idnits 2.17.1 draft-farinacci-lisp-te-10.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 (March 14, 2016) is 2963 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RFC 6830 (Obsoleted by RFC 9300, RFC 9301) ** Obsolete normative reference: RFC 6833 (Obsoleted by RFC 9301) == Outdated reference: A later version (-22) exists of draft-ietf-lisp-lcaf-12 == Outdated reference: A later version (-19) exists of draft-ermagan-lisp-nat-traversal-10 Summary: 3 errors (**), 0 flaws (~~), 5 warnings (==), 1 comment (--).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: September 15, 2016 cisco Systems 6 P. Lahiri 7 March 14, 2016 9 LISP Traffic Engineering Use-Cases 10 draft-farinacci-lisp-te-10 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 15, 2016. 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-10.txt . . . . . . . . 15 76 B.2. Changes to draft-farinacci-lisp-te-09.txt . . . . . . . . 16 77 B.3. Changes to draft-farinacci-lisp-te-08.txt . . . . . . . . 16 78 B.4. Changes to draft-farinacci-lisp-te-07.txt . . . . . . . . 16 79 B.5. Changes to draft-farinacci-lisp-te-06.txt . . . . . . . . 16 80 B.6. Changes to draft-farinacci-lisp-te-05.txt . . . . . . . . 16 81 B.7. Changes to draft-farinacci-lisp-te-04.txt . . . . . . . . 16 82 B.8. Changes to draft-farinacci-lisp-te-03.txt . . . . . . . . 16 83 B.9. Changes to draft-farinacci-lisp-te-02.txt . . . . . . . . 16 84 B.10. Changes to draft-farinacci-lisp-te-01.txt . . . . . . . . 17 85 B.11. Changes to draft-farinacci-lisp-te-00.txt . . . . . . . . 17 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 88 1. Requirements Language 90 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 91 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 92 document are to be interpreted as described in RFC 2119 [RFC2119]. 94 2. Introduction 96 This document describes the Locator/Identifier Separation Protocol 97 (LISP), which provides a set of functions for routers to exchange 98 information used to map from non globally routeable Endpoint 99 Identifiers (EIDs) to routeable Routing Locators (RLOCs). It also 100 defines a mechanism for these LISP routers to encapsulate IP packets 101 addressed with EIDs for transmission across the Internet that uses 102 RLOCs for routing and forwarding. 104 When LISP routers encapsulate packets to other LISP routers, the path 105 stretch is typically 1, meaning the packet travels on a direct path 106 from the encapsulating ITR to the decapsulating ETR at the 107 destination site. The direct path is determined by the underlying 108 routing protocol and metrics it uses to find the shortest path. 110 This specification will examine how reencapsulating tunnels [RFC6830] 111 can be used so a packet can take an adminstratively specified path, a 112 congestion avoidance path, a failure recovery path, or multiple load- 113 shared paths, as it travels from ITR to ETR. By introducing an 114 Explicit Locator Path (ELP) locator encoding [LISP-LCAF], an ITR can 115 encapsulate a packet to a Reencapsulating Tunnel Router (RTR) which 116 decapsulates the packet, then encapsulates it to the next locator in 117 the ELP. 119 3. Definition of Terms 121 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 122 IPv6) value used in the source and destination address fields of 123 the first (most inner) LISP header of a packet. The host obtains 124 a destination EID the same way it obtains an destination address 125 today, for example through a Domain Name System (DNS) [RFC1034] 126 lookup or Session Invitation Protocol (SIP) [RFC3261] exchange. 127 The source EID is obtained via existing mechanisms used to set a 128 host's "local" IP address. An EID used on the public Internet 129 must have the same properties as any other IP address used in that 130 manner; this means, among other things, that it must be globally 131 unique. An EID is allocated to a host from an EID-prefix block 132 associated with the site where the host is located. An EID can be 133 used by a host to refer to other hosts. EIDs MUST NOT be used as 134 LISP RLOCs. Note that EID blocks MAY be assigned in a 135 hierarchical manner, independent of the network topology, to 136 facilitate scaling of the mapping database. In addition, an EID 137 block assigned to a site may have site-local structure 138 (subnetting) for routing within the site; this structure is