idnits 2.17.1 draft-farinacci-lisp-te-12.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 (February 28, 2017) is 2604 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RFC 6830 (Obsoleted by RFC 9300, RFC 9301) ** Obsolete normative reference: RFC 6833 (Obsoleted by RFC 9301) == Outdated reference: A later version (-19) exists of draft-ermagan-lisp-nat-traversal-11 Summary: 3 errors (**), 0 flaws (~~), 4 warnings (==), 1 comment (--).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: September 1, 2017 cisco Systems 6 P. Lahiri 7 February 28, 2017 9 LISP Traffic Engineering Use-Cases 10 draft-farinacci-lisp-te-12 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 http://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 September 1, 2017. 38 Copyright Notice 40 Copyright (c) 2017 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 (http://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 . . . . . . . . . . . . . . . . . . . . . . . . 3 57 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 3 58 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5 59 5. Explicit Locator Paths . . . . . . . . . . . . . . . . . . . 6 60 5.1. ELP Re-optimization . . . . . . . . . . . . . . . . . . . 8 61 5.2. Using Recursion . . . . . . . . . . . . . . . . . . . . . 8 62 5.3. ELP Selection based on Class of Service . . . . . . . . . 9 63 5.4. Packet Loop Avoidance . . . . . . . . . . . . . . . . . . 10 64 6. Service Chaining . . . . . . . . . . . . . . . . . . . . . . 10 65 7. RLOC Probing by RTRs . . . . . . . . . . . . . . . . . . . . 10 66 8. Interworking Considerations . . . . . . . . . . . . . . . . . 11 67 9. Multicast Considerations . . . . . . . . . . . . . . . . . . 12 68 10. Security Considerations . . . . . . . . . . . . . . . . . . . 14 69 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 70 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 71 12.1. Normative References . . . . . . . . . . . . . . . . . . 14 72 12.2. Informative References . . . . . . . . . . . . . . . . . 15 73 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 15 74 Appendix B. Document Change Log . . . . . . . . . . . . . . . . 15 75 B.1. Changes to draft-farinacci-lisp-te-12.txt . . . . . . . . 15 76 B.2. Changes to draft-farinacci-lisp-te-11.txt . . . . . . . . 16 77 B.3. Changes to draft-farinacci-lisp-te-10.txt . . . . . . . . 16 78 B.4. Changes to draft-farinacci-lisp-te-09.txt . . . . . . . . 16 79 B.5. Changes to draft-farinacci-lisp-te-08.txt . . . . . . . . 16 80 B.6. Changes to draft-farinacci-lisp-te-07.txt . . . . . . . . 16 81 B.7. Changes to draft-farinacci-lisp-te-06.txt . . . . . . . . 16 82 B.8. Changes to draft-farinacci-lisp-te-05.txt . . . . . . . . 16 83 B.9. Changes to draft-farinacci-lisp-te-04.txt . . . . . . . . 16 84 B.10. Changes to draft-farinacci-lisp-te-03.txt . . . . . . . . 17 85 B.11. Changes to draft-farinacci-lisp-te-02.txt . . . . . . . . 17 86 B.12. Changes to draft-farinacci-lisp-te-01.txt . . . . . . . . 17 87 B.13. Changes to draft-farinacci-lisp-te-00.txt . . . . . . . . 17 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 90 1. Requirements Language 92 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 93 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 94 document are to be interpreted as described in RFC 2119 [RFC2119]. 96 2. Introduction 98 This document describes the Locator/Identifier Separation Protocol 99 (LISP), which provides a set of functions for routers to exchange 100 information used to map from non globally routeable Endpoint 101 Identifiers (EIDs) to routeable Routing Locators (RLOCs). It also 102 defines a mechanism for these LISP routers to encapsulate IP packets 103 addressed with EIDs for transmission across the Internet that uses 104 RLOCs for routing and forwarding. 