idnits 2.17.1 draft-ietf-lisp-te-03.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- == There are 8 instances of lines with private range IPv4 addresses in the document. If these are generic example addresses, they should be changed to use any of the ranges defined in RFC 6890 (or successor): 192.0.2.x, 198.51.100.x or 203.0.113.x. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: An ELP that is first used by an ITR must be inspected for encoding loops. If any RLOC appears twice in the ELP, it MUST not be used. -- The document date (October 15, 2018) is 2020 days in the past. Is this intentional? Checking references for intended status: Experimental ---------------------------------------------------------------------------- ** Obsolete normative reference: RFC 2460 (Obsoleted by RFC 8200) ** Obsolete normative reference: RFC 6830 (Obsoleted by RFC 9300, RFC 9301) ** Obsolete normative reference: RFC 6833 (Obsoleted by RFC 9301) == Outdated reference: A later version (-19) exists of draft-ermagan-lisp-nat-traversal-15 Summary: 3 errors (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force D. Farinacci 3 Internet-Draft lispers.net 4 Intended status: Experimental M. Kowal 5 Expires: April 18, 2019 cisco Systems 6 P. Lahiri 7 October 15, 2018 9 LISP Traffic Engineering Use-Cases 10 draft-ietf-lisp-te-03 12 Abstract 14 This document describes how LISP reencapsulating tunnels can be used 15 for Traffic Engineering purposes. The mechanisms described in this 16 document require no LISP protocol changes but do introduce a new 17 locator (RLOC) encoding. The Traffic Engineering features provided 18 by these LISP mechanisms can span intra-domain, inter-domain, or 19 combination of both. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at https://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on April 18, 2019. 38 Copyright Notice 40 Copyright (c) 2018 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (https://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Requirements Language . . . . . . . . . . . . . . . . . . . . 2 56 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 3 58 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4 59 5. Explicit Locator Paths . . . . . . . . . . . . . . . . . . . 6 60 5.1. ELP Re-optimization . . . . . . . . . . . . . . . . . . . 7 61 5.2. Using Recursion . . . . . . . . . . . . . . . . . . . . . 8 62 5.3. ELP Selection based on Class of Service . . . . . . . . . 8 63 5.4. Packet Loop Avoidance . . . . . . . . . . . . . . . . . . 10 64 6. Service Chaining . . . . . . . . . . . . . . . . . . . . . . 10 65 7. RLOC Probing by RTRs . . . . . . . . . . . . . . . . . . . . 10 66 8. ELP Probing . . . . . . . . . . . . . . . . . . . . . . . . . 10 67 9. Interworking Considerations . . . . . . . . . . . . . . . . . 11 68 10. Multicast Considerations . . . . . . . . . . . . . . . . . . 12 69 11. Security Considerations . . . . . . . . . . . . . . . . . . . 14 70 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 71 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 72 13.1. Normative References . . . . . . . . . . . . . . . . . . 14 73 13.2. Informative References . . . . . . . . . . . . . . . . . 15 74 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 15 75 Appendix B. Document Change Log . . . . . . . . . . . . . . . . 15 76 B.1. Changes to draft-ietf-lisp-te-03 . . . . . . . . . . . . 15 77 B.2. Changes to draft-ietf-lisp-te-02 . . . . . . . . . . . . 15 78 B.3. Changes to draft-ietf-lisp-te-01 . . . . . . . . . . . . 16 79 B.4. Changes to draft-ietf-lisp-te-00 . . . . . . . . . . . . 16 80 B.5. Changes to draft-farinacci-lisp-te-02 through -12 . . . . 16 81 B.6. Changes to draft-farinacci-lisp-te-01.txt . . . . . . . . 16 82 B.7. Changes to draft-farinacci-lisp-te-00.txt . . . . . . . . 16 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 85 1. Requirements Language 87 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 88 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 89 document are to be interpreted as described in RFC 2119 [RFC2119]. 