not 139 visible to the global routing system. In theory, the bit string 140 that represents an EID for one device can represent an RLOC for a 141 different device. As the architecture is realized, if a given bit 142 string is both an RLOC and an EID, it must refer to the same 143 entity in both cases. When used in discussions with other 144 Locator/ID separation proposals, a LISP EID will be called a 145 "LEID". Throughout this document, any references to "EID" refers 146 to an LEID. 148 Routing Locator (RLOC): A RLOC is an IPv4 [RFC0791] or IPv6 149 [RFC2460] address of an egress tunnel router (ETR). A RLOC is the 150 output of an EID-to-RLOC mapping lookup. An EID maps to one or 151 more RLOCs. Typically, RLOCs are numbered from topologically- 152 aggregatable blocks that are assigned to a site at each point to 153 which it attaches to the global Internet; where the topology is 154 defined by the connectivity of provider networks, RLOCs can be 155 thought of as PA addresses. Multiple RLOCs can be assigned to the 156 same ETR device or to multiple ETR devices at a site. 158 Reencapsulating Tunnel Router (RTR): An RTR is a router that acts 159 as an ETR (or PETR) by decapsulating packets where the destination 160 address in the "outer" IP header is one of its own RLOCs. Then 161 acts as an ITR (or PITR) by making a decision where to encapsulate 162 the packet based on the next locator in the ELP towards the final 163 destination ETR. 165 Explicit Locator Path (ELP): The ELP is an explicit list of RLOCs 166 for each RTR a packet must travel to along its path toward a final 167 destination ETR (or PETR). The list is a strict ordering where 168 each RLOC in the list is visited. However, the path from one RTR 169 to another is determined by the underlying routing protocol and 170 how the infrastructure assigns metrics and policies for the path. 172 Recursive Tunneling: Recursive tunneling occurs when a packet has 173 more than one LISP IP header. Additional layers of tunneling MAY 174 be employed to implement traffic engineering or other re-routing 175 as needed. When this is done, an additional "outer" LISP header 176 is added and the original RLOCs are preserved in the "inner" 177 header. Any references to tunnels in this specification refers to 178 dynamic encapsulating tunnels and they are never statically 179 configured. 181 Reencapsulating Tunnels: Reencapsulating tunneling occurs when an 182 ETR removes a LISP header, then acts as an ITR to prepend another 183 LISP header. Doing this allows a packet to be re-routed by the 184 reencapsulating router without adding the overhead of additional 185 tunnel headers. Any references to tunnels in this specification 186 refers to dynamic encapsulating tunnels and they are never 187 statically configured. When using multiple mapping database 188 systems, care must be taken to not create reencapsulation loops 189 through misconfiguration. 191 4. Overview 193 Typically, a packet's path from source EID to destination EID travels 194 through the locator core via the encapsulating ITR directly to the 195 decapsulating ETR as the following diagram illustrates: 197 Legend: 199 seid: Packet is originated by source EID 'seid'. 201 deid: Packet is consumed by destination EID 'deid'. 203 A,B,C,D : Core routers in different ASes. 205 ---> : The physical topological path between two routers. 207 ===> : A multi-hop LISP dynamic tunnel between LISP routers. 209 Core Network 210 Source site (----------------------------) Destination Site 211 +--------+ ( ) +---------+ 212 | \ ( ) / | 213 | seid ITR ---(---> A --> B --> C --> D ---)---> ETR deid | 214 | / || ( ) ^^ \ | 215 +--------+ || ( ) || +---------+ 216 || (----------------------------) || 217 || || 218 =========================================== 219 LISP Tunnel 221 Typical Data Path from ITR to ETR 223 Let's introduce RTRs 'X' and 'Y' so that, for example, if it is 224 desirable to route around the path from B to C, one could provide an 225 ELP of (X,Y,etr): 227 Core Network 228 Source site (----------------------------) Destination Site 229 +--------+ ( ) +---------+ 230 | \ ( ) / | 231 | seid ITR ---(---> A --> B --> C --> D ---)---> ETR deid | 232 | / || ( / ^ ) ^^ \ | 233 | / || ( | \ ) || \ | 234 +-------+ || ( v | ) || +--------+ 235 || ( X ======> Y ) || 236 || ( ^^ || ) || 237 || (--------||---------||-------) || 238 || || || || 239 ================= ================= 240 LISP Tunnel LISP Tunnel 242 ELP tunnel path ITR ==> X, then X ==> Y, and then Y ==> ETR 244 There are various reasons why the path from 'seid' to 'deid' may want 245 to avoid the path from B to C. To list a few: 247 o There may not be sufficient capacity provided by the networks that 248 connect B and C together. 