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Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Unused Reference: 'I-D.ietf-lisp-eid-anonymity' is defined on line 580, but no explicit reference was found in the text ** Obsolete normative reference: RFC 6830 (Obsoleted by RFC 9300, RFC 9301) == Outdated reference: A later version (-15) exists of draft-farinacci-lisp-geo-10 == Outdated reference: A later version (-16) exists of draft-ietf-lisp-eid-anonymity-09 == Outdated reference: A later version (-13) exists of draft-ietf-lisp-eid-mobility-07 == Outdated reference: A later version (-29) exists of draft-ietf-lisp-sec-22 Summary: 1 error (**), 0 flaws (~~), 6 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group D. Farinacci 3 Internet-Draft lispers.net 4 Intended status: Experimental P. Pillay-Esnault 5 Expires: October 28, 2021 Independent 6 April 26, 2021 8 LISP Predictive RLOCs 9 draft-ietf-lisp-predictive-rlocs-08 11 Abstract 13 This specification describes a method to achieve near-zero packet 14 loss when an EID is roaming quickly across RLOCs. 16 Requirements Language 18 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 19 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 20 document are to be interpreted as described in [RFC2119]. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at https://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on October 28, 2021. 39 Copyright Notice 41 Copyright (c) 2021 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (https://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 3 58 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3 59 4. Design Details . . . . . . . . . . . . . . . . . . . . . . . 5 60 4.1. RLE Encoding . . . . . . . . . . . . . . . . . . . . . . 6 61 4.2. Packet Delivery Optimizations . . . . . . . . . . . . . . 7 62 4.3. Trading Off Replication Cost . . . . . . . . . . . . . . 8 63 5. Directional Paths with Intersections . . . . . . . . . . . . 9 64 6. Multicast Considerations . . . . . . . . . . . . . . . . . . 10 65 7. Multiple Address-Family Considerations . . . . . . . . . . . 11 66 8. Scaling Considerations . . . . . . . . . . . . . . . . . . . 11 67 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 68 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 69 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 70 11.1. Normative References . . . . . . . . . . . . . . . . . . 12 71 11.2. Informative References . . . . . . . . . . . . . . . . . 13 72 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 14 73 Appendix B. Document Change Log . . . . . . . . . . . . . . . . 14 74 B.1. Changes to draft-ietf-lisp-predictive-rlocs-08 . . . . . 14 75 B.2. Changes to draft-ietf-lisp-predictive-rlocs-07 . . . . . 14 76 B.3. Changes to draft-ietf-lisp-predictive-rlocs-06 . . . . . 14 77 B.4. Changes to draft-ietf-lisp-predictive-rlocs-05 . . . . . 14 78 B.5. Changes to draft-ietf-lisp-predictive-rlocs-04 . . . . . 14 79 B.6. Changes to draft-ietf-lisp-predictive-rlocs-03 . . . . . 14 80 B.7. Changes to draft-ietf-lisp-predictive-rlocs-02 . . . . . 15 81 B.8. Changes to draft-ietf-lisp-predictive-rlocs-01 . . . . . 15 82 B.9. Changes to draft-ietf-lisp-predictive-rlocs-00 . . . . . 15 83 B.10. Changes to draft-farinacci-lisp-predictive-rlocs-02 . . . 15 84 B.11. Changes to draft-farinacci-lisp-predictive-rlocs-01 . . . 15 85 B.12. Changes to draft-farinacci-lisp-predictive-rlocs-00 . . . 15 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 88 1. Introduction 90 The LISP architecture [RFC6830] specifies two namespaces, End-Point 91 IDs (EIDs) and Routing Locators (RLOCs). An EID identifies a node in 92 the network and the RLOC indicates the EID's topological location. 