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Checking references for intended status: Experimental ---------------------------------------------------------------------------- == Unused Reference: 'I-D.ietf-lisp-eid-anonymity' is defined on line 576, 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explicit reference was found in the text ** Obsolete normative reference: RFC 6830 (Obsoleted by RFC 9300, RFC 9301) == Outdated reference: A later version (-15) exists of draft-farinacci-lisp-geo-07 == Outdated reference: A later version (-16) exists of draft-ietf-lisp-eid-anonymity-06 == Outdated reference: A later version (-13) exists of draft-ietf-lisp-eid-mobility-03 == Outdated reference: A later version (-29) exists of draft-ietf-lisp-sec-17 Summary: 1 error (**), 0 flaws (~~), 6 warnings (==), 1 comment (--).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: November 16, 2019 Huawei Technologies 6 May 15, 2019 8 LISP Predictive RLOCs 9 draft-ietf-lisp-predictive-rlocs-04 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 November 16, 2019. 39 Copyright Notice 41 Copyright (c) 2019 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-04 . . . . . 14 75 B.2. Changes to draft-ietf-lisp-predictive-rlocs-03 . . . . . 14 76 B.3. Changes to draft-ietf-lisp-predictive-rlocs-02 . . . . . 14 77 B.4. Changes to draft-ietf-lisp-predictive-rlocs-01 . . . . . 14 78 B.5. Changes to draft-ietf-lisp-predictive-rlocs-00 . . . . . 14 79 B.6. Changes to draft-farinacci-lisp-predictive-rlocs-02 . . . 15 80 B.7. Changes to draft-farinacci-lisp-predictive-rlocs-01 . . . 15 81 B.8. Changes to draft-farinacci-lisp-predictive-rlocs-00 . . . 15 82 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 84 1. Introduction 86 The LISP architecture [RFC6830] specifies two namespaces, End-Point 87 IDs (EIDs) and Routing Locators (RLOCs). An EID identifies a node in 88 the network and the RLOC indicates the EID's topological location. 89 When an node roams in the network, its EID remains fixed and 90 unchanged but the RLOCs associated with it change to reflect its new 91 topological attachment point. This specification will focus EIDs and 92 RLOCs residing in separate nodes. An EID is assigned to a host node 93 that roams while the RLOCs are assigned to network nodes that stay 94 stationary and are part of the network topology. For example, a set 95 of devices on an aircraft are assigned EIDs, and base stations on the 96 ground attached to the Internet infrastructure are configured as LISP 97 xTRs where their RLOCs are used for the bindings of the EIDs on the 98 aircraft up in the air. 100 The scope of this specification will not emphasize general physical 101 roaming as an aircraft would do in the sky but in a direction that is 102 more predictable such as a train traveling on a track or vehicle that 103 travels along a road. 105 2. Definition of Terms 107 Roaming-EID - is a network node that moves from one topological 108 location in the network to another. The network node uses the 109 same EID when it is roaming. That is, the EID address does not 110 change for reasons of mobility. A roaming-EID can also be a 111 roaming EID-prefix where a set of EIDs covered by the prefix are 112 all roaming and fate-sharing the same set of RLOCs at the same 113 time. 115 Predictive RLOCs - is a set of ordered RLOCs in a list each assigned 116 to LISP xTRs where the next RLOC in the list has high probability 117 it will be the next LISP xTR in a physical path going in a single 118 predictable direction. 