idnits 2.17.1 draft-farinacci-lisp-te-11.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 (September 5, 2016) is 2789 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RFC 6830 (Obsoleted by RFC 9300, RFC 9301) ** Obsolete normative reference: RFC 6833 (Obsoleted by RFC 9301) == Outdated reference: A later version (-22) exists of draft-ietf-lisp-lcaf-14 == Outdated reference: A later version (-19) exists of draft-ermagan-lisp-nat-traversal-11 Summary: 3 errors (**), 0 flaws (~~), 5 warnings (==), 1 comment (--).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: March 9, 2017 cisco Systems 6 P. Lahiri 7 September 5, 2016 9 LISP Traffic Engineering Use-Cases 10 draft-farinacci-lisp-te-11 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 March 9, 2017. 38 Copyright Notice 40 Copyright (c) 2016 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-11.txt . . . . . . . . 15 76 B.2. Changes to draft-farinacci-lisp-te-10.txt . . . . . . . . 16 77 B.3. Changes to draft-farinacci-lisp-te-09.txt . . . . . . . . 16 78 B.4. Changes to draft-farinacci-lisp-te-08.txt . . . . . . . . 16 79 B.5. Changes to draft-farinacci-lisp-te-07.txt . . . . . . . . 16 80 B.6. Changes to draft-farinacci-lisp-te-06.txt . . . . . . . . 16 81 B.7. Changes to draft-farinacci-lisp-te-05.txt . . . . . . . . 16 82 B.8. Changes to draft-farinacci-lisp-te-04.txt . . . . . . . . 16 83 B.9. Changes to draft-farinacci-lisp-te-03.txt . . . . . . . . 16 84 B.10. Changes to draft-farinacci-lisp-te-02.txt . . . . . . . . 17 85 B.11. Changes to draft-farinacci-lisp-te-01.txt . . . . . . . . 17 86 B.12. Changes to draft-farinacci-lisp-te-00.txt . . . . . . . . 17 87 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 89 1. Requirements Language 91 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 92 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 93 document are to be interpreted as described in RFC 2119 [RFC2119]. 95 2. Introduction 97 This document describes the Locator/Identifier Separation Protocol 98 (LISP), which provides a set of functions for routers to exchange 99 information used to map from non globally routeable Endpoint 100 Identifiers (EIDs) to routeable Routing Locators (RLOCs). It also 101 defines a mechanism for these LISP routers to encapsulate IP packets 102 addressed with EIDs for transmission across the Internet that uses 103 RLOCs for routing and forwarding. 105 When LISP routers encapsulate packets to other LISP routers, the path 106 stretch is typically 1, meaning the packet travels on a direct path 107 from the encapsulating ITR to the decapsulating ETR at the 108 destination site. The direct path is determined by the underlying 109 routing protocol and metrics it uses to find the shortest path. 111 This specification will examine how reencapsulating tunnels [RFC6830] 112 can be used so a packet can take an adminstratively specified path, a 113 congestion avoidance path, a failure recovery path, or multiple load- 114 shared paths, as it travels from ITR to ETR. By introducing an 115 Explicit Locator Path (ELP) locator encoding [LISP-LCAF], an ITR can 116 encapsulate a packet to a Reencapsulating Tunnel Router (RTR) which 117 decapsulates the packet, then encapsulates it to the next locator in 118 the ELP. 120 3. Definition of Terms 122 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 123 IPv6) value used in the source and destination address fields of 124 the first (most inner) LISP header of a packet. The host obtains 125 a destination EID the same way it obtains an destination address 126 today, for example through a Domain Name System (DNS) [RFC1034] 127 lookup or Session Invitation Protocol (SIP) [RFC3261] exchange. 128 The source EID is obtained via existing mechanisms used to set a 129 host's "local" IP address. An EID used on the public Internet 130 must have the same properties as any other IP address used in that 131 manner; this means, among other things, that it must be globally 132 unique. An EID is allocated to a host from an EID-prefix block 133 associated with the site where the host is located. An EID can be 134 used by a host to refer to other hosts. EIDs MUST NOT be used as 135 LISP RLOCs. Note that EID blocks MAY be assigned in a 136 hierarchical manner, independent of the network topology, to 137 facilitate scaling of the mapping database. In addition, an EID 138 block assigned to a site may