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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 20, 2018 D. Lewis 6 Cisco Systems 7 A. Cabellos (Ed.) 8 UPC/BarcelonaTech 9 March 19, 2018 11 The Locator/ID Separation Protocol (LISP) 12 draft-ietf-lisp-rfc6830bis-12 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 20, 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. Database Map-Versioning . . . . . . . . . . . . . . . . 29 83 14. Multicast Considerations . . . . . . . . . . . . . . . . . . 29 84 15. Router Performance Considerations . . . . . . . . . . . . . . 30 85 16. Security Considerations . . . . . . . . . . . . . . . . . . . 31 86 17. Network Management Considerations . . . . . . . . . . . . . . 32 87 18. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 88 18.1. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . 32 89 19. References . . . . . . . . . . . . . . . . . . . . . . . . . 32 90 19.1. Normative References . . . . . . . . . . . . . . . . . . 32 91 19.2. Informative References . . . . . . . . . . . . . . . . . 33 92 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 38 93 Appendix B. Document Change Log . . . . . . . . . . . . . . . . 38 94 B.1. Changes to draft-ietf-lisp-rfc6830bis-12 . . . . . . . . 39 95 B.2. Changes to draft-ietf-lisp-rfc6830bis-11 . . . . . . . . 39 96 B.3. Changes to draft-ietf-lisp-rfc6830bis-10 . . . . . . . . 39 97 B.4. Changes to draft-ietf-lisp-rfc6830bis-09 . . . . . . . . 39 98 B.5. Changes to draft-ietf-lisp-rfc6830bis-08 . . . . . . . . 40 99 B.6. Changes to draft-ietf-lisp-rfc6830bis-07 . . . . . . . . 40 100 B.7. Changes to draft-ietf-lisp-rfc6830bis-06 . . . . . . . . 40 101 B.8. Changes to draft-ietf-lisp-rfc6830bis-05 . . . . . . . . 41 102 B.9. Changes to draft-ietf-lisp-rfc6830bis-04 . . . . . . . . 41 103 B.10. Changes to draft-ietf-lisp-rfc6830bis-03 . . . . . . . . 41 104 B.11. Changes to draft-ietf-lisp-rfc6830bis-02 . . . . . . . . 41 105 B.12. Changes to draft-ietf-lisp-rfc6830bis-01 . . . . . . . . 41 106 B.13. Changes to draft-ietf-lisp-rfc6830bis-00 . . . . . . . . 41 107 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 42 109 1. Introduction 111 This document describes the Locator/Identifier Separation Protocol 112 (LISP). LISP is an encapsulation protocol built around the 113 fundamental idea of separating the topological location of a network 114 attachment point from the node's identity [CHIAPPA]. As a result 115 LISP creates two namespaces: Endpoint Identifiers (EIDs), that are 116 used to identify end-hosts (e.g., nodes or Virtual Machines) and 117 routable Routing Locators (RLOCs), used to identify network 118 attachment points. LISP then defines functions for mapping between 119 the two namespaces and for encapsulating traffic originated by 120 devices using non-routable EIDs for transport across a network 121 infrastructure that routes and forwards using RLOCs. LISP 122 encapsulation uses a dynamic form of tunneling where no static 123 provisioning is required or necessary. 125 LISP is an overlay protocol that separates control from Data-Plane, 126 this document specifies the Data-Plane, how LISP-capable routers 127 (Tunnel Routers) exchange packets by encapsulating them to the 128 appropriate location. Tunnel routers are equipped with a cache, 129 called Map-Cache, that contains EID-to-RLOC mappings. The Map-Cache 130 is populated using the LISP Control-Plane protocol 131 [I-D.ietf-lisp-rfc6833bis]. 133 LISP does not require changes to either host protocol stack or to 134 underlay routers. By separating the EID from the RLOC space, LISP 135 offers native Traffic Engineering, multihoming and mobility, among 136 other features. 138 Creation of LISP was initially motivated by discussions during the 139 IAB-sponsored Routing and Addressing Workshop held in Amsterdam in 140 October 2006 (see [RFC4984]). 142 This document specifies the LISP Data-Plane encapsulation and other 143 LISP forwarding node functionality while [I-D.ietf-lisp-rfc6833bis] 144 specifies the LISP control plane. LISP deployment guidelines can be 145 found in [RFC7215] and [RFC6835] describes considerations for network 146 operational management. Finally, [I-D.ietf-lisp-introduction] 147 describes the LISP architecture. 149 2. Requirements Notation 151 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 152 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 153 document are to be interpreted as described in [RFC2119]. 155 3. Definition of Terms 157 Address Family Identifier (AFI): AFI is a term used to describe an 158 address encoding in a packet. An address family that pertains to 159 the Data-Plane. See [AFN] and [RFC3232] for details. An AFI 160 value of 0 used in this specification indicates an unspecified 161 encoded address where the length of the address is 0 octets 162 following the 16-bit AFI value of 0. 