106 When LISP routers encapsulate packets to other LISP routers, the path 107 stretch is typically 1, meaning the packet travels on a direct path 108 from the encapsulating ITR to the decapsulating ETR at the 109 destination site. The direct path is determined by the underlying 110 routing protocol and metrics it uses to find the shortest path. 112 This specification will examine how reencapsulating tunnels [RFC6830] 113 can be used so a packet can take an adminstratively specified path, a 114 congestion avoidance path, a failure recovery path, or multiple load- 115 shared paths, as it travels from ITR to ETR. By introducing an 116 Explicit Locator Path (ELP) locator encoding [RFC8060], an ITR can 117 encapsulate a packet to a Reencapsulating Tunnel Router (RTR) which 118 decapsulates the packet, then encapsulates it to the next locator in 119 the ELP. 121 3. Definition of Terms 123 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 124 IPv6) value used in the source and destination address fields of 125 the first (most inner) LISP header of a packet. The host obtains 126 a destination EID the same way it obtains an destination address 127 today, for example through a Domain Name System (DNS) [RFC1034] 128 lookup or Session Invitation Protocol (SIP) [RFC3261] exchange. 129 The source EID is obtained via existing mechanisms used to set a 130 host's "local" IP address. An EID used on the public Internet 131 must have the same properties as any other IP address used in that 132 manner; this means, among other things, that it must be globally 133 unique. An EID is allocated to a host from an EID-prefix block 134 associated with the site where the host is located. An EID can be 135 used by a host to refer to other hosts. EIDs MUST NOT be used as 136 LISP RLOCs. Note that EID blocks MAY be assigned in a 137 hierarchical manner, independent of the network topology, to 138 facilitate scaling of the mapping database. In addition, an EID 139 block assigned to a site may have site-local structure 140 (subnetting) for routing within the site; this structure is not 141 visible to the global routing system. In theory, the bit string 142 that represents an EID for one device can represent an RLOC for a 143 different device. As the architecture is realized, if a given bit 144 string is both an RLOC and an EID, it must refer to the same 145 entity in both cases. When used in discussions with other 146 Locator/ID separation proposals, a LISP EID will be called a 147 "LEID". Throughout this document, any references to "EID" refers 148 to an LEID. 150 Routing Locator (RLOC): A RLOC is an IPv4 [RFC0791] or IPv6 151 [RFC2460] address of an egress tunnel router (ETR). A RLOC is the 152 output of an EID-to-RLOC mapping lookup. An EID maps to one or 153 more RLOCs. Typically, RLOCs are numbered from topologically- 154 aggregatable blocks that are assigned to a site at each point to 155 which it attaches to the global Internet; where the topology is 156 defined by the connectivity of provider networks, RLOCs can be 157 thought of as PA addresses. Multiple RLOCs can be assigned to the 158 same ETR device or to multiple ETR devices at a site. 160 Reencapsulating Tunnel Router (RTR): An RTR is a router that acts 161 as an ETR (or PETR) by decapsulating packets where the destination 162 address in the "outer" IP header is one of its own RLOCs. Then 163 acts as an ITR (or PITR) by making a decision where to encapsulate 164 the packet based on the next locator in the ELP towards the final 165 destination ETR. 167 Explicit Locator Path (ELP): The ELP is an explicit list of RLOCs 168 for each RTR a packet must travel to along its path toward a final 169 destination ETR (or PETR). The list is a strict ordering where 170 each RLOC in the list is visited. However, the path from one RTR 171 to another is determined by the underlying routing protocol and 172 how the infrastructure assigns metrics and policies for the path. 174 Recursive Tunneling: Recursive tunneling occurs when a packet has 175 more than one LISP IP header. Additional layers of tunneling MAY 176 be employed to implement traffic engineering or other re-routing 177 as needed. When this is done, an additional "outer" LISP header 178 is added and the original RLOCs are preserved in the "inner" 179 header. Any references to tunnels in this specification refers to 180 dynamic encapsulating tunnels and they are never statically 181 configured. 