120 Road-Side-Units (RSUs) - is a network node that acts as a router, 121 more specifically as a LISP xTR. The xTR automatically discovers 122 roaming-EIDs that come into network connectivity range and relays 123 packets to and from the roaming-EID. RSUs are typically deployed 124 along a directional path like a train track or road and are in 125 connectivity range of devices that travel along the directional 126 path. 128 3. Overview 130 The goal of this specification is to describe a make-before-break 131 EID-mobility mechanism that offers near-zero packet loss. Offering 132 minimal packet loss, not only allows transport layers to operate more 133 efficiently, but because an EID does not change while moving, 134 transport layer session continuity is maintained. To achieve these 135 requirements, a mechanism that reacts to the mobility event is 136 necessary but not sufficient. So the question is not that there 137 isn't a reaction but when it happens. By using some predictive 138 algorithms, we can guess with high probability where the EID will 139 roam to next. We can achieve this to a point where packet data will 140 be at the new location when the EID arrives. 142 First we should examine both the send and receive directions with 143 respect to the roaming-EID. Refer to Figure 1 for discussion. We 144 show a network node with a fixed EID address assigned to a roaming- 145 EID moving along a train track. And there are LISP xTRs deployed as 146 Road-Side-Units to support the connectivity between the roaming-EID 147 and the infrastructure or to another roaming-EID. 149 Roaming-EID ----> 151 ====//====//====//====//====//====//====//====//===//====//====//==== 152 // // // // // // // // // // // 153 ====//====//====//====//====//====//====//====//===//====//====//==== 155 xTR xTR xTR xTR xTR xTR 156 A B C D E F 158 Figure 1: Directional Mobility 160 For the send direction from roaming-EID to any destination can be 161 accomplish as a local decision. As long as the roaming-EID is in 162 signal range to any xTR along the path, it can use it to forward 163 packets. The LISP xTR, acting as an ITR, can forward packets to 164 destinations in non-LISP sites as well as to stationary and roaming 165 EIDs in LISP sites. This is accomplished by using the LISP overlay 166 via dynamic packet encapsulation. When the roaming-EID sends 167 packets, the LISP xTR must discover the EID and MAY register the EID 168 with a set of RLOCs to the mapping system 169 [I-D.ietf-lisp-eid-mobility]. The discovery process is important 170 because the LISP xTR, acting as an ETR for decapsulating packets that 171 arrive, needs to know what local ports or radios to send packets to 172 the roaming-EID. 174 Much of the focus of this design is on the packet direction to the 175 roaming-EID. And how remote LISP ITRs find the current location 176 (RLOCs) quickly when the roaming-EID is moving at high speed. This 177 specification solves the fast roaming with the introduction of the 178 Predictive-RLOCs algorithm. 180 Since a safe assumption is that the roaming-EID is going in one 181 direction and cannot deviate from it allows us to know a priori the 182 next set of RLOCs the roaming-EID will pass by. Referring to 183 Figure 1, if the roaming-EID is in range near xTR-A, then as it 184 moves, it will at some point pass by xTR-B and xTR-C, and so on. As 185 the roaming-EID moves, one could time when the EID is mapped to RLOC 186 A, and when it should change to RLOC B and so on. However, the speed 187 of movement of the roaming-EID won't be constant and the variables 188 involved in consistent timing cannot be relied on. Furthermore, 189 timing the move is not a make-before-break algorithm, meaning the 190 reaction of the binding happens at the time the roaming-EID is 191 discovered by an xTR. One cannot achieve fast hand-offs when message 192 signaling will be required to inform remote ITRs of the new binding. 194 The Predictive RLOCs algorithm allows a set of RLOCs, in an ordered 195 list, to be provided to remote ITRs so they have the information 196 available and local for when they need to use it. Therefore, no 197 control-plane message signaling occurs when the roaming-EID is 198 discovered by LISP xTRs. 200 4. Design Details 202 Predictive RLOCs accommodates for encapsulated packets to be 203 delivered to Road-Side-Unit LISP xTRs regardless where the roaming- 204 EID is currently positioned. 