93 When an node roams in the network, its EID remains fixed and 94 unchanged but the RLOCs associated with it change to reflect its new 95 topological attachment point. This specification will focus EIDs and 96 RLOCs residing in separate nodes. An EID is assigned to a host node 97 that roams while the RLOCs are assigned to network nodes that stay 98 stationary and are part of the network topology. For example, a set 99 of devices on an aircraft are assigned EIDs, and base stations on the 100 ground attached to the Internet infrastructure are configured as LISP 101 xTRs where their RLOCs are used for the bindings of the EIDs on the 102 aircraft up in the air. 104 The scope of this specification will not emphasize general physical 105 roaming as an aircraft would do in the sky but in a direction that is 106 more predictable such as a train traveling on a track or vehicle that 107 travels along a road. 109 2. Definition of Terms 111 Roaming-EID - is a network node that moves from one topological 112 location in the network to another. The network node uses the 113 same EID when it is roaming. That is, the EID address does not 114 change for reasons of mobility. A roaming-EID can also be a 115 roaming EID-prefix where a set of EIDs covered by the prefix are 116 all roaming and fate-sharing the same set of RLOCs at the same 117 time. 119 Predictive RLOCs - is a set of ordered RLOCs in a list each assigned 120 to LISP xTRs where the next RLOC in the list has high probability 121 it will be the next LISP xTR in a physical path going in a single 122 predictable direction. 124 Road-Side-Units (RSUs) - is a network node that acts as a router, 125 more specifically as a LISP xTR. The xTR automatically discovers 126 roaming-EIDs that come into network connectivity range and relays 127 packets to and from the roaming-EID. RSUs are typically deployed 128 along a directional path like a train track or road and are in 129 connectivity range of devices that travel along the directional 130 path. 132 3. Overview 134 The goal of this specification is to describe a make-before-break 135 EID-mobility mechanism that offers near-zero packet loss. Offering 136 minimal packet loss, not only allows transport layers to operate more 137 efficiently, but because an EID does not change while moving, 138 transport layer session continuity is maintained. To achieve these 139 requirements, a mechanism that reacts to the mobility event is 140 necessary but not sufficient. So the question is not that there 141 isn't a reaction but when it happens. By using some predictive 142 algorithms, we can guess with high probability where the EID will 143 roam to next. We can achieve this to a point where packet data will 144 be at the new location when the EID arrives. 146 First we should examine both the send and receive directions with 147 respect to the roaming-EID. Refer to Figure 1 for discussion. We 148 show a network node with a fixed EID address assigned to a roaming- 149 EID moving along a train track. And there are LISP xTRs deployed as 150 Road-Side-Units to support the connectivity between the roaming-EID 151 and the infrastructure or to another roaming-EID. 153 Roaming-EID ----> 155 ====//====//====//====//====//====//====//====//===//====//====//==== 156 // // // // // // // // // // // 157 ====//====//====//====//====//====//====//====//===//====//====//==== 159 xTR xTR xTR xTR xTR xTR 160 A B C D E F 162 Figure 1: Directional Mobility 164 For the send direction from roaming-EID to any destination can be 165 accomplish as a local decision. As long as the roaming-EID is in 166 signal range to any xTR along the path, it can use it to forward 167 packets. The LISP xTR, acting as an ITR, can forward packets to 168 destinations in non-LISP sites as well as to stationary and roaming 169 EIDs in LISP sites. This is accomplished by using the LISP overlay 170 via dynamic packet encapsulation. When the roaming-EID sends 171 packets, the LISP xTR must discover the EID and MAY register the EID 172 with a set of RLOCs to the mapping system 173 [I-D.ietf-lisp-eid-mobility]. The discovery process is important 174 because the LISP xTR, acting as an ETR for decapsulating packets that 175 arrive, needs to know what local ports or radios to send packets to 176 the roaming-EID. 178 Much of the focus of this design is on the packet direction to the 179 roaming-EID. And how remote LISP ITRs find the current location 180 (RLOCs) quickly when the roaming-EID is moving at high speed. This 181 specification solves the fast roaming with the introduction of the 182 Predictive-RLOCs algorithm. 