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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group D. Farinacci 3 Internet-Draft V. Fuller 4 Intended status: Standards Track D. Meyer 5 Expires: September 6, 2018 D. Lewis 6 Cisco Systems 7 A. Cabellos (Ed.) 8 UPC/BarcelonaTech 9 March 5, 2018 11 The Locator/ID Separation Protocol (LISP) 12 draft-ietf-lisp-rfc6830bis-11 14 Abstract 16 This document describes the data-plane protocol for the Locator/ID 17 Separation Protocol (LISP). LISP defines two namespaces, End-point 18 Identifiers (EIDs) that identify end-hosts and Routing Locators 19 (RLOCs) that identify network attachment points. With this, LISP 20 effectively separates control from data, and allows routers to create 21 overlay networks. LISP-capable routers exchange encapsulated packets 22 according to EID-to-RLOC mappings stored in a local map-cache. 24 LISP requires no change to either host protocol stacks or to underlay 25 routers and offers Traffic Engineering, multihoming and mobility, 26 among other features. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at https://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on September 6, 2018. 45 Copyright Notice 47 Copyright (c) 2018 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (https://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 63 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4 64 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 4 65 4. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . 8 66 4.1. Packet Flow Sequence . . . . . . . . . . . . . . . . . . 10 67 5. LISP Encapsulation Details . . . . . . . . . . . . . . . . . 12 68 5.1. LISP IPv4-in-IPv4 Header Format . . . . . . . . . . . . . 12 69 5.2. LISP IPv6-in-IPv6 Header Format . . . . . . . . . . . . . 13 70 5.3. Tunnel Header Field Descriptions . . . . . . . . . . . . 14 71 6. LISP EID-to-RLOC Map-Cache . . . . . . . . . . . . . . . . . 19 72 7. Dealing with Large Encapsulated Packets . . . . . . . . . . . 19 73 7.1. A Stateless Solution to MTU Handling . . . . . . . . . . 20 74 7.2. A Stateful Solution to MTU Handling . . . . . . . . . . . 21 75 8. Using Virtualization and Segmentation with LISP . . . . . . . 21 76 9. Routing Locator Selection . . . . . . . . . . . . . . . . . . 22 77 10. Routing Locator Reachability . . . . . . . . . . . . . . . . 24 78 10.1. Echo Nonce Algorithm . . . . . . . . . . . . . . . . . . 25 79 11. EID Reachability within a LISP Site . . . . . . . . . . . . . 26 80 12. Routing Locator Hashing . . . . . . . . . . . . . . . . . . . 27 81 13. Changing the Contents of EID-to-RLOC Mappings . . . . . . . . 28 82 13.1. Clock Sweep . . . . . . . . . . . . . . . . . . . . . . 29 83 13.2. Database Map-Versioning . . . . . . . . . . . . . . . . 29 84 14. Multicast Considerations . . . . . . . . . . . . . . . . . . 30 85 15. Router Performance Considerations . . . . . . . . . . . . . . 31 86 16. Security Considerations . . . . . . . . . . . . . . . . . . . 31 87 17. Network Management Considerations . . . . . . . . . . . . . . 32 88 18. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 89 18.1. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . 33 90 19. References . . . . . . . . . . . . . . . . . . . . . . . . . 33 91 19.1. Normative References . . . . . . . . . . . . . . . . . . 33 92 19.2. Informative References . . . . . . . . . . . . . . . . . 34 94 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 39 95 Appendix B. Document Change Log . . . . . . . . . . . . . . . . 39 96 B.1. Changes to draft-ietf-lisp-rfc6830bis-11 . . . . . . . . 40 97 B.2. Changes to draft-ietf-lisp-rfc6830bis-10 . . . . . . . . 40 98 B.3. Changes to draft-ietf-lisp-rfc6830bis-09 . . . . . . . . 40 99 B.4. Changes to draft-ietf-lisp-rfc6830bis-08 . . . . . . . . 40 100 B.5. Changes to draft-ietf-lisp-rfc6830bis-07 . . . . . . . . 41 101 B.6. Changes to draft-ietf-lisp-rfc6830bis-06 . . . . . . . . 41 102 B.7. Changes to draft-ietf-lisp-rfc6830bis-05 . . . . . . . . 41 103 B.8. Changes to draft-ietf-lisp-rfc6830bis-04 . . . . . . . . 41 104 B.9. Changes to draft-ietf-lisp-rfc6830bis-03 . . . . . . . . 42 105 B.10. Changes to draft-ietf-lisp-rfc6830bis-02 . . . . . . . . 42 106 B.11. Changes to draft-ietf-lisp-rfc6830bis-01 . . . . . . . . 42 107 B.12. Changes to draft-ietf-lisp-rfc6830bis-00 . . . . . . . . 42 108 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 42 110 1. Introduction 112 This document describes the Locator/Identifier Separation Protocol 113 (LISP). LISP is an encapsulation protocol built around the 114 fundamental idea of separating the topological location of a network 115 attachment point from the node's identity [CHIAPPA]. As a result 116 LISP creates two namespaces: Endpoint Identifiers (EIDs), that are 117 used to identify end-hosts (e.g., nodes or Virtual Machines) and 118 routable Routing Locators (RLOCs), used to identify network 119 attachment points. LISP then defines functions for mapping between 120 the two namespaces and for encapsulating traffic originated by 121 devices using non-routable EIDs for transport across a network 122 infrastructure that routes and forwards using RLOCs. LISP 123 encapsulation uses a dynamic form of tunneling where no static 124 provisioning is required or necessary. 126 LISP is an overlay protocol that separates control from data-plane, 127 this document specifies the data-plane, how LISP-capable routers 128 (Tunnel Routers) exchange packets by encapsulating them to the 129 appropriate location. Tunnel routers are equipped with a cache, 130 called map-cache, that contains EID-to-RLOC mappings. The map-cache 131 is populated using the LISP Control-Plane protocol 132 [I-D.ietf-lisp-rfc6833bis]. 134 LISP does not require changes to either host protocol stack or to 135 underlay routers. By separating the EID from the RLOC space, LISP 136 offers native Traffic Engineering, multihoming and mobility, among 137 other features. 139 Creation of LISP was initially motivated by discussions during the 140 IAB-sponsored Routing and Addressing Workshop held in Amsterdam in 141 October 2006 (see [RFC4984]). 143 This document specifies the LISP data-plane encapsulation and other 144 LISP forwarding node functionality while [I-D.ietf-lisp-rfc6833bis] 145 specifies the LISP control plane. LISP deployment guidelines can be 146 found in [RFC7215] and [RFC6835] describes considerations for network 147 operational management. Finally, [I-D.ietf-lisp-introduction] 148 describes the LISP architecture. 150 2. Requirements Notation 152 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 153 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 154 document are to be interpreted as described in [RFC2119]. 156 3. Definition of Terms 158 Address Family Identifier (AFI): AFI is a term used to describe an 159 address encoding in a packet. An address family that pertains to 160 the data-plane. See [AFN] and [RFC3232] for details. An AFI 161 value of 0 used in this specification indicates an unspecified 162 encoded address where the length of the address is 0 octets 163 following the 16-bit AFI value of 0. 165 Anycast Address: Anycast Address is a term used in this document to 166 refer to the same IPv4 or IPv6 address configured and used on 167 multiple systems at the same time. An EID or RLOC can be an 168 anycast address in each of their own address spaces. 170 Client-side: Client-side is a term used in this document to indicate 171 a connection initiation attempt by an end-system represented by an 172 EID. 174 Data-Probe: A Data-Probe is a LISP-encapsulated data packet where 175 the inner-header destination address equals the outer-header 176 destination address used to trigger a Map-Reply by a decapsulating 177 ETR. In addition, the original packet is decapsulated and 178 delivered to the destination host if the destination EID is in the 179 EID-Prefix range configured on the ETR. Otherwise, the packet is 180 discarded. A Data-Probe is used in some of the mapping database 181 designs to "probe" or request a Map-Reply from an ETR; in other 182 cases, Map-Requests are used. See each mapping database design 183 for details. When using Data-Probes, by sending Map-Requests on 184 the underlying routing system, EID-Prefixes must be advertised. 186 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 187 packet where the destination address in the "outer" IP header is 188 one of its own RLOCs. The router strips the "outer" header and 189 forwards the packet based on the next IP header found. In 190 general, an ETR receives LISP-encapsulated IP packets from the 191 Internet on one side and sends decapsulated IP packets to site 192 end-systems on the other side. ETR functionality does not have to 193 be limited to a router device. A server host can be the endpoint 194 of a LISP tunnel as well. 196 EID-to-RLOC Database: The EID-to-RLOC Database is a global 197 distributed database that contains all known EID-Prefix-to-RLOC 198 mappings. Each potential ETR typically contains a small piece of 199 the database: the EID-to-RLOC mappings for the EID-Prefixes 200 "behind" the router. These map to one of the router's own 201 globally visible IP addresses. Note that there MAY be transient 202 conditions when the EID-Prefix for the site and Locator-Set for 203 each EID-Prefix may not be the same on all ETRs. This has no 204 negative implications, since a partial set of Locators can be 205 used. 207 EID-to-RLOC Map-Cache: The EID-to-RLOC map-cache is generally 208 short-lived, on-demand table in an ITR that stores, tracks, and is 209 responsible for timing out and otherwise validating EID-to-RLOC 210 mappings. This cache is distinct from the full "database" of EID- 211 to-RLOC mappings; it is dynamic, local to the ITR(s), and 212 relatively small, while the database is distributed, relatively 213 static, and much more global in scope. 215 EID-Prefix: An EID-Prefix is a power-of-two block of EIDs that are 216 allocated to a site by an address allocation authority. EID- 217 Prefixes are associated with a set of RLOC addresses. EID-Prefix 218 allocations can be broken up into smaller blocks when an RLOC set 219 is to be associated with the larger EID-Prefix block. 221 End-System: An end-system is an IPv4 or IPv6 device that originates 222 packets with a single IPv4 or IPv6 header. The end-system 223 supplies an EID value for the destination address field of the IP 224 header when communicating globally (i.e., outside of its routing 225 domain). An end-system can be a host computer, a switch or router 226 device, or any network appliance. 228 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 229 IPv6) value used in the source and destination address fields of 230 the first (most inner) LISP header of a packet. The host obtains 231 a destination EID the same way it obtains a destination address 232 today, for example, through a Domain Name System (DNS) [RFC1034] 233 lookup or Session Initiation Protocol (SIP) [RFC3261] exchange. 