idnits 2.17.1 draft-farinacci-lisp-te-04.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 (January 13, 2014) is 3756 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RFC 6830 (Obsoleted by RFC 9300, RFC 9301) ** Obsolete normative reference: RFC 6833 (Obsoleted by RFC 9301) == Outdated reference: A later version (-22) exists of draft-ietf-lisp-lcaf-03 == Outdated reference: A later version (-19) exists of draft-ermagan-lisp-nat-traversal-04 Summary: 3 errors (**), 0 flaws (~~), 5 warnings (==), 1 comment (--).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 P. Lahiri 5 Expires: July 17, 2014 Juniper Networks 6 M. Kowal 7 cisco Systems 8 January 13, 2014 10 LISP Traffic Engineering Use-Cases 11 draft-farinacci-lisp-te-04 13 Abstract 15 This document describes how LISP reencapsulating tunnels can be used 16 for Traffic Engineering purposes. The mechanisms described in this 17 document require no LISP protocol changes but do introduce a new 18 locator (RLOC) encoding. The Traffic Engineering features provided 19 by these LISP mechanisms can span intra-domain, inter-domain, or 20 combination of both. 22 Status of this Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on July 17, 2014. 39 Copyright Notice 41 Copyright (c) 2014 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 57 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 58 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 5 59 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 60 5. Explicit Locator Paths . . . . . . . . . . . . . . . . . . . . 9 61 5.1. ELP Re-optimization . . . . . . . . . . . . . . . . . . . 10 62 5.2. Using Recursion . . . . . . . . . . . . . . . . . . . . . 10 63 5.3. ELP Selection based on Class of Service . . . . . . . . . 11 64 5.4. Packet Loop Avoidance . . . . . . . . . . . . . . . . . . 12 65 6. Service Chaining . . . . . . . . . . . . . . . . . . . . . . . 13 66 7. RLOC Probing by RTRs . . . . . . . . . . . . . . . . . . . . . 14 67 8. Interworking Considerations . . . . . . . . . . . . . . . . . 15 68 9. Multicast Considerations . . . . . . . . . . . . . . . . . . . 16 69 10. Security Considerations . . . . . . . . . . . . . . . . . . . 18 70 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 71 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 72 12.1. Normative References . . . . . . . . . . . . . . . . . . . 20 73 12.2. Informative References . . . . . . . . . . . . . . . . . . 20 74 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 22 75 Appendix B. Document Change Log . . . . . . . . . . . . . . . . . 23 76 B.1. Changes to draft-farinacci-lisp-te-04.txt . . . . . . . . 23 77 B.2. Changes to draft-farinacci-lisp-te-03.txt . . . . . . . . 23 78 B.3. Changes to draft-farinacci-lisp-te-02.txt . . . . . . . . 23 79 B.4. Changes to draft-farinacci-lisp-te-01.txt . . . . . . . . 23 80 B.5. Changes to draft-farinacci-lisp-te-00.txt . . . . . . . . 23 81 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24 83 1. Requirements Language 85 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 86 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 87 document are to be interpreted as described in RFC 2119 [RFC2119]. 89 2. Introduction 91 This document describes the Locator/Identifier Separation Protocol 92 (LISP), which provides a set of functions for routers to exchange 93 information used to map from non globally routeable Endpoint 94 Identifiers (EIDs) to routeable Routing Locators (RLOCs). It also 95 defines a mechanism for these LISP routers to encapsulate IP packets 96 addressed with EIDs for transmission across the Internet that uses 97 RLOCs for routing and forwarding. 99 When LISP routers encapsulate packets to other LISP routers, the path 100 stretch is typically 1, meaning the packet travels on a direct path 101 from the encapsulating ITR to the decapsulating ETR at the 102 destination site. The direct path is determined by the underlying 103 routing protocol and metrics it uses to find the shortest path. 105 This specification will examine how reencapsulating tunnels [RFC6830] 106 can be used so a packet can take an adminstratively specified path, a 107 congestion avoidance path, a failure recovery path, or multiple load- 108 shared paths, as it travels from ITR to ETR. By introducing an 109 Explicit Locator Path (ELP) locator encoding [LISP-LCAF], an ITR can 110 encapsulate a packet to a Reencapsulating Tunnel Router (RTR) which 111 decapsulates the packet, then encapsulates it to the next locator in 112 the ELP. 114 3. Definition of Terms 116 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 117 IPv6) value used in the source and destination address fields of 118 the first (most inner) LISP header of a packet. The host obtains 119 a destination EID the same way it obtains an destination address 120 today, for example through a Domain Name System (DNS) [RFC1034] 121 lookup or Session Invitation Protocol (SIP) [RFC3261] exchange. 