91 2. Introduction 93 This document describes the Locator/Identifier Separation Protocol 94 (LISP), which provides a set of functions for routers to exchange 95 information used to map from non globally routeable Endpoint 96 Identifiers (EIDs) to routeable Routing Locators (RLOCs). It also 97 defines a mechanism for these LISP routers to encapsulate IP packets 98 addressed with EIDs for transmission across the Internet that uses 99 RLOCs for routing and forwarding. 101 When LISP routers encapsulate packets to other LISP routers, the path 102 stretch is typically 1, meaning the packet travels on a direct path 103 from the encapsulating ITR to the decapsulating ETR at the 104 destination site. The direct path is determined by the underlying 105 routing protocol and metrics it uses to find the shortest path. 107 This specification will examine how reencapsulating tunnels [RFC6830] 108 can be used so a packet can take an adminstratively specified path, a 109 congestion avoidance path, a failure recovery path, or multiple load- 110 shared paths, as it travels from ITR to ETR. By introducing an 111 Explicit Locator Path (ELP) locator encoding [RFC8060], an ITR can 112 encapsulate a packet to a Reencapsulating Tunnel Router (RTR) which 113 decapsulates the packet, then encapsulates it to the next locator in 114 the ELP. 116 3. Definition of Terms 118 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 119 IPv6) value used in the source and destination address fields of 120 the first (most inner) LISP header of a packet. The host obtains 121 a destination EID the same way it obtains an destination address 122 today, for example through a Domain Name System (DNS) [RFC1034] 123 lookup or Session Invitation Protocol (SIP) [RFC3261] exchange. 124 The source EID is obtained via existing mechanisms used to set a 125 host's "local" IP address. An EID used on the public Internet 126 must have the same properties as any other IP address used in that 127 manner; this means, among other things, that it must be globally 128 unique. An EID is allocated to a host from an EID-prefix block 129 associated with the site where the host is located. An EID can be 130 used by a host to refer to other hosts. EIDs MUST NOT be used as 131 LISP RLOCs. Note that EID blocks MAY be assigned in a 132 hierarchical manner, independent of the network topology, to 133 facilitate scaling of the mapping database. In addition, an EID 134 block assigned to a site may have site-local structure 135 (subnetting) for routing within the site; this structure is not 136 visible to the global routing system. In theory, the bit string 137 that represents an EID for one device can represent an RLOC for a 138 different device. As the architecture is realized, if a given bit 139 string is both an RLOC and an EID, it must refer to the same 140 entity in both cases. When used in discussions with other 141 Locator/ID separation proposals, a LISP EID will be called a 142 "LEID". Throughout this document, any references to "EID" refers 143 to an LEID. 145 Routing Locator (RLOC): A RLOC is an IPv4 [RFC0791] or IPv6 146 [RFC2460] address of an egress tunnel router (ETR). A RLOC is the 147 output of an EID-to-RLOC mapping lookup. An EID maps to one or 148 more RLOCs. Typically, RLOCs are numbered from topologically- 149 aggregatable blocks that are assigned to a site at each point to 150 which it attaches to the global Internet; where the topology is 151 defined by the connectivity of provider networks, RLOCs can be 152 thought of as PA addresses. Multiple RLOCs can be assigned to the 153 same ETR device or to multiple ETR devices at a site. 155 Reencapsulating Tunnel Router (RTR): An RTR is a router that acts 156 as an ETR (or PETR) by decapsulating packets where the destination 157 address in the "outer" IP header is one of its own RLOCs. Then 158 acts as an ITR (or PITR) by making a decision where to encapsulate 159 the packet based on the next locator in the ELP towards the final 160 destination ETR. 162 Explicit Locator Path (ELP): The ELP is an explicit list of RLOCs 163 for each RTR a packet must travel to along its path toward a final 164 destination