250 o There may be a policy reason to avoid the ASes that make up the 251 path between B and C. 253 o There may be a failure on the path between B and C which makes the 254 path unreliable. 256 o There may be monitoring or traffic inspection resources close to 257 RTRs X and Y that do network accounting or measurement. 259 o There may be a chain of services performed at RTRs X and Y 260 regardless if the path from ITR to ETR is through B and C. 262 5. Explicit Locator Paths 264 The notation for a general formatted ELP is (x, y, etr) which 265 represents the list of RTRs a packet SHOULD travel through to reach 266 the final tunnel hop to the ETR. 268 The procedure for using an ELP at each tunnel hop is as follows: 270 1. The ITR will retrieve the ELP from the mapping database. 272 2. The ITR will encapsulate the packet to RLOC 'x'. 274 3. The RTR with RLOC 'x' will decapsulate the packet. It will use 275 the decapsulated packet's destination address as a lookup into 276 the mapping database to retrieve the ELP. 278 4. RTR 'x' will encapsulate the packet to RTR with RLOC 'y'. 280 5. The RTR with RLOC 'y' will decapsulate the packet. It will use 281 the decapsulated packet's destination address as a lookup into 282 the mapping database to retrieve the ELP. 284 6. RTR 'y' will encapsulate the packet on the final tunnel hop to 285 ETR with RLOC 'etr'. 287 7. The ETR will decapsulate the packet and deliver the packet to the 288 EID inside of its site. 290 The specific format for the ELP can be found in [LISP-LCAF]. It is 291 defined that an ELP will appear as a single encoded locator in a 292 locator-set. Say for instance, we have a mapping entry for EID- 293 prefix 10.0.0.0/8 that is reachable via 4 locators. Two locators are 294 being used as active/active and the other two are used as active/ 295 active if the first two go unreachable (as noted by the priority 296 assignments below). This is what the mapping entry would look like: 298 EID-prefix: 10.0.0.0/8 299 Locator-set: ETR-A: priority 1, weight 50 300 ETR-B: priority 1, weight 50 301 ETR-C: priority 2, weight 50 302 ETR-D: priority 2, weight 50 304 If an ELP is going to be used to have a policy path to ETR-A and 305 possibly another policy path to ETR-B, the locator-set would be 306 encoded as follows: 308 EID-prefix: 10.0.0.0/8 309 Locator-set: (x, y, ETR-A): priority 1, weight 50 310 (q, r, ETR-B): priority 1, weight 50 311 ETR-C: priority 2, weight 50 312 ETR-D: priority 2, weight 50 314 The mapping entry with ELP locators is registered to the mapping 315 database system just like any other mapping entry would. The 316 registration is typically performed by the ETR(s) that are assigned 317 and own the EID-prefix. That is, the destination site makes the 318 choice of the RTRs in the ELP. However, it may be common practice 319 for a provisioning system to program the mapping database with ELPs. 321 Another case where a locator-set can be used for flow-based load- 322 sharing across multiple paths to the same destination site: 324 EID-prefix: 10.0.0.0/8 325 Locator-set: (x, y, ETR-A): priority 1, weight 75 326 (q, r, ETR-A): priority 1, weight 25 328 Using this mapping entry, an ITR would load split 75% of the EID 329 flows on the (x, y, ETR-A) ELP path and 25% of the EID flows on the 330 (q, r, ETR-A) ELP path. If any of the ELPs go down, then the other 331 can take 100% of the load. 333 5.1. ELP Re-optimization 335 ELP re-optimization is a process of changing the RLOCs of an ELP due 336 to underlying network change conditions. Just like when there is any 337 locator change for a locator-set, the procedures from the main LISP 338 specification [RFC6830] are followed. 