122 The source EID is obtained via existing mechanisms used to set a 123 host's "local" IP address. An EID used on the public Internet 124 must have the same properties as any other IP address used in that 125 manner; this means, among other things, that it must be globally 126 unique. An EID is allocated to a host from an EID-prefix block 127 associated with the site where the host is located. An EID can be 128 used by a host to refer to other hosts. EIDs MUST NOT be used as 129 LISP RLOCs. Note that EID blocks MAY be assigned in a 130 hierarchical manner, independent of the network topology, to 131 facilitate scaling of the mapping database. In addition, an EID 132 block assigned to a site may have site-local structure 133 (subnetting) for routing within the site; this structure is not 134 visible to the global routing system. In theory, the bit string 135 that represents an EID for one device can represent an RLOC for a 136 different device. As the architecture is realized, if a given bit 137 string is both an RLOC and an EID, it must refer to the same 138 entity in both cases. When used in discussions with other 139 Locator/ID separation proposals, a LISP EID will be called a 140 "LEID". Throughout this document, any references to "EID" refers 141 to an LEID. 143 Routing Locator (RLOC): A RLOC is an IPv4 [RFC0791] or IPv6 144 [RFC2460] address of an egress tunnel router (ETR). A RLOC is the 145 output of an EID-to-RLOC mapping lookup. An EID maps to one or 146 more RLOCs. Typically, RLOCs are numbered from topologically- 147 aggregatable blocks that are assigned to a site at each point to 148 which it attaches to the global Internet; where the topology is 149 defined by the connectivity of provider networks, RLOCs can be 150 thought of as PA addresses. Multiple RLOCs can be assigned to the 151 same ETR device or to multiple ETR devices at a site. 153 Reencapsulating Tunnel Router (RTR): An RTR is a router that acts 154 as an ETR (or PETR) by decapsulating packets where the destination 155 address in the "outer" IP header is one of its own RLOCs. Then 156 acts as an ITR (or PITR) by making a decision where to encapsulate 157 the packet based on the next locator in the ELP towards the final 158 destination ETR. 160 Explicit Locator Path (ELP): The ELP is an explicit list of RLOCs 161 for each RTR a packet must travel to along its path toward a final 162 destination ETR (or PETR). The list is a strict ordering where 163 each RLOC in the list is visited. However, the path from one RTR 164 to another is determined by the underlying routing protocol and 165 how the infrastructure assigns metrics and policies for the path. 167 Recursive Tunneling: Recursive tunneling occurs when a packet has 168 more than one LISP IP header. Additional layers of tunneling MAY 169 be employed to implement traffic engineering or other re-routing 170 as needed. When this is done, an additional "outer" LISP header 171 is added and the original RLOCs are preserved in the "inner" 172 header. Any references to tunnels in this specification refers to 173 dynamic encapsulating tunnels and they are never statically 174 configured. 176 Reencapsulating Tunnels: Reencapsulating tunneling occurs when an 177 ETR removes a LISP header, then acts as an ITR to prepend another 178 LISP header. Doing this allows a packet to be re-routed by the 179 reencapsulating router without adding the overhead of additional 180 tunnel headers. Any references to tunnels in this specification 181 refers to dynamic encapsulating tunnels and they are never 182 statically configured. When using multiple mapping database 183 systems, care must be taken to not create reencapsulation loops 184 through misconfiguration. 