ETR (or PETR). The list is a strict ordering where 165 each RLOC in the list is visited. However, the path from one RTR 166 to another is determined by the underlying routing protocol and 167 how the infrastructure assigns metrics and policies for the path. 169 Recursive Tunneling: Recursive tunneling occurs when a packet has 170 more than one LISP IP header. Additional layers of tunneling MAY 171 be employed to implement traffic engineering or other re-routing 172 as needed. When this is done, an additional "outer" LISP header 173 is added and the original RLOCs are preserved in the "inner" 174 header. Any references to tunnels in this specification refers to 175 dynamic encapsulating tunnels and they are never statically 176 configured. 178 Reencapsulating Tunnels: Reencapsulating tunneling occurs when an 179 ETR removes a LISP header, then acts as an ITR to prepend another 180 LISP header. Doing this allows a packet to be re-routed by the 181 reencapsulating router without adding the overhead of additional 182 tunnel headers. Any references to tunnels in this specification 183 refers to dynamic encapsulating tunnels and they are never 184 statically configured. When using multiple mapping database 185 systems, care must be taken to not create reencapsulation loops 186 through misconfiguration. 188 4. Overview 190 Typically, a packet's path from source EID to destination EID travels 191 through the locator core via the encapsulating ITR directly to the 192 decapsulating ETR as the following diagram illustrates: 194 Legend: 196 seid: Packet is originated by source EID 'seid'. 198 deid: Packet is consumed by destination EID 'deid'. 200 A,B,C,D : Core routers in different ASes. 202 ---> : The physical topological path between two routers. 204 ===> : A multi-hop LISP dynamic tunnel between LISP routers. 206 Core Network 207 Source site (----------------------------) Destination Site 208 +--------+ ( ) +---------+ 209 | \ ( ) / | 210 | seid ITR ---(---> A --> B --> C --> D ---)---> ETR deid | 211 | / || ( ) ^^ \ | 212 +--------+ || ( ) || +---------+ 213 || (----------------------------) || 214 || || 215 =========================================== 216 LISP Tunnel 218 Typical Data Path from ITR to ETR 220 Let's introduce RTRs 'X' and 'Y' so that, for example, if it is 221 desirable to route around the path from B to C, one could provide an 222 ELP of (X,Y,etr): 224 Core Network 225 Source site (----------------------------) Destination Site 226 +--------+ ( ) +---------+ 227 | \ ( ) / | 228 | seid ITR ---(---> A --> B --> C --> D ---)---> ETR deid | 229 | / || ( / ^ ) ^^ \ | 230 | / || ( | \ ) || \ | 231 +-------+ || ( v | ) || +--------+ 232 || ( X ======> Y ) || 233 || ( ^^ || ) || 234 || (--------||---------||-------) || 235 || || || || 236 ================= ================= 237 LISP Tunnel LISP Tunnel 239 ELP tunnel path ITR ==> X, then X ==> Y, and then Y ==> ETR 241 There are various reasons why the path from 'seid' to 'deid' may want 242 to avoid the path from B to C. To list a few: 244 o There may not be sufficient capacity provided by the networks that 245 connect B and C together. 247 o There may be a policy reason to avoid the ASes that make up the 248 path between B and C. 250 o There may be a failure on the path between B and C which makes the 251 path unreliable. 253 o There may be monitoring or traffic inspection resources close to 254 RTRs X and Y that do network accounting or measurement. 256 o There may be a chain of services performed at RTRs X and Y 257 regardless if the path from ITR to ETR is through B and C. 259 5. Explicit Locator Paths 261 The notation for a general formatted ELP is (x, y, etr) which 262 represents the list of RTRs a packet SHOULD travel through to reach 263 the final tunnel hop to the ETR. 265 The procedure for using an ELP at each tunnel hop is as follows: 267 1. The ITR will retrieve the ELP from the mapping database. 269 2. The ITR will encapsulate the packet to RLOC 'x'. 271 3. The RTR with RLOC 'x' will decapsulate the packet. It will use 272 the decapsulated packet's destination address as a lookup into 273 the mapping database to retrieve the ELP. 275 4. RTR 'x' will encapsulate the packet to RTR with RLOC 'y'. 