206 Referring to Figure 1, the following sequence is performed: 208 1. The Predictive RLOCs are registered to the mapping system as a 209 LCAF encoded Replication List Entry (RLE) Type [RFC8060]. The 210 registration can happen by one or more RSUs or by a third-party. 211 When registered by an RSU, and when no coordination is desired, 212 they each register their own RLOC with merge-semantics so the 213 list can be created and maintained in the LISP Map-Server. When 214 registered by a third-party, the complete list of RLOCs can be 215 included in the RLE. 217 2. There can be multiple RLEs present each as different RLOC- 218 records so a remote ITR can select one RLOC-record versus the 219 other based in priority and weight policy [RFC6830]. 221 3. When a remote ITR receives a packet destined for a roaming-EID, 222 it encapsulates and replicates to each RLOC in the RLE thereby 223 delivering the packet to the locations the roaming-EID is about 224 to appear. There are some cases where packets will go to 225 locations where the roaming-EID has already been, but see 226 Section 4.2 for packet delivery optimizations. 228 4. When the ETR resident RSU receives an encapsulated packet, it 229 decapsulates the packet and then determines if the roaming-EID 230 had been previously discovered. If the EID has not been 231 discovered, the ETR drops the packet. Otherwise, the ETR 232 delivers the decapsulated packet on the port interface the 233 roaming-EID was discovered on. 235 4.1. RLE Encoding 237 The LCAF [RFC8060] Replication List Entry (RLE) will be used to 238 encode the Predictive RLOCs in an RLOC-record for Map-Registers, Map- 239 Reply, and Map-Notify messages [RFC6830]. 241 0 1 2 3 242 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 1 243 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 244 | AFI = 16387 | Rsvd1 | Flags | 245 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 246 | Type = 13 | Rsvd2 | 4 + n | 247 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 248 | Rsvd3 | Rsvd4 | Level Value | 249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 250 | AFI = x | RTR/ETR #1 ... | 251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 252 | Rsvd3 | Rsvd4 | Level Value | 253 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 254 | AFI = x | RTR/ETR #n ... | 255 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 257 When the RLOC-record contains an RLE with RLOC entries all with the 258 same level value, it means the physical order listed is the 259 directional path of the RSUs. This will typically be the result of a 260 third-party doing the registration where it knows ahead of time the 261 RSU deployment. 263 When each RSU is registering with merge-semantics on their own, the 264 level number is used to place them in an ordered list. Since the 265 registrations come at different times and therefore arrive in 266 different order than the physical RSU path, the level number creates 267 the necessary sequencing. Each RSU needs to know its position in the 268 path relative to other RSUs. For example, in xTR-B, it would 269 register with level 1 since it is after xTR-A (and before xTR-C). So 270 if the registration order was xTR-B with level 1, xTR-C with level 2, 271 and xTR-A with level 0, the RLE list stored in the mapping system 272 would be (xTR-A, xTR-B, xTR-C). It is recommended that level numbers 273 be assigned in increments of 10 so latter insertion is possible. 275 The use of Geo-Prefixes and Geo-Points [I-D.farinacci-lisp-geo] can 276 be used to compare the physical presence of each RSU with respect to 277 each other, so they can choose level numbers to sequence themselves. 