234 The source EID is obtained via existing mechanisms used to set a 235 host's "local" IP address. An EID used on the public Internet 236 MUST have the same properties as any other IP address used in that 237 manner; this means, among other things, that it MUST be globally 238 unique. An EID is allocated to a host from an EID-Prefix block 239 associated with the site where the host is located. An EID can be 240 used by a host to refer to other hosts. Note that EID blocks MAY 241 be assigned in a hierarchical manner, independent of the network 242 topology, to facilitate scaling of the mapping database. In 243 addition, an EID block assigned to a site MAY have site-local 244 structure (subnetting) for routing within the site; this structure 245 is not visible to the global routing system. In theory, the bit 246 string that represents an EID for one device can represent an RLOC 247 for a different device. When used in discussions with other 248 Locator/ID separation proposals, a LISP EID will be called an 249 "LEID". Throughout this document, any references to "EID" refer 250 to an LEID. 252 Ingress Tunnel Router (ITR): An ITR is a router that resides in a 253 LISP site. Packets sent by sources inside of the LISP site to 254 destinations outside of the site are candidates for encapsulation 255 by the ITR. The ITR treats the IP destination address as an EID 256 and performs an EID-to-RLOC mapping lookup. The router then 257 prepends an "outer" IP header with one of its routable RLOCs (in 258 the RLOC space) in the source address field and the result of the 259 mapping lookup in the destination address field. Note that this 260 destination RLOC MAY be an intermediate, proxy device that has 261 better knowledge of the EID-to-RLOC mapping closer to the 262 destination EID. In general, an ITR receives IP packets from site 263 end-systems on one side and sends LISP-encapsulated IP packets 264 toward the Internet on the other side. 266 Specifically, when a service provider prepends a LISP header for 267 Traffic Engineering purposes, the router that does this is also 268 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 269 on the outer destination address (the originating ITR's supplied 270 RLOC) or the inner destination address (the originating host's 271 supplied EID). 273 LISP Header: LISP header is a term used in this document to refer 274 to the outer IPv4 or IPv6 header, a UDP header, and a LISP- 275 specific 8-octet header that follow the UDP header and that an ITR 276 prepends or an ETR strips. 278 LISP Router: A LISP router is a router that performs the functions 279 of any or all of the following: ITR, ETR, RTR, Proxy-ITR (PITR), 280 or Proxy-ETR (PETR). 282 LISP Site: LISP site is a set of routers in an edge network that are 283 under a single technical administration. LISP routers that reside 284 in the edge network are the demarcation points to separate the 285 edge network from the core network. 287 Locator-Status-Bits (LSBs): Locator-Status-Bits are present in the 288 LISP header. They are used by ITRs to inform ETRs about the up/ 289 down status of all ETRs at the local site. These bits are used as 290 a hint to convey up/down router status and not path reachability 291 status. The LSBs can be verified by use of one of the Locator 292 reachability algorithms described in Section 10. 294 Negative Mapping Entry: A negative mapping entry, also known as a 295 negative cache entry, is an EID-to-RLOC entry where an EID-Prefix 296 is advertised or stored with no RLOCs. That is, the Locator-Set 297 for the EID-to-RLOC entry is empty or has an encoded Locator count 298 of 0. This type of entry could be used to describe a prefix from 299 a non-LISP site, which is explicitly not in the mapping database. 300 There are a set of well-defined actions that are encoded in a 301 Negative Map-Reply. 303 Proxy-ETR (PETR): A PETR is defined and described in [RFC6832]. A 304 PETR acts like an ETR but does so on behalf of LISP sites that 305 send packets to destinations at non-LISP sites. 307 Proxy-ITR (PITR): A PITR is defined and described in [RFC6832]. A 308 PITR acts like an ITR but does so on behalf of non-LISP sites that 309 send packets to destinations at LISP sites. 311 Recursive Tunneling: Recursive Tunneling occurs when a packet has 312 more than one LISP IP header. Additional layers of tunneling MAY 313 be employed to implement Traffic Engineering or other re-routing 314 as needed. When this is done, an additional "outer" LISP header 315 is added, and the original RLOCs are preserved in the "inner" 316 header. 318 Re-Encapsulating Tunneling Router (RTR): An RTR acts like an ETR to 319 remove a LISP header, then acts as an ITR to prepend a new LISP 320 header. This is known as Re-encapsulating Tunneling. Doing this 321 allows a packet to be re-routed by the RTR without adding the 322 overhead of additional tunnel headers. When using multiple 323 mapping database systems, care must be taken to not create re- 324 encapsulation loops through misconfiguration. 326 Route-Returnability: Route-returnability is an assumption that the 327 underlying routing system will deliver packets to the destination. 328 When combined with a nonce that is provided by a sender and 329 returned by a receiver, this limits off-path data insertion. A 330 route-returnability check is verified when a message is sent with 331 a nonce, another message is returned with the same nonce, and the 332 destination of the original message appears as the source of the 333 returned message. 335 Routing Locator (RLOC): An RLOC is an IPv4 [RFC0791] or IPv6 336 [RFC8200] address of an Egress Tunnel Router (ETR). An RLOC is 337 the output of an EID-to-RLOC mapping lookup. An EID maps to zero 338 or more RLOCs. Typically, RLOCs are numbered from blocks that are 339 assigned to a site at each point to which it attaches to the 340 underlay network; where the topology is defined by the 341 connectivity of provider networks. Multiple RLOCs can be assigned 342 to the same ETR device or to multiple ETR devices at a site. 344 Server-side: Server-side is a term used in this document to indicate 345 that a connection initiation attempt is being accepted for a 346 destination EID. 348 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 349 network that strips an outer LISP header for Traffic Engineering 350 purposes. 352 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 353 network that prepends an additional LISP header for Traffic 354 Engineering purposes. 356 xTR: An xTR is a reference to an ITR or ETR when direction of data 357 flow is not part of the context description. "xTR" refers to the 358 router that is the tunnel endpoint and is used synonymously with 359 the term "Tunnel Router". For example, "An xTR can be located at 360 the Customer Edge (CE) router" indicates both ITR and ETR 361 functionality at the CE router. 363 4. Basic Overview 365 One key concept of LISP is that end-systems operate the same way they 366 do today. The IP addresses that hosts use for tracking sockets and 367 connections, and for sending and receiving packets, do not change. 368 In LISP terminology, these IP addresses are called Endpoint 369 Identifiers (EIDs). 371 Routers continue to forward packets based on IP destination 372 addresses. When a packet is LISP encapsulated, these addresses are 373 referred to as Routing Locators (RLOCs). Most routers along a path 374 between two hosts will not change; they continue to perform routing/ 375 forwarding lookups on the destination addresses. For routers between 376 the source host and the ITR as well as routers from the ETR to the 377 destination host, the destination address is an EID. For the routers 378 between the ITR and the ETR, the destination address is an RLOC. 380 Another key LISP concept is the "Tunnel Router". A Tunnel Router 381 prepends LISP headers on host-originated packets and strips them 382 prior to final delivery to their destination. The IP addresses in 383 this "outer header" are RLOCs. During end-to-end packet exchange 384 between two Internet hosts, an ITR prepends a new LISP header to each 385 packet, and an ETR strips the new header. The ITR performs EID-to- 386 RLOC lookups to determine the routing path to the ETR, which has the 387 RLOC as one of its IP addresses. 389 Some basic rules governing LISP are: 391 o End-systems only send to addresses that are EIDs. EIDs are 392 typically IP addresses assigned to hosts (other types of EID are 393 supported by LISP, see [RFC8060] for further information). End- 394 systems don't know that addresses are EIDs versus RLOCs but assume 395 that packets get to their intended destinations. In a system 396 where LISP is deployed, LISP routers intercept EID-addressed 397 packets and assist in delivering them across the network core 398 where EIDs cannot be routed. The procedure a host uses to send IP 399 packets does not change. 401 o LISP routers mostly deal with Routing Locator addresses. See 402 details in Section 4.1 to clarify what is meant by "mostly". 404 o RLOCs are always IP addresses assigned to routers, preferably 405 topologically oriented addresses from provider CIDR (Classless 406 Inter-Domain Routing) blocks. 408 o When a router originates packets, it MAY use as a source address 409 either an EID or RLOC. When acting as a host (e.g., when 410 terminating a transport session such as Secure SHell (SSH), 411 TELNET, or the Simple Network Management Protocol (SNMP)), it MAY 412 use an EID that is explicitly assigned for that purpose. An EID 413 that identifies the router as a host MUST NOT be used as an RLOC; 414 an EID is only routable within the scope of a site. A typical BGP 415 configuration might demonstrate this "hybrid" EID/RLOC usage where 416 a router could use its "host-like" EID to terminate iBGP sessions 417 to other routers in a site while at the same time using RLOCs to 418 terminate eBGP sessions to routers outside the site. 420 o Packets with EIDs in them are not expected to be delivered end-to- 421 end in the absence of an EID-to-RLOC mapping operation. They are 422 expected to be used locally for intra-site communication or to be 423 encapsulated for inter-site communication. 425 o EIDs MAY also be structured (subnetted) in a manner suitable for 426 local routing within an Autonomous System (AS). 428 An additional LISP header MAY be prepended to packets by a TE-ITR 429 when re-routing of the path for a packet is desired. A potential 430 use-case for this would be an ISP router that needs to perform 431 Traffic Engineering for packets flowing through its network. In such 432 a situation, termed "Recursive Tunneling", an ISP transit acts as an 433 additional ITR, and the RLOC it uses for the new prepended header 434 would be either a TE-ETR within the ISP (along an intra-ISP traffic 435 engineered path) or a TE-ETR within another ISP (an inter-ISP traffic 436 engineered path, where an agreement to build such a path exists). 438 In order to avoid excessive packet overhead as well as possible 439 encapsulation loops, this document recommends that a maximum of two 440 LISP headers can be prepended to a packet. For initial LISP 441 deployments, it is assumed that two headers is sufficient, where the 442 first prepended header is used at a site for Location/Identity 443 separation and the second prepended header is used inside a service 444 provider for Traffic Engineering purposes. 446 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 447 For example, the ITR for a particular end-to-end packet exchange 448 might be the first-hop or default router within a site for the source 449 host. Similarly, the ETR might be the last-hop router directly 450 connected to the destination host. Another example, perhaps for a 451 VPN service outsourced to an ISP by a site, the ITR could be the 452 site's border router at the service provider attachment point. 