have site-local structure 139 (subnetting) for routing within the site; this structure is not 140 visible to the global routing system. In theory, the bit string 141 that represents an EID for one device can represent an RLOC for a 142 different device. As the architecture is realized, if a given bit 143 string is both an RLOC and an EID, it must refer to the same 144 entity in both cases. When used in discussions with other 145 Locator/ID separation proposals, a LISP EID will be called a 146 "LEID". Throughout this document, any references to "EID" refers 147 to an LEID. 149 Routing Locator (RLOC): A RLOC is an IPv4 [RFC0791] or IPv6 150 [RFC2460] address of an egress tunnel router (ETR). A RLOC is the 151 output of an EID-to-RLOC mapping lookup. An EID maps to one or 152 more RLOCs. Typically, RLOCs are numbered from topologically- 153 aggregatable blocks that are assigned to a site at each point to 154 which it attaches to the global Internet; where the topology is 155 defined by the connectivity of provider networks, RLOCs can be 156 thought of as PA addresses. Multiple RLOCs can be assigned to the 157 same ETR device or to multiple ETR devices at a site. 159 Reencapsulating Tunnel Router (RTR): An RTR is a router that acts 160 as an ETR (or PETR) by decapsulating packets where the destination 161 address in the "outer" IP header is one of its own RLOCs. Then 162 acts as an ITR (or PITR) by making a decision where to encapsulate 163 the packet based on the next locator in the ELP towards the final 164 destination ETR. 166 Explicit Locator Path (ELP): The ELP is an explicit list of RLOCs 167 for each RTR a packet must travel to along its path toward a final 168 destination ETR (or PETR). The list is a strict ordering where 169 each RLOC in the list is visited. However, the path from one RTR 170 to another is determined by the underlying routing protocol and 171 how the infrastructure assigns metrics and policies for the path. 173 Recursive Tunneling: Recursive tunneling occurs when a packet has 174 more than one LISP IP header. Additional layers of tunneling MAY 175 be employed to implement traffic engineering or other re-routing 176 as needed. When this is done, an additional "outer" LISP header 177 is added and the original RLOCs are preserved in the "inner" 178 header. Any references to tunnels in this specification refers to 179 dynamic encapsulating tunnels and they are never statically 180 configured. 182 Reencapsulating Tunnels: Reencapsulating tunneling occurs when an 183 ETR removes a LISP header, then acts as an ITR to prepend another 184 LISP header. Doing this allows a packet to be re-routed by the 185 reencapsulating router without adding the overhead of additional 186 tunnel headers. Any references to tunnels in this specification 187 refers to dynamic encapsulating tunnels and they are never 188 statically configured. When using multiple mapping database 189 systems, care must be taken to not create reencapsulation loops 190 through misconfiguration. 192 4. Overview 194 Typically, a packet's path from source EID to destination EID travels 195 through the locator core via the encapsulating ITR directly to the 196 decapsulating ETR as the following diagram illustrates: 198 Legend: 200 seid: Packet is originated by source EID 'seid'. 202 deid: Packet is consumed by destination EID 'deid'. 204 A,B,C,D : Core routers in different ASes. 206 ---> : The physical topological path between two routers. 208 ===> : A multi-hop LISP dynamic tunnel between LISP routers. 210 Core Network 211 Source site (----------------------------) Destination Site 212 +--------+ ( ) +---------+ 213 | \ ( ) / | 214 | seid ITR ---(---> A --> B --> C --> D ---)---> ETR deid | 215 | / || ( ) ^^ \ | 216 +--------+ || ( ) || +---------+ 217 || (----------------------------) || 218 || || 219 =========================================== 220 LISP Tunnel 222 Typical Data Path from ITR to ETR 224 Let's introduce RTRs 'X' and 'Y' so that, for example, if it is 225 desirable to route around the path from B to C, one could provide an 226 ELP of (X,Y,etr): 228 Core Network 229 Source site (----------------------------) Destination Site 230 +--------+ ( ) +---------+ 231 | \ ( ) / | 232 | seid ITR ---(---> A --> B --> C --> D ---)---> ETR deid | 233 | / || ( / ^ ) ^^ \ | 234 | / || ( | \ ) || \ | 235 +-------+ || ( v | ) || +--------+ 236 || ( X ======> Y ) || 237 || ( ^^ || ) || 238 || (--------||---------||-------) || 239 || || || || 240 ================= ================= 241 LISP Tunnel LISP Tunnel 243 ELP tunnel path ITR ==> X, then X ==> Y, and then Y ==> ETR 245 There are various reasons why the path from 'seid' to 'deid' may want 246 to avoid the path from B to C. To list a few: 248 o There may not be sufficient capacity provided by the networks that 249 connect B and C together. 