186 4. Overview 188 Typically, a packet's path from source EID to destination EID travels 189 through the locator core via the encapsulating ITR directly to the 190 decapsulating ETR as the following diagram illustrates: 192 Legend: 194 seid: Packet is originated by source EID 'seid'. 196 deid: Packet is consumed by destination EID 'deid'. 198 A,B,C,D : Core routers in different ASes. 200 ---> : The physical topological path between two routers. 202 ===> : A multi-hop LISP dynamic tunnel between LISP routers. 204 Core Network 205 Source site (----------------------------) Destination Site 206 +--------+ ( ) +---------+ 207 | \ ( ) / | 208 | seid ITR ---(---> A --> B --> C --> D ---)---> ETR deid | 209 | / || ( ) ^^ \ | 210 +--------+ || ( ) || +---------+ 211 || (----------------------------) || 212 || || 213 =========================================== 214 LISP Tunnel 216 Typical Data Path from ITR to ETR 218 Let's introduce RTRs 'X' and 'Y' so that, for example, if it is 219 desirable to route around the path from B to C, one could provide an 220 ELP of (X,Y,etr): 222 Core Network 223 Source site (----------------------------) Destination Site 224 +--------+ ( ) +---------+ 225 | \ ( ) / | 226 | seid ITR ---(---> A --> B --> C --> D ---)---> ETR deid | 227 | / || ( / ^ ) ^^ \ | 228 | / || ( | \ ) || \ | 229 +-------+ || ( v | ) || +--------+ 230 || ( X ======> Y ) || 231 || ( ^^ || ) || 232 || (--------||---------||-------) || 233 || || || || 234 ================= ================= 235 LISP Tunnel LISP Tunnel 237 ELP tunnel path ITR ==> X, then X ==> Y, and then Y ==> ETR 239 There are various reasons why the path from 'seid' to 'deid' may want 240 to avoid the path from B to C. To list a few: 242 o There may not be sufficient capacity provided by the networks that 243 connect B and C together. 245 o There may be a policy reason to avoid the ASes that make up the 246 path between B and C. 248 o There may be a failure on the path between B and C which makes the 249 path unreliable. 251 o There may be monitoring or traffic inspection resources close to 252 RTRs X and Y that do network accounting or measurement. 254 o There may be a chain of services performed at RTRs X and Y 255 regardless if the path from ITR to ETR is through B and C. 257 5. Explicit Locator Paths 259 The notation for a general formatted ELP is (x, y, etr) which 260 represents the list of RTRs a packet SHOULD travel through to reach 261 the final tunnel hop to the ETR. 263 The procedure for using an ELP at each tunnel hop is as follows: 265 1. The ITR will retrieve the ELP from the mapping database. 267 2. The ITR will encapsulate the packet to RLOC 'x'. 269 3. The RTR with RLOC 'x' will decapsulate the packet. It will use 270 the decapsulated packet's destination address as a lookup into 271 the mapping database to retrieve the ELP. 273 4. RTR 'x' will encapsulate the packet to RTR with RLOC 'y'. 275 5. The RTR with RLOC 'y' 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 6. RTR 'y' will encapsulate the packet on the final tunnel hop to 280 ETR with RLOC 'etr'. 282 7. The ETR will decapsulate the packet and deliver the packet to the 283 EID inside of its site. 285 The specific format for the ELP can be found in [LISP-LCAF]. It is 286 defined that an ELP will appear as a single encoded locator in a 287 locator-set. Say for instance, we have a mapping entry for EID- 288 prefix 10.0.0.0/8 that is reachable via 4 locators. Two locators are 289 being used as active/active and the other two are used as active/ 290 active if the first two go unreachable (as noted by the priority 291 assignments below). This is what the mapping entry would look like: 293 EID-prefix: 10.0.0.0/8 294 Locator-set: ETR-A: priority 1, weight 50 295 ETR-B: priority 1, weight 50 296 ETR-C: priority 2, weight 50 297 ETR-D: priority 2, weight 50 299 If an ELP is going to be used to have a policy path to ETR-A and 300 possibly another policy path to ETR-B, the locator-set would be 301 encoded as follows: 303 EID-prefix: 10.0.0.0/8 304 Locator-set: (x, y, ETR-A): priority 1, weight 50 305 (q, r, ETR-B): priority 1, weight 50 306 ETR-C: priority 2, weight 50 307 ETR-D: priority 2, weight 50 309 The mapping entry with ELP locators is registered to the mapping 310 database system just like any other mapping entry would. The 311 registration is typically performed by the ETR(s) that are assigned 312 and own the EID-prefix. That is, the destination site makes the 313 choice of the RTRs in the