340 When a RLOC from an ELP is changed, Map-Notify messages [RFC6833] can 341 be used to inform the existing RTRs in the ELP so they can do a 342 lookup to obtain the latest version of the ELP. Map-Notify messages 343 can also be sent to new RTRs in an ELP so they can get the ELP in 344 advance to receiving packets that will use the ELP. This can 345 minimize packet loss during mapping database lookups in RTRs. 347 5.2. Using Recursion 349 In the previous examples, we showed how an ITR encapsulates using an 350 ELP of (x, y, etr). When a packet is encapsulated by the ITR to RTR 351 'x', the RTR may want a policy path to RTR 'y' and run another level 352 of reencapsulating tunnels for packets destined to RTR 'y'. In this 353 case, RTR 'x' does not encapsulate packets to 'y' but rather performs 354 a mapping database lookup on the address 'y', requests the ELP for 355 RTR 'y', and encapsulates packets to the first-hop of the returned 356 ELP. This can be done when using a public or private mapping 357 database. The decision to use address 'y' as an encapsulation 358 address versus a lookup address is based on the L-bit setting for 'y' 359 in the ELP entry. The decision and policy of ELP encodings are local 360 to the entity which registers the EID-prefix associated with the ELP. 362 Another example of recursion is when the ITR uses the ELP (x, y, etr) 363 to first prepend a header with a destination RLOC of the ETR and then 364 prepend another header and encapsulate the packet to RTR 'x'. When 365 RTR 'x' decapsulates the packet, rather than doing a mapping database 366 lookup on RTR 'y' the last example showed, instead RTR 'x' does a 367 mapping database lookup on ETR 'etr'. In this scenario, RTR 'x' can 368 choose an ELP from the locator-set by considering the source RLOC 369 address of the ITR versus considering the source EID. 371 This additional level of recursion also brings advantages for the 372 provider of RTR 'x' to store less state. Since RTR 'x' does not need 373 to look at the inner most header, it does not need to store EID 374 state. It only stores an entry for RTR 'y' which many EID flows 375 could share for scaling benefits. The locator-set for entry 'y' 376 could either be a list of typical locators, a list of ELPs, or 377 combination of both. Another advantage is that packet load-splitting 378 can be accomplished by examining the source of a packet. If the 379 source is an ITR versus the source being the last-hop of an ELP the 380 last-hop selected, different forwarding paths can be used. 382 5.3. ELP Selection based on Class of Service 384 Paths to an ETR may want to be selected based on different classes of 385 service. Packets from a set of sources that have premium service can 386 use ELP paths that are less congested where normal sources use ELP 387 paths that compete for less resources or use longer paths for best 388 effort service. 390 Using source/destination lookups into the mapping database can yield 391 different ELPs. So for example, a premium service flow with 392 (source=1.1.1.1, dest=10.1.1.1) can be described by using the 393 following mapping entry: 395 EID-prefix: (1.0.0.0/8, 10.0.0.0/8) 396 Locator-set: (x, y, ETR-A): priority 1, weight 50 397 (q, r, ETR-A): priority 1, weight 50 399 And all other best-effort sources would use different mapping entry 400 described by: 402 EID-prefix: (0.0.0.0/0, 10.0.0.0/8) 403 Locator-set: (x, x', y, y', ETR-A): priority 1, weight 50 404 (q, q', r, r', ETR-A): priority 1, weight 50 406 If the source/destination lookup is coupled with recursive lookups, 407 then an ITR can encapsulate to the ETR, prepending a header that 408 selects source address ITR-1 based on the premium class of service 409 source, or selects source address ITR-2 for best-effort sources with 410 normal class of service. The ITR then does another lookup in the 411 mapping database on the prepended header using lookup key 412 (source=ITR-1, dest=10.1.1.1) that returns the following mapping 413 entry: 415 EID-prefix: (ITR-1, 10.0.0.0/8) 416 Locator-set: (x, y, ETR-A): priority 1, weight 50 417 (q, r, ETR-A): priority 1, weight 50 419 And all other sources would use different mapping entry with a lookup 420 key of (source=ITR-2, dest=10.1.1.1): 422 EID-prefix: (ITR-2, 10.0.0.0/8) 423 Locator-set: (x, x', y, y', ETR-A): priority 1, weight 50 424 (q, q', r, r', ETR-A): priority 1, weight 50 426 This will scale the mapping system better by having fewer source/ 427 destination combinations. Refer to the Source/Dest LCAF type 428 described in [LISP-LCAF] for encoding EIDs in Map-Request and Map- 429 Register messages. 