251 o There may be a policy reason to avoid the ASes that make up the 252 path between B and C. 254 o There may be a failure on the path between B and C which makes the 255 path unreliable. 257 o There may be monitoring or traffic inspection resources close to 258 RTRs X and Y that do network accounting or measurement. 260 o There may be a chain of services performed at RTRs X and Y 261 regardless if the path from ITR to ETR is through B and C. 263 5. Explicit Locator Paths 265 The notation for a general formatted ELP is (x, y, etr) which 266 represents the list of RTRs a packet SHOULD travel through to reach 267 the final tunnel hop to the ETR. 269 The procedure for using an ELP at each tunnel hop is as follows: 271 1. The ITR will retrieve the ELP from the mapping database. 273 2. The ITR will encapsulate the packet to RLOC 'x'. 275 3. The RTR with RLOC 'x' will decapsulate the packet. It will use 276 the decapsulated packet's destination address as a lookup into 277 the mapping database to retrieve the ELP. 279 4. RTR 'x' will encapsulate the packet to RTR with RLOC 'y'. 281 5. The RTR with RLOC 'y' will decapsulate the packet. It will use 282 the decapsulated packet's destination address as a lookup into 283 the mapping database to retrieve the ELP. 285 6. RTR 'y' will encapsulate the packet on the final tunnel hop to 286 ETR with RLOC 'etr'. 288 7. The ETR will decapsulate the packet and deliver the packet to the 289 EID inside of its site. 291 The specific format for the ELP can be found in [LISP-LCAF]. It is 292 defined that an ELP will appear as a single encoded locator in a 293 locator-set. Say for instance, we have a mapping entry for EID- 294 prefix 10.0.0.0/8 that is reachable via 4 locators. Two locators are 295 being used as active/active and the other two are used as active/ 296 active if the first two go unreachable (as noted by the priority 297 assignments below). This is what the mapping entry would look like: 299 EID-prefix: 10.0.0.0/8 300 Locator-set: ETR-A: priority 1, weight 50 301 ETR-B: priority 1, weight 50 302 ETR-C: priority 2, weight 50 303 ETR-D: priority 2, weight 50 305 If an ELP is going to be used to have a policy path to ETR-A and 306 possibly another policy path to ETR-B, the locator-set would be 307 encoded as follows: 309 EID-prefix: 10.0.0.0/8 310 Locator-set: (x, y, ETR-A): priority 1, weight 50 311 (q, r, ETR-B): priority 1, weight 50 312 ETR-C: priority 2, weight 50 313 ETR-D: priority 2, weight 50 315 The mapping entry with ELP locators is registered to the mapping 316 database system just like any other mapping entry would. The 317 registration is typically performed by the ETR(s) that are assigned 318 and own the EID-prefix. That is, the destination site makes the 319 choice of the RTRs in the ELP. However, it may be common practice 320 for a provisioning system to program the mapping database with ELPs. 322 Another case where a locator-set can be used for flow-based load- 323 sharing across multiple paths to the same destination site: 325 EID-prefix: 10.0.0.0/8 326 Locator-set: (x, y, ETR-A): priority 1, weight 75 327 (q, r, ETR-A): priority 1, weight 25 329 Using this mapping entry, an ITR would load split 75% of the EID 330 flows on the (x, y, ETR-A) ELP path and 25% of the EID flows on the 331 (q, r, ETR-A) ELP path. If any of the ELPs go down, then the other 332 can take 100% of the load. 334 5.1. ELP Re-optimization 336 ELP re-optimization is a process of changing the RLOCs of an ELP due 337 to underlying network change conditions. Just like when there is any 338 locator change for a locator-set, the procedures from the main LISP 339 specification [RFC6830] are followed. 