183 Reencapsulating Tunnels: Reencapsulating tunneling occurs when an 184 ETR removes a LISP header, then acts as an ITR to prepend another 185 LISP header. Doing this allows a packet to be re-routed by the 186 reencapsulating router without adding the overhead of additional 187 tunnel headers. Any references to tunnels in this specification 188 refers to dynamic encapsulating tunnels and they are never 189 statically configured. When using multiple mapping database 190 systems, care must be taken to not create reencapsulation loops 191 through misconfiguration. 193 4. Overview 195 Typically, a packet's path from source EID to destination EID travels 196 through the locator core via the encapsulating ITR directly to the 197 decapsulating ETR as the following diagram illustrates: 199 Legend: 201 seid: Packet is originated by source EID 'seid'. 203 deid: Packet is consumed by destination EID 'deid'. 205 A,B,C,D : Core routers in different ASes. 207 ---> : The physical topological path between two routers. 209 ===> : A multi-hop LISP dynamic tunnel between LISP routers. 211 Core Network 212 Source site (----------------------------) Destination Site 213 +--------+ ( ) +---------+ 214 | \ ( ) / | 215 | seid ITR ---(---> A --> B --> C --> D ---)---> ETR deid | 216 | / || ( ) ^^ \ | 217 +--------+ || ( ) || +---------+ 218 || (----------------------------) || 219 || || 220 =========================================== 221 LISP Tunnel 223 Typical Data Path from ITR to ETR 225 Let's introduce RTRs 'X' and 'Y' so that, for example, if it is 226 desirable to route around the path from B to C, one could provide an 227 ELP of (X,Y,etr): 229 Core Network 230 Source site (----------------------------) Destination Site 231 +--------+ ( ) +---------+ 232 | \ ( ) / | 233 | seid ITR ---(---> A --> B --> C --> D ---)---> ETR deid | 234 | / || ( / ^ ) ^^ \ | 235 | / || ( | \ ) || \ | 236 +-------+ || ( v | ) || +--------+ 237 || ( X ======> Y ) || 238 || ( ^^ || ) || 239 || (--------||---------||-------) || 240 || || || || 241 ================= ================= 242 LISP Tunnel LISP Tunnel 244 ELP tunnel path ITR ==> X, then X ==> Y, and then Y ==> ETR 246 There are various reasons why the path from 'seid' to 'deid' may want 247 to avoid the path from B to C. To list a few: 249 o There may not be sufficient capacity provided by the networks that 250 connect B and C together. 252 o There may be a policy reason to avoid the ASes that make up the 253 path between B and C. 255 o There may be a failure on the path between B and C which makes the 256 path unreliable. 258 o There may be monitoring or traffic inspection resources close to 259 RTRs X and Y that do network accounting or measurement. 261 o There may be a chain of services performed at RTRs X and Y 262 regardless if the path from ITR to ETR is through B and C. 264 5. Explicit Locator Paths 266 The notation for a general formatted ELP is (x, y, etr) which 267 represents the list of RTRs a packet SHOULD travel through to reach 268 the final tunnel hop to the ETR. 270 The procedure for using an ELP at each tunnel hop is as follows: 272 1. The ITR will retrieve the ELP from the mapping database. 274 2. The ITR will encapsulate the packet to RLOC 'x'. 276 3. The RTR with RLOC 'x' will decapsulate the packet. It will use 277 the decapsulated packet's destination address as a lookup into 278 the mapping database to retrieve the ELP. 280 4. RTR 'x' will encapsulate the packet to RTR with RLOC 'y'. 282 5. The RTR with RLOC 'y' will decapsulate the packet. It will use 283 the decapsulated packet's destination address as a lookup into 284 the mapping database to retrieve the ELP. 286 6. RTR 'y' will encapsulate the packet on the final tunnel hop to 287 ETR with RLOC 'etr'. 