277 5. The RTR with RLOC 'y' will decapsulate the packet. It will use 278 the decapsulated packet's destination address as a lookup into 279 the mapping database to retrieve the ELP. 281 6. RTR 'y' will encapsulate the packet on the final tunnel hop to 282 ETR with RLOC 'etr'. 284 7. The ETR will decapsulate the packet and deliver the packet to the 285 EID inside of its site. 287 The specific format for the ELP can be found in [RFC8060]. It is 288 defined that an ELP will appear as a single encoded locator in a 289 locator-set. Say for instance, we have a mapping entry for EID- 290 prefix 10.0.0.0/8 that is reachable via 4 locators. Two locators are 291 being used as active/active and the other two are used as active/ 292 active if the first two go unreachable (as noted by the priority 293 assignments below). This is what the mapping entry would look like: 295 EID-prefix: 10.0.0.0/8 296 Locator-set: ETR-A: priority 1, weight 50 297 ETR-B: priority 1, weight 50 298 ETR-C: priority 2, weight 50 299 ETR-D: priority 2, weight 50 301 If an ELP is going to be used to have a policy path to ETR-A and 302 possibly another policy path to ETR-B, the locator-set would be 303 encoded as follows: 305 EID-prefix: 10.0.0.0/8 306 Locator-set: (x, y, ETR-A): priority 1, weight 50 307 (q, r, ETR-B): priority 1, weight 50 308 ETR-C: priority 2, weight 50 309 ETR-D: priority 2, weight 50 311 The mapping entry with ELP locators is registered to the mapping 312 database system just like any other mapping entry would. The 313 registration is typically performed by the ETR(s) that are assigned 314 and own the EID-prefix. That is, the destination site makes the 315 choice of the RTRs in the ELP. However, it may be common practice 316 for a provisioning system to program the mapping database with ELPs. 318 Another case where a locator-set can be used for flow-based load- 319 sharing across multiple paths to the same destination site: 321 EID-prefix: 10.0.0.0/8 322 Locator-set: (x, y, ETR-A): priority 1, weight 75 323 (q, r, ETR-A): priority 1, weight 25 325 Using this mapping entry, an ITR would load split 75% of the EID 326 flows on the (x, y, ETR-A) ELP path and 25% of the EID flows on the 327 (q, r, ETR-A) ELP path. If any of the ELPs go down, then the other 328 can take 100% of the load. 330 5.1. ELP Re-optimization 332 ELP re-optimization is a process of changing the RLOCs of an ELP due 333 to underlying network change conditions. Just like when there is any 334 locator change for a locator-set, the procedures from the main LISP 335 specification [RFC6830] are followed. 337 When a RLOC from an ELP is changed, Map-Notify messages [RFC6833] can 338 be used to inform the existing RTRs in the ELP so they can do a 339 lookup to obtain the latest version of the ELP. Map-Notify messages 340 can also be sent to new RTRs in an ELP so they can get the ELP in 341 advance to receiving packets that will use the ELP. This can 342 minimize packet loss during mapping database lookups in RTRs. 344 5.2. Using Recursion 346 In the previous examples, we showed how an ITR encapsulates using an 347 ELP of (x, y, etr). When a packet is encapsulated by the ITR to RTR 348 'x', the RTR may want a policy path to RTR 'y' and run another level 349 of reencapsulating tunnels for packets destined to RTR 'y'. In this 350 case, RTR 'x' does not encapsulate packets to 'y' but rather performs 351 a mapping database lookup on the address 'y', requests the ELP for 352 RTR 'y', and encapsulates packets to the first-hop of the returned 353 ELP. This can be done when using a public or private mapping 354 database. The decision to use address 'y' as an encapsulation 355 address versus a lookup address is based on the L-bit setting for 'y' 356 in the ELP entry. The decision and policy of ELP encodings are local 357 to the entity which registers the EID-prefix associated with the ELP. 359 Another example of recursion is when the ITR uses the ELP (x, y, etr) 360 to first prepend a header with a destination