ELP. However, it may be common practice 314 for a provisioning system to program the mapping database with ELPs. 316 Another case where a locator-set can be used for flow-based load- 317 sharing across multiple paths to the same destination site: 319 EID-prefix: 10.0.0.0/8 320 Locator-set: (x, y, ETR-A): priority 1, weight 75 321 (q, r, ETR-A): priority 1, weight 25 323 Using this mapping entry, an ITR would load split 75% of the EID 324 flows on the (x, y, ETR-A) ELP path and 25% of the EID flows on the 325 (q, r, ETR-A) ELP path. If any of the ELPs go down, then the other 326 can take 100% of the load. 328 5.1. ELP Re-optimization 330 ELP re-optimization is a process of changing the RLOCs of an ELP due 331 to underlying network change conditions. Just like when there is any 332 locator change for a locator-set, the procedures from the main LISP 333 specification [RFC6830] are followed. 335 When a RLOC from an ELP is changed, Map-Notify messages [RFC6833] can 336 be used to inform the existing RTRs in the ELP so they can do a 337 lookup to obtain the latest version of the ELP. Map-Notify messages 338 can also be sent to new RTRs in an ELP so they can get the ELP in 339 advance to receiving packets that will use the ELP. This can 340 minimize packet loss during mapping database lookups in RTRs. 342 5.2. Using Recursion 344 In the previous examples, we showed how an ITR encapsulates using an 345 ELP of (x, y, etr). When a packet is encapsulated from the ITR to 346 RTR 'x', the RTR may want a policy path to RTR 'y' and run another 347 level of reencapsulating tunnels for packets destined to RTR 'y'. In 348 this case, RTR 'x' does not decapsulate packets from the ITR, but 349 rather performs a mapping database lookup on the address 'y'. This 350 can be done when using a public or private mapping database. The 351 decision to use address 'y' as an encapsulation address versus a 352 lookup address is based on the L-bit setting for 'y' in the ELP 353 entry. The decision and policy of ELP encodings are local to the 354 entity which registers the EID-prefix associated with the ELP. 356 Another example of recursion is when the ITR uses the ELP (x, y, etr) 357 to first prepend a header with a destination RLOC of the ETR and then 358 prepend another header and encapsulate the packet to RTR 'x'. When 359 RTR 'x' decapsulates the packet, rather than doing a mapping database 360 lookup on RTR 'y' the last example showed, instead RTR 'x' does a 361 mapping database lookup on ETR 'etr'. In this scenario, RTR 'x' can 362 choose an ELP from the locator-set by considering the source RLOC 363 address of the ITR versus considering the source EID. 365 This additional level of recursion also brings advantages for the 366 provider of RTR 'x' to store less state. Since RTR 'x' does not need 367 to look at the inner most header, it does not need to store EID 368 state. It only stores an entry for RTR 'y' which many EID flows 369 could share for scaling benefits. The locator-set for entry 'y' 370 could either be a list of typical locators, a list of ELPs, or 371 combination of both. Another advantage is that packet load-splitting 372 can be accomplished by examining the source of a packet. If the 373 source is an ITR versus the source being the last-hop of an ELP the 374 last-hop selected, different forwarding paths can be used. 376 5.3. ELP Selection based on Class of Service 378 Paths to an ETR may want to be selected based on different classes of 379 service. Packets from a set of sources that have premium service can 380 use ELP paths that are less congested where normal sources use ELP 381 paths that compete for less resources or use longer paths for best 382 effort service. 384 Using source/destination lookups into the mapping database can yield 385 different ELPs. So for example, a premium service flow with 386 (source=1.1.1.1, dest=10.1.1.1) can be described by using the 387 following mapping entry: 389 EID-prefix: (1.0.0.0/8, 10.0.0.0/8) 390 Locator-set: (x, y, ETR-A): priority 1, weight 50 391 (q, r, ETR-A): priority 1, weight 50 393 And all other best-effort sources would use different mapping entry 394 described by: 396 EID-prefix: (0.0.0.0/0, 10.0.0.0/8) 397 Locator-set: (x, x', y, y', ETR-A): priority 1, weight 50 398 (q, q', r, r', ETR-A): priority 1, weight 50 400 If the source/destination lookup is coupled with recursive lookups, 