164 Anycast Address: Anycast Address is a term used in this document to 165 refer to the same IPv4 or IPv6 address configured and used on 166 multiple systems at the same time. An EID or RLOC can be an 167 anycast address in each of their own address spaces. 169 Client-side: Client-side is a term used in this document to indicate 170 a connection initiation attempt by an end-system represented by an 171 EID. 173 Data-Probe: A Data-Probe is a LISP-encapsulated data packet where 174 the inner-header destination address equals the outer-header 175 destination address used to trigger a Map-Reply by a decapsulating 176 ETR. In addition, the original packet is decapsulated and 177 delivered to the destination host if the destination EID is in the 178 EID-Prefix range configured on the ETR. Otherwise, the packet is 179 discarded. A Data-Probe is used in some of the mapping database 180 designs to "probe" or request a Map-Reply from an ETR; in other 181 cases, Map-Requests are used. See each mapping database design 182 for details. When using Data-Probes, by sending Map-Requests on 183 the underlying routing system, EID-Prefixes must be advertised. 185 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 186 packet where the destination address in the "outer" IP header is 187 one of its own RLOCs. The router strips the "outer" header and 188 forwards the packet based on the next IP header found. In 189 general, an ETR receives LISP-encapsulated IP packets from the 190 Internet on one side and sends decapsulated IP packets to site 191 end-systems on the other side. ETR functionality does not have to 192 be limited to a router device. A server host can be the endpoint 193 of a LISP tunnel as well. 195 EID-to-RLOC Database: The EID-to-RLOC Database is a global 196 distributed database that contains all known EID-Prefix-to-RLOC 197 mappings. Each potential ETR typically contains a small piece of 198 the database: the EID-to-RLOC mappings for the EID-Prefixes 199 "behind" the router. These map to one of the router's own 200 globally visible IP addresses. Note that there MAY be transient 201 conditions when the EID-Prefix for the site and Locator-Set for 202 each EID-Prefix may not be the same on all ETRs. This has no 203 negative implications, since a partial set of Locators can be 204 used. 206 EID-to-RLOC Map-Cache: The EID-to-RLOC Map-Cache is generally 207 short-lived, on-demand table in an ITR that stores, tracks, and is 208 responsible for timing out and otherwise validating EID-to-RLOC 209 mappings. This cache is distinct from the full "database" of EID- 210 to-RLOC mappings; it is dynamic, local to the ITR(s), and 211 relatively small, while the database is distributed, relatively 212 static, and much more global in scope. 214 EID-Prefix: An EID-Prefix is a power-of-two block of EIDs that are 215 allocated to a site by an address allocation authority. EID- 216 Prefixes are associated with a set of RLOC addresses. EID-Prefix 217 allocations can be broken up into smaller blocks when an RLOC set 218 is to be associated with the larger EID-Prefix block. 220 End-System: An end-system is an IPv4 or IPv6 device that originates 221 packets with a single IPv4 or IPv6 header. The end-system 222 supplies an EID value for the destination address field of the IP 223 header when communicating globally (i.e., outside of its routing 224 domain). An end-system can be a host computer, a switch or router 225 device, or any network appliance. 227 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 228 IPv6) value used in the source and destination address fields of 229 the first (most inner) LISP header of a packet. The host obtains 230 a destination EID the same way it obtains a destination address 231 today, for example, through a Domain Name System (DNS) [RFC1034] 232 lookup or Session Initiation Protocol (SIP) [RFC3261] exchange. 233 The source EID is obtained via existing mechanisms used to set a 234 host's "local" IP address. An EID used on the public Internet 235 MUST have the same properties as any other IP address used in that 236 manner; this means, among other things, that it MUST be globally 237 unique. An EID is allocated to a host from an EID-Prefix block 238 associated with the site where the host is located. An EID can be 239 used by a host to refer to other hosts. Note that EID blocks MAY 240 be assigned in a hierarchical manner, independent of the network 241 topology, to facilitate scaling of the mapping database. In 242 addition, an EID block assigned to a site MAY have site-local 243 structure (subnetting) for routing within the site; this structure 244 is not visible to the global routing system. In theory, the bit 245 string that represents an EID for one device can represent an RLOC 246 for a different device. When used in discussions with other 247 