453 Mixing and matching of site-operated, ISP-operated, and other Tunnel 454 Routers is allowed for maximum flexibility. 456 4.1. Packet Flow Sequence 458 This section provides an example of the unicast packet flow, 459 including also control-plane information as specified in 460 [I-D.ietf-lisp-rfc6833bis]. The example also assumes the following 461 conditions: 463 o Source host "host1.abc.example.com" is sending a packet to 464 "host2.xyz.example.com", exactly what host1 would do if the site 465 was not using LISP. 467 o Each site is multihomed, so each Tunnel Router has an address 468 (RLOC) assigned from the service provider address block for each 469 provider to which that particular Tunnel Router is attached. 471 o The ITR(s) and ETR(s) are directly connected to the source and 472 destination, respectively, but the source and destination can be 473 located anywhere in the LISP site. 475 o A Map-Request is sent for an external destination when the 476 destination is not found in the forwarding table or matches a 477 default route. Map-Requests are sent to the mapping database 478 system by using the LISP control-plane protocol documented in 479 [I-D.ietf-lisp-rfc6833bis]. 481 o Map-Replies are sent on the underlying routing system topology 482 using the [I-D.ietf-lisp-rfc6833bis] control-plane protocol. 484 Client host1.abc.example.com wants to communicate with server 485 host2.xyz.example.com: 487 1. host1.abc.example.com wants to open a TCP connection to 488 host2.xyz.example.com. It does a DNS lookup on 489 host2.xyz.example.com. An A/AAAA record is returned. This 490 address is the destination EID. The locally assigned address of 491 host1.abc.example.com is used as the source EID. An IPv4 or IPv6 492 packet is built and forwarded through the LISP site as a normal 493 IP packet until it reaches a LISP ITR. 495 2. The LISP ITR must be able to map the destination EID to an RLOC 496 of one of the ETRs at the destination site. The specific method 497 used to do this is not described in this example. See 498 [I-D.ietf-lisp-rfc6833bis] for further information. 500 3. The ITR sends a LISP Map-Request as specified in 501 [I-D.ietf-lisp-rfc6833bis]. Map-Requests SHOULD be rate-limited. 503 4. The mapping system helps forwarding the Map-Request to the 504 corresponding ETR. When the Map-Request arrives at one of the 505 ETRs at the destination site, it will process the packet as a 506 control message. 508 5. The ETR looks at the destination EID of the Map-Request and 509 matches it against the prefixes in the ETR's configured EID-to- 510 RLOC mapping database. This is the list of EID-Prefixes the ETR 511 is supporting for the site it resides in. If there is no match, 512 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 513 returned to the ITR. 515 6. The ITR receives the Map-Reply message, parses the message (to 516 check for format validity), and stores the mapping information 517 from the packet. This information is stored in the ITR's EID-to- 518 RLOC map-cache. Note that the map-cache is an on-demand cache. 519 An ITR will manage its map-cache in such a way that optimizes for 520 its resource constraints. 522 7. Subsequent packets from host1.abc.example.com to 523 host2.xyz.example.com will have a LISP header prepended by the 524 ITR using the appropriate RLOC as the LISP header destination 525 address learned from the ETR. Note that the packet MAY be sent 526 to a different ETR than the one that returned the Map-Reply due 527 to the source site's hashing policy or the destination site's 528 Locator-Set policy. 530 8. The ETR receives these packets directly (since the destination 531 address is one of its assigned IP addresses), checks the validity 532 of the addresses, strips the LISP header, and forwards packets to 533 the attached destination host. 535 9. In order to defer the need for a mapping lookup in the reverse 536 direction, an ETR can OPTIONALLY create a cache entry that maps 537 the source EID (inner-header source IP address) to the source 538 RLOC (outer-header source IP address) in a received LISP packet. 539 Such a cache entry is termed a "glean mapping" and only contains 540 a single RLOC for the EID in question. More complete information 541 about additional RLOCs SHOULD be verified by sending a LISP Map- 542 Request for that EID. Both the ITR and the ETR MAY also 543 influence the decision the other makes in selecting an RLOC. 545 5. LISP Encapsulation Details 547 Since additional tunnel headers are prepended, the packet becomes 548 larger and can exceed the MTU of any link traversed from the ITR to 549 the ETR. It is RECOMMENDED in IPv4 that packets do not get 550 fragmented as they are encapsulated by the ITR. Instead, the packet 551 is dropped and an ICMP Unreachable/Fragmentation-Needed message is 552 returned to the source. 554 In the case when fragmentation is needed, this specification 555 RECOMMENDS that implementations provide support for one of the 556 proposed fragmentation and reassembly schemes. Two existing schemes 557 are detailed in Section 7. 559 Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP 560 architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner 561 header is in IPv4 packet format and the outer header is in IPv6 562 packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner header 563 is in IPv6 packet format and the outer header is in IPv4 packet 564 format). The next sub-sections illustrate packet formats for the 565 homogeneous case (IPv4-in-IPv4 and IPv6-in-IPv6), but all 4 566 combinations MUST be supported. Additional types of EIDs are defined 567 in [RFC8060]. 569 5.1. LISP IPv4-in-IPv4 Header Format 570 0 1 2 3 571 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 572 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 573 / |Version| IHL | DSCP |ECN| Total Length | 574 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 575 | | Identification |Flags| Fragment Offset | 576 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 577 OH | Time to Live | Protocol = 17 | Header Checksum | 578 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 579 | | Source Routing Locator | 580 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 581 \ | Destination Routing Locator | 582 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 583 / | Source Port = xxxx | Dest Port = 4341 | 584 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 585 \ | UDP Length | UDP Checksum | 586 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 587 L |N|L|E|V|I|R|K|K| Nonce/Map-Version | 588 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 589 S / | Instance ID/Locator-Status-Bits | 590 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 591 / |Version| IHL | DSCP |ECN| Total Length | 592 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 593 | | Identification |Flags| Fragment Offset | 594 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 595 IH | Time to Live | Protocol | Header Checksum | 596 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 597 | | Source EID | 598 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 599 \ | Destination EID | 600 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 602 IHL = IP-Header-Length 604 5.2. LISP IPv6-in-IPv6 Header Format 606 0 1 2 3 607 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 608 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 609 / |Version| DSCP |ECN| Flow Label | 610 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 611 | | Payload Length | Next Header=17| Hop Limit | 612 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 613 | | 614 O + + 615 u | | 616 t + Source Routing Locator + 617 e | | 618 r + + 619 | | 620 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 621 d | | 622 r + + 623 | | 624 ^ + Destination Routing Locator + 625 | | | 626 \ + + 627 \ | | 628 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 629 / | Source Port = xxxx | Dest Port = 4341 | 630 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 631 \ | UDP Length | UDP Checksum | 632 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 633 L |N|L|E|V|I|R|K|K| Nonce/Map-Version | 634 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 635 S / | Instance ID/Locator-Status-Bits | 636 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 637 / |Version| DSCP |ECN| Flow Label | 638 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 639 / | Payload Length | Next Header | Hop Limit | 640 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 641 | | 642 I + + 643 n | | 644 n + Source EID + 645 e | | 646 r + + 647 | | 648 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 649 d | | 650 r + + 651 | | 652 ^ + Destination EID + 653 \ | | 654 \ + + 655 \ | | 656 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 658 5.3. Tunnel Header Field Descriptions 660 Inner Header (IH): The inner header is the header on the 661 datagram received from the originating host [RFC0791] [RFC8200] 662 [RFC2474]. The source and destination IP addresses are EIDs. 664 Outer Header: (OH) The outer header is a new header prepended by an 665 ITR. The address fields contain RLOCs obtained from the ingress 666 router's EID-to-RLOC Cache. The IP protocol number is "UDP (17)" 667 from [RFC0768]. The setting of the Don't Fragment (DF) bit 668 'Flags' field is according to rules listed in Sections 7.1 and 669 7.2. 671 UDP Header: The UDP header contains an ITR selected source port when 672 encapsulating a packet. See Section 12 for details on the hash 673 algorithm used to select a source port based on the 5-tuple of the 674 inner header. The destination port MUST be set to the well-known 675 IANA-assigned port value 4341. 677 UDP Checksum: The 'UDP Checksum' field SHOULD be transmitted as zero 678 by an ITR for either IPv4 [RFC0768] and IPv6 encapsulation 679 [RFC6935] [RFC6936]. When a packet with a zero UDP checksum is 680 received by an ETR, the ETR MUST accept the packet for 681 decapsulation. When an ITR transmits a non-zero value for the UDP 682 checksum, it MUST send a correctly computed value in this field. 683 When an ETR receives a packet with a non-zero UDP checksum, it MAY 684 choose to verify the checksum value. If it chooses to perform 685 such verification, and the verification fails, the packet MUST be 686 silently dropped. If the ETR chooses not to perform the 687 verification, or performs the verification successfully, the 688 packet MUST be accepted for decapsulation. The handling of UDP 689 zero checksums over IPv6 for all tunneling protocols, including 690 LISP, is subject to the applicability statement in [RFC6936]. 692 UDP Length: The 'UDP Length' field is set for an IPv4-encapsulated 693 packet to be the sum of the inner-header IPv4 Total Length plus 694 the UDP and LISP header lengths. For an IPv6-encapsulated packet, 695 the 'UDP Length' field is the sum of the inner-header IPv6 Payload 696 Length, the size of the IPv6 header (40 octets), and the size of 697 the UDP and LISP headers. 699 N: The N-bit is the nonce-present bit. When this bit is set to 1, 700 the low-order 24 bits of the first 32 bits of the LISP header 701 contain a Nonce. See Section 10.1 for details. Both N- and 702 V-bits MUST NOT be set in the same packet. If they are, a 703 decapsulating ETR MUST treat the 'Nonce/Map-Version' field as 704 having a Nonce value present. 