431 5.4. Packet Loop Avoidance 433 An ELP that is first used by an ITR must be inspected for encoding 434 loops. If any RLOC appears twice in the ELP, it MUST not be used. 436 Since it is expected that multiple mapping systems will be used, 437 there can be a loop across ELPs when registered in different mapping 438 systems. The TTL copying procedures for reencapsulating tunnels and 439 recursive tunnels in [RFC6830] MUST be followed. 441 6. Service Chaining 443 An ELP can be used to deploy services at each reencapsulation point 444 in the network. One example is to implement a scrubber service when 445 a destination EID is being DoS attacked. That is, when a DoS attack 446 is recognized when the encapsulation path is between ITR and ETR, an 447 ELP can be registered for a destination EID to the mapping database 448 system. The ELP can include an RTR so the ITR can encapsulate 449 packets to the RTR which will decapsulate and deliver packets to a 450 scrubber service device. The scrubber could decide if the offending 451 packets are dropped or allowed to be sent to the destination EID. In 452 which case, the scurbber delivers packets back to the RTR which 453 encapsulates to the ETR. 455 7. RLOC Probing by RTRs 457 Since an RTR knows the next tunnel hop to encapsulate to, it can 458 monitor the reachability of the next-hop RTR RLOC by doing RLOC- 459 probing according to the procedures in [RFC6830]. When the RLOC is 460 determined unreachable by the RLOC-probing mechanisms, the RTR can 461 use another locator in the locator-set. That could be the final ETR, 462 a RLOC of another RTR, or an ELP where it must search for itself and 463 use the next RLOC in the ELP list to encapsulate to. 465 RLOC-probing can also be used to measure delay on the path between 466 RTRs and when it is desirable switch to another lower delay ELP. 468 8. Interworking Considerations 470 [RFC6832] defines procedures for how non-LISP sites talk to LISP 471 sites. The network elements defined in the Interworking 472 specification, the proxy ITR (PITR) and proxy ETR (PETR) (as well as 473 their multicast counterparts defined in [RFC6831]) can participate in 474 LISP-TE. That is, a PITR and a PETR can appear in an ELP list and 475 act as an RTR. 477 Note when an RLOC appears in an ELP, it can be of any address-family. 478 There can be a mix of IPv4 and IPv6 locators present in the same ELP. 479 This can provide benefits where islands of one address-family or the 480 other are supported and connectivity across them is necessary. For 481 instance, an ELP can look like: 483 (x4, a46, b64, y4, etr) 485 Where an IPv4 ITR will encapsulate using an IPv4 RLOC 'x4' and 'x4' 486 could reach an IPv4 RLOC 'a46', but RTR 'a46' encapsulates to an IPv6 487 RLOC 'b64' when the network between them is IPv6-only. Then RTR 488 'b64' encapsulates to IPv4 RLOC 'y4' if the network between them is 489 dual-stack. 491 Note that RTRs can be used for NAT-traversal scenarios [LISP-NATT] as 492 well to reduce the state in both an xTR that resides behind a NAT and 493 the state the NAT needs to maintain. In this case, the xTR only 494 needs a default map-cache entry pointing to the RTR for outbound 495 traffic and all remote ITRs can reach EIDs through the xTR behind a 496 NAT via a single RTR (or a small set RTRs for redundancy). 498 RTRs have some scaling features to reduce the number of locator-set 499 changes, the amount of state, and control packet overhead: 501 o When ITRs and PITRs are using a small set of RTRs for 502 encapsulating to "orders of magnitude" more EID-prefixes, the 503 probability of locator-set changes are limited to the RTR RLOC 504 changes versus the RLOC changes for the ETRs associated with the 505 EID-prefixes if the ITRs and PITRs were directly encapsulating to 506 the ETRs. This comes at an expense in packet stretch, but 507 depending on RTR placement, this expense can be mitigated. 509 o When RTRs are on-path between many pairwise EID flows, ITRs and 510 PITRs can store a small number of coarse EID-prefixes. 512 o RTRs can be used to help scale RLOC-probing. Instead of ITRs 513 RLOC-probing all ETRs for each destination site it has cached, the 514 ITRs can probe a smaller set of RTRs which in turn, probe the 515 destination sites. 