184 Since a safe assumption is that the roaming-EID is going in one 185 direction and cannot deviate from it allows us to know a priori the 186 next set of RLOCs the roaming-EID will pass by. Referring to 187 Figure 1, if the roaming-EID is in range near xTR-A, then as it 188 moves, it will at some point pass by xTR-B and xTR-C, and so on. As 189 the roaming-EID moves, one could time when the EID is mapped to RLOC 190 A, and when it should change to RLOC B and so on. However, the speed 191 of movement of the roaming-EID won't be constant and the variables 192 involved in consistent timing cannot be relied on. Furthermore, 193 timing the move is not a make-before-break algorithm, meaning the 194 reaction of the binding happens at the time the roaming-EID is 195 discovered by an xTR. One cannot achieve fast hand-offs when message 196 signaling will be required to inform remote ITRs of the new binding. 198 The Predictive RLOCs algorithm allows a set of RLOCs, in an ordered 199 list, to be provided to remote ITRs so they have the information 200 available and local for when they need to use it. Therefore, no 201 control-plane message signaling occurs when the roaming-EID is 202 discovered by LISP xTRs. 204 4. Design Details 206 Predictive RLOCs accommodates for encapsulated packets to be 207 delivered to Road-Side-Unit LISP xTRs regardless where the roaming- 208 EID is currently positioned. 210 Referring to Figure 1, the following sequence is performed: 212 1. The Predictive RLOCs are registered to the mapping system as a 213 LCAF encoded Replication List Entry (RLE) Type [RFC8060]. The 214 registration can happen by one or more RSUs or by a third-party. 215 When registered by an RSU, and when no coordination is desired, 216 they each register their own RLOC with merge-semantics so the 217 list can be created and maintained in the LISP Map-Server. When 218 registered by a third-party, the complete list of RLOCs can be 219 included in the RLE. 221 2. There can be multiple RLEs present each as different RLOC- 222 records so a remote ITR can select one RLOC-record versus the 223 other based in priority and weight policy [RFC6830]. 225 3. When a remote ITR receives a packet destined for a roaming-EID, 226 it encapsulates and replicates to each RLOC in the RLE thereby 227 delivering the packet to the locations the roaming-EID is about 228 to appear. There are some cases where packets will go to 229 locations where the roaming-EID has already been, but see 230 Section 4.2 for packet delivery optimizations. 232 4. When the ETR resident RSU receives an encapsulated packet, it 233 decapsulates the packet and then determines if the roaming-EID 234 had been previously discovered. If the EID has not been 235 discovered, the ETR drops the packet. Otherwise, the ETR 236 delivers the decapsulated packet on the port interface the 237 roaming-EID was discovered on. 239 4.1. RLE Encoding 241 The LCAF [RFC8060] Replication List Entry (RLE) will be used to 242 encode the Predictive RLOCs in an RLOC-record for Map-Registers, Map- 243 Reply, and Map-Notify messages [RFC6830]. 245 0 1 2 3 246 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 247 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 248 | AFI = 16387 | Rsvd1 | Flags | 249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 250 | Type = 13 | Rsvd2 | 4 + n | 251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 252 | Rsvd3 | Rsvd4 | Level Value | 253 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 254 | AFI = x | RTR/ETR #1 ... | 255 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 256 | Rsvd3 | Rsvd4 | Level Value | 257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 258 | AFI = x | RTR/ETR #n ... | 259 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 261 When the RLOC-record contains an RLE with RLOC entries all with the 262 same level value, it means the physical order listed is the 263 directional path of the RSUs. This will typically be the result of a 264 third-party doing the registration where it knows ahead of time the 265 RSU deployment. 267 When each RSU is registering with merge-semantics on their own, the 268 level number is used to place them in an ordered list. Since the 269 registrations come at different times and therefore arrive in 270 different order than the physical RSU path, the level number creates 271 the necessary sequencing. Each RSU needs to know its position in the 272 path relative to other RSUs. For example, in xTR-B, it would 273 register with level 1 since it is after xTR-A (and before xTR-C). So 274 if the registration order was xTR-B with level 1, xTR-C with level 2, 275 and xTR-A with level 0, the RLE list stored in the mapping system 276 would be (xTR-A, xTR-B, xTR-C). It is recommended that level numbers 277 be assigned in increments of 10 so latter insertion is possible. 