289 7. The ETR will decapsulate the packet and deliver the packet to the 290 EID inside of its site. 292 The specific format for the ELP can be found in [RFC8060]. It is 293 defined that an ELP will appear as a single encoded locator in a 294 locator-set. Say for instance, we have a mapping entry for EID- 295 prefix 10.0.0.0/8 that is reachable via 4 locators. Two locators are 296 being used as active/active and the other two are used as active/ 297 active if the first two go unreachable (as noted by the priority 298 assignments below). This is what the mapping entry would look like: 300 EID-prefix: 10.0.0.0/8 301 Locator-set: ETR-A: priority 1, weight 50 302 ETR-B: priority 1, weight 50 303 ETR-C: priority 2, weight 50 304 ETR-D: priority 2, weight 50 306 If an ELP is going to be used to have a policy path to ETR-A and 307 possibly another policy path to ETR-B, the locator-set would be 308 encoded as follows: 310 EID-prefix: 10.0.0.0/8 311 Locator-set: (x, y, ETR-A): priority 1, weight 50 312 (q, r, ETR-B): priority 1, weight 50 313 ETR-C: priority 2, weight 50 314 ETR-D: priority 2, weight 50 316 The mapping entry with ELP locators is registered to the mapping 317 database system just like any other mapping entry would. The 318 registration is typically performed by the ETR(s) that are assigned 319 and own the EID-prefix. That is, the destination site makes the 320 choice of the RTRs in the ELP. However, it may be common practice 321 for a provisioning system to program the mapping database with ELPs. 323 Another case where a locator-set can be used for flow-based load- 324 sharing across multiple paths to the same destination site: 326 EID-prefix: 10.0.0.0/8 327 Locator-set: (x, y, ETR-A): priority 1, weight 75 328 (q, r, ETR-A): priority 1, weight 25 330 Using this mapping entry, an ITR would load split 75% of the EID 331 flows on the (x, y, ETR-A) ELP path and 25% of the EID flows on the 332 (q, r, ETR-A) ELP path. If any of the ELPs go down, then the other 333 can take 100% of the load. 335 5.1. ELP Re-optimization 337 ELP re-optimization is a process of changing the RLOCs of an ELP due 338 to underlying network change conditions. Just like when there is any 339 locator change for a locator-set, the procedures from the main LISP 340 specification [RFC6830] are followed. 342 When a RLOC from an ELP is changed, Map-Notify messages [RFC6833] can 343 be used to inform the existing RTRs in the ELP so they can do a 344 lookup to obtain the latest version of the ELP. Map-Notify messages 345 can also be sent to new RTRs in an ELP so they can get the ELP in 346 advance to receiving packets that will use the ELP. This can 347 minimize packet loss during mapping database lookups in RTRs. 349 5.2. Using Recursion 351 In the previous examples, we showed how an ITR encapsulates using an 352 ELP of (x, y, etr). When a packet is encapsulated by the ITR to RTR 353 'x', the RTR may want a policy path to RTR 'y' and run another level 354 of reencapsulating tunnels for packets destined to RTR 'y'. In this 355 case, RTR 'x' does not encapsulate packets to 'y' but rather performs 356 a mapping database lookup on the address 'y', requests the ELP for 357 RTR 'y', and encapsulates packets to the first-hop of the returned 358 ELP. This can be done when using a public or private mapping 359 database. The decision to use address 'y' as an encapsulation 360 address versus a lookup address is based on the L-bit setting for 'y' 361 in the ELP entry. The decision and policy of ELP encodings are local 362 to the entity which registers the EID-prefix associated with the ELP. 364 Another example of recursion is when the ITR uses the ELP (x, y, etr) 365 to first prepend a header with a destination RLOC of the ETR and then 366 prepend another header and encapsulate the packet to RTR 'x'. When 367 RTR 'x' decapsulates the packet, rather than doing a mapping database 368 lookup on RTR 'y' the last example showed, instead RTR 'x' does a 369 mapping database lookup on ETR 'etr'. In this scenario, RTR 'x' can 370 choose an ELP from the locator-set by considering the source RLOC 371 address of the ITR versus considering the source EID. 