517 9. Multicast Considerations 519 ELPs have application in multicast environments. Just like RTRs can 520 be used to provide connectivity across different address family 521 islands, RTRs can help concatenate a multicast region of the network 522 to one that does not support native multicast. 524 Note there are various combinations of connectivity that can be 525 accomplished with the deployment of RTRs and ELPs: 527 o Providing multicast forwarding between IPv4-only-unicast regions 528 and IPv4-multicast regions. 530 o Providing multicast forwarding between IPv6-only-unicast regions 531 and IPv6-multicast regions. 533 o Providing multicast forwarding between IPv4-only-unicast regions 534 and IPv6-multicast regions. 536 o Providing multicast forwarding between IPv6-only-unicast regions 537 and IPv4-multicast regions. 539 o Providing multicast forwarding between IPv4-multicast regions and 540 IPv6-multicast regions. 542 An ITR or PITR can do a (S-EID,G) lookup into the mapping database. 543 What can be returned is a typical locator-set that could be made up 544 of the various RLOC addresses: 546 Multicast EID key: (seid, G) 547 Locator-set: ETR-A: priority 1, weight 25 548 ETR-B: priority 1, weight 25 549 g1: priority 1, weight 25 550 g2: priority 1, weight 25 552 An entry for host 'seid' sending to application group 'G' 554 The locator-set above can be used as a replication list. That is 555 some RLOCs listed can be unicast RLOCs and some can be delivery group 556 RLOCs. A unicast RLOC in this case is used to encapsulate a 557 multicast packet originated by a multicast source EID into a unicast 558 packet for unicast delivery on the underlying network. ETR-A could 559 be a IPv4 unicast RLOC address and ETR-B could be a IPv6 unicast RLOC 560 address. 562 A delivery group address is used when a multicast packet originated 563 by a multicast source EID is encapsulated in a multicast packet for 564 multicast delivery on the underlying network. Group address 'g1' 565 could be a IPv4 delivery group RLOC and group address 'g2' could be 566 an IPv6 delivery group RLOC. 568 Flexibility for these various types of connectivity combinations can 569 be achieved and provided by the mapping database system. And the RTR 570 placement allows the connectivity to occur where the differences in 571 network functionality are located. 573 Extending this concept by allowing ELPs in locator-sets, one could 574 have this locator-set registered in the mapping database for (seid, 575 G). For example: 577 Multicast EID key: (seid, G) 578 Locator-set: (x, y, ETR-A): priority 1, weight 50 579 (a, g, b, ETR-B): priority 1, weight 50 581 Using ELPs for multicast flows 583 In the above situation, an ITR would encapsulate a multicast packet 584 originated by a multicast source EID to the RTR with unicast RLOC 585 'x'. Then RTR 'x' would decapsulate and unicast encapsulate to RTR 586 'y' ('x' or 'y' could be either IPv4 or IPv6 unicast RLOCs), which 587 would decapsulate and unicast encapsulate to the final RLOC 'ETR-A'. 588 The ETR 'ETR-A' would decapsulate and deliver the multicast packet 589 natively to all the receivers joined to application group 'G' inside 590 the LISP site. 592 Let's look at the ITR using the ELP (a, g, b, ETR-B). Here the 593 encapsulation path would be the ITR unicast encapsulates to unicast 594 RLOC 'a'. RTR 'a' multicast encapsulates to delivery group 'g'. The 595 packet gets to all ETRs that have joined delivery group 'g' so they 596 can deliver the multicast packet to joined receivers of application 597 group 'G' in their sites. RTR 'b' is also joined to delivery group 598 'g'. Since it is in the ELP, it will be the only RTR that unicast 599 encapsulates the multicast packet to ETR 'ETR-B'. Lastly, 'ETR-B' 600 decapsulates and delivers the multicast packet to joined receivers to 601 application group 'G' in its LISP site. 603 As one can see there are all sorts of opportunities to provide 604 multicast connectivity across a network with non-congruent support 605 for multicast and different address-families. One can also see how 606 using the mapping database can allow flexible forms of delivery 607 policy, rerouting, and congestion control management in multicast 608 environments. 610 10. Security Considerations 612 When an RTR receives a LISP encapsulated packet, it can look at the 613 outer source address to verify that RLOC is the one listed as the 614 previous hop in the ELP list. If the outer source RLOC address 615 appears before the RLOC which matches the outer destination RLOC 616 address, the decapsulating RTR (or ETR if last hop), MAY choose to 617 drop the packet. 