RLOC of the ETR and then 361 prepend another header and encapsulate the packet to RTR 'x'. When 362 RTR 'x' decapsulates the packet, rather than doing a mapping database 363 lookup on RTR 'y' the last example showed, instead RTR 'x' does a 364 mapping database lookup on ETR 'etr'. In this scenario, RTR 'x' can 365 choose an ELP from the locator-set by considering the source RLOC 366 address of the ITR versus considering the source EID. 368 This additional level of recursion also brings advantages for the 369 provider of RTR 'x' to store less state. Since RTR 'x' does not need 370 to look at the inner most header, it does not need to store EID 371 state. It only stores an entry for RTR 'y' which many EID flows 372 could share for scaling benefits. The locator-set for entry 'y' 373 could either be a list of typical locators, a list of ELPs, or 374 combination of both. Another advantage is that packet load-splitting 375 can be accomplished by examining the source of a packet. If the 376 source is an ITR versus the source being the last-hop of an ELP the 377 last-hop selected, different forwarding paths can be used. 379 5.3. ELP Selection based on Class of Service 381 Paths to an ETR may want to be selected based on different classes of 382 service. Packets from a set of sources that have premium service can 383 use ELP paths that are less congested where normal sources use ELP 384 paths that compete for less resources or use longer paths for best 385 effort service. 387 Using source/destination lookups into the mapping database can yield 388 different ELPs. So for example, a premium service flow with 389 (source=1.1.1.1, dest=10.1.1.1) can be described by using the 390 following mapping entry: 392 EID-prefix: (1.0.0.0/8, 10.0.0.0/8) 393 Locator-set: (x, y, ETR-A): priority 1, weight 50 394 (q, r, ETR-A): priority 1, weight 50 396 And all other best-effort sources would use different mapping entry 397 described by: 399 EID-prefix: (0.0.0.0/0, 10.0.0.0/8) 400 Locator-set: (x, x', y, y', ETR-A): priority 1, weight 50 401 (q, q', r, r', ETR-A): priority 1, weight 50 403 If the source/destination lookup is coupled with recursive lookups, 404 then an ITR can encapsulate to the ETR, prepending a header that 405 selects source address ITR-1 based on the premium class of service 406 source, or selects source address ITR-2 for best-effort sources with 407 normal class of service. The ITR then does another lookup in the 408 mapping database on the prepended header using lookup key 409 (source=ITR-1, dest=10.1.1.1) that returns the following mapping 410 entry: 412 EID-prefix: (ITR-1, 10.0.0.0/8) 413 Locator-set: (x, y, ETR-A): priority 1, weight 50 414 (q, r, ETR-A): priority 1, weight 50 416 And all other sources would use different mapping entry with a lookup 417 key of (source=ITR-2, dest=10.1.1.1): 419 EID-prefix: (ITR-2, 10.0.0.0/8) 420 Locator-set: (x, x', y, y', ETR-A): priority 1, weight 50 421 (q, q', r, r', ETR-A): priority 1, weight 50 423 This will scale the mapping system better by having fewer source/ 424 destination combinations. Refer to the Source/Dest LCAF type 425 described in [RFC8060] for encoding EIDs in Map-Request and Map- 426 Register messages. 428 5.4. Packet Loop Avoidance 430 An ELP that is first used by an ITR must be inspected for encoding 431 loops. If any RLOC appears twice in the ELP, it MUST not be used. 433 Since it is expected that multiple mapping systems will be used, 434 there can be a loop across ELPs when registered in different mapping 435 systems. The TTL copying procedures for reencapsulating tunnels and 436 recursive tunnels in [RFC6830] MUST be followed. 