401 then an ITR can encapsulate to the ETR, prepending a header that 402 selects source address ITR-1 based on the premium class of service 403 source, or selects source address ITR-2 for best-effort sources with 404 normal class of service. The ITR then does another lookup in the 405 mapping database on the prepended header using lookup key 406 (source=ITR-1, dest=10.1.1.1) that returns the following mapping 407 entry: 409 EID-prefix: (ITR-1, 10.0.0.0/8) 410 Locator-set: (x, y, ETR-A): priority 1, weight 50 411 (q, r, ETR-A): priority 1, weight 50 413 And all other sources would use different mapping entry with a lookup 414 key of (source=ITR-2, dest=10.1.1.1): 416 EID-prefix: (ITR-2, 10.0.0.0/8) 417 Locator-set: (x, x', y, y', ETR-A): priority 1, weight 50 418 (q, q', r, r', ETR-A): priority 1, weight 50 420 This will scale the mapping system better by having fewer source/ 421 destination combinations. Refer to the Source/Dest LCAF type 422 described in [LISP-LCAF] for encoding EIDs in Map-Request and Map- 423 Register messages. 425 5.4. Packet Loop Avoidance 427 An ELP that is first used by an ITR must be inspected for encoding 428 loops. If any RLOC appears twice in the ELP, it MUST not be used. 430 Since it is expected that multiple mapping systems will be used, 431 there can be a loop across ELPs when registered in different mapping 432 systems. The TTL copying procedures for reencapsulating tunnels and 433 recursive tunnels in [RFC6830] MUST be followed. 435 6. Service Chaining 437 An ELP can be used to deploy services at each reencapsulation point 438 in the network. One example is to implement a scrubber service when 439 a destination EID is being DoS attacked. That is, when a DoS attack 440 is recognized when the encapsulation path is between ITR and ETR, an 441 ELP can be registered for a destination EID to the mapping database 442 system. The ELP can include an RTR so the ITR can encapsulate 443 packets to the RTR which will decapsulate and deliver packets to a 444 scrubber service device. The scrubber could decide if the offending 445 packets are dropped or allowed to be sent to the destination EID. In 446 which case, the scurbber delivers packets back to the RTR which 447 encapsulates to the ETR. 449 7. RLOC Probing by RTRs 451 Since an RTR knows the next tunnel hop to encapsulate to, it can 452 monitor the reachability of the next-hop RTR RLOC by doing RLOC- 453 probing according to the procedures in [RFC6830]. When the RLOC is 454 determined unreachable by the RLOC-probing mechanisms, the RTR can 455 use another locator in the locator-set. That could be the final ETR, 456 a RLOC of another RTR, or an ELP where it must search for itself and 457 use the next RLOC in the ELP list to encapsulate to. 459 RLOC-probing can also be used to measure delay on the path between 460 RTRs and when it is desirable switch to another lower delay ELP. 462 8. Interworking Considerations 464 [RFC6832] defines procedures for how non-LISP sites talk to LISP 465 sites. The network elements defined in the Interworking 466 specification, the proxy ITR (PITR) and proxy ETR (PETR) (as well as 467 their multicast counterparts defined in [RFC6831]) can participate in 468 LISP-TE. That is, a PITR and a PETR can appear in an ELP list and 469 act as an RTR. 471 Note when an RLOC appears in an ELP, it can be of any address-family. 472 There can be a mix of IPv4 and IPv6 locators present in the same ELP. 473 This can provide benefits where islands of one address-family or the 474 other are supported and connectivity across them is necessary. For 475 instance, an ELP can look like: 477 (x4, a46, b64, y4, etr) 479 Where an IPv4 ITR will encapsulate using an IPv4 RLOC 'x4' and 'x4' 480 could reach an IPv4 RLOC 'a46', but RTR 'a46' encapsulates to an IPv6 481 RLOC 'b64' when the network between them is IPv6-only. Then RTR 482 'b64' encapsulates to IPv4 RLOC 'y4' if the network between them is 483 dual-stack. 485 Note that RTRs can be used for NAT-traversal scenarios [LISP-NATT] as 486 well to reduce the state in both an xTR that resides behind a NAT and 487 the state the NAT needs to maintain. In this case, the xTR only 488 needs a default map-cache entry pointing to the RTR for outbound 489 traffic and all remote ITRs can reach EIDs through the xTR behind a 490 NAT via a single RTR (or a small set RTRs for redundancy). 