373 This additional level of recursion also brings advantages for the 374 provider of RTR 'x' to store less state. Since RTR 'x' does not need 375 to look at the inner most header, it does not need to store EID 376 state. It only stores an entry for RTR 'y' which many EID flows 377 could share for scaling benefits. The locator-set for entry 'y' 378 could either be a list of typical locators, a list of ELPs, or 379 combination of both. Another advantage is that packet load-splitting 380 can be accomplished by examining the source of a packet. If the 381 source is an ITR versus the source being the last-hop of an ELP the 382 last-hop selected, different forwarding paths can be used. 384 5.3. ELP Selection based on Class of Service 386 Paths to an ETR may want to be selected based on different classes of 387 service. Packets from a set of sources that have premium service can 388 use ELP paths that are less congested where normal sources use ELP 389 paths that compete for less resources or use longer paths for best 390 effort service. 392 Using source/destination lookups into the mapping database can yield 393 different ELPs. So for example, a premium service flow with 394 (source=1.1.1.1, dest=10.1.1.1) can be described by using the 395 following mapping entry: 397 EID-prefix: (1.0.0.0/8, 10.0.0.0/8) 398 Locator-set: (x, y, ETR-A): priority 1, weight 50 399 (q, r, ETR-A): priority 1, weight 50 401 And all other best-effort sources would use different mapping entry 402 described by: 404 EID-prefix: (0.0.0.0/0, 10.0.0.0/8) 405 Locator-set: (x, x', y, y', ETR-A): priority 1, weight 50 406 (q, q', r, r', ETR-A): priority 1, weight 50 408 If the source/destination lookup is coupled with recursive lookups, 409 then an ITR can encapsulate to the ETR, prepending a header that 410 selects source address ITR-1 based on the premium class of service 411 source, or selects source address ITR-2 for best-effort sources with 412 normal class of service. The ITR then does another lookup in the 413 mapping database on the prepended header using lookup key 414 (source=ITR-1, dest=10.1.1.1) that returns the following mapping 415 entry: 417 EID-prefix: (ITR-1, 10.0.0.0/8) 418 Locator-set: (x, y, ETR-A): priority 1, weight 50 419 (q, r, ETR-A): priority 1, weight 50 421 And all other sources would use different mapping entry with a lookup 422 key of (source=ITR-2, dest=10.1.1.1): 424 EID-prefix: (ITR-2, 10.0.0.0/8) 425 Locator-set: (x, x', y, y', ETR-A): priority 1, weight 50 426 (q, q', r, r', ETR-A): priority 1, weight 50 428 This will scale the mapping system better by having fewer source/ 429 destination combinations. Refer to the Source/Dest LCAF type 430 described in [RFC8060] for encoding EIDs in Map-Request and Map- 431 Register messages. 433 5.4. Packet Loop Avoidance 435 An ELP that is first used by an ITR must be inspected for encoding 436 loops. If any RLOC appears twice in the ELP, it MUST not be used. 438 Since it is expected that multiple mapping systems will be used, 439 there can be a loop across ELPs when registered in different mapping 440 systems. The TTL copying procedures for reencapsulating tunnels and 441 recursive tunnels in [RFC6830] MUST be followed. 443 6. Service Chaining 445 An ELP can be used to deploy services at each reencapsulation point 446 in the network. One example is to implement a scrubber service when 447 a destination EID is being DoS attacked. That is, when a DoS attack 448 is recognized when the encapsulation path is between ITR and ETR, an 449 ELP can be registered for a destination EID to the mapping database 450 system. The ELP can include an RTR so the ITR can encapsulate 451 packets to the RTR which will decapsulate and deliver packets to a 452 scrubber service device. The scrubber could decide if the offending 453 packets are dropped or allowed to be sent to the destination EID. In 454 which case, the scurbber delivers packets back to the RTR which 455 encapsulates to the ETR. 457 7. RLOC Probing by RTRs 459 Since an RTR knows the next tunnel hop to