Locator/ID separation proposals, a LISP EID will be called an 248 "LEID". Throughout this document, any references to "EID" refer 249 to an LEID. 251 Ingress Tunnel Router (ITR): An ITR is a router that resides in a 252 LISP site. Packets sent by sources inside of the LISP site to 253 destinations outside of the site are candidates for encapsulation 254 by the ITR. The ITR treats the IP destination address as an EID 255 and performs an EID-to-RLOC mapping lookup. The router then 256 prepends an "outer" IP header with one of its routable RLOCs (in 257 the RLOC space) in the source address field and the result of the 258 mapping lookup in the destination address field. Note that this 259 destination RLOC MAY be an intermediate, proxy device that has 260 better knowledge of the EID-to-RLOC mapping closer to the 261 destination EID. In general, an ITR receives IP packets from site 262 end-systems on one side and sends LISP-encapsulated IP packets 263 toward the Internet on the other side. 265 Specifically, when a service provider prepends a LISP header for 266 Traffic Engineering purposes, the router that does this is also 267 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 268 on the outer destination address (the originating ITR's supplied 269 RLOC) or the inner destination address (the originating host's 270 supplied EID). 272 LISP Header: LISP header is a term used in this document to refer 273 to the outer IPv4 or IPv6 header, a UDP header, and a LISP- 274 specific 8-octet header that follow the UDP header and that an ITR 275 prepends or an ETR strips. 277 LISP Router: A LISP router is a router that performs the functions 278 of any or all of the following: ITR, ETR, RTR, Proxy-ITR (PITR), 279 or Proxy-ETR (PETR). 281 LISP Site: LISP site is a set of routers in an edge network that are 282 under a single technical administration. LISP routers that reside 283 in the edge network are the demarcation points to separate the 284 edge network from the core network. 286 Locator-Status-Bits (LSBs): Locator-Status-Bits are present in the 287 LISP header. They are used by ITRs to inform ETRs about the up/ 288 down status of all ETRs at the local site. These bits are used as 289 a hint to convey up/down router status and not path reachability 290 status. The LSBs can be verified by use of one of the Locator 291 reachability algorithms described in Section 10. 293 Negative Mapping Entry: A negative mapping entry, also known as a 294 negative cache entry, is an EID-to-RLOC entry where an EID-Prefix 295 is advertised or stored with no RLOCs. That is, the Locator-Set 296 for the EID-to-RLOC entry is empty or has an encoded Locator count 297 of 0. This type of entry could be used to describe a prefix from 298 a non-LISP site, which is explicitly not in the mapping database. 299 There are a set of well-defined actions that are encoded in a 300 Negative Map-Reply. 302 Proxy-ETR (PETR): A PETR is defined and described in [RFC6832]. A 303 PETR acts like an ETR but does so on behalf of LISP sites that 304 send packets to destinations at non-LISP sites. 306 Proxy-ITR (PITR): A PITR is defined and described in [RFC6832]. A 307 PITR acts like an ITR but does so on behalf of non-LISP sites that 308 send packets to destinations at LISP sites. 310 Recursive Tunneling: Recursive Tunneling occurs when a packet has 311 more than one LISP IP header. Additional layers of tunneling MAY 312 be employed to implement Traffic Engineering or other re-routing 313 as needed. When this is done, an additional "outer" LISP header 314 is added, and the original RLOCs are preserved in the "inner" 315 header. 317 Re-Encapsulating Tunneling Router (RTR): An RTR acts like an ETR to 318 remove a LISP header, then acts as an ITR to prepend a new LISP 319 header. This is known as Re-encapsulating Tunneling. Doing this 320 allows a packet to be re-routed by the RTR without adding the 321 overhead of additional tunnel headers. When using multiple 322 mapping database systems, care must be taken to not create re- 323 encapsulation loops through misconfiguration. 325 Route-Returnability: Route-returnability is an assumption that the 326 underlying routing system will deliver packets to the destination. 327 When combined with a nonce that is provided by a sender and 328 returned by a receiver, this limits off-path data insertion. A 329 route-returnability check is verified when a message is sent with 330 a nonce, another message is returned with the same nonce, and the 331 destination of the original message appears as the source of the 332 returned message. 