279 The use of Geo-Prefixes and Geo-Points [I-D.farinacci-lisp-geo] can 280 be used to compare the physical presence of each RSU with respect to 281 each other, so they can choose level numbers to sequence themselves. 282 Also if the xTRs register with a Geo-Point in an RLOC-record, then 283 perhaps the Map-Server could sequence the RLE list. 285 4.2. Packet Delivery Optimizations 287 Since the remote ITR will replicate to all RLOCs in the RLE, a 288 situation is created where packets go to RLOCs that don't need to. 289 For instance, if the roaming-EID is along side of xTR-B and the RLE 290 is (xTR-A, xTR-B, xTR-C), there is no reason to replicate to xTR-A 291 since the roaming-EID has passed it and the the signal range is weak 292 or lost. However, replicating to xTR-B and xTR-C is important to 293 deliver packets to where the roaming-EID resides and where it is 294 about to go to. 296 A simple data-plane option, which converges fairly quickly is to have 297 the remote xTR, acting as an ETR, when packets are sent from the 298 roaming-EID, examine the source RLOC in the outer header of the 299 encapsulated packet. If the source RLOC is xTR-B, the remote xTR can 300 determine that the roaming-EID has moved past xTR-A and no longer 301 needs to encapsulate packets to xTR-A's RLOC. 303 In addition, the remote ITR can use RLOC-probing to determine if each 304 RLOC in the RLE is reachable. And if not reachable, exclude from the 305 list of RLOCs to replicate to. 307 This solution also handles the case where xTR-A and xTR-B may overlap 308 in radio signal range, but the signal is weak from the roaming-EID to 309 xTR-A but stronger to xTR-B. In this case, the roaming-EID selects 310 xTR-B to send packets that inform the remote xTR that return packets 311 should not be encapsulated to xTR-A. 313 There are also situations where the RSUs are in signal range of each 314 other in which case they could report reachability status of each 315 other. The use of the Locator-Status-Bits of the LISP encapsulation 316 header could be used to convey this information to the remote xTR. 317 This would only occur when the roaming-EID was discovered by both 318 xTR-A and xTR-B so it was possible for either xTR to reach the 319 roaming-EID. Either an IGP like routing protocol would be required 320 to allow each xTR to know the other could reach the roaming-EID or a 321 path trace tool (i.e. traceroute) could be originated by one xTR 322 targeted for the roaming-EID but MAC-forwarded through the other xTR. 323 These and other roaming-EID reachability mechanisms are work in 324 progress and for further study. 326 When a remote ITR is doing "Directional Mobility" and replicating to 327 the last RLOC in the RLE list, it has a decision to guess where the 328 roaming-EID will move to next. Conservatively, an ITR can replicate 329 to the entire set of RLOCs in the RLE list and wait to see if the 330 roaming-EID moves to one of the RLOCs in the RLE list. 332 Or more liberally, the remote ITR can assume the new roaming 333 direction. For example, with an RLE list of (xTR-A, xTR-B, xTR-C, 334 xTR-D) and the roaming-EID is at D, the remote ITR can replicate to 335 all of A, B, C and D to determine where the roaming-EID will move to 336 next. If the roaming-EID moves to C after it was at D, it is 337 possible that the EID is moving in the opposite direction from C to B 338 to A. This would be known as "Back-n-Forth Mobility". If an 339 implementation is configured to support this for a particluar EID, 340 the remote ITR could replicate in this sequence as the roaming-EID 341 moves from A to D and back to A: (A, B, C, D), (B, C, D), (C, D), (D, 342 C, B, A), (C, B, A), (B, A), and again (A, B, C, D). 