492 RTRs have some scaling features to reduce the number of locator-set 493 changes, the amount of state, and control packet overhead: 495 o When ITRs and PITRs are using a small set of RTRs for 496 encapsulating to "orders of magnitude" more EID-prefixes, the 497 probability of locator-set changes are limited to the RTR RLOC 498 changes versus the RLOC changes for the ETRs associated with the 499 EID-prefixes if the ITRs and PITRs were directly encapsulating to 500 the ETRs. This comes at an expense in packet stretch, but 501 depending on RTR placement, this expense can be mitigated. 503 o When RTRs are on-path between many pairwise EID flows, ITRs and 504 PITRs can store a small number of coarse EID-prefixes. 506 o RTRs can be used to help scale RLOC-probing. Instead of ITRs 507 RLOC-probing all ETRs for each destination site it has cached, the 508 ITRs can probe a smaller set of RTRs which in turn, probe the 509 destination sites. 511 9. Multicast Considerations 513 ELPs have application in multicast environments. Just like RTRs can 514 be used to provide connectivity across different address family 515 islands, RTRs can help concatenate a multicast region of the network 516 to one that does not support native multicast. 518 Note there are various combinations of connectivity that can be 519 accomplished with the deployment of RTRs and ELPs: 521 o Providing multicast forwarding between IPv4-only-unicast regions 522 and IPv4-multicast regions. 524 o Providing multicast forwarding between IPv6-only-unicast regions 525 and IPv6-multicast regions. 527 o Providing multicast forwarding between IPv4-only-unicast regions 528 and IPv6-multicast regions. 530 o Providing multicast forwarding between IPv6-only-unicast regions 531 and IPv4-multicast regions. 533 o Providing multicast forwarding between IPv4-multicast regions and 534 IPv6-multicast regions. 536 An ITR or PITR can do a (S-EID,G) lookup into the mapping database. 537 What can be returned is a typical locator-set that could be made up 538 of the various RLOC addresses: 540 Multicast EID key: (seid, G) 541 Locator-set: ETR-A: priority 1, weight 25 542 ETR-B: priority 1, weight 25 543 g1: priority 1, weight 25 544 g2: priority 1, weight 25 546 An entry for host 'seid' sending to application group 'G' 548 The locator-set above can be used as a replication list. That is 549 some RLOCs listed can be unicast RLOCs and some can be delivery group 550 RLOCs. A unicast RLOC in this case is used to encapsulate a 551 multicast packet originated by a multicast source EID into a unicast 552 packet for unicast delivery on the underlying network. ETR-A could 553 be a IPv4 unicast RLOC address and ETR-B could be a IPv6 unicast RLOC 554 address. 556 A delivery group address is used when a multicast packet originated 557 by a multicast source EID is encapsulated in a multicast packet for 558 multicast delivery on the underlying network. Group address 'g1' 559 could be a IPv4 delivery group RLOC and group address 'g2' could be 560 an IPv6 delivery group RLOC. 562 Flexibility for these various types of connectivity combinations can 563 be achieved and provided by the mapping database system. And the RTR 564 placement allows the connectivity to occur where the differences in 565 network functionality are located. 567 Extending this concept by allowing ELPs in locator-sets, one could 568 have this locator-set registered in the mapping database for (seid, 569 G). For example: 571 Multicast EID key: (seid, G) 572 Locator-set: (x, y, ETR-A): priority 1, weight 50 573 (a, g, b, ETR-B): priority 1, weight 50 575 Using ELPs for multicast flows 577 In the above situation, an ITR would encapsulate a multicast packet 578 originated by a multicast source EID to the RTR with unicast RLOC 579 'x'. Then RTR 'x' would decapsulate and unicast encapsulate to RTR 580 'y' ('x' or 'y' could be either IPv4 or IPv6 unicast RLOCs), which 581 would decapsulate and unicast encapsulate to the final RLOC 'ETR-A'. 