706 L: The L-bit is the 'Locator-Status-Bits' field enabled bit. When 707 this bit is set to 1, the Locator-Status-Bits in the second 708 32 bits of the LISP header are in use. 710 x 1 x x 0 x x x 711 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 712 |N|L|E|V|I|R|K|K| Nonce/Map-Version | 713 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 714 | Locator-Status-Bits | 715 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 717 E: The E-bit is the echo-nonce-request bit. This bit MUST be ignored 718 and has no meaning when the N-bit is set to 0. When the N-bit is 719 set to 1 and this bit is set to 1, an ITR is requesting that the 720 nonce value in the 'Nonce' field be echoed back in LISP- 721 encapsulated packets when the ITR is also an ETR. See 722 Section 10.1 for details. 724 V: The V-bit is the Map-Version present bit. When this bit is set to 725 1, the N-bit MUST be 0. Refer to Section 13.2 for more details. 726 This bit indicates that the LISP header is encoded in this 727 case as: 729 0 x 0 1 x x x x 730 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 731 |N|L|E|V|I|R|K|K| Source Map-Version | Dest Map-Version | 732 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 733 | Instance ID/Locator-Status-Bits | 734 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 736 I: The I-bit is the Instance ID bit. See Section 8 for more details. 737 When this bit is set to 1, the 'Locator-Status-Bits' field is 738 reduced to 8 bits and the high-order 24 bits are used as an 739 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 740 are transmitted as zero and ignored on receipt. The format of the 741 LISP header would look like this: 743 x x x x 1 x x x 744 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 745 |N|L|E|V|I|R|K|K| Nonce/Map-Version | 746 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 747 | Instance ID | LSBs | 748 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 750 R: The R-bit is a Reserved bit for future use. It MUST be set to 0 751 on transmit and MUST be ignored on receipt. 753 KK: The KK-bits are a 2-bit field used when encapsulated packets are 754 encrypted. The field is set to 00 when the packet is not 755 encrypted. See [RFC8061] for further information. 757 LISP Nonce: The LISP 'Nonce' field is a 24-bit value that is 758 randomly generated by an ITR when the N-bit is set to 1. Nonce 759 generation algorithms are an implementation matter but are 760 required to generate different nonces when sending to different 761 destinations. However, the same nonce can be used for a period of 762 time when encapsulating to the same ETR. The nonce is also used 763 when the E-bit is set to request the nonce value to be echoed by 764 the other side when packets are returned. When the E-bit is clear 765 but the N-bit is set, a remote ITR is either echoing a previously 766 requested echo-nonce or providing a random nonce. See 767 Section 10.1 for more details. 769 LISP Locator-Status-Bits (LSBs): When the L-bit is also set, the 770 'Locator-Status-Bits' field in the LISP header is set by an ITR to 771 indicate to an ETR the up/down status of the Locators in the 772 source site. Each RLOC in a Map-Reply is assigned an ordinal 773 value from 0 to n-1 (when there are n RLOCs in a mapping entry). 774 The Locator-Status-Bits are numbered from 0 to n-1 from the least 775 significant bit of the field. The field is 32 bits when the I-bit 776 is set to 0 and is 8 bits when the I-bit is set to 1. When a 777 Locator-Status-Bit is set to 1, the ITR is indicating to the ETR 778 that the RLOC associated with the bit ordinal has up status. See 779 Section 10 for details on how an ITR can determine the status of 780 the ETRs at the same site. When a site has multiple EID-Prefixes 781 that result in multiple mappings (where each could have a 782 different Locator-Set), the Locator-Status-Bits setting in an 783 encapsulated packet MUST reflect the mapping for the EID-Prefix 784 that the inner-header source EID address matches. If the LSB for 785 an anycast Locator is set to 1, then there is at least one RLOC 786 with that address, and the ETR is considered 'up'. 788 When doing ITR/PITR encapsulation: 790 o The outer-header 'Time to Live' field (or 'Hop Limit' field, in 791 the case of IPv6) SHOULD be copied from the inner-header 'Time to 792 Live' field. 794 o The outer-header 'Differentiated Services Code Point' (DSCP) field 795 (or the 'Traffic Class' field, in the case of IPv6) SHOULD be 796 copied from the inner-header DSCP field ('Traffic Class' field, in 797 the case of IPv6) considering the exception listed below. 799 o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 800 of the IPv6 'Traffic Class' field) requires special treatment in 801 order to avoid discarding indications of congestion [RFC3168]. 802 ITR encapsulation MUST copy the 2-bit 'ECN' field from the inner 803 header to the outer header. Re-encapsulation MUST copy the 2-bit 804 'ECN' field from the stripped outer header to the new outer 805 header. 807 When doing ETR/PETR decapsulation: 809 o The inner-header 'Time to Live' field (or 'Hop Limit' field, in 810 the case of IPv6) SHOULD be copied from the outer-header 'Time to 811 Live' field, when the Time to Live value of the outer header is 812 less than the Time to Live value of the inner header. Failing to 813 perform this check can cause the Time to Live of the inner header 814 to increment across encapsulation/decapsulation cycles. This 815 check is also performed when doing initial encapsulation, when a 816 packet comes to an ITR or PITR destined for a LISP site. 818 o The inner-header 'Differentiated Services Code Point' (DSCP) field 819 (or the 'Traffic Class' field, in the case of IPv6) SHOULD be 820 copied from the outer-header DSCP field ('Traffic Class' field, in 821 the case of IPv6) considering the exception listed below. 823 o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 824 of the IPv6 'Traffic Class' field) requires special treatment in 825 order to avoid discarding indications of congestion [RFC3168]. If 826 the 'ECN' field contains a congestion indication codepoint (the 827 value is '11', the Congestion Experienced (CE) codepoint), then 828 ETR decapsulation MUST copy the 2-bit 'ECN' field from the 829 stripped outer header to the surviving inner header that is used 830 to forward the packet beyond the ETR. These requirements preserve 831 CE indications when a packet that uses ECN traverses a LISP tunnel 832 and becomes marked with a CE indication due to congestion between 833 the tunnel endpoints. 835 Note that if an ETR/PETR is also an ITR/PITR and chooses to re- 836 encapsulate after decapsulating, the net effect of this is that the 837 new outer header will carry the same Time to Live as the old outer 838 header minus 1. 840 Copying the Time to Live (TTL) serves two purposes: first, it 841 preserves the distance the host intended the packet to travel; 842 second, and more importantly, it provides for suppression of looping 843 packets in the event there is a loop of concatenated tunnels due to 844 misconfiguration. 846 The Explicit Congestion Notification ('ECN') field occupies bits 6 847 and 7 of both the IPv4 'Type of Service' field and the IPv6 'Traffic 848 Class' field [RFC3168]. The 'ECN' field requires special treatment 849 in order to avoid discarding indications of congestion [RFC3168]. An 850 ITR/PITR encapsulation MUST copy the 2-bit 'ECN' field from the inner 851 header to the outer header. Re-encapsulation MUST copy the 2-bit 852 'ECN' field from the stripped outer header to the new outer header. 853 If the 'ECN' field contains a congestion indication codepoint (the 854 value is '11', the Congestion Experienced (CE) codepoint), then ETR/ 855 PETR decapsulation MUST copy the 2-bit 'ECN' field from the stripped 856 outer header to the surviving inner header that is used to forward 857 the packet beyond the ETR. These requirements preserve CE 858 indications when a packet that uses ECN traverses a LISP tunnel and 859 becomes marked with a CE indication due to congestion between the 860 tunnel endpoints. 862 6. LISP EID-to-RLOC Map-Cache 864 ITRs and PITRs maintain an on-demand cache, referred as LISP EID-to- 865 RLOC Map-Cache, that contains mappings from EID-prefixes to locator 866 sets. The cache is used to encapsulate packets from the EID space to 867 the corresponding RLOC network attachment point. 869 When an ITR/PITR receives a packet from inside of the LISP site to 870 destinations outside of the site a longest-prefix match lookup of the 871 EID is done to the map-cache. 873 When the lookup succeeds, the Locator-Set retrieved from the map- 874 cache is used to send the packet to the EID's topological location. 876 If the lookup fails, the ITR/PITR needs to retrieve the mapping using 877 the LISP control-plane protocol [I-D.ietf-lisp-rfc6833bis]. The 878 mapping is then stored in the local map-cache to forward subsequent 879 packets addressed to the same EID-prefix. 881 The map-cache is a local cache of mappings, entries are expired based 882 on the associated Time to live. In addition, entries can be updated 883 with more current information, see Section 13 for further information 884 on this. Finally, the map-cache also contains reachability 885 information about EIDs and RLOCs, and uses LISP reachability 886 information mechanisms to determine the reachability of RLOCs, see 887 Section 10 for the specific mechanisms. 889 7. Dealing with Large Encapsulated Packets 891 This section proposes two mechanisms to deal with packets that exceed 892 the path MTU between the ITR and ETR. 894 It is left to the implementor to decide if the stateless or stateful 895 mechanism SHOULD be implemented. Both or neither can be used, since 896 it is a local decision in the ITR regarding how to deal with MTU 897 issues, and sites can interoperate with differing mechanisms. 899 Both stateless and stateful mechanisms also apply to Re-encapsulating 900 and Recursive Tunneling, so any actions below referring to an ITR 901 also apply to a TE-ITR. 903 7.1. A Stateless Solution to MTU Handling 905 An ITR stateless solution to handle MTU issues is described as 906 follows: 908 1. Define H to be the size, in octets, of the outer header an ITR 909 prepends to a packet. This includes the UDP and LISP header 910 lengths. 912 2. Define L to be the size, in octets, of the maximum-sized packet 913 an ITR can send to an ETR without the need for the ITR or any 914 intermediate routers to fragment the packet. 