344 The roaming-EID could be doing "Circular Mobility" where it moves 345 from A to D directionally, next from D-to-A, and then back to A to D 346 directionally again. This form of mobility is just as predicatable 347 as "Back-n-Forth Mobility" since a consistent pattern can be relied 348 on. Both of these mobility forms can be achieved with near-zero 349 packet loss. 351 On the other hand, the roaming-EID can be roaming arbitrarily using 352 "Random Mobility" where it could roam in the following combinations: 353 A-to-B, A-to-C, A-to-D, B-to-A, B-to-C, B-to-D, C-to-A, C-to-B, C-to- 354 D, D-to-A, D-to-B, or D-to-C. In this situation, when a return 355 packet arrives at the ITR, it could then just replicate to where the 356 roaming-EID is at rest and do so for a short period of time before it 357 replciates to the entire RLE list again. Using the wrong time period 358 could lead to packet loss. All these types of mobility can be 359 supported by the remote ITR in a local manner without consulting or 360 depending on any other LISP system. It is left for further study, if 361 any of the mobility types above should be encoded in the mapping 362 system. 364 4.3. Trading Off Replication Cost 366 If RLE lists are large, packet replication can occur to locations 367 well before the roaming-EID arrives. Making RLE lists small is 368 useful without sacrificing hand-off issues or incurring packet loss 369 to the application. By having overlapping RLEs in separate RLOC- 370 records we a simple mechanism to solve this problem. Here is an 371 example mapping entry to illustrate the point: 373 EID = , RLOC-records: 374 RLOC = (RLE: xTR-A, xTR-B) 375 RLOC = (RLE: xTR-B, xTR-C, xTR-D, xTR-E) 376 RLOC = (RLE: xTR-E, xTR-F) 378 When the remote ITR is encapsulating to xTR-B as a decision to use 379 the first RLOC-record, it can decide to move to use the second RLOC- 380 record because xTR-B is the last entry in the first RLOC-record and 381 the first entry in the second RLOC-record. When there are 382 overlapping RLEs, the remote ITR can decide when it is more efficient 383 to switch over. For example, when the roaming-EID is in range of 384 xTR-A, the remote ITR uses the first RLOC-record so the wasted 385 replication cost is to xTR-B only versus a worse cost when using the 386 second RLOC-record. But when the roaming-EID is in range of xTR-B, 387 then replicating to the other xTRs in the second RLOC-record may be 388 crucial if the roaming-EID has increased speed. And when the 389 roaming-EID may be at rest in a parked mode, then the remote ITR 390 encapsulates to only xTR-F using the third RLOC-record since the 391 roaming-EID has moved past xTR-E. 393 In addition, to eliminate unnecessary replication to xTRs further 394 down a directional path, GEO-prefixes [I-D.farinacci-lisp-geo] can be 395 used so only nearby xTRs that the roaming-EID is about to come in 396 contact with are the only ones to receive encapsulated packets. 398 Even when replication lists are not large, we can reduce the cost of 399 replication that the entire network bears by moving the replicator 400 away from the the source (i.e. the ITR) and closer to the RSUs (i.e. 401 the ETRs). See the use of RTRs for Replication Engineering 402 techniques in [RFC8378]. 404 5. Directional Paths with Intersections 406 A roaming-EID could be registered to the mapping system with the 407 following nested RLE mapping: 409 EID = , RLOC-records: 410 RLOC = (RLE: xTR-A, xTR-B, xTR-C, (RLE: xTR-X, xTR-Y, xTR-Z), 411 (RLE: xTR-I, xTR-J, xTR-K), xTR-D, xTR-E) 413 The mapping entry above describes 3 directional paths where the 414 ordered list has encoded one-level of two nested RLEs to denote 415 intersections in a horizontal path. Which is drawn as: 417 | | xTR-K 418 | | 419 | | 420 | | xTR-J 421 | | 422 | | 423 Roaming | | xTR-I 424 EID ----> | | 425 --------------------------------------- ------------------------------ 426 --------------------------------------- ------------------------------ 427 xTR-A xTR-B xTR-C | | xTR-D xTR-E 428 | | 429 | | xTR-X 430 | | 431 | | 432 | | xTR-Y 433 | | 434 | | 435 | | xTR-Z 437 When the roaming-EID is on the horizontal path, the remote-ITRs 438 typically replicate to the rest the of the xTRs in the ordered list. 439 When a list has nested RLEs, the replication should occur to at least 440 the first RLOC in a nested RLE list. So if the remote-ITR is 441 replicating to xTR-C, xTR-D, and xTR-E, it should also replicate to 442 xTR-X and xTR-I anticipating a possible turn at the intersection. 