582 The ETR 'ETR-A' would decapsulate and deliver the multicast packet 583 natively to all the receivers joined to application group 'G' inside 584 the LISP site. 586 Let's look at the ITR using the ELP (a, g, b, ETR-B). Here the 587 encapsulation path would be the ITR unicast encapsulates to unicast 588 RLOC 'a'. RTR 'a' multicast encapsulates to delivery group 'g'. The 589 packet gets to all ETRs that have joined delivery group 'g' so they 590 can deliver the multicast packet to joined receivers of application 591 group 'G' in their sites. RTR 'b' is also joined to delivery group 592 'g'. Since it is in the ELP, it will be the only RTR that unicast 593 encapsulates the multicast packet to ETR 'ETR-B'. Lastly, 'ETR-B' 594 decapsulates and delivers the multicast packet to joined receivers to 595 application group 'G' in its LISP site. 597 As one can see there are all sorts of opportunities to provide 598 multicast connectivity across a network with non-congruent support 599 for multicast and different address-families. One can also see how 600 using the mapping database can allow flexible forms of delivery 601 policy, rerouting, and congestion control management in multicast 602 environments. 604 10. Security Considerations 606 When an RTR receives a LISP encapsulated packet, it can look at the 607 outer source address to verify that RLOC is the one listed as the 608 previous hop in the ELP list. If the outer source RLOC address 609 appears before the RLOC which matches the outer destination RLOC 610 address, the decapsulating RTR (or ETR if last hop), MAY choose to 611 drop the packet. 613 11. IANA Considerations 615 At this time there are no requests for IANA. 617 12. References 619 12.1. Normative References 621 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 622 September 1981. 624 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 625 STD 13, RFC 1034, November 1987. 627 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 628 Requirement Levels", BCP 14, RFC 2119, March 1997. 630 [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 631 (IPv6) Specification", RFC 2460, December 1998. 633 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 634 A., Peterson, J., Sparks, R., Handley, M., and E. 635 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 636 June 2002. 638 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 639 Locator/ID Separation Protocol (LISP)", RFC 6830, 640 January 2013. 642 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 643 Locator/ID Separation Protocol (LISP) for Multicast 644 Environments", RFC 6831, January 2013. 646 [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 647 "Interworking between Locator/ID Separation Protocol 648 (LISP) and Non-LISP Sites", RFC 6832, January 2013. 650 [RFC6833] Fuller, V. and D. Farinacci, "Locator/ID Separation 651 Protocol (LISP) Map-Server Interface", RFC 6833, 652 January 2013. 654 12.2. Informative References 656 [LISP-LCAF] 657 Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 658 Address Format", draft-ietf-lisp-lcaf-03.txt (work in 659 progress). 661 [LISP-NATT] 662 Ermagan, V., Farinacci, D., Lewis, D., Skriver, J., Maino, 663 F., and C. White, "NAT traversal for LISP", 664 draft-ermagan-lisp-nat-traversal-04.txt (work in 665 progress). 667 Appendix A. Acknowledgments 669 The authors would like to thank the following people for their ideas 670 and comments. They are Albert Cabellos, Khalid Raza, and Vina 671 Ermagan, and Gregg Schudel. 673 Appendix B. Document Change Log 675 B.1. Changes to draft-farinacci-lisp-te-04.txt 677 o Resubmitted draft due to document timeout. 679 o Updated Informative References section. 681 B.2. Changes to draft-farinacci-lisp-te-03.txt 683 o Update LISP references to their RFC pointers and document timer. 685 B.3. Changes to draft-farinacci-lisp-te-02.txt 687 o Update references and document timer. 689 B.4. Changes to draft-farinacci-lisp-te-01.txt 691 o Posted July 2012. 693 o Add the Lookup bit to allow an ELP to be a list of encapsulation 694 and/or mapping database lookup addresses. 696 o Indicate that ELPs can be used for service chaining. 698 o Add text to indicate that Map-Notify messages can be sent to new 699 RTRs in a ELP so their map-caches can be pre-populated to avoid 700 mapping database lookup packet loss. 702 o Fixes to editorial comments from Gregg. 704 B.5. Changes to draft-farinacci-lisp-te-00.txt 706 o Initial draft posted March 2012. 708 Authors' Addresses 710 Dino Farinacci 711 lispers.net 712 San Jose, California 713 USA 715 Phone: 408-718-2001 716 Email: farinacci@gmail.com 718 Parantap Lahiri 719 Juniper Networks 720 Sunnyvale, CA 721 USA 723 Email: parantap.lahiri@gmail.com 725 Michael Kowal 726 cisco Systems 727 111 Wood Avenue South 728 ISELIN, NJ 729 USA 731 Email: mikowal@cisco.com