619 11. IANA Considerations 621 At this time there are no requests for IANA. 623 12. References 625 12.1. Normative References 627 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 628 DOI 10.17487/RFC0791, September 1981, 629 . 631 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 632 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 633 . 635 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 636 Requirement Levels", BCP 14, RFC 2119, 637 DOI 10.17487/RFC2119, March 1997, 638 . 640 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 641 (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460, 642 December 1998, . 644 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 645 A., Peterson, J., Sparks, R., Handley, M., and E. 646 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 647 DOI 10.17487/RFC3261, June 2002, 648 . 650 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 651 Locator/ID Separation Protocol (LISP)", RFC 6830, 652 DOI 10.17487/RFC6830, January 2013, 653 . 655 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 656 Locator/ID Separation Protocol (LISP) for Multicast 657 Environments", RFC 6831, DOI 10.17487/RFC6831, January 658 2013, . 660 [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 661 "Interworking between Locator/ID Separation Protocol 662 (LISP) and Non-LISP Sites", RFC 6832, 663 DOI 10.17487/RFC6832, January 2013, 664 . 666 [RFC6833] Fuller, V. and D. Farinacci, "Locator/ID Separation 667 Protocol (LISP) Map-Server Interface", RFC 6833, 668 DOI 10.17487/RFC6833, January 2013, 669 . 671 12.2. Informative References 673 [LISP-LCAF] 674 Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 675 Address Format", draft-ietf-lisp-lcaf-12.txt (work in 676 progress). 678 [LISP-NATT] 679 Ermagan, V., Farinacci, D., Lewis, D., Skriver, J., Maino, 680 F., and C. White, "NAT traversal for LISP", draft-ermagan- 681 lisp-nat-traversal-10.txt (work in progress). 683 Appendix A. Acknowledgments 685 The authors would like to thank the following people for their ideas 686 and comments. They are Albert Cabellos, Khalid Raza, and Vina 687 Ermagan, and Gregg Schudel. 689 Appendix B. Document Change Log 691 B.1. Changes to draft-farinacci-lisp-te-10.txt 693 o Posted March 2016. 695 o Update references and document timer. 697 B.2. Changes to draft-farinacci-lisp-te-09.txt 699 o Posted September 2015. 701 o Update references and document timer. 703 B.3. Changes to draft-farinacci-lisp-te-08.txt 705 o Posted March 2015. 707 o Update references and document timer. 709 B.4. Changes to draft-farinacci-lisp-te-07.txt 711 o Posted September 2014. 713 o Update references and document timer. 715 B.5. Changes to draft-farinacci-lisp-te-06.txt 717 o Posted March 2014. 719 o Fix Parantap's affliation to self. 721 B.6. Changes to draft-farinacci-lisp-te-05.txt 723 o Posted March 2014. 725 o Fix text in "Using Recursion" section based on comment Jinghao 726 Wang provided. 728 B.7. Changes to draft-farinacci-lisp-te-04.txt 730 o Resubmitted draft due to document timeout. 732 o Updated Informative References section. 734 B.8. Changes to draft-farinacci-lisp-te-03.txt 736 o Update LISP references to their RFC pointers and document timer. 738 B.9. Changes to draft-farinacci-lisp-te-02.txt 740 o Update references and document timer. 742 B.10. Changes to draft-farinacci-lisp-te-01.txt 744 o Posted July 2012. 746 o Add the Lookup bit to allow an ELP to be a list of encapsulation 747 and/or mapping database lookup addresses. 749 o Indicate that ELPs can be used for service chaining. 751 o Add text to indicate that Map-Notify messages can be sent to new 752 RTRs in a ELP so their map-caches can be pre-populated to avoid 753 mapping database lookup packet loss. 755 o Fixes to editorial comments from Gregg. 757 B.11. Changes to draft-farinacci-lisp-te-00.txt 759 o Initial draft posted March 2012. 761 Authors' Addresses 763 Dino Farinacci 764 lispers.net 765 San Jose, California 766 USA 768 Phone: 408-718-2001 769 Email: farinacci@gmail.com 771 Michael Kowal 772 cisco Systems 773 111 Wood Avenue South 774 ISELIN, NJ 775 USA 777 Email: mikowal@cisco.com 779 Parantap Lahiri 780 USA 782 Email: parantap.lahiri@gmail.com