438 6. Service Chaining 440 An ELP can be used to deploy services at each reencapsulation point 441 in the network. One example is to implement a scrubber service when 442 a destination EID is being DoS attacked. That is, when a DoS attack 443 is recognized when the encapsulation path is between ITR and ETR, an 444 ELP can be registered for a destination EID to the mapping database 445 system. The ELP can include an RTR so the ITR can encapsulate 446 packets to the RTR which will decapsulate and deliver packets to a 447 scrubber service device. The scrubber could decide if the offending 448 packets are dropped or allowed to be sent to the destination EID. In 449 which case, the scurbber delivers packets back to the RTR which 450 encapsulates to the ETR. 452 7. RLOC Probing by RTRs 454 Since an RTR knows the next tunnel hop to encapsulate to, it can 455 monitor the reachability of the next-hop RTR RLOC by doing RLOC- 456 probing according to the procedures in [RFC6830]. When the RLOC is 457 determined unreachable by the RLOC-probing mechanisms, the RTR can 458 use another locator in the locator-set. That could be the final ETR, 459 a RLOC of another RTR, or an ELP where it must search for itself and 460 use the next RLOC in the ELP list to encapsulate to. 462 RLOC-probing can also be used to measure delay on the path between 463 RTRs and when it is desirable switch to another lower delay ELP. 465 8. ELP Probing 467 Since an ELP-node knows the reachabiliy of the next ELP-node in a ELP 468 by using RLOC probing, the sum of reachability can determine the 469 reachability of the entire path. A head-end ITR/RTR/PITR can 470 determine the quality of a path and decide to select one path from 471 another based on the telemetry data gathered by RLOC-probing for each 472 encapsulation hop. 474 ELP-probing mechanism details can be found in [I-D.filyurin-lisp-elp- 475 probing]. 477 9. Interworking Considerations 479 [RFC6832] defines procedures for how non-LISP sites talk to LISP 480 sites. The network elements defined in the Interworking 481 specification, the proxy ITR (PITR) and proxy ETR (PETR) (as well as 482 their multicast counterparts defined in [RFC6831]) can participate in 483 LISP-TE. That is, a PITR and a PETR can appear in an ELP list and 484 act as an RTR. 486 Note when an RLOC appears in an ELP, it can be of any address-family. 487 There can be a mix of IPv4 and IPv6 locators present in the same ELP. 488 This can provide benefits where islands of one address-family or the 489 other are supported and connectivity across them is necessary. For 490 instance, an ELP can look like: 492 (x4, a46, b64, y4, etr) 494 Where an IPv4 ITR will encapsulate using an IPv4 RLOC 'x4' and 'x4' 495 could reach an IPv4 RLOC 'a46', but RTR 'a46' encapsulates to an IPv6 496 RLOC 'b64' when the network between them is IPv6-only. Then RTR 497 'b64' encapsulates to IPv4 RLOC 'y4' if the network between them is 498 dual-stack. 500 Note that RTRs can be used for NAT-traversal scenarios 501 [I-D.ermagan-lisp-nat-traversal] as well to reduce the state in both 502 an xTR that resides behind a NAT and the state the NAT needs to 503 maintain. In this case, the xTR only needs a default map-cache entry 504 pointing to the RTR for outbound traffic and all remote ITRs can 505 reach EIDs through the xTR behind a NAT via a single RTR (or a small 506 set RTRs for redundancy). 508 RTRs have some scaling features to reduce the number of locator-set 509 changes, the amount of state, and control packet overhead: 511 o When ITRs and PITRs are using a small set of RTRs for 512 encapsulating to "orders of magnitude" more EID-prefixes, the 513 probability of locator-set changes are limited to the RTR RLOC 514 changes versus the RLOC changes for the ETRs associated with the 515 EID-prefixes if the ITRs and PITRs were directly encapsulating to 516 the ETRs. This comes at an expense in packet stretch, but 517 depending on RTR placement, this expense can be mitigated. 519 o When RTRs are on-path between many pairwise EID flows, ITRs and 520 PITRs can store a small number of coarse EID-prefixes. 522 o RTRs can be used to help scale RLOC-probing. Instead of ITRs 523 RLOC-probing all ETRs for each destination site it has cached, the 524 ITRs can probe a smaller set of RTRs which in turn, probe the 525 destination sites. 527 10. Multicast Considerations 529 ELPs have application in multicast environments. Just like RTRs can 530 be used to provide connectivity across different address family 531 islands, RTRs can help concatenate a multicast region of the network 532 to one that does not support native multicast. 