encapsulate to, it can 460 monitor the reachability of the next-hop RTR RLOC by doing RLOC- 461 probing according to the procedures in [RFC6830]. When the RLOC is 462 determined unreachable by the RLOC-probing mechanisms, the RTR can 463 use another locator in the locator-set. That could be the final ETR, 464 a RLOC of another RTR, or an ELP where it must search for itself and 465 use the next RLOC in the ELP list to encapsulate to. 467 RLOC-probing can also be used to measure delay on the path between 468 RTRs and when it is desirable switch to another lower delay ELP. 470 8. Interworking Considerations 472 [RFC6832] defines procedures for how non-LISP sites talk to LISP 473 sites. The network elements defined in the Interworking 474 specification, the proxy ITR (PITR) and proxy ETR (PETR) (as well as 475 their multicast counterparts defined in [RFC6831]) can participate in 476 LISP-TE. That is, a PITR and a PETR can appear in an ELP list and 477 act as an RTR. 479 Note when an RLOC appears in an ELP, it can be of any address-family. 480 There can be a mix of IPv4 and IPv6 locators present in the same ELP. 481 This can provide benefits where islands of one address-family or the 482 other are supported and connectivity across them is necessary. For 483 instance, an ELP can look like: 485 (x4, a46, b64, y4, etr) 487 Where an IPv4 ITR will encapsulate using an IPv4 RLOC 'x4' and 'x4' 488 could reach an IPv4 RLOC 'a46', but RTR 'a46' encapsulates to an IPv6 489 RLOC 'b64' when the network between them is IPv6-only. Then RTR 490 'b64' encapsulates to IPv4 RLOC 'y4' if the network between them is 491 dual-stack. 493 Note that RTRs can be used for NAT-traversal scenarios 494 [I-D.ermagan-lisp-nat-traversal] as well to reduce the state in both 495 an xTR that resides behind a NAT and the state the NAT needs to 496 maintain. In this case, the xTR only needs a default map-cache entry 497 pointing to the RTR for outbound traffic and all remote ITRs can 498 reach EIDs through the xTR behind a NAT via a single RTR (or a small 499 set RTRs for redundancy). 501 RTRs have some scaling features to reduce the number of locator-set 502 changes, the amount of state, and control packet overhead: 504 o When ITRs and PITRs are using a small set of RTRs for 505 encapsulating to "orders of magnitude" more EID-prefixes, the 506 probability of locator-set changes are limited to the RTR RLOC 507 changes versus the RLOC changes for the ETRs associated with the 508 EID-prefixes if the ITRs and PITRs were directly encapsulating to 509 the ETRs. This comes at an expense in packet stretch, but 510 depending on RTR placement, this expense can be mitigated. 512 o When RTRs are on-path between many pairwise EID flows, ITRs and 513 PITRs can store a small number of coarse EID-prefixes. 515 o RTRs can be used to help scale RLOC-probing. Instead of ITRs 516 RLOC-probing all ETRs for each destination site it has cached, the 517 ITRs can probe a smaller set of RTRs which in turn, probe the 518 destination sites. 520 9. Multicast Considerations 522 ELPs have application in multicast environments. Just like RTRs can 523 be used to provide connectivity across different address family 524 islands, RTRs can help concatenate a multicast region of the network 525 to one that does not support native multicast. 527 Note there are various combinations of connectivity that can be 528 accomplished with the deployment of RTRs and ELPs: 530 o Providing multicast forwarding between IPv4-only-unicast regions 531 and IPv4-multicast regions. 533 o Providing multicast forwarding between IPv6-only-unicast regions 534 and IPv6-multicast regions. 536 o Providing multicast forwarding between IPv4-only-unicast regions 537 and IPv6-multicast regions. 539 o Providing multicast forwarding between IPv6-only-unicast regions 540 and IPv4-multicast regions. 542 o Providing multicast forwarding between IPv4-multicast regions and 543 IPv6-multicast regions. 545 An ITR or PITR can do a (S-EID,G) lookup into the mapping database. 