334 Routing Locator (RLOC): An RLOC is an IPv4 [RFC0791] or IPv6 335 [RFC8200] address of an Egress Tunnel Router (ETR). An RLOC is 336 the output of an EID-to-RLOC mapping lookup. An EID maps to zero 337 or more RLOCs. Typically, RLOCs are numbered from blocks that are 338 assigned to a site at each point to which it attaches to the 339 underlay network; where the topology is defined by the 340 connectivity of provider networks. Multiple RLOCs can be assigned 341 to the same ETR device or to multiple ETR devices at a site. 343 Server-side: Server-side is a term used in this document to indicate 344 that a connection initiation attempt is being accepted for a 345 destination EID. 347 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 348 network that strips an outer LISP header for Traffic Engineering 349 purposes. 351 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 352 network that prepends an additional LISP header for Traffic 353 Engineering purposes. 355 xTR: An xTR is a reference to an ITR or ETR when direction of data 356 flow is not part of the context description. "xTR" refers to the 357 router that is the tunnel endpoint and is used synonymously with 358 the term "Tunnel Router". For example, "An xTR can be located at 359 the Customer Edge (CE) router" indicates both ITR and ETR 360 functionality at the CE router. 362 4. Basic Overview 364 One key concept of LISP is that end-systems operate the same way they 365 do today. The IP addresses that hosts use for tracking sockets and 366 connections, and for sending and receiving packets, do not change. 367 In LISP terminology, these IP addresses are called Endpoint 368 Identifiers (EIDs). 370 Routers continue to forward packets based on IP destination 371 addresses. When a packet is LISP encapsulated, these addresses are 372 referred to as Routing Locators (RLOCs). Most routers along a path 373 between two hosts will not change; they continue to perform routing/ 374 forwarding lookups on the destination addresses. For routers between 375 the source host and the ITR as well as routers from the ETR to the 376 destination host, the destination address is an EID. For the routers 377 between the ITR and the ETR, the destination address is an RLOC. 379 Another key LISP concept is the "Tunnel Router". A Tunnel Router 380 prepends LISP headers on host-originated packets and strips them 381 prior to final delivery to their destination. The IP addresses in 382 this "outer header" are RLOCs. During end-to-end packet exchange 383 between two Internet hosts, an ITR prepends a new LISP header to each 384 packet, and an ETR strips the new header. The ITR performs EID-to- 385 RLOC lookups to determine the routing path to the ETR, which has the 386 RLOC as one of its IP addresses. 388 Some basic rules governing LISP are: 390 o End-systems only send to addresses that are EIDs. EIDs are 391 typically IP addresses assigned to hosts (other types of EID are 392 supported by LISP, see [RFC8060] for further information). End- 393 systems don't know that addresses are EIDs versus RLOCs but assume 394 that packets get to their intended destinations. In a system 395 where LISP is deployed, LISP routers intercept EID-addressed 396 packets and assist in delivering them across the network core 397 where EIDs cannot be routed. The procedure a host uses to send IP 398 packets does not change. 400 o LISP routers mostly deal with Routing Locator addresses. See 401 details in Section 4.1 to clarify what is meant by "mostly". 403 o RLOCs are always IP addresses assigned to routers, preferably 404 topologically oriented addresses from provider CIDR (Classless 405 Inter-Domain Routing) blocks. 407 o When a router originates packets, it MAY use as a source address 408 either an EID or RLOC. When acting as a host (e.g., when 409 terminating a transport session such as Secure SHell (SSH), 410 TELNET, or the Simple Network Management Protocol (SNMP)), it MAY 411 use an EID that is explicitly assigned for that purpose. An EID 412 that identifies the router as a host MUST NOT be used as an RLOC; 413 an EID is only routable within the scope of a site. A typical BGP 414 configuration might demonstrate this "hybrid" EID/RLOC usage where 415 a router could use its "host-like" EID to terminate iBGP sessions 416 to other routers in a site while at the same time using RLOCs to 417 terminate eBGP sessions to routers outside the site. 419 o Packets with EIDs in them are not expected to be delivered end-to- 420 end in the absence of an EID-to-RLOC mapping operation. They are 421 expected to be used locally for intra-site communication or to be 422 encapsulated for inter-site communication. 424 o EIDs MAY also be structured (subnetted) in a manner suitable for 425 local routing within an Autonomous System (AS). 