443 But when the roaming-EID is known to be at xTR-D (a left or right 444 hand turn was not taken), replication should only occur to xTR-D and 445 xTR-E. Once either xTR-I or xTR-X is determined to be where the 446 roaming-EID resides, then the replication occurs on the respective 447 directional path only. 449 When nested RLEs are used it may be difficult to get merge-semantics 450 to work when each xTR registers itself. So it is suggested a third- 451 party registers nested RLEs. It is left to further study to 452 understand better how to automate this. 454 6. Multicast Considerations 456 In this design, the remote ITR is receiving a unicast packet from an 457 EID and replicating and encapsulating to each RLOC in an RLE list. 458 This form of replication is no different than a traditional multicast 459 replication function. So replicating multicast packets in the same 460 fashion is a fallout from this design. 462 If there are multiple roaming-EIDs joined to the same multicast group 463 but reside at different RSUs, a merge has to be done of any pruned 464 RLEs used for forwarding. So if roaming-EID-1 resides at xTR-A and 465 roaming-EID-2 resides at xTR-B and the RLE list is (xTR-A, xTR-B, 466 xTR-C), and they are joined to the same multicast group, then 467 replication occurs to all of xTR-A, xTR-B, and xTR-C. Even since 468 roaming-EID-2 is past xTR-A, packets need to be delivered to xTR-A 469 for roaming-EID-1. In addition, packets need to be delivered to 470 xTR-C because roaming-EID-1 and roaming-EID-2 will get to xTR-C (and 471 roaming-EID-1 may get there sooner if it is traveling faster than 472 roaming-EID-2). 474 When a roaming-EID is a multicast source, procedures from [RFC8378] 475 are used to deliver packets to multicast group members anywhere in 476 the network. The solution requires no signaling to the RSUs. When 477 RSUs receive multicast packets from a roaming-EID, they do a 478 (roaming-EID,G) mapping database lookup to find the replication list 479 of ETRs to encapsulate to. 481 7. Multiple Address-Family Considerations 483 Note that roaming-EIDs can be assigned IPv6 EID addresses while the 484 RSU xTRs could be using IPv4 RLOC addresses. Any combination of 485 address-families can be supported as well as for multicast packet 486 forwarding, where (S,G) are IPv6 addresses entries and replication is 487 done with IPv4 RLOCs in the outer header. 489 8. Scaling Considerations 491 One can imagine there will be a large number of roaming-EIDs. So 492 there is a strong desire to efficiently store state in the mapping 493 database and the in remote ITRs map-caches. It is likely, that 494 roaming-EIDs may share the same path and move at the same speed (EID 495 devices on a train) and therefore share the same Predictive RLOCs. 496 And since EIDs are not reassigned for mobility purposes or may be 497 temporal , they will not be topologically aggregatable, so they 498 cannot compress into a single EID-prefix mapping entry that share the 499 same RLOC-set. 501 By using a level of indirection with the mapping system this problem 502 can be solved. The following mapping entries could exist in the 503 mapping database: 505 EID = , RLOC-records: 506 RLOC = (afi=: "am-train-to-paris") 507 EID = , RLOC-records: 508 RLOC = (afi=: "am-train-to-paris") 509 EID = , RLOC-records: 510 RLOC = (afi=: "am-train-to-paris") 512 EID = "am-train-to-paris", RLOC-records: 513 RLOC = (afi=lcaf/RLE-type: xTR-A, xTR-B, xTR-C) 515 EID = "am-train-to-paris-passengers", RLOC-records: 516 RLOC = (afi=lcaf/afi-list-type: , , ) 518 Each passenger that boards a train has their EID registered to point 519 to the name of the train "am-train-to-paris". And then the train 520 with EID "am-train-to-paris" stores the Predictive RLOC-set. When a 521 remote-ITR wants to encapsulate packets for an EID, it looks up the 522 EID in the mapping database gets the name "am-train-to-paris" 523 returned. Then the remote-ITR does another lookup for the name "am- 524 train-to-paris" to get the RLE list returned. 526 When new EIDs board the train, the RLE mapping entry does not need to 527 be modified. Only an EID-to-name mapping is registered for the 528 specific new EID. Optionally, another name "am-train-to-paris- 529 passengers" can be registered as an EID to allow mapping to all 530 specific EIDs which are on the train. This can be used for 531 inventory, billing, or security purposes. 