341 When a RLOC from an ELP is changed, Map-Notify messages [RFC6833] can 342 be used to inform the existing RTRs in the ELP so they can do a 343 lookup to obtain the latest version of the ELP. Map-Notify messages 344 can also be sent to new RTRs in an ELP so they can get the ELP in 345 advance to receiving packets that will use the ELP. This can 346 minimize packet loss during mapping database lookups in RTRs. 348 5.2. Using Recursion 350 In the previous examples, we showed how an ITR encapsulates using an 351 ELP of (x, y, etr). When a packet is encapsulated by the ITR to RTR 352 'x', the RTR may want a policy path to RTR 'y' and run another level 353 of reencapsulating tunnels for packets destined to RTR 'y'. In this 354 case, RTR 'x' does not encapsulate packets to 'y' but rather performs 355 a mapping database lookup on the address 'y', requests the ELP for 356 RTR 'y', and encapsulates packets to the first-hop of the returned 357 ELP. This can be done when using a public or private mapping 358 database. The decision to use address 'y' as an encapsulation 359 address versus a lookup address is based on the L-bit setting for 'y' 360 in the ELP entry. The decision and policy of ELP encodings are local 361 to the entity which registers the EID-prefix associated with the ELP. 363 Another example of recursion is when the ITR uses the ELP (x, y, etr) 364 to first prepend a header with a destination RLOC of the ETR and then 365 prepend another header and encapsulate the packet to RTR 'x'. When 366 RTR 'x' decapsulates the packet, rather than doing a mapping database 367 lookup on RTR 'y' the last example showed, instead RTR 'x' does a 368 mapping database lookup on ETR 'etr'. In this scenario, RTR 'x' can 369 choose an ELP from the locator-set by considering the source RLOC 370 address of the ITR versus considering the source EID. 372 This additional level of recursion also brings advantages for the 373 provider of RTR 'x' to store less state. Since RTR 'x' does not need 374 to look at the inner most header, it does not need to store EID 375 state. It only stores an entry for RTR 'y' which many EID flows 376 could share for scaling benefits. The locator-set for entry 'y' 377 could either be a list of typical locators, a list of ELPs, or 378 combination of both. Another advantage is that packet load-splitting 379 can be accomplished by examining the source of a packet. If the 380 source is an ITR versus the source being the last-hop of an ELP the 381 last-hop selected, different forwarding paths can be used. 383 5.3. ELP Selection based on Class of Service 385 Paths to an ETR may want to be selected based on different classes of 386 service. Packets from a set of sources that have premium service can 387 use ELP paths that are less congested where normal sources use ELP 388 paths that compete for less resources or use longer paths for best 389 effort service. 391 Using source/destination lookups into the mapping database can yield 392 different ELPs. So for example, a premium service flow with 393 (source=1.1.1.1, dest=10.1.1.1) can be described by using the 394 following mapping entry: 396 EID-prefix: (1.0.0.0/8, 10.0.0.0/8) 397 Locator-set: (x, y, ETR-A): priority 1, weight 50 398 (q, r, ETR-A): priority 1, weight 50 400 And all other best-effort sources would use different mapping entry 401 described by: 403 EID-prefix: (0.0.0.0/0, 10.0.0.0/8) 404 Locator-set: (x, x', y, y', ETR-A): priority 1, weight 50 405 (q, q', r, r', ETR-A): priority 1, weight 50 407 If the source/destination lookup is coupled with recursive lookups, 408 then an ITR can encapsulate to the ETR, prepending a header that 409 selects source address ITR-1 based on the premium class of service 410 source, or selects source address ITR-2 for best-effort sources with 411 normal class of service. The ITR then does another lookup in the 412 mapping database on the prepended header using lookup key 413 (source=ITR-1, dest=10.1.1.1) that returns the following mapping 414 entry: 416 EID-prefix: (ITR-1, 10.0.0.0/8) 417 Locator-set: (x, y, ETR-A): priority 1, weight 50 418 (q, r, ETR-A): priority 1, weight 50 420 And all other sources would use different mapping entry with a lookup 421 key of (source=ITR-2, dest=10.1.1.1): 423 EID-prefix: (ITR-2, 10.0.0.0/8) 424 Locator-set: (x, x', y, y', ETR-A): priority 1, weight 50 425 (q, q', r, r', ETR-A): priority 1, weight 50 427 This will scale the mapping system better by having fewer source/ 428 destination combinations. Refer to the Source/Dest LCAF type 429 described in [LISP-LCAF] for encoding EIDs in Map-Request and Map- 430 Register messages. 