427 An additional LISP header MAY be prepended to packets by a TE-ITR 428 when re-routing of the path for a packet is desired. A potential 429 use-case for this would be an ISP router that needs to perform 430 Traffic Engineering for packets flowing through its network. In such 431 a situation, termed "Recursive Tunneling", an ISP transit acts as an 432 additional ITR, and the RLOC it uses for the new prepended header 433 would be either a TE-ETR within the ISP (along an intra-ISP traffic 434 engineered path) or a TE-ETR within another ISP (an inter-ISP traffic 435 engineered path, where an agreement to build such a path exists). 437 In order to avoid excessive packet overhead as well as possible 438 encapsulation loops, this document recommends that a maximum of two 439 LISP headers can be prepended to a packet. For initial LISP 440 deployments, it is assumed that two headers is sufficient, where the 441 first prepended header is used at a site for Location/Identity 442 separation and the second prepended header is used inside a service 443 provider for Traffic Engineering purposes. 445 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 446 For example, the ITR for a particular end-to-end packet exchange 447 might be the first-hop or default router within a site for the source 448 host. Similarly, the ETR might be the last-hop router directly 449 connected to the destination host. Another example, perhaps for a 450 VPN service outsourced to an ISP by a site, the ITR could be the 451 site's border router at the service provider attachment point. 452 Mixing and matching of site-operated, ISP-operated, and other Tunnel 453 Routers is allowed for maximum flexibility. 455 4.1. Packet Flow Sequence 457 This section provides an example of the unicast packet flow, 458 including also Control-Plane information as specified in 459 [I-D.ietf-lisp-rfc6833bis]. The example also assumes the following 460 conditions: 462 o Source host "host1.abc.example.com" is sending a packet to 463 "host2.xyz.example.com", exactly what host1 would do if the site 464 was not using LISP. 466 o Each site is multihomed, so each Tunnel Router has an address 467 (RLOC) assigned from the service provider address block for each 468 provider to which that particular Tunnel Router is attached. 470 o The ITR(s) and ETR(s) are directly connected to the source and 471 destination, respectively, but the source and destination can be 472 located anywhere in the LISP site. 474 o A Map-Request is sent for an external destination when the 475 destination is not found in the forwarding table or matches a 476 default route. Map-Requests are sent to the mapping database 477 system by using the LISP Control-Plane protocol documented in 478 [I-D.ietf-lisp-rfc6833bis]. 480 o Map-Replies are sent on the underlying routing system topology 481 using the [I-D.ietf-lisp-rfc6833bis] Control-Plane protocol. 483 Client host1.abc.example.com wants to communicate with server 484 host2.xyz.example.com: 486 1. host1.abc.example.com wants to open a TCP connection to 487 host2.xyz.example.com. It does a DNS lookup on 488 host2.xyz.example.com. An A/AAAA record is returned. This 489 address is the destination EID. The locally assigned address of 490 host1.abc.example.com is used as the source EID. An IPv4 or IPv6 491 packet is built and forwarded through the LISP site as a normal 492 IP packet until it reaches a LISP ITR. 494 2. The LISP ITR must be able to map the destination EID to an RLOC 495 of one of the ETRs at the destination site. The specific method 496 used to do this is not described in this example. See 497 [I-D.ietf-lisp-rfc6833bis] for further information. 499 3. The ITR sends a LISP Map-Request as specified in 500 [I-D.ietf-lisp-rfc6833bis]. Map-Requests SHOULD be rate-limited. 502 4. The mapping system helps forwarding the Map-Request to the 503 corresponding ETR. When the Map-Request arrives at one of the 504 ETRs at the destination site, it will process the packet as a 505 control message. 507 5. The ETR looks at the destination EID of the Map-Request and 508 matches it against the prefixes in the ETR's configured EID-to- 509 RLOC mapping database. This is the list of EID-Prefixes the ETR 510 is supporting for the site it resides in. If there is no match, 511 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 512 returned to the ITR. 514 6. The ITR receives the Map-Reply message, parses the message (to 515 check for format validity), and stores the mapping information 516 from the packet. This information is stored in the ITR's EID-to- 517 RLOC Map-Cache. Note that the Map-Cache is an on-demand cache. 518 An ITR will manage its Map-Cache in such a way that optimizes for 519 its resource constraints. 521 7. Subsequent packets from host1.abc.example.com to 522 host2.xyz.example.com will have a LISP header prepended by the 523 ITR using the appropriate RLOC as the LISP header destination 524 address learned from the ETR. Note that the packet MAY be sent 525 to a different ETR than the one that returned the Map-Reply due 526 to the source site's hashing policy or the destination site's 527 Locator-Set policy. 