278 Also if the xTRs register with a Geo-Point in an RLOC-record, then 279 perhaps the Map-Server could sequence the RLE list. 281 4.2. Packet Delivery Optimizations 283 Since the remote ITR will replicate to all RLOCs in the RLE, a 284 situation is created where packets go to RLOCs that don't need to. 285 For instance, if the roaming-EID is along side of xTR-B and the RLE 286 is (xTR-A, xTR-B, xTR-C), there is no reason to replicate to xTR-A 287 since the roaming-EID has passed it and the the signal range is weak 288 or lost. However, replicating to xTR-B and xTR-C is important to 289 deliver packets to where the roaming-EID resides and where it is 290 about to go to. 292 A simple data-plane option, which converges fairly quickly is to have 293 the remote xTR, acting as an ETR, when packets are sent from the 294 roaming-EID, examine the source RLOC in the outer header of the 295 encapsulated packet. If the source RLOC is xTR-B, the remote xTR can 296 determine that the roaming-EID has moved past xTR-A and no longer 297 needs to encapsulate packets to xTR-A's RLOC. 299 In addition, the remote ITR can use RLOC-probing to determine if each 300 RLOC in the RLE is reachable. And if not reachable, exclude from the 301 list of RLOCs to replicate to. 303 This solution also handles the case where xTR-A and xTR-B may overlap 304 in radio signal range, but the signal is weak from the roaming-EID to 305 xTR-A but stronger to xTR-B. In this case, the roaming-EID selects 306 xTR-B to send packets that inform the remote xTR that return packets 307 should not be encapsulated to xTR-A. 309 There are also situations where the RSUs are in signal range of each 310 other in which case they could report reachability status of each 311 other. The use of the Locator-Status-Bits of the LISP encapsulation 312 header could be used to convey this information to the remote xTR. 313 This would only occur when the roaming-EID was discovered by both 314 xTR-A and xTR-B so it was possible for either xTR to reach the 315 roaming-EID. Either an IGP like routing protocol would be required 316 to allow each xTR to know the other could reach the roaming-EID or a 317 path trace tool (i.e. traceroute) could be originated by one xTR 318 targeted for the roaming-EID but MAC-forwarded through the other xTR. 319 These and other roaming-EID reachability mechanisms are work in 320 progress and for further study. 322 When a remote ITR is doing "Directional Mobility" and replicating to 323 the last RLOC in the RLE list, it has a decision to guess where the 324 roaming-EID will move to next. Conservatively, an ITR can replicate 325 to the entire set of RLOCs in the RLE list and wait to see if the 326 roaming-EID moves to one of the RLOCs in the RLE list. 328 Or more liberally, the remote ITR can assume the new roaming 329 direction. For example, with an RLE list of (xTR-A, xTR-B, xTR-C, 330 xTR-D) and the roaming-EID is at D, the remote ITR can replicate to 331 all of A, B, C and D to determine where the roaming-EID will move to 332 next. If the roaming-EID moves to C after it was at D, it is 333 possible that the EID is moving in the opposite direction from C to B 334 to A. This would be known as "Back-n-Forth Mobility". If an 335 implementation is configured to support this for a particluar EID, 336 the remote ITR could replicate in this sequence as the roaming-EID 337 moves from A to D and back to A: (A, B, C, D), (B, C, D), (C, D), (D, 338 C, B, A), (C, B, A), (B, A), and again (A, B, C, D). 340 The roaming-EID could be doing "Circular Mobility" where it moves 341 from A to D directionally, next from D-to-A, and then back to A to D 342 directionally again. This form of mobility is just as predicatable 343 as "Back-n-Forth Mobility" since a consistent pattern can be relied 344 on. Both of these mobility forms can be achieved with near-zero 345 packet loss. 347 On the other hand, the roaming-EID can be roaming arbitrarily using 348 "Random Mobility" where it could roam in the following combinations: 349 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- 350 D, D-to-A, D-to-B, or D-to-C. In this situation, when a return 351 packet arrives at the ITR, it could then just replicate to where the 352 roaming-EID is at rest and do so for a short period of time before it 353 replciates to the entire RLE list again. Using the wrong time period 354 could lead to packet loss. All these types of mobility can be 355 supported by the remote ITR in a local manner without consulting or 356 depending on any other LISP system. It is left for further study, if 357 any of the mobility types above should be encoded in the mapping 358 system. 