432 5.4. Packet Loop Avoidance 434 An ELP that is first used by an ITR must be inspected for encoding 435 loops. If any RLOC appears twice in the ELP, it MUST not be used. 437 Since it is expected that multiple mapping systems will be used, 438 there can be a loop across ELPs when registered in different mapping 439 systems. The TTL copying procedures for reencapsulating tunnels and 440 recursive tunnels in [RFC6830] MUST be followed. 442 6. Service Chaining 444 An ELP can be used to deploy services at each reencapsulation point 445 in the network. One example is to implement a scrubber service when 446 a destination EID is being DoS attacked. That is, when a DoS attack 447 is recognized when the encapsulation path is between ITR and ETR, an 448 ELP can be registered for a destination EID to the mapping database 449 system. The ELP can include an RTR so the ITR can encapsulate 450 packets to the RTR which will decapsulate and deliver packets to a 451 scrubber service device. The scrubber could decide if the offending 452 packets are dropped or allowed to be sent to the destination EID. In 453 which case, the scurbber delivers packets back to the RTR which 454 encapsulates to the ETR. 456 7. RLOC Probing by RTRs 458 Since an RTR knows the next tunnel hop to encapsulate to, it can 459 monitor the reachability of the next-hop RTR RLOC by doing RLOC- 460 probing according to the procedures in [RFC6830]. When the RLOC is 461 determined unreachable by the RLOC-probing mechanisms, the RTR can 462 use another locator in the locator-set. That could be the final ETR, 463 a RLOC of another RTR, or an ELP where it must search for itself and 464 use the next RLOC in the ELP list to encapsulate to. 466 RLOC-probing can also be used to measure delay on the path between 467 RTRs and when it is desirable switch to another lower delay ELP. 469 8. Interworking Considerations 471 [RFC6832] defines procedures for how non-LISP sites talk to LISP 472 sites. The network elements defined in the Interworking 473 specification, the proxy ITR (PITR) and proxy ETR (PETR) (as well as 474 their multicast counterparts defined in [RFC6831]) can participate in 475 LISP-TE. That is, a PITR and a PETR can appear in an ELP list and 476 act as an RTR. 478 Note when an RLOC appears in an ELP, it can be of any address-family. 479 There can be a mix of IPv4 and IPv6 locators present in the same ELP. 480 This can provide benefits where islands of one address-family or the 481 other are supported and connectivity across them is necessary. For 482 instance, an ELP can look like: 484 (x4, a46, b64, y4, etr) 486 Where an IPv4 ITR will encapsulate using an IPv4 RLOC 'x4' and 'x4' 487 could reach an IPv4 RLOC 'a46', but RTR 'a46' encapsulates to an IPv6 488 RLOC 'b64' when the network between them is IPv6-only. Then RTR 489 'b64' encapsulates to IPv4 RLOC 'y4' if the network between them is 490 dual-stack. 492 Note that RTRs can be used for NAT-traversal scenarios [LISP-NATT] as 493 well to reduce the state in both an xTR that resides behind a NAT and 494 the state the NAT needs to maintain. In this case, the xTR only 495 needs a default map-cache entry pointing to the RTR for outbound 496 traffic and all remote ITRs can reach EIDs through the xTR behind a 497 NAT via a single RTR (or a small set RTRs for redundancy). 499 RTRs have some scaling features to reduce the number of locator-set 500 changes, the amount of state, and control packet overhead: 502 o When ITRs and PITRs are using a small set of RTRs for 503 encapsulating to "orders of magnitude" more EID-prefixes, the 504 probability of locator-set changes are limited to the RTR RLOC 505 changes versus the RLOC changes for the ETRs associated with the 506 EID-prefixes if the ITRs and PITRs were directly encapsulating to 507 the ETRs. This comes at an expense in packet stretch, but 508 depending on RTR placement, this expense can be mitigated. 510 o When RTRs are on-path between many pairwise EID flows, ITRs and 511 PITRs can store a small number of coarse EID-prefixes. 513 o RTRs can be used to help scale RLOC-probing. Instead of ITRs 514 RLOC-probing all ETRs for each destination site it has cached, the 515 ITRs can probe a smaller set of RTRs which in turn, probe the 516 destination sites. 518 9. Multicast Considerations 520 ELPs have application in multicast environments. Just like RTRs can 521 be used to provide connectivity across different address family 522 islands, RTRs can help concatenate a multicast region of the network 523 to one that does not support native multicast. 