916 3. Define an architectural constant S for the maximum size of a 917 packet, in octets, an ITR MUST receive from the source so the 918 effective MTU can be met. That is, L = S + H. 920 When an ITR receives a packet from a site-facing interface and adds H 921 octets worth of encapsulation to yield a packet size greater than L 922 octets (meaning the received packet size was greater than S octets 923 from the source), it resolves the MTU issue by first splitting the 924 original packet into 2 equal-sized fragments. A LISP header is then 925 prepended to each fragment. The size of the encapsulated fragments 926 is then (S/2 + H), which is less than the ITR's estimate of the path 927 MTU between the ITR and its correspondent ETR. 929 When an ETR receives encapsulated fragments, it treats them as two 930 individually encapsulated packets. It strips the LISP headers and 931 then forwards each fragment to the destination host of the 932 destination site. The two fragments are reassembled at the 933 destination host into the single IP datagram that was originated by 934 the source host. Note that reassembly can happen at the ETR if the 935 encapsulated packet was fragmented at or after the ITR. 937 This behavior is performed by the ITR when the source host originates 938 a packet with the 'DF' field of the IP header set to 0. When the 939 'DF' field of the IP header is set to 1, or the packet is an IPv6 940 packet originated by the source host, the ITR will drop the packet 941 when the size is greater than L and send an ICMP Unreachable/ 942 Fragmentation-Needed message to the source with a value of S, where S 943 is (L - H). 945 When the outer-header encapsulation uses an IPv4 header, an 946 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 947 can be avoided. An implementation MAY set the DF bit in such headers 948 to 0 if it has good reason to believe there are unresolvable path MTU 949 issues between the sending ITR and the receiving ETR. 951 This specification RECOMMENDS that L be defined as 1500. 953 7.2. A Stateful Solution to MTU Handling 955 An ITR stateful solution to handle MTU issues is described as follows 956 and was first introduced in [OPENLISP]: 958 1. The ITR will keep state of the effective MTU for each Locator per 959 Map-Cache entry. The effective MTU is what the core network can 960 deliver along the path between the ITR and ETR. 962 2. When an IPv6-encapsulated packet, or an IPv4-encapsulated packet 963 with the DF bit set to 1, exceeds what the core network can 964 deliver, one of the intermediate routers on the path will send an 965 ICMP Unreachable/Fragmentation-Needed message to the ITR. The 966 ITR will parse the ICMP message to determine which Locator is 967 affected by the effective MTU change and then record the new 968 effective MTU value in the Map-Cache entry. 970 3. When a packet is received by the ITR from a source inside of the 971 site and the size of the packet is greater than the effective MTU 972 stored with the Map-Cache entry associated with the destination 973 EID the packet is for, the ITR will send an ICMP Unreachable/ 974 Fragmentation-Needed message back to the source. The packet size 975 advertised by the ITR in the ICMP Unreachable/Fragmentation- 976 Needed message is the effective MTU minus the LISP encapsulation 977 length. 979 Even though this mechanism is stateful, it has advantages over the 980 stateless IP fragmentation mechanism, by not involving the 981 destination host with reassembly of ITR fragmented packets. 983 8. Using Virtualization and Segmentation with LISP 985 There are several cases where segregation is needed at the EID level. 986 For instance, this is the case for deployments containing overlapping 987 addresses, traffic isolation policies or multi-tenant virtualization. 988 For these and other scenarios where segregation is needed, Instance 989 IDs are used. 991 An Instance ID can be carried in a LISP-encapsulated packet. An ITR 992 that prepends a LISP header will copy a 24-bit value used by the LISP 993 router to uniquely identify the address space. The value is copied 994 to the 'Instance ID' field of the LISP header, and the I-bit is set 995 to 1. 997 When an ETR decapsulates a packet, the Instance ID from the LISP 998 header is used as a table identifier to locate the forwarding table 999 to use for the inner destination EID lookup. 1001 For example, an 802.1Q VLAN tag or VPN identifier could be used as a 1002 24-bit Instance ID. See [I-D.ietf-lisp-vpn] for LISP VPN use-case 1003 details. 1005 The Instance ID that is stored in the mapping database when LISP-DDT 1006 [RFC8111] is used is 32 bits in length. That means the control-plane 1007 can store more instances than a given data-plane can use. Multiple 1008 data-planes can use the same 32-bit space as long as the low-order 24 1009 bits don't overlap among xTRs. 1011 9. Routing Locator Selection 1013 The map-cache contains the state used by ITRs and PITRs to 1014 encapsulate packets. When an ITR/PITR receives a packet from inside 1015 the LISP site to a destination outside of the site a longest-prefix 1016 match lookup of the EID is done to the map-cache (see Section 6). 1017 The lookup returns a single Locator-Set containing a list of RLOCs 1018 corresponding to the EID's topological location. Each RLOC in the 1019 Locator-Set is associated with a 'Priority' and 'Weight', this 1020 information is used to select the RLOC to encapsulate. 1022 The RLOC with the lowest 'Priority' is selected. An RLOC with 1023 'Priority' 255 means that MUST NOT be used for forwarding. When 1024 multiple RLOC have the same 'Priority' then the 'Weight' states how 1025 to load balance traffic among them. The value of the 'Weight' 1026 represents the relative weight of the total packets that match the 1027 maping entry. 1029 The following are different scenarios for choosing RLOCs and the 1030 controls that are available: 1032 o The server-side returns one RLOC. The client-side can only use 1033 one RLOC. The server-side has complete control of the selection. 1035 o The server-side returns a list of RLOCs where a subset of the list 1036 has the same best Priority. The client can only use the subset 1037 list according to the weighting assigned by the server-side. In 1038 this case, the server-side controls both the subset list and load- 1039 splitting across its members. The client-side can use RLOCs 1040 outside of the subset list if it determines that the subset list 1041 is unreachable (unless RLOCs are set to a Priority of 255). Some 1042 sharing of control exists: the server-side determines the 1043 destination RLOC list and load distribution while the client-side 1044 has the option of using alternatives to this list if RLOCs in the 1045 list are unreachable. 1047 o The server-side sets a Weight of zero for the RLOC subset list. 1048 In this case, the client-side can choose how the traffic load is 1049 spread across the subset list. Control is shared by the server- 1050 side determining the list and the client-side determining load 1051 distribution. Again, the client can use alternative RLOCs if the 1052 server-provided list of RLOCs is unreachable. 1054 o Either side (more likely the server-side ETR) decides not to send 1055 a Map-Request. For example, if the server-side ETR does not send 1056 Map-Requests, it gleans RLOCs from the client-side ITR, giving the 1057 client-side ITR responsibility for bidirectional RLOC reachability 1058 and preferability. Server-side ETR gleaning of the client-side 1059 ITR RLOC is done by caching the inner-header source EID and the 1060 outer-header source RLOC of received packets. The client-side ITR 1061 controls how traffic is returned and can alternate using an outer- 1062 header source RLOC, which then can be added to the list the 1063 server-side ETR uses to return traffic. Since no Priority or 1064 Weights are provided using this method, the server-side ETR MUST 1065 assume that each client-side ITR RLOC uses the same best Priority 1066 with a Weight of zero. In addition, since EID-Prefix encoding 1067 cannot be conveyed in data packets, the EID-to-RLOC Cache on 1068 Tunnel Routers can grow to be very large. 1070 Alternatively, RLOC information MAY be gleaned from received tunneled 1071 packets or EID-to-RLOC Map-Request messages. A "gleaned" Map-Cache 1072 entry, one learned from the source RLOC of a received encapsulated 1073 packet, is only stored and used for a few seconds, pending 1074 verification. Verification is performed by sending a Map-Request to 1075 the source EID (the inner-header IP source address) of the received 1076 encapsulated packet. A reply to this "verifying Map-Request" is used 1077 to fully populate the Map-Cache entry for the "gleaned" EID and is 1078 stored and used for the time indicated from the 'TTL' field of a 1079 received Map-Reply. When a verified Map-Cache entry is stored, data 1080 gleaning no longer occurs for subsequent packets that have a source 1081 EID that matches the EID-Prefix of the verified entry. This 1082 "gleaning" mechanism is OPTIONAL, refer to Section 16 for security 1083 issues regarding this mechanism. 1085 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1086 reachable when the R-bit for the Locator record is set to 1. When 1087 the R-bit is set to 0, an ITR or PITR MUST NOT encapsulate to the 1088 RLOC. Neither the information contained in a Map-Reply nor that 1089 stored in the mapping database system provides reachability 1090 information for RLOCs. Note that reachability is not part of the 1091 mapping system and is determined using one or more of the Routing 1092 Locator reachability algorithms described in the next section. 1094 10. Routing Locator Reachability 1096 Several data-plane mechanisms for determining RLOC reachability are 1097 currently defined. Please note that additional control-plane based 1098 reachability mechanisms are defined in [I-D.ietf-lisp-rfc6833bis]. 1100 1. An ETR MAY examine the Locator-Status-Bits in the LISP header of 1101 an encapsulated data packet received from an ITR. If the ETR is 1102 also acting as an ITR and has traffic to return to the original 1103 ITR site, it can use this status information to help select an 1104 RLOC. 1106 2. When an ETR receives an encapsulated packet from an ITR, the 1107 source RLOC from the outer header of the packet is likely up. 1109 3. An ITR/ETR pair can use the 'Echo-Noncing' Locator reachability 1110 algorithms described in this section. 1112 When determining Locator up/down reachability by examining the 1113 Locator-Status-Bits from the LISP-encapsulated data packet, an ETR 1114 will receive up-to-date status from an encapsulating ITR about 1115 reachability for all ETRs at the site. CE-based ITRs at the source 1116 site can determine reachability relative to each other using the site 1117 IGP as follows: 1119 o Under normal circumstances, each ITR will advertise a default 1120 route into the site IGP. 1122 o If an ITR fails or if the upstream link to its PE fails, its 1123 default route will either time out or be withdrawn. 1125 Each ITR can thus observe the presence or lack of a default route 1126 originated by the others to determine the Locator-Status-Bits it sets 1127 for them. 1129 When ITRs at the site are not deployed in CE routers, the IGP can 1130 still be used to determine the reachability of Locators, provided 1131 they are injected into the IGP. This is typically done when a /32 1132 address is configured on a loopback interface. 1134 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1135 Locator-Status-Bits in a LISP-encapsulated packet are numbered from 0 1136 to n-1 starting with the least significant bit. For example, if an 1137 RLOC listed in the 3rd position of the Map-Reply goes down (ordinal 1138 value 2), then all ITRs at the site will clear the 3rd least 1139 significant bit (xxxx x0xx) of the 'Locator-Status-Bits' field for 1140 the packets they encapsulate. 