360 4.3. Trading Off Replication Cost 362 If RLE lists are large, packet replication can occur to locations 363 well before the roaming-EID arrives. Making RLE lists small is 364 useful without sacrificing hand-off issues or incurring packet loss 365 to the application. By having overlapping RLEs in separate RLOC- 366 records we a simple mechanism to solve this problem. Here is an 367 example mapping entry to illustrate the point: 369 EID = , RLOC-records: 370 RLOC = (RLE: xTR-A, xTR-B) 371 RLOC = (RLE: xTR-B, xTR-C, xTR-D, xTR-E) 372 RLOC = (RLE: xTR-E, xTR-F) 374 When the remote ITR is encapsulating to xTR-B as a decision to use 375 the first RLOC-record, it can decide to move to use the second RLOC- 376 record because xTR-B is the last entry in the first RLOC-record and 377 the first entry in the second RLOC-record. When there are 378 overlapping RLEs, the remote ITR can decide when it is more efficient 379 to switch over. For example, when the roaming-EID is in range of 380 xTR-A, the remote ITR uses the first RLOC-record so the wasted 381 replication cost is to xTR-B only versus a worse cost when using the 382 second RLOC-record. But when the roaming-EID is in range of xTR-B, 383 then replicating to the other xTRs in the second RLOC-record may be 384 crucial if the roaming-EID has increased speed. And when the 385 roaming-EID may be at rest in a parked mode, then the remote ITR 386 encapsulates to only xTR-F using the third RLOC-record since the 387 roaming-EID has moved past xTR-E. 389 In addition, to eliminate unnecessary replication to xTRs further 390 down a directional path, GEO-prefixes [I-D.farinacci-lisp-geo] can be 391 used so only nearby xTRs that the roaming-EID is about to come in 392 contact with are the only ones to receive encapsulated packets. 394 Even when replication lists are not large, we can reduce the cost of 395 replication that the entire network bears by moving the replicator 396 away from the the source (i.e. the ITR) and closer to the RSUs (i.e. 397 the ETRs). See the use of RTRs for Replication Engineering 398 techniques in [RFC8378]. 400 5. Directional Paths with Intersections 402 A roaming-EID could be registered to the mapping system with the 403 following nested RLE mapping: 405 EID = , RLOC-records: 406 RLOC = (RLE: xTR-A, xTR-B, xTR-C, (RLE: xTR-X, xTR-Y, xTR-Z), 407 (RLE: xTR-I, xTR-J, xTR-K), xTR-D, xTR-E) 409 The mapping entry above describes 3 directional paths where the 410 ordered list has encoded one-level of two nested RLEs to denote 411 intersections in a horizontal path. Which is drawn as: 413 | | xTR-K 414 | | 415 | | 416 | | xTR-J 417 | | 418 | | 419 Roaming | | xTR-I 420 EID ----> | | 421 --------------------------------------- ------------------------------ 422 --------------------------------------- ------------------------------ 423 xTR-A xTR-B xTR-C | | xTR-D xTR-E 424 | | 425 | | xTR-X 426 | | 427 | | 428 | | xTR-Y 429 | | 430 | | 431 | | xTR-Z 433 When the roaming-EID is on the horizontal path, the remote-ITRs 434 typically replicate to the rest the of the xTRs in the ordered list. 435 When a list has nested RLEs, the replication should occur to at least 436 the first RLOC in a nested RLE list. So if the remote-ITR is 437 replicating to xTR-C, xTR-D, and xTR-E, it should also replicate to 438 xTR-X and xTR-I anticipating a possible turn at the intersection. 