used by level-n RTRs to level-n+1 RTRs. 764 The following mapping would be encoded in a Map-Reply sent by a Map- 765 Server and stored in the ITR. The ITR would use RTR1 until it went 766 unreachable and then switch to use RTR2: 768 EID-record: (S,G) 769 RLOC-record: RTR1, p1 770 RLOC-record: RTR2, p2 772 9. Security Considerations 774 [I-D.ietf-lisp-sec] defines a set of security mechanisms that provide 775 origin authentication, integrity and anti-replay protection to LISP's 776 EID-to-RLOC mapping data conveyed via mapping lookup process. LISP- 777 SEC also enables verification of authorization on EID-prefix claims 778 in Map-Reply messages. 780 Additional security mechanisms to protect the LISP Map-Register 781 messages are defined in [RFC6833]. 783 The security of the Mapping System Infrastructure depends on the 784 particular mapping database used. The [I-D.ietf-lisp-ddt] 785 specification, as an example, defines a public-key based mechanism 786 that provides origin authentication and integrity protection to the 787 LISP DDT protocol. 789 Map-Replies received by the source-ITR can be signed (by the Map- 790 Server) so the ITR knows the replication-list is from a legit source. 792 Data-plane encryption can be used when doing unicast rep- 793 encapsulation as described in [RFC8061]. For further study we will 794 look how to do multicast rep-encapsulation. 796 10. IANA Considerations 798 This document has no IANA implications 800 11. Acknowledgements 802 The authors want to thank Greg Shepherd, Joel Halpern and Sharon 803 Barkai for their insightful contribution to shaping the ideas in this 804 document. Thanks also goes to Jimmy Kyriannis, Paul Vinciguerra, 805 Florin Coras, and Yan Filyurin for testing an implementation of this 806 draft. 808 12. References 810 12.1. Normative References 812 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 813 Requirement Levels", BCP 14, RFC 2119, 814 DOI 10.17487/RFC2119, March 1997, 815 . 817 [RFC3618] Fenner, B., Ed. and D. Meyer, Ed., "Multicast Source 818 Discovery Protocol (MSDP)", RFC 3618, 819 DOI 10.17487/RFC3618, October 2003, 820 . 822 [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, 823 "Protocol Independent Multicast - Sparse Mode (PIM-SM): 824 Protocol Specification (Revised)", RFC 4601, 825 DOI 10.17487/RFC4601, August 2006, 826 . 828 [RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for 829 IP", RFC 4607, DOI 10.17487/RFC4607, August 2006, 830 . 832 12.2. Informative References 834 [I-D.coras-lisp-re] 835 Coras, F., Cabellos-Aparicio, A., Domingo-Pascual, J., 836 Maino, F., and D. Farinacci, "LISP Replication 837 Engineering", draft-coras-lisp-re-08 (work in progress), 838 November 2015. 840 [I-D.farinacci-lisp-mr-signaling] 841 Farinacci, D. and M. Napierala, "LISP Control-Plane 842 Multicast Signaling", draft-farinacci-lisp-mr-signaling-06 843 (work in progress), February 2015. 845 [I-D.ietf-lisp-ddt] 846 Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A. 847 Smirnov, "LISP Delegated Database Tree", draft-ietf-lisp- 848 ddt-09 (work in progress), January 2017. 850 [I-D.ietf-lisp-sec] 851 Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D. 852 Saucez, "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-12 853 (work in progress), November 2016. 855 [I-D.portoles-lisp-eid-mobility] 856 Portoles-Comeras, M., Ashtaputre, V., Moreno, V., Maino, 857 F., and D. Farinacci, "LISP L2/L3 EID Mobility Using a 858 Unified Control Plane", draft-portoles-lisp-eid- 859 mobility-02 (work in progress), April 2017. 861 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 862 Locator/ID Separation Protocol (LISP)", RFC 6830, 863 DOI 10.17487/RFC6830, January 2013, 864 . 866 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 867 Locator/ID Separation Protocol (LISP) for Multicast 868 Environments", RFC 6831, DOI 10.17487/RFC6831, January 869 2013, . 871 [RFC6833] Fuller, V. and D. Farinacci, "Locator/ID Separation 872 Protocol (LISP) Map-Server Interface", RFC 6833, 873 DOI 10.17487/RFC6833, January 2013, 874 . 876 [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 877 Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, 878 February 2017, . 880 [RFC8061] Farinacci, D. and B. Weis, "Locator/ID Separation Protocol 881 (LISP) Data-Plane Confidentiality", RFC 8061, 882 DOI 10.17487/RFC8061, February 2017, 883 . 885 Appendix A. Document Change Log 887 A.1. Changes to draft-ietf-lisp-signal-free-multicast-03 889 o Posted April 2017. 891 o Add "Multi-Homing Considerations" section to describe the case 892 where a source LISP site has multiple ITRs and the multicast 893 distribution tree at the source site branches to more than one 894 ITR. And at receiver sites where there are multiple ETRs and 895 multiple RLOCs per ETR. 897 A.2. Changes to draft-ietf-lisp-signal-free-multicast-02 899 o Posted October 2016. 901 o Updated document expiration timer. 903 A.3. Changes to draft-ietf-lisp-signal-free-multicast-01 905 o Posted April 2016. 907 o Add text to define RTRs and indicate how RTR level number is used 908 for LISP-RE. 910 o Draw figure 2 that shows a LISP-RE topology. 912 o Indicate that PIM-ASM or (*,G) trees can be supported in LISP 913 Signal-Free Multicast. 915 A.4. Changes to draft-ietf-lisp-signal-free-multicast-00 917 o Posted late December 2015. 919 o Converted draft-farinacci-lisp-signal-free-multicast-04 into LISP 920 working group draft. 922 A.5. Changes to draft-farinacci-lisp-signal-free-multicast-04 924 o Posted early December 2015. 926 o Update references and document timer. 928 A.6. Changes to draft-farinacci-lisp-signal-free-multicast-03 930 o Posted June 2015. 932 o Update references and document timer. 934 A.7. Changes to draft-farinacci-lisp-signal-free-multicast-02 936 o Posted December 2014. 938 o Added section about how LISP-RE can use the mechanisms from 939 signal-free-multicast so we can avoid head-end replication and 940 avoid signalling across a layered RE topology. 942 A.8. Changes to draft-farinacci-lisp-signal-free-multicast-01 944 o Posted June 2014. 946 o Changes based on implementation experience of this draft. 948 A.9. Changes to draft-farinacci-lisp-signal-free-multicast-00 950 o Posted initial draft February 2014. 952 Authors' Addresses 954 Victor Moreno 955 Cisco Systems 956 170 Tasman Drive 957 San Jose, California 95134 958 USA 960 Email: vimoreno@cisco.com 962 Dino Farinacci 963 lispers.net 964 San Jose, CA 95120 965 USA 967 Email: farinacci@gmail.com