525 Note there are various combinations of connectivity that can be 526 accomplished with the deployment of RTRs and ELPs: 528 o Providing multicast forwarding between IPv4-only-unicast regions 529 and IPv4-multicast regions. 531 o Providing multicast forwarding between IPv6-only-unicast regions 532 and IPv6-multicast regions. 534 o Providing multicast forwarding between IPv4-only-unicast regions 535 and IPv6-multicast regions. 537 o Providing multicast forwarding between IPv6-only-unicast regions 538 and IPv4-multicast regions. 540 o Providing multicast forwarding between IPv4-multicast regions and 541 IPv6-multicast regions. 543 An ITR or PITR can do a (S-EID,G) lookup into the mapping database. 544 What can be returned is a typical locator-set that could be made up 545 of the various RLOC addresses: 547 Multicast EID key: (seid, G) 548 Locator-set: ETR-A: priority 1, weight 25 549 ETR-B: priority 1, weight 25 550 g1: priority 1, weight 25 551 g2: priority 1, weight 25 553 An entry for host 'seid' sending to application group 'G' 555 The locator-set above can be used as a replication list. That is 556 some RLOCs listed can be unicast RLOCs and some can be delivery group 557 RLOCs. A unicast RLOC in this case is used to encapsulate a 558 multicast packet originated by a multicast source EID into a unicast 559 packet for unicast delivery on the underlying network. ETR-A could 560 be a IPv4 unicast RLOC address and ETR-B could be a IPv6 unicast RLOC 561 address. 563 A delivery group address is used when a multicast packet originated 564 by a multicast source EID is encapsulated in a multicast packet for 565 multicast delivery on the underlying network. Group address 'g1' 566 could be a IPv4 delivery group RLOC and group address 'g2' could be 567 an IPv6 delivery group RLOC. 569 Flexibility for these various types of connectivity combinations can 570 be achieved and provided by the mapping database system. And the RTR 571 placement allows the connectivity to occur where the differences in 572 network functionality are located. 574 Extending this concept by allowing ELPs in locator-sets, one could 575 have this locator-set registered in the mapping database for (seid, 576 G). For example: 578 Multicast EID key: (seid, G) 579 Locator-set: (x, y, ETR-A): priority 1, weight 50 580 (a, g, b, ETR-B): priority 1, weight 50 582 Using ELPs for multicast flows 584 In the above situation, an ITR would encapsulate a multicast packet 585 originated by a multicast source EID to the RTR with unicast RLOC 586 'x'. Then RTR 'x' would decapsulate and unicast encapsulate to RTR 587 'y' ('x' or 'y' could be either IPv4 or IPv6 unicast RLOCs), which 588 would decapsulate and unicast encapsulate to the final RLOC 'ETR-A'. 589 The ETR 'ETR-A' would decapsulate and deliver the multicast packet 590 natively to all the receivers joined to application group 'G' inside 591 the LISP site. 593 Let's look at the ITR using the ELP (a, g, b, ETR-B). Here the 594 encapsulation path would be the ITR unicast encapsulates to unicast 595 RLOC 'a'. RTR 'a' multicast encapsulates to delivery group 'g'. The 596 packet gets to all ETRs that have joined delivery group 'g' so they 597 can deliver the multicast packet to joined receivers of application 598 group 'G' in their sites. RTR 'b' is also joined to delivery group 599 'g'. Since it is in the ELP, it will be the only RTR that unicast 600 encapsulates the multicast packet to ETR 'ETR-B'. Lastly, 'ETR-B' 601 decapsulates and delivers the multicast packet to joined receivers to 602 application group 'G' in its LISP site. 604 As one can see there are all sorts of opportunities to provide 605 multicast connectivity across a network with non-congruent support 606 for multicast and different address-families. One can also see how 607 using the mapping database can allow flexible forms of delivery 608 policy, rerouting, and congestion control management in multicast 609 environments. 611 10. Security Considerations 613 When an RTR receives a LISP encapsulated packet, it can look at the 614 outer source address to verify that RLOC is the one listed as the 615 previous hop in the ELP list. If the outer source RLOC address 616 appears before the RLOC which matches the outer destination RLOC 617 address, the decapsulating RTR (or ETR if last hop), MAY choose to 618 drop the packet. 