1142 When an ETR decapsulates a packet, it will check for any change in 1143 the 'Locator-Status-Bits' field. When a bit goes from 1 to 0, the 1144 ETR, if acting also as an ITR, will refrain from encapsulating 1145 packets to an RLOC that is indicated as down. It will only resume 1146 using that RLOC if the corresponding Locator-Status-Bit returns to a 1147 value of 1. Locator-Status-Bits are associated with a Locator-Set 1148 per EID-Prefix. Therefore, when a Locator becomes unreachable, the 1149 Locator-Status-Bit that corresponds to that Locator's position in the 1150 list returned by the last Map-Reply will be set to zero for that 1151 particular EID-Prefix. Refer to Section 16 for security related 1152 issues regarding Locator-Status-Bits. 1154 When an ETR decapsulates a packet, it knows that it is reachable from 1155 the encapsulating ITR because that is how the packet arrived. In 1156 most cases, the ETR can also reach the ITR but cannot assume this to 1157 be true, due to the possibility of path asymmetry. In the presence 1158 of unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD 1159 NOT use the lack of return traffic as an indication that the ETR is 1160 unreachable. Instead, it MUST use an alternate mechanism to 1161 determine reachability. 1163 10.1. Echo Nonce Algorithm 1165 When data flows bidirectionally between Locators from different 1166 sites, a data-plane mechanism called "nonce echoing" can be used to 1167 determine reachability between an ITR and ETR. When an ITR wants to 1168 solicit a nonce echo, it sets the N- and E-bits and places a 24-bit 1169 nonce [RFC4086] in the LISP header of the next encapsulated data 1170 packet. 1172 When this packet is received by the ETR, the encapsulated packet is 1173 forwarded as normal. When the ETR next sends a data packet to the 1174 ITR, it includes the nonce received earlier with the N-bit set and 1175 E-bit cleared. The ITR sees this "echoed nonce" and knows that the 1176 path to and from the ETR is up. 1178 The ITR will set the E-bit and N-bit for every packet it sends while 1179 in the echo-nonce-request state. The time the ITR waits to process 1180 the echoed nonce before it determines the path is unreachable is 1181 variable and is a choice left for the implementation. 1183 If the ITR is receiving packets from the ETR but does not see the 1184 nonce echoed while being in the echo-nonce-request state, then the 1185 path to the ETR is unreachable. This decision MAY be overridden by 1186 other Locator reachability algorithms. Once the ITR determines that 1187 the path to the ETR is down, it can switch to another Locator for 1188 that EID-Prefix. 1190 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 1191 be implementing both ITR and ETR functionality for the echo nonce 1192 mechanism to operate. 1194 The ITR and ETR MAY both go into the echo-nonce-request state at the 1195 same time. The number of packets sent or the time during which echo 1196 nonce requests are sent is an implementation-specific setting. 1197 However, when an ITR is in the echo-nonce-request state, it can echo 1198 the ETR's nonce in the next set of packets that it encapsulates and 1199 subsequently continue sending echo-nonce-request packets. 1201 This mechanism does not completely solve the forward path 1202 reachability problem, as traffic may be unidirectional. That is, the 1203 ETR receiving traffic at a site MAY not be the same device as an ITR 1204 that transmits traffic from that site, or the site-to-site traffic is 1205 unidirectional so there is no ITR returning traffic. 1207 The echo-nonce algorithm is bilateral. That is, if one side sets the 1208 E-bit and the other side is not enabled for echo-noncing, then the 1209 echoing of the nonce does not occur and the requesting side may 1210 erroneously consider the Locator unreachable. An ITR SHOULD only set 1211 the E-bit in an encapsulated data packet when it knows the ETR is 1212 enabled for echo-noncing. This is conveyed by the E-bit in the RLOC- 1213 probe Map-Reply message. 1215 11. EID Reachability within a LISP Site 1217 A site MAY be multihomed using two or more ETRs. The hosts and 1218 infrastructure within a site will be addressed using one or more EID- 1219 Prefixes that are mapped to the RLOCs of the relevant ETRs in the 1220 mapping system. One possible failure mode is for an ETR to lose 1221 reachability to one or more of the EID-Prefixes within its own site. 1222 When this occurs when the ETR sends Map-Replies, it can clear the 1223 R-bit associated with its own Locator. And when the ETR is also an 1224 ITR, it can clear its Locator-Status-Bit in the encapsulation data 1225 header. 1227 It is recognized that there are no simple solutions to the site 1228 partitioning problem because it is hard to know which part of the 1229 EID-Prefix range is partitioned and which Locators can reach any sub- 1230 ranges of the EID-Prefixes. Note that this is not a new problem 1231 introduced by the LISP architecture. The problem exists today when a 1232 multihomed site uses BGP to advertise its reachability upstream. 1234 12. Routing Locator Hashing 1236 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message 1237 that is stored in the map-cache of a requesting ITR, the Locator-Set 1238 for the EID-Prefix MAY contain different Priority and Weight values 1239 for each locator address. When more than one best Priority Locator 1240 exists, the ITR can decide how to load-share traffic against the 1241 corresponding Locators. 1243 The following hash algorithm MAY be used by an ITR to select a 1244 Locator for a packet destined to an EID for the EID-to-RLOC mapping: 1246 1. Either a source and destination address hash or the traditional 1247 5-tuple hash can be used. The traditional 5-tuple hash includes 1248 the source and destination addresses; source and destination TCP, 1249 UDP, or Stream Control Transmission Protocol (SCTP) port numbers; 1250 and the IP protocol number field or IPv6 next-protocol fields of 1251 a packet that a host originates from within a LISP site. When a 1252 packet is not a TCP, UDP, or SCTP packet, the source and 1253 destination addresses only from the header are used to compute 1254 the hash. 1256 2. Take the hash value and divide it by the number of Locators 1257 stored in the Locator-Set for the EID-to-RLOC mapping. 1259 3. The remainder will yield a value of 0 to "number of Locators 1260 minus 1". Use the remainder to select the Locator in the 1261 Locator-Set. 1263 Note that when a packet is LISP encapsulated, the source port number 1264 in the outer UDP header needs to be set. Selecting a hashed value 1265 allows core routers that are attached to Link Aggregation Groups 1266 (LAGs) to load-split the encapsulated packets across member links of 1267 such LAGs. Otherwise, core routers would see a single flow, since 1268 packets have a source address of the ITR, for packets that are 1269 originated by different EIDs at the source site. A suggested setting 1270 for the source port number computed by an ITR is a 5-tuple hash 1271 function on the inner header, as described above. 1273 Many core router implementations use a 5-tuple hash to decide how to 1274 balance packet load across members of a LAG. The 5-tuple hash 1275 includes the source and destination addresses of the packet and the 1276 source and destination ports when the protocol number in the packet 1277 is TCP or UDP. For this reason, UDP encoding is used for LISP 1278 encapsulation. 1280 13. Changing the Contents of EID-to-RLOC Mappings 1282 Since the LISP architecture uses a caching scheme to retrieve and 1283 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 1284 date mapping is to re-request the mapping. However, the ITRs do not 1285 know when the mappings change, and the ETRs do not keep track of 1286 which ITRs requested its mappings. For scalability reasons, it is 1287 desirable to maintain this approach but need to provide a way for 1288 ETRs to change their mappings and inform the sites that are currently 1289 communicating with the ETR site using such mappings. 1291 This section defines data-plane mechanisms for updating EID-to-RLOC 1292 mappings. Additionally, the Solicit-Map Request (SMR) control-plane 1293 updating mechanism is specified in [I-D.ietf-lisp-rfc6833bis]. 1295 When adding a new Locator record in lexicographic order to the end of 1296 a Locator-Set, it is easy to update mappings. We assume that new 1297 mappings will maintain the same Locator ordering as the old mapping 1298 but will just have new Locators appended to the end of the list. So, 1299 some ITRs can have a new mapping while other ITRs have only an old 1300 mapping that is used until they time out. When an ITR has only an 1301 old mapping but detects bits set in the Locator-Status-Bits that 1302 correspond to Locators beyond the list it has cached, it simply 1303 ignores them. However, this can only happen for locator addresses 1304 that are lexicographically greater than the locator addresses in the 1305 existing Locator-Set. 1307 When a Locator record is inserted in the middle of a Locator-Set, to 1308 maintain lexicographic order, SMR procedure 1309 [I-D.ietf-lisp-rfc6833bis] is used to inform ITRs and PITRs of the 1310 new Locator-Status-Bit mappings. 1312 When a Locator record is removed from a Locator-Set, ITRs that have 1313 the mapping cached will not use the removed Locator because the xTRs 1314 will set the Locator-Status-Bit to 0. So, even if the Locator is in 1315 the list, it will not be used. For new mapping requests, the xTRs 1316 can set the Locator AFI to 0 (indicating an unspecified address), as 1317 well as setting the corresponding Locator-Status-Bit to 0. This 1318 forces ITRs with old or new mappings to avoid using the removed 1319 Locator. 1321 If many changes occur to a mapping over a long period of time, one 1322 will find empty record slots in the middle of the Locator-Set and new 1323 records appended to the Locator-Set. At some point, it would be 1324 useful to compact the Locator-Set so the Locator-Status-Bit settings 1325 can be efficiently packed. 1327 We propose here two approaches for Locator-Set compaction: one 1328 operational mechanism (clock sweep) and one protocol mechanisms (Map- 1329 Versioning). Please note that in addition the Solicit-Map Request 1330 (specified in [I-D.ietf-lisp-rfc6833bis]) is a control-plane 1331 mechanisms that can be used to update EID-to-RLOC mappings. 1333 13.1. Clock Sweep 1335 The clock sweep approach uses planning in advance and the use of 1336 count-down TTLs to time out mappings that have already been cached. 1337 The default setting for an EID-to-RLOC mapping TTL is 24 hours. So, 1338 there is a 24-hour window to time out old mappings. The following 1339 clock sweep procedure is used: 1341 1. 24 hours before a mapping change is to take effect, a network 1342 administrator configures the ETRs at a site to start the clock 1343 sweep window. 1345 2. During the clock sweep window, ETRs continue to send Map-Reply 1346 messages with the current (unchanged) mapping records. The TTL 1347 for these mappings is set to 1 hour. 1349 3. 24 hours later, all previous cache entries will have timed out, 1350 and any active cache entries will time out within 1 hour. During 1351 this 1-hour window, the ETRs continue to send Map-Reply messages 1352 with the current (unchanged) mapping records with the TTL set to 1353 1 minute. 