546 What can be returned is a typical locator-set that could be made up 547 of the various RLOC addresses: 549 Multicast EID key: (seid, G) 550 Locator-set: ETR-A: priority 1, weight 25 551 ETR-B: priority 1, weight 25 552 g1: priority 1, weight 25 553 g2: priority 1, weight 25 555 An entry for host 'seid' sending to application group 'G' 557 The locator-set above can be used as a replication list. That is 558 some RLOCs listed can be unicast RLOCs and some can be delivery group 559 RLOCs. A unicast RLOC in this case is used to encapsulate a 560 multicast packet originated by a multicast source EID into a unicast 561 packet for unicast delivery on the underlying network. ETR-A could 562 be a IPv4 unicast RLOC address and ETR-B could be a IPv6 unicast RLOC 563 address. 565 A delivery group address is used when a multicast packet originated 566 by a multicast source EID is encapsulated in a multicast packet for 567 multicast delivery on the underlying network. Group address 'g1' 568 could be a IPv4 delivery group RLOC and group address 'g2' could be 569 an IPv6 delivery group RLOC. 571 Flexibility for these various types of connectivity combinations can 572 be achieved and provided by the mapping database system. And the RTR 573 placement allows the connectivity to occur where the differences in 574 network functionality are located. 576 Extending this concept by allowing ELPs in locator-sets, one could 577 have this locator-set registered in the mapping database for (seid, 578 G). For example: 580 Multicast EID key: (seid, G) 581 Locator-set: (x, y, ETR-A): priority 1, weight 50 582 (a, g, b, ETR-B): priority 1, weight 50 584 Using ELPs for multicast flows 586 In the above situation, an ITR would encapsulate a multicast packet 587 originated by a multicast source EID to the RTR with unicast RLOC 588 'x'. Then RTR 'x' would decapsulate and unicast encapsulate to RTR 589 'y' ('x' or 'y' could be either IPv4 or IPv6 unicast RLOCs), which 590 would decapsulate and unicast encapsulate to the final RLOC 'ETR-A'. 591 The ETR 'ETR-A' would decapsulate and deliver the multicast packet 592 natively to all the receivers joined to application group 'G' inside 593 the LISP site. 595 Let's look at the ITR using the ELP (a, g, b, ETR-B). Here the 596 encapsulation path would be the ITR unicast encapsulates to unicast 597 RLOC 'a'. RTR 'a' multicast encapsulates to delivery group 'g'. The 598 packet gets to all ETRs that have joined delivery group 'g' so they 599 can deliver the multicast packet to joined receivers of application 600 group 'G' in their sites. RTR 'b' is also joined to delivery group 601 'g'. Since it is in the ELP, it will be the only RTR that unicast 602 encapsulates the multicast packet to ETR 'ETR-B'. Lastly, 'ETR-B' 603 decapsulates and delivers the multicast packet to joined receivers to 604 application group 'G' in its LISP site. 606 As one can see there are all sorts of opportunities to provide 607 multicast connectivity across a network with non-congruent support 608 for multicast and different address-families. One can also see how 609 using the mapping database can allow flexible forms of delivery 610 policy, rerouting, and congestion control management in multicast 611 environments. 613 10. Security Considerations 615 When an RTR receives a LISP encapsulated packet, it can look at the 616 outer source address to verify that RLOC is the one listed as the 617 previous hop in the ELP list. If the outer source RLOC address 618 appears before the RLOC which matches the outer destination RLOC 619 address, the decapsulating RTR (or ETR if last hop), MAY choose to 620 drop the packet. 622 11. IANA Considerations 624 At this time there are no requests for IANA. 626 12. References 628 12.1. Normative References 630 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 631 DOI 10.17487/RFC0791, September 1981, 632 . 634 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 635 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 636 . 