620 11. IANA Considerations 622 At this time there are no requests for IANA. 624 12. References 626 12.1. Normative References 628 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 629 DOI 10.17487/RFC0791, September 1981, 630 . 632 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 633 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 634 . 636 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 637 Requirement Levels", BCP 14, RFC 2119, 638 DOI 10.17487/RFC2119, March 1997, 639 . 641 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 642 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 643 December 1998, . 645 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 646 A., Peterson, J., Sparks, R., Handley, M., and E. 647 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 648 DOI 10.17487/RFC3261, June 2002, 649 . 651 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 652 Locator/ID Separation Protocol (LISP)", RFC 6830, 653 DOI 10.17487/RFC6830, January 2013, 654 . 656 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 657 Locator/ID Separation Protocol (LISP) for Multicast 658 Environments", RFC 6831, DOI 10.17487/RFC6831, January 659 2013, . 661 [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 662 "Interworking between Locator/ID Separation Protocol 663 (LISP) and Non-LISP Sites", RFC 6832, 664 DOI 10.17487/RFC6832, January 2013, 665 . 667 [RFC6833] Fuller, V. and D. Farinacci, "Locator/ID Separation 668 Protocol (LISP) Map-Server Interface", RFC 6833, 669 DOI 10.17487/RFC6833, January 2013, 670 . 672 12.2. Informative References 674 [LISP-LCAF] 675 Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 676 Address Format", draft-ietf-lisp-lcaf-14.txt (work in 677 progress). 679 [LISP-NATT] 680 Ermagan, V., Farinacci, D., Lewis, D., Skriver, J., Maino, 681 F., and C. White, "NAT traversal for LISP", draft-ermagan- 682 lisp-nat-traversal-11.txt (work in progress). 684 Appendix A. Acknowledgments 686 The authors would like to thank the following people for their ideas 687 and comments. They are Albert Cabellos, Khalid Raza, and Vina 688 Ermagan, and Gregg Schudel. 690 Appendix B. Document Change Log 692 B.1. Changes to draft-farinacci-lisp-te-11.txt 694 o Posted September 2016. 696 o Update references and document timer. 698 B.2. Changes to draft-farinacci-lisp-te-10.txt 700 o Posted March 2016. 702 o Update references and document timer. 704 B.3. Changes to draft-farinacci-lisp-te-09.txt 706 o Posted September 2015. 708 o Update references and document timer. 710 B.4. Changes to draft-farinacci-lisp-te-08.txt 712 o Posted March 2015. 714 o Update references and document timer. 716 B.5. Changes to draft-farinacci-lisp-te-07.txt 718 o Posted September 2014. 720 o Update references and document timer. 722 B.6. Changes to draft-farinacci-lisp-te-06.txt 724 o Posted March 2014. 726 o Fix Parantap's affliation to self. 728 B.7. Changes to draft-farinacci-lisp-te-05.txt 730 o Posted March 2014. 732 o Fix text in "Using Recursion" section based on comment Jinghao 733 Wang provided. 735 B.8. Changes to draft-farinacci-lisp-te-04.txt 737 o Resubmitted draft due to document timeout. 739 o Updated Informative References section. 741 B.9. Changes to draft-farinacci-lisp-te-03.txt 743 o Update LISP references to their RFC pointers and document timer. 745 B.10. Changes to draft-farinacci-lisp-te-02.txt 747 o Update references and document timer. 749 B.11. Changes to draft-farinacci-lisp-te-01.txt 751 o Posted July 2012. 753 o Add the Lookup bit to allow an ELP to be a list of encapsulation 754 and/or mapping database lookup addresses. 756 o Indicate that ELPs can be used for service chaining. 758 o Add text to indicate that Map-Notify messages can be sent to new 759 RTRs in a ELP so their map-caches can be pre-populated to avoid 760 mapping database lookup packet loss. 762 o Fixes to editorial comments from Gregg. 764 B.12. Changes to draft-farinacci-lisp-te-00.txt 766 o Initial draft posted March 2012. 768 Authors' Addresses 770 Dino Farinacci 771 lispers.net 772 San Jose, California 773 USA 775 Phone: 408-718-2001 776 Email: farinacci@gmail.com 778 Michael Kowal 779 cisco Systems 780 111 Wood Avenue South 781 ISELIN, NJ 782 USA 784 Email: mikowal@cisco.com 786 Parantap Lahiri 787 USA 789 Email: parantap.lahiri@gmail.com