534 Note there are various combinations of connectivity that can be 535 accomplished with the deployment of RTRs and ELPs: 537 o Providing multicast forwarding between IPv4-only-unicast regions 538 and IPv4-multicast regions. 540 o Providing multicast forwarding between IPv6-only-unicast regions 541 and IPv6-multicast regions. 543 o Providing multicast forwarding between IPv4-only-unicast regions 544 and IPv6-multicast regions. 546 o Providing multicast forwarding between IPv6-only-unicast regions 547 and IPv4-multicast regions. 549 o Providing multicast forwarding between IPv4-multicast regions and 550 IPv6-multicast regions. 552 An ITR or PITR can do a (S-EID,G) lookup into the mapping database. 553 What can be returned is a typical locator-set that could be made up 554 of the various RLOC addresses: 556 Multicast EID key: (seid, G) 557 Locator-set: ETR-A: priority 1, weight 25 558 ETR-B: priority 1, weight 25 559 g1: priority 1, weight 25 560 g2: priority 1, weight 25 562 An entry for host 'seid' sending to application group 'G' 564 The locator-set above can be used as a replication list. That is 565 some RLOCs listed can be unicast RLOCs and some can be delivery group 566 RLOCs. A unicast RLOC in this case is used to encapsulate a 567 multicast packet originated by a multicast source EID into a unicast 568 packet for unicast delivery on the underlying network. ETR-A could 569 be a IPv4 unicast RLOC address and ETR-B could be a IPv6 unicast RLOC 570 address. 572 A delivery group address is used when a multicast packet originated 573 by a multicast source EID is encapsulated in a multicast packet for 574 multicast delivery on the underlying network. Group address 'g1' 575 could be a IPv4 delivery group RLOC and group address 'g2' could be 576 an IPv6 delivery group RLOC. 578 Flexibility for these various types of connectivity combinations can 579 be achieved and provided by the mapping database system. And the RTR 580 placement allows the connectivity to occur where the differences in 581 network functionality are located. 583 Extending this concept by allowing ELPs in locator-sets, one could 584 have this locator-set registered in the mapping database for (seid, 585 G). For example: 587 Multicast EID key: (seid, G) 588 Locator-set: (x, y, ETR-A): priority 1, weight 50 589 (a, g, b, ETR-B): priority 1, weight 50 591 Using ELPs for multicast flows 593 In the above situation, an ITR would encapsulate a multicast packet 594 originated by a multicast source EID to the RTR with unicast RLOC 595 'x'. Then RTR 'x' would decapsulate and unicast encapsulate to RTR 596 'y' ('x' or 'y' could be either IPv4 or IPv6 unicast RLOCs), which 597 would decapsulate and unicast encapsulate to the final RLOC 'ETR-A'. 598 The ETR 'ETR-A' would decapsulate and deliver the multicast packet 599 natively to all the receivers joined to application group 'G' inside 600 the LISP site. 602 Let's look at the ITR using the ELP (a, g, b, ETR-B). Here the 603 encapsulation path would be the ITR unicast encapsulates to unicast 604 RLOC 'a'. RTR 'a' multicast encapsulates to delivery group 'g'. The 605 packet gets to all ETRs that have joined delivery group 'g' so they 606 can deliver the multicast packet to joined receivers of application 607 group 'G' in their sites. RTR 'b' is also joined to delivery group 608 'g'. Since it is in the ELP, it will be the only RTR that unicast 609 encapsulates the multicast packet to ETR 'ETR-B'. Lastly, 'ETR-B' 610 decapsulates and delivers the multicast packet to joined receivers to 611 application group 'G' in its LISP site. 613 As one can see there are all sorts of opportunities to provide 614 multicast connectivity across a network with non-congruent support 615 for multicast and different address-families. One can also see how 616 using the mapping database can allow flexible forms of delivery 617 policy, rerouting, and congestion control management in multicast 618 environments. 