638 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 639 Requirement Levels", BCP 14, RFC 2119, 640 DOI 10.17487/RFC2119, March 1997, 641 . 643 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 644 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 645 December 1998, . 647 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 648 A., Peterson, J., Sparks, R., Handley, M., and E. 649 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 650 DOI 10.17487/RFC3261, June 2002, 651 . 653 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 654 Locator/ID Separation Protocol (LISP)", RFC 6830, 655 DOI 10.17487/RFC6830, January 2013, 656 . 658 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 659 Locator/ID Separation Protocol (LISP) for Multicast 660 Environments", RFC 6831, DOI 10.17487/RFC6831, January 661 2013, . 663 [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 664 "Interworking between Locator/ID Separation Protocol 665 (LISP) and Non-LISP Sites", RFC 6832, 666 DOI 10.17487/RFC6832, January 2013, 667 . 669 [RFC6833] Fuller, V. and D. Farinacci, "Locator/ID Separation 670 Protocol (LISP) Map-Server Interface", RFC 6833, 671 DOI 10.17487/RFC6833, January 2013, 672 . 674 [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 675 Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, 676 February 2017, . 678 12.2. Informative References 680 [I-D.ermagan-lisp-nat-traversal] 681 Ermagan, V., Farinacci, D., Lewis, D., Skriver, J., Maino, 682 F., and C. White, "NAT traversal for LISP", draft-ermagan- 683 lisp-nat-traversal-11 (work in progress), August 2016. 685 Appendix A. Acknowledgments 687 The authors would like to thank the following people for their ideas 688 and comments. They are Albert Cabellos, Khalid Raza, and Vina 689 Ermagan, and Gregg Schudel. 691 Appendix B. Document Change Log 693 B.1. Changes to draft-farinacci-lisp-te-12.txt 695 o Posted February 2017. 697 o Update references and document timer. 699 B.2. Changes to draft-farinacci-lisp-te-11.txt 701 o Posted September 2016. 703 o Update references and document timer. 705 B.3. Changes to draft-farinacci-lisp-te-10.txt 707 o Posted March 2016. 709 o Update references and document timer. 711 B.4. Changes to draft-farinacci-lisp-te-09.txt 713 o Posted September 2015. 715 o Update references and document timer. 717 B.5. Changes to draft-farinacci-lisp-te-08.txt 719 o Posted March 2015. 721 o Update references and document timer. 723 B.6. Changes to draft-farinacci-lisp-te-07.txt 725 o Posted September 2014. 727 o Update references and document timer. 729 B.7. Changes to draft-farinacci-lisp-te-06.txt 731 o Posted March 2014. 733 o Fix Parantap's affliation to self. 735 B.8. Changes to draft-farinacci-lisp-te-05.txt 737 o Posted March 2014. 739 o Fix text in "Using Recursion" section based on comment Jinghao 740 Wang provided. 742 B.9. Changes to draft-farinacci-lisp-te-04.txt 744 o Resubmitted draft due to document timeout. 746 o Updated Informative References section. 748 B.10. Changes to draft-farinacci-lisp-te-03.txt 750 o Update LISP references to their RFC pointers and document timer. 752 B.11. Changes to draft-farinacci-lisp-te-02.txt 754 o Update references and document timer. 756 B.12. Changes to draft-farinacci-lisp-te-01.txt 758 o Posted July 2012. 760 o Add the Lookup bit to allow an ELP to be a list of encapsulation 761 and/or mapping database lookup addresses. 763 o Indicate that ELPs can be used for service chaining. 765 o Add text to indicate that Map-Notify messages can be sent to new 766 RTRs in a ELP so their map-caches can be pre-populated to avoid 767 mapping database lookup packet loss. 769 o Fixes to editorial comments from Gregg. 771 B.13. Changes to draft-farinacci-lisp-te-00.txt 773 o Initial draft posted March 2012. 775 Authors' Addresses 777 Dino Farinacci 778 lispers.net 779 San Jose, California 780 USA 782 Phone: 408-718-2001 783 Email: farinacci@gmail.com 785 Michael Kowal 786 cisco Systems 787 111 Wood Avenue South 788 ISELIN, NJ 789 USA 791 Email: mikowal@cisco.com 792 Parantap Lahiri 793 USA 795 Email: parantap.lahiri@gmail.com