439 But when the roaming-EID is known to be at xTR-D (a left or right 440 hand turn was not taken), replication should only occur to xTR-D and 441 xTR-E. Once either xTR-I or xTR-X is determined to be where the 442 roaming-EID resides, then the replication occurs on the respective 443 directional path only. 445 When nested RLEs are used it may be difficult to get merge-semantics 446 to work when each xTR registers itself. So it is suggested a third- 447 party registers nested RLEs. It is left to further study to 448 understand better how to automate this. 450 6. Multicast Considerations 452 In this design, the remote ITR is receiving a unicast packet from an 453 EID and replicating and encapsulating to each RLOC in an RLE list. 454 This form of replication is no different than a traditional multicast 455 replication function. So replicating multicast packets in the same 456 fashion is a fallout from this design. 458 If there are multiple roaming-EIDs joined to the same multicast group 459 but reside at different RSUs, a merge has to be done of any pruned 460 RLEs used for forwarding. So if roaming-EID-1 resides at xTR-A and 461 roaming-EID-2 resides at xTR-B and the RLE list is (xTR-A, xTR-B, 462 xTR-C), and they are joined to the same multicast group, then 463 replication occurs to all of xTR-A, xTR-B, and xTR-C. Even since 464 roaming-EID-2 is past xTR-A, packets need to be delivered to xTR-A 465 for roaming-EID-1. In addition, packets need to be delivered to 466 xTR-C because roaming-EID-1 and roaming-EID-2 will get to xTR-C (and 467 roaming-EID-1 may get there sooner if it is traveling faster than 468 roaming-EID-2). 470 When a roaming-EID is a multicast source, procedures from [RFC8378] 471 are used to deliver packets to multicast group members anywhere in 472 the network. The solution requires no signaling to the RSUs. When 473 RSUs receive multicast packets from a roaming-EID, they do a 474 (roaming-EID,G) mapping database lookup to find the replication list 475 of ETRs to encapsulate to. 477 7. Multiple Address-Family Considerations 479 Note that roaming-EIDs can be assigned IPv6 EID addresses while the 480 RSU xTRs could be using IPv4 RLOC addresses. Any combination of 481 address-families can be supported as well as for multicast packet 482 forwarding, where (S,G) are IPv6 addresses entries and replication is 483 done with IPv4 RLOCs in the outer header. 485 8. Scaling Considerations 487 One can imagine there will be a large number of roaming-EIDs. So 488 there is a strong desire to efficiently store state in the mapping 489 database and the in remote ITRs map-caches. It is likely, that 490 roaming-EIDs may share the same path and move at the same speed (EID 491 devices on a train) and therefore share the same Predictive RLOCs. 492 And since EIDs are not reassigned for mobility purposes or may be 493 temporal , they will not be topologically aggregatable, so they 494 cannot compress into a single EID-prefix mapping entry that share the 495 same RLOC-set. 497 By using a level of indirection with the mapping system this problem 498 can be solved. The following mapping entries could exist in the 499 mapping database: 501 EID = , RLOC-records: 502 RLOC = (afi=: "am-train-to-paris") 503 EID = , RLOC-records: 504 RLOC = (afi=: "am-train-to-paris") 505 EID = , RLOC-records: 506 RLOC = (afi=: "am-train-to-paris") 508 EID = "am-train-to-paris", RLOC-records: 509 RLOC = (afi=lcaf/RLE-type: xTR-A, xTR-B, xTR-C) 511 EID = "am-train-to-paris-passengers", RLOC-records: 512 RLOC = (afi=lcaf/afi-list-type: , , ) 514 Each passenger that boards a train has their EID registered to point 515 to the name of the train "am-train-to-paris". And then the train 516 with EID "am-train-to-paris" stores the Predictive RLOC-set. When a 517 remote-ITR wants to encapsulate packets for an EID, it looks up the 518 EID in the mapping database gets the name "am-train-to-paris" 519 returned. Then the remote-ITR does another lookup for the name "am- 520 train-to-paris" to get the RLE list returned. 522 When new EIDs board the train, the RLE mapping entry does not need to 523 be modified. Only an EID-to-name mapping is registered for the 524 specific new EID. Optionally, another name "am-train-to-paris- 525 passengers" can be registered as an EID to allow mapping to all 526 specific EIDs which are on the train. This can be used for 527 inventory, billing, or security purposes. 