1355 4. At the end of the 1-hour window, the ETRs will send Map-Reply 1356 messages with the new (changed) mapping records. So, any active 1357 caches can get the new mapping contents right away if not cached, 1358 or in 1 minute if they had the mapping cached. The new mappings 1359 are cached with a TTL equal to the TTL in the Map-Reply. 1361 13.2. Database Map-Versioning 1363 When there is unidirectional packet flow between an ITR and ETR, and 1364 the EID-to-RLOC mappings change on the ETR, it needs to inform the 1365 ITR so encapsulation to a removed Locator can stop and can instead be 1366 started to a new Locator in the Locator-Set. 1368 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 1369 Number. This is known as the Destination Map-Version Number. ITRs 1370 include the Destination Map-Version Number in packets they 1371 encapsulate to the site. When an ETR decapsulates a packet and 1372 detects that the Destination Map-Version Number is less than the 1373 current version for its mapping, the SMR procedure described in 1374 [I-D.ietf-lisp-rfc6833bis] occurs. 1376 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 1377 Version Number. This is known as the Source Map-Version Number. 1378 When an ETR decapsulates a packet and detects that the Source Map- 1379 Version Number is greater than the last Map-Version Number sent in a 1380 Map-Reply from the ITR's site, the ETR will send a Map-Request to one 1381 of the ETRs for the source site. 1383 A Map-Version Number is used as a sequence number per EID-Prefix, so 1384 values that are greater are considered to be more recent. A value of 1385 0 for the Source Map-Version Number or the Destination Map-Version 1386 Number conveys no versioning information, and an ITR does no 1387 comparison with previously received Map-Version Numbers. 1389 A Map-Version Number can be included in Map-Register messages as 1390 well. This is a good way for the Map-Server to assure that all ETRs 1391 for a site registering to it will be synchronized according to Map- 1392 Version Number. 1394 See [RFC6834] for a more detailed analysis and description of 1395 Database Map-Versioning. 1397 14. Multicast Considerations 1399 A multicast group address, as defined in the original Internet 1400 architecture, is an identifier of a grouping of topologically 1401 independent receiver host locations. The address encoding itself 1402 does not determine the location of the receiver(s). The multicast 1403 routing protocol, and the network-based state the protocol creates, 1404 determine where the receivers are located. 1406 In the context of LISP, a multicast group address is both an EID and 1407 a Routing Locator. Therefore, no specific semantic or action needs 1408 to be taken for a destination address, as it would appear in an IP 1409 header. Therefore, a group address that appears in an inner IP 1410 header built by a source host will be used as the destination EID. 1411 The outer IP header (the destination Routing Locator address), 1412 prepended by a LISP router, can use the same group address as the 1413 destination Routing Locator, use a multicast or unicast Routing 1414 Locator obtained from a Mapping System lookup, or use other means to 1415 determine the group address mapping. 1417 With respect to the source Routing Locator address, the ITR prepends 1418 its own IP address as the source address of the outer IP header. 1419 Just like it would if the destination EID was a unicast address. 1420 This source Routing Locator address, like any other Routing Locator 1421 address, MUST be globally routable. 1423 There are two approaches for LISP-Multicast, one that uses native 1424 multicast routing in the underlay with no support from the Mapping 1425 System and the other that uses only unicast routing in the underlay 1426 with support from the Mapping System. See [RFC6831] and 1427 [I-D.ietf-lisp-signal-free-multicast], respectively, for details. 1428 Details for LISP-Multicast and interworking with non-LISP sites are 1429 described in [RFC6831] and [RFC6832]. 1431 15. Router Performance Considerations 1433 LISP is designed to be very "hardware-based forwarding friendly". A 1434 few implementation techniques can be used to incrementally implement 1435 LISP: 1437 o When a tunnel-encapsulated packet is received by an ETR, the outer 1438 destination address may not be the address of the router. This 1439 makes it challenging for the control plane to get packets from the 1440 hardware. This may be mitigated by creating special Forwarding 1441 Information Base (FIB) entries for the EID-Prefixes of EIDs served 1442 by the ETR (those for which the router provides an RLOC 1443 translation). These FIB entries are marked with a flag indicating 1444 that control-plane processing SHOULD be performed. The forwarding 1445 logic of testing for particular IP protocol number values is not 1446 necessary. There are a few proven cases where no changes to 1447 existing deployed hardware were needed to support the LISP data- 1448 plane. 1450 o On an ITR, prepending a new IP header consists of adding more 1451 octets to a MAC rewrite string and prepending the string as part 1452 of the outgoing encapsulation procedure. Routers that support 1453 Generic Routing Encapsulation (GRE) tunneling [RFC2784] or 6to4 1454 tunneling [RFC3056] may already support this action. 1456 o A packet's source address or interface the packet was received on 1457 can be used to select VRF (Virtual Routing/Forwarding). The VRF's 1458 routing table can be used to find EID-to-RLOC mappings. 1460 For performance issues related to map-cache management, see 1461 Section 16. 1463 16. Security Considerations 1465 Security considerations for LISP are discussed in [RFC7833]. 1467 A complete LISP threat analysis can be found in [RFC7835], in what 1468 follows we provide a summary. 1470 The optional mechanisms of gleaning is offered to directly obtain a 1471 mapping from the LISP encapsulated packets. Specifically, an xTR can 1472 learn the EID-to-RLOC mapping by inspecting the source RLOC and 1473 source EID of an encapsulated packet, and insert this new mapping 1474 into its map-cache. An off-path attacker can spoof the source EID 1475 address to divert the traffic sent to the victim's spoofed EID. If 1476 the attacker spoofs the source RLOC, it can mount a DoS attack by 1477 redirecting traffic to the spoofed victim's RLOC, potentially 1478 overloading it. 1480 The LISP Data-Plane defines several mechanisms to monitor RLOC data- 1481 plane reachability, in this context Locator-Status Bits, Nonce- 1482 Present and Echo-Nonce bits of the LISP encapsulation header can be 1483 manipulated by an attacker to mount a DoS attack. An off-path 1484 attacker able to spoof the RLOC of a victim's xTR can manipulate such 1485 mechanisms to declare a set of RLOCs unreachable. This can be used 1486 also, for instance, to declare only one RLOC reachable with the aim 1487 of overload it. 1489 Map-Versioning is a data-plane mechanism used to signal a peering xTR 1490 that a local EID-to-RLOC mapping has been updated, so that the 1491 peering xTR uses LISP Control-Plane signaling message to retrieve a 1492 fresh mapping. This can be used by an attacker to forge the map- 1493 versioning field of a LISP encapsulated header and force an excessive 1494 amount of signaling between xTRs that may overload them. 1496 Most of the attack vectors can be mitigated with careful deployment 1497 and configuration, information learned opportunistically (such as LSB 1498 or gleaning) SHOULD be verified with other reachability mechanisms. 1499 In addition, systematic rate-limitation and filtering is an effective 1500 technique to mitigate attacks that aim to overload the control-plane. 1502 17. Network Management Considerations 1504 Considerations for network management tools exist so the LISP 1505 protocol suite can be operationally managed. These mechanisms can be 1506 found in [RFC7052] and [RFC6835]. 1508 18. IANA Considerations 1510 This section provides guidance to the Internet Assigned Numbers 1511 Authority (IANA) regarding registration of values related to this 1512 data-plane LISP specification, in accordance with BCP 26 [RFC8126]. 1514 18.1. LISP UDP Port Numbers 1516 The IANA registry has allocated UDP port number 4341 for the LISP 1517 data-plane. IANA has updated the description for UDP port 4341 as 1518 follows: 1520 lisp-data 4341 udp LISP Data Packets 1522 19. References 1524 19.1. Normative References 1526 [I-D.ietf-lisp-rfc6833bis] 1527 Fuller, V., Farinacci, D., and A. Cabellos-Aparicio, 1528 "Locator/ID Separation Protocol (LISP) Control-Plane", 1529 draft-ietf-lisp-rfc6833bis-07 (work in progress), December 1530 2017. 1532 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 1533 DOI 10.17487/RFC0768, August 1980, 1534 . 1536 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 1537 DOI 10.17487/RFC0791, September 1981, 1538 . 1540 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1541 "Definition of the Differentiated Services Field (DS 1542 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1543 DOI 10.17487/RFC2474, December 1998, 1544 . 1546 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 1547 of Explicit Congestion Notification (ECN) to IP", 1548 RFC 3168, DOI 10.17487/RFC3168, September 2001, 1549 . 1551 [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, 1552 "Randomness Requirements for Security", BCP 106, RFC 4086, 1553 DOI 10.17487/RFC4086, June 2005, 1554 . 1556 [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility 1557 Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July 1558 2011, . 1560 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1561 (IPv6) Specification", STD 86, RFC 8200, 1562 DOI 10.17487/RFC8200, July 2017, 1563 . 1565 19.2. Informative References 1567 [AFN] IANA, "Address Family Numbers", August 2016, 1568 . 1570 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed", 1571 1999, 1572 . 1574 [I-D.ietf-lisp-eid-mobility] 1575 Portoles-Comeras, M., Ashtaputre, V., Moreno, V., Maino, 1576 F., and D. Farinacci, "LISP L2/L3 EID Mobility Using a 1577 Unified Control Plane", draft-ietf-lisp-eid-mobility-01 1578 (work in progress), November 2017. 1580 [I-D.ietf-lisp-introduction] 1581 Cabellos-Aparicio, A. and D. Saucez, "An Architectural 1582 Introduction to the Locator/ID Separation Protocol 1583 (LISP)", draft-ietf-lisp-introduction-13 (work in 1584 progress), April 2015. 1586 [I-D.ietf-lisp-mn] 1587 Farinacci, D., Lewis, D., Meyer, D., and C. White, "LISP 1588 Mobile Node", draft-ietf-lisp-mn-01 (work in progress), 1589 October 2017. 1591 [I-D.ietf-lisp-predictive-rlocs] 1592 Farinacci, D. and P. Pillay-Esnault, "LISP Predictive 1593 RLOCs", draft-ietf-lisp-predictive-rlocs-01 (work in 1594 progress), November 2017. 1596 [I-D.ietf-lisp-sec] 1597 Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D. 1598 Saucez, "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-14 1599 (work in progress), October 2017. 1601 [I-D.ietf-lisp-signal-free-multicast] 1602 Moreno, V. and D. Farinacci, "Signal-Free LISP Multicast", 1603 draft-ietf-lisp-signal-free-multicast-08 (work in 1604 progress), February 2018. 1606 [I-D.ietf-lisp-vpn] 1607 Moreno, V. and D. Farinacci, "LISP Virtual Private 1608 Networks (VPNs)", draft-ietf-lisp-vpn-01 (work in 1609 progress), November 2017. 