620 11. Security Considerations 622 When an RTR receives a LISP encapsulated packet, it can look at the 623 outer source address to verify that RLOC is the one listed as the 624 previous hop in the ELP list. If the outer source RLOC address 625 appears before the RLOC which matches the outer destination RLOC 626 address, the decapsulating RTR (or ETR if last hop), MAY choose to 627 drop the packet. 629 12. IANA Considerations 631 At this time there are no requests for IANA. 633 13. References 635 13.1. Normative References 637 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 638 DOI 10.17487/RFC0791, September 1981, 639 . 641 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 642 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 643 . 645 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 646 Requirement Levels", BCP 14, RFC 2119, 647 DOI 10.17487/RFC2119, March 1997, 648 . 650 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 651 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 652 December 1998, . 654 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 655 A., Peterson, J., Sparks, R., Handley, M., and E. 656 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 657 DOI 10.17487/RFC3261, June 2002, 658 . 660 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 661 Locator/ID Separation Protocol (LISP)", RFC 6830, 662 DOI 10.17487/RFC6830, January 2013, 663 . 665 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 666 Locator/ID Separation Protocol (LISP) for Multicast 667 Environments", RFC 6831, DOI 10.17487/RFC6831, January 668 2013, . 670 [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 671 "Interworking between Locator/ID Separation Protocol 672 (LISP) and Non-LISP Sites", RFC 6832, 673 DOI 10.17487/RFC6832, January 2013, 674 . 676 [RFC6833] Fuller, V. and D. Farinacci, "Locator/ID Separation 677 Protocol (LISP) Map-Server Interface", RFC 6833, 678 DOI 10.17487/RFC6833, January 2013, 679 . 681 [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 682 Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, 683 February 2017, . 685 13.2. Informative References 687 [I-D.ermagan-lisp-nat-traversal] 688 Ermagan, V., Farinacci, D., Lewis, D., Skriver, J., Maino, 689 F., and C. White, "NAT traversal for LISP", draft-ermagan- 690 lisp-nat-traversal-15 (work in progress), October 2018. 692 Appendix A. Acknowledgments 694 The authors would like to thank the following people for their ideas 695 and comments. They are Albert Cabellos, Khalid Raza, and Vina 696 Ermagan, Gregg Schudel, Yan Filyurin, Robert Raszuk, and Truman 697 Boyes. 699 Appendix B. Document Change Log 701 B.1. Changes to draft-ietf-lisp-te-03 703 o Posted October 2018. 705 o Update document timer and references. 707 B.2. Changes to draft-ietf-lisp-te-02 709 o Posted April 2018. 711 o Update document timer and references. 713 B.3. Changes to draft-ietf-lisp-te-01 715 o Posted October 2017. 717 o Added section on ELP-probing that tells an ITR/RTR/PITR the 718 feasibility and reachability of an Explicit Lcoator Path. 720 B.4. Changes to draft-ietf-lisp-te-00 722 o Posted April 2017. 724 o Changed draft-farinacci-lisp-te-12 to working group document. 726 B.5. Changes to draft-farinacci-lisp-te-02 through -12 728 o Many postings from January 2013 through February 2017. 730 o Update references and document timer. 732 B.6. Changes to draft-farinacci-lisp-te-01.txt 734 o Posted July 2012. 736 o Add the Lookup bit to allow an ELP to be a list of encapsulation 737 and/or mapping database lookup addresses. 739 o Indicate that ELPs can be used for service chaining. 741 o Add text to indicate that Map-Notify messages can be sent to new 742 RTRs in a ELP so their map-caches can be pre-populated to avoid 743 mapping database lookup packet loss. 745 o Fixes to editorial comments from Gregg. 747 B.7. Changes to draft-farinacci-lisp-te-00.txt 749 o Initial draft posted March 2012. 751 Authors' Addresses 753 Dino Farinacci 754 lispers.net 755 San Jose, California 756 USA 758 Phone: 408-718-2001 759 Email: farinacci@gmail.com 760 Michael Kowal 761 cisco Systems 762 111 Wood Avenue South 763 ISELIN, NJ 764 USA 766 Email: mikowal@cisco.com 768 Parantap Lahiri 769 USA 771 Email: parantap.lahiri@gmail.com