529 This optimization comes at a cost of a 2-stage lookup. However, if 530 both sets of mapping entries are registered to the same Map-Server, a 531 combined RLOC-set could be returned. This idea is for further study. 533 9. Security Considerations 535 LISP has procedures for supporting both control-plane security 536 [I-D.ietf-lisp-sec] and data-plane security [RFC8061]. 538 10. IANA Considerations 540 At this time there are no requests for IANA. 542 11. References 544 11.1. Normative References 546 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 547 Requirement Levels", BCP 14, RFC 2119, 548 DOI 10.17487/RFC2119, March 1997, 549 . 551 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 552 Locator/ID Separation Protocol (LISP)", RFC 6830, 553 DOI 10.17487/RFC6830, January 2013, 554 . 556 [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 557 Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, 558 February 2017, . 560 [RFC8061] Farinacci, D. and B. Weis, "Locator/ID Separation Protocol 561 (LISP) Data-Plane Confidentiality", RFC 8061, 562 DOI 10.17487/RFC8061, February 2017, 563 . 565 [RFC8378] Moreno, V. and D. Farinacci, "Signal-Free Locator/ID 566 Separation Protocol (LISP) Multicast", RFC 8378, 567 DOI 10.17487/RFC8378, May 2018, 568 . 570 11.2. Informative References 572 [I-D.farinacci-lisp-geo] 573 Farinacci, D., "LISP Geo-Coordinate Use-Cases", draft- 574 farinacci-lisp-geo-07 (work in progress), April 2019. 576 [I-D.ietf-lisp-eid-anonymity] 577 Farinacci, D., Pillay-Esnault, P., and W. Haddad, "LISP 578 EID Anonymity", draft-ietf-lisp-eid-anonymity-06 (work in 579 progress), April 2019. 581 [I-D.ietf-lisp-eid-mobility] 582 Portoles-Comeras, M., Ashtaputre, V., Moreno, V., Maino, 583 F., and D. Farinacci, "LISP L2/L3 EID Mobility Using a 584 Unified Control Plane", draft-ietf-lisp-eid-mobility-03 585 (work in progress), November 2018. 587 [I-D.ietf-lisp-sec] 588 Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D. 589 Saucez, "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-17 590 (work in progress), November 2018. 592 Appendix A. Acknowledgments 594 The author would like to thank the LISP WG for their review and 595 acceptance of this draft. 597 Appendix B. Document Change Log 599 [RFC Editor: Please delete this section on publication as RFC.] 601 B.1. Changes to draft-ietf-lisp-predictive-rlocs-04 603 o Posted May 2019. 605 o Update document timer and references. 607 B.2. Changes to draft-ietf-lisp-predictive-rlocs-03 609 o Posted November 2018. 611 o Update document timer and references. 613 B.3. Changes to draft-ietf-lisp-predictive-rlocs-02 615 o Posted May 2018. 617 o Update document timer and references. 619 B.4. Changes to draft-ietf-lisp-predictive-rlocs-01 621 o Posted November 2017. 623 o Update document timer and references. 625 o Reflect comments from Prague meeting presentation. There is no 626 need for "RLE Usage Types" as suggested. The ITR can treat what 627 RLOCs it replicates to as a local matter via implementation 628 configuration. RLE Directional is default. Circular rotation, 629 back-n-forth, and random selection of RLOCs is up to the ITR. 631 B.5. Changes to draft-ietf-lisp-predictive-rlocs-00 633 o Posted June 2017. 635 o Make this specification a working group document. It is a copy of 636 draft-farinacci-lisp-predictive-rlocs-02. 638 B.6. Changes to draft-farinacci-lisp-predictive-rlocs-02 640 o Posted May 2017 to update document timer. 642 B.7. Changes to draft-farinacci-lisp-predictive-rlocs-01 644 o Posted November 2016 to update document timer. 646 B.8. Changes to draft-farinacci-lisp-predictive-rlocs-00 648 o Initial post April 2016. 650 Authors' Addresses 652 Dino Farinacci 653 lispers.net 654 San Jose, CA 655 USA 657 Email: farinacci@gmail.com 659 Padma Pillay-Esnault 660 Huawei Technologies 661 San Clara, CA 662 USA 664 Email: padma@huawei.com