1611 [LISA96] Lear, E., Tharp, D., Katinsky, J., and J. Coffin, 1612 "Renumbering: Threat or Menace?", Usenix Tenth System 1613 Administration Conference (LISA 96), October 1996. 1615 [OPENLISP] 1616 Iannone, L., Saucez, D., and O. Bonaventure, "OpenLISP 1617 Implementation Report", Work in Progress, July 2008. 1619 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 1620 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 1621 . 1623 [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G., 1624 and E. Lear, "Address Allocation for Private Internets", 1625 BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996, 1626 . 1628 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1629 Requirement Levels", BCP 14, RFC 2119, 1630 DOI 10.17487/RFC2119, March 1997, 1631 . 1633 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 1634 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 1635 DOI 10.17487/RFC2784, March 2000, 1636 . 1638 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 1639 via IPv4 Clouds", RFC 3056, DOI 10.17487/RFC3056, February 1640 2001, . 1642 [RFC3232] Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced 1643 by an On-line Database", RFC 3232, DOI 10.17487/RFC3232, 1644 January 2002, . 1646 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 1647 A., Peterson, J., Sparks, R., Handley, M., and E. 1648 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 1649 DOI 10.17487/RFC3261, June 2002, 1650 . 1652 [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for 1653 Renumbering an IPv6 Network without a Flag Day", RFC 4192, 1654 DOI 10.17487/RFC4192, September 2005, 1655 . 1657 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 1658 (CIDR): The Internet Address Assignment and Aggregation 1659 Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August 1660 2006, . 1662 [RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route 1663 Optimization for Mobile IPv6", RFC 4866, 1664 DOI 10.17487/RFC4866, May 2007, 1665 . 1667 [RFC4984] Meyer, D., Ed., Zhang, L., Ed., and K. Fall, Ed., "Report 1668 from the IAB Workshop on Routing and Addressing", 1669 RFC 4984, DOI 10.17487/RFC4984, September 2007, 1670 . 1672 [RFC5944] Perkins, C., Ed., "IP Mobility Support for IPv4, Revised", 1673 RFC 5944, DOI 10.17487/RFC5944, November 2010, 1674 . 1676 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 1677 Locator/ID Separation Protocol (LISP) for Multicast 1678 Environments", RFC 6831, DOI 10.17487/RFC6831, January 1679 2013, . 1681 [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 1682 "Interworking between Locator/ID Separation Protocol 1683 (LISP) and Non-LISP Sites", RFC 6832, 1684 DOI 10.17487/RFC6832, January 2013, 1685 . 1687 [RFC6834] Iannone, L., Saucez, D., and O. Bonaventure, "Locator/ID 1688 Separation Protocol (LISP) Map-Versioning", RFC 6834, 1689 DOI 10.17487/RFC6834, January 2013, 1690 . 1692 [RFC6835] Farinacci, D. and D. Meyer, "The Locator/ID Separation 1693 Protocol Internet Groper (LIG)", RFC 6835, 1694 DOI 10.17487/RFC6835, January 2013, 1695 . 1697 [RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and 1698 UDP Checksums for Tunneled Packets", RFC 6935, 1699 DOI 10.17487/RFC6935, April 2013, 1700 . 1702 [RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement 1703 for the Use of IPv6 UDP Datagrams with Zero Checksums", 1704 RFC 6936, DOI 10.17487/RFC6936, April 2013, 1705 . 1707 [RFC7052] Schudel, G., Jain, A., and V. Moreno, "Locator/ID 1708 Separation Protocol (LISP) MIB", RFC 7052, 1709 DOI 10.17487/RFC7052, October 2013, 1710 . 1712 [RFC7215] Jakab, L., Cabellos-Aparicio, A., Coras, F., Domingo- 1713 Pascual, J., and D. Lewis, "Locator/Identifier Separation 1714 Protocol (LISP) Network Element Deployment 1715 Considerations", RFC 7215, DOI 10.17487/RFC7215, April 1716 2014, . 1718 [RFC7833] Howlett, J., Hartman, S., and A. Perez-Mendez, Ed., "A 1719 RADIUS Attribute, Binding, Profiles, Name Identifier 1720 Format, and Confirmation Methods for the Security 1721 Assertion Markup Language (SAML)", RFC 7833, 1722 DOI 10.17487/RFC7833, May 2016, 1723 . 1725 [RFC7835] Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID 1726 Separation Protocol (LISP) Threat Analysis", RFC 7835, 1727 DOI 10.17487/RFC7835, April 2016, 1728 . 1730 [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 1731 Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, 1732 February 2017, . 1734 [RFC8061] Farinacci, D. and B. Weis, "Locator/ID Separation Protocol 1735 (LISP) Data-Plane Confidentiality", RFC 8061, 1736 DOI 10.17487/RFC8061, February 2017, 1737 . 1739 [RFC8111] Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A. 1740 Smirnov, "Locator/ID Separation Protocol Delegated 1741 Database Tree (LISP-DDT)", RFC 8111, DOI 10.17487/RFC8111, 1742 May 2017, . 1744 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1745 Writing an IANA Considerations Section in RFCs", BCP 26, 1746 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1747 . 1749 Appendix A. Acknowledgments 1751 An initial thank you goes to Dave Oran for planting the seeds for the 1752 initial ideas for LISP. His consultation continues to provide value 1753 to the LISP authors. 1755 A special and appreciative thank you goes to Noel Chiappa for 1756 providing architectural impetus over the past decades on separation 1757 of location and identity, as well as detailed reviews of the LISP 1758 architecture and documents, coupled with enthusiasm for making LISP a 1759 practical and incremental transition for the Internet. 1761 The authors would like to gratefully acknowledge many people who have 1762 contributed discussions and ideas to the making of this proposal. 1763 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 1764 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 1765 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 1766 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 1767 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 1768 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 1769 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 1770 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 1771 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 1772 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 1773 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 1774 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 1775 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 1776 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 1777 Ermagan, Fabio Maino, Victor Moreno, Chris White, Clarence Filsfils, 1778 Alia Atlas, Florin Coras and Alberto Rodriguez. 1780 This work originated in the Routing Research Group (RRG) of the IRTF. 1781 An individual submission was converted into the IETF LISP working 1782 group document that became this RFC. 1784 The LISP working group would like to give a special thanks to Jari 1785 Arkko, the Internet Area AD at the time that the set of LISP 1786 documents were being prepared for IESG last call, and for his 1787 meticulous reviews and detailed commentaries on the 7 working group 1788 last call documents progressing toward standards-track RFCs. 1790 Appendix B. Document Change Log 1792 [RFC Editor: Please delete this section on publication as RFC.] 1794 B.1. Changes to draft-ietf-lisp-rfc6830bis-11 1796 o Posted March 2018. 1798 o Removed sections 16, 17 and 18 (Mobility, Deployment and 1799 Traceroute considerations). This text must be placed in a new OAM 1800 document. 1802 B.2. Changes to draft-ietf-lisp-rfc6830bis-10 1804 o Posted March 2018. 1806 o Updated section 'Router Locator Selection' stating that the data- 1807 plane MUST follow what's stored in the map-cache (priorities and 1808 weights). 1810 o Section 'Routing Locator Reachability': Removed bullet point 2 1811 (ICMP Network/Host Unreachable),3 (hints from BGP),4 (ICMP Port 1812 Unreachable),5 (receive a Map-Reply as a response) and RLOC 1813 probing 1815 o Removed 'Solicit-Map Request'. 1817 B.3. Changes to draft-ietf-lisp-rfc6830bis-09 1819 o Posted January 2018. 1821 o Add more details in section 5.3 about DSCP processing during 1822 encapsulation and decapsulation. 1824 o Added clarity to definitions in the Definition of Terms section 1825 from various commenters. 1827 o Removed PA and PI definitions from Definition of Terms section. 1829 o More editorial changes. 1831 o Removed 4342 from IANA section and move to RFC6833 IANA section. 1833 B.4. Changes to draft-ietf-lisp-rfc6830bis-08 1835 o Posted January 2018. 1837 o Remove references to research work for any protocol mechanisms. 1839 o Document scanned to make sure it is RFC 2119 compliant. 1841 o Made changes to reflect comments from document WG shepherd Luigi 1842 Iannone. 1844 o Ran IDNITs on the document. 1846 B.5. Changes to draft-ietf-lisp-rfc6830bis-07 1848 o Posted November 2017. 1850 o Rephrase how Instance-IDs are used and don't refer to [RFC1918] 1851 addresses. 1853 B.6. Changes to draft-ietf-lisp-rfc6830bis-06 1855 o Posted October 2017. 1857 o Put RTR definition before it is used. 1859 o Rename references that are now working group drafts. 1861 o Remove "EIDs MUST NOT be used as used by a host to refer to other 1862 hosts. Note that EID blocks MAY LISP RLOCs". 1864 o Indicate what address-family can appear in data packets. 1866 o ETRs may, rather than will, be the ones to send Map-Replies. 1868 o Recommend, rather than mandate, max encapsulation headers to 2. 1870 o Reference VPN draft when introducing Instance-ID. 1872 o Indicate that SMRs can be sent when ITR/ETR are in the same node. 1874 o Clarify when private addreses can be used. 1876 B.7. Changes to draft-ietf-lisp-rfc6830bis-05 1878 o Posted August 2017. 1880 o Make it clear that a Reencapsulating Tunnel Router is an RTR. 1882 B.8. Changes to draft-ietf-lisp-rfc6830bis-04 1884 o Posted July 2017. 1886 o Changed reference of IPv6 RFC2460 to RFC8200. 1888 o Indicate that the applicability statement for UDP zero checksums 1889 over IPv6 adheres to RFC6936. 1891 B.9. Changes to draft-ietf-lisp-rfc6830bis-03 1893 o Posted May 2017. 1895 o Move the control-plane related codepoints in the IANA 1896 Considerations section to RFC6833bis. 1898 B.10. Changes to draft-ietf-lisp-rfc6830bis-02 1900 o Posted April 2017. 1902 o Reflect some editorial comments from Damien Sausez. 1904 B.11. Changes to draft-ietf-lisp-rfc6830bis-01 1906 o Posted March 2017. 1908 o Include references to new RFCs published. 1910 o Change references from RFC6833 to RFC6833bis. 1912 o Clarified LCAF text in the IANA section. 1914 o Remove references to "experimental". 1916 B.12. Changes to draft-ietf-lisp-rfc6830bis-00 1918 o Posted December 2016. 1920 o Created working group document from draft-farinacci-lisp 1921 -rfc6830-00 individual submission. No other changes made. 1923 Authors' Addresses 1925 Dino Farinacci 1926 Cisco Systems 1927 Tasman Drive 1928 San Jose, CA 95134 1929 USA 1931 EMail: farinacci@gmail.com 1932 Vince Fuller 1933 Cisco Systems 1934 Tasman Drive 1935 San Jose, CA 95134 1936 USA 1938 EMail: vince.fuller@gmail.com 1940 Dave Meyer 1941 Cisco Systems 1942 170 Tasman Drive 1943 San Jose, CA 1944 USA 1946 EMail: dmm@1-4-5.net 1948 Darrel Lewis 1949 Cisco Systems 1950 170 Tasman Drive 1951 San Jose, CA 1952 USA 1954 EMail: darlewis@cisco.com 1956 Albert Cabellos 1957 UPC/BarcelonaTech 1958 Campus Nord, C. Jordi Girona 1-3 1959 Barcelona, Catalunya 1960 Spain 1962 EMail: acabello@ac.upc.edu