533 This optimization comes at a cost of a 2-stage lookup. However, if 534 both sets of mapping entries are registered to the same Map-Server, a 535 combined RLOC-set could be returned. This idea is for further study. 537 9. Security Considerations 539 LISP has procedures for supporting both control-plane security 540 [I-D.ietf-lisp-sec] and data-plane security [RFC8061]. 542 10. IANA Considerations 544 At this time there are no requests for IANA. 546 11. References 548 11.1. Normative References 550 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 551 Requirement Levels", BCP 14, RFC 2119, 552 DOI 10.17487/RFC2119, March 1997, 553 . 555 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 556 Locator/ID Separation Protocol (LISP)", RFC 6830, 557 DOI 10.17487/RFC6830, January 2013, 558 . 560 [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 561 Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, 562 February 2017, . 564 [RFC8061] Farinacci, D. and B. Weis, "Locator/ID Separation Protocol 565 (LISP) Data-Plane Confidentiality", RFC 8061, 566 DOI 10.17487/RFC8061, February 2017, 567 . 569 [RFC8378] Moreno, V. and D. Farinacci, "Signal-Free Locator/ID 570 Separation Protocol (LISP) Multicast", RFC 8378, 571 DOI 10.17487/RFC8378, May 2018, 572 . 574 11.2. Informative References 576 [I-D.farinacci-lisp-geo] 577 Farinacci, D., "LISP Geo-Coordinate Use-Cases", draft- 578 farinacci-lisp-geo-10 (work in progress), October 2020. 580 [I-D.ietf-lisp-eid-anonymity] 581 Farinacci, D., Pillay-Esnault, P., and W. Haddad, "LISP 582 EID Anonymity", draft-ietf-lisp-eid-anonymity-09 (work in 583 progress), October 2020. 585 [I-D.ietf-lisp-eid-mobility] 586 Portoles-Comeras, M., Ashtaputre, V., Moreno, V., Maino, 587 F., and D. Farinacci, "LISP L2/L3 EID Mobility Using a 588 Unified Control Plane", draft-ietf-lisp-eid-mobility-07 589 (work in progress), January 2021. 591 [I-D.ietf-lisp-sec] 592 Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D. 593 Saucez, "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-22 594 (work in progress), January 2021. 596 Appendix A. Acknowledgments 598 The author would like to thank the LISP WG for their review and 599 acceptance of this draft. 601 Appendix B. Document Change Log 603 [RFC Editor: Please delete this section on publication as RFC.] 605 B.1. Changes to draft-ietf-lisp-predictive-rlocs-08 607 o Posted March 2021. 609 o Update document timer and references. 611 B.2. Changes to draft-ietf-lisp-predictive-rlocs-07 613 o Posted November 2020. 615 o Update document timer and references. 617 B.3. Changes to draft-ietf-lisp-predictive-rlocs-06 619 o Posted May 2020. 621 o Update document timer and references. 623 B.4. Changes to draft-ietf-lisp-predictive-rlocs-05 625 o Posted November 2019. 627 o Update document timer and references. 629 B.5. Changes to draft-ietf-lisp-predictive-rlocs-04 631 o Posted May 2019. 633 o Update document timer and references. 635 B.6. Changes to draft-ietf-lisp-predictive-rlocs-03 637 o Posted November 2018. 639 o Update document timer and references. 641 B.7. Changes to draft-ietf-lisp-predictive-rlocs-02 643 o Posted May 2018. 645 o Update document timer and references. 647 B.8. Changes to draft-ietf-lisp-predictive-rlocs-01 649 o Posted November 2017. 651 o Update document timer and references. 653 o Reflect comments from Prague meeting presentation. There is no 654 need for "RLE Usage Types" as suggested. The ITR can treat what 655 RLOCs it replicates to as a local matter via implementation 656 configuration. RLE Directional is default. Circular rotation, 657 back-n-forth, and random selection of RLOCs is up to the ITR. 659 B.9. Changes to draft-ietf-lisp-predictive-rlocs-00 661 o Posted June 2017. 663 o Make this specification a working group document. It is a copy of 664 draft-farinacci-lisp-predictive-rlocs-02. 666 B.10. Changes to draft-farinacci-lisp-predictive-rlocs-02 668 o Posted May 2017 to update document timer. 670 B.11. Changes to draft-farinacci-lisp-predictive-rlocs-01 672 o Posted November 2016 to update document timer. 674 B.12. Changes to draft-farinacci-lisp-predictive-rlocs-00 676 o Initial post April 2016. 678 Authors' Addresses 680 Dino Farinacci 681 lispers.net 682 San Jose, CA 683 USA 685 Email: farinacci@gmail.com 686 Padma Pillay-Esnault 687 Independent 688 San Clara, CA 689 USA 691 Email: padma.ietf@gmail.com