529 8. The ETR receives these packets directly (since the destination 530 address is one of its assigned IP addresses), checks the validity 531 of the addresses, strips the LISP header, and forwards packets to 532 the attached destination host. 534 9. In order to defer the need for a mapping lookup in the reverse 535 direction, an ETR can OPTIONALLY create a cache entry that maps 536 the source EID (inner-header source IP address) to the source 537 RLOC (outer-header source IP address) in a received LISP packet. 538 Such a cache entry is termed a "glean mapping" and only contains 539 a single RLOC for the EID in question. More complete information 540 about additional RLOCs SHOULD be verified by sending a LISP Map- 541 Request for that EID. Both the ITR and the ETR MAY also 542 influence the decision the other makes in selecting an RLOC. 544 5. LISP Encapsulation Details 546 Since additional tunnel headers are prepended, the packet becomes 547 larger and can exceed the MTU of any link traversed from the ITR to 548 the ETR. It is RECOMMENDED in IPv4 that packets do not get 549 fragmented as they are encapsulated by the ITR. Instead, the packet 550 is dropped and an ICMP Unreachable/Fragmentation-Needed message is 551 returned to the source. 553 In the case when fragmentation is needed, this specification 554 RECOMMENDS that implementations provide support for one of the 555 proposed fragmentation and reassembly schemes. Two existing schemes 556 are detailed in Section 7. 558 Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP 559 architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner 560 header is in IPv4 packet format and the outer header is in IPv6 561 packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner header 562 is in IPv6 packet format and the outer header is in IPv4 packet 563 format). The next sub-sections illustrate packet formats for the 564 homogeneous case (IPv4-in-IPv4 and IPv6-in-IPv6), but all 4 565 combinations MUST be supported. Additional types of EIDs are defined 566 in [RFC8060]. 568 5.1. LISP IPv4-in-IPv4 Header Format 569 0 1 2 3 570 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 1 571 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 572 / |Version| IHL | DSCP |ECN| Total Length | 573 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 574 | | Identification |Flags| Fragment Offset | 575 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 576 OH | Time to Live | Protocol = 17 | Header Checksum | 577 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 578 | | Source Routing Locator | 579 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 580 \ | Destination Routing Locator | 581 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 582 / | Source Port = xxxx | Dest Port = 4341 | 583 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 584 \ | UDP Length | UDP Checksum | 585 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 586 L |N|L|E|V|I|R|K|K| Nonce/Map-Version | 587 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 588 S / | Instance ID/Locator-Status-Bits | 589 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 590 / |Version| IHL | DSCP |ECN| Total Length | 591 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 592 | | Identification |Flags| Fragment Offset | 593 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 594 IH | Time to Live | Protocol | Header Checksum | 595 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 596 | | Source EID | 597 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 598 \ | Destination EID | 599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 601 IHL = IP-Header-Length 603 5.2. LISP IPv6-in-IPv6 Header Format 605 0 1 2 3 606 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 1 607 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 608 / |Version| DSCP |ECN| Flow Label | 609 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 610 | | Payload Length | Next Header=17| Hop Limit | 611 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 612 | | 613 O + + 614 u | | 615 t + Source Routing Locator + 616 e | | 617 r + + 618 | | 619 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 620 d | | 621 r + + 622 | | 623 ^ + Destination Routing Locator + 624 | | | 625 \ + + 626 \ | | 627 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 628 / | Source Port = xxxx | Dest Port = 4341 | 629 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 630 \ | UDP Length | UDP Checksum | 631 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 632 L |N|L|E|V|I|R|K|K| Nonce/Map-Version | 633 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 634 S / | Instance ID/Locator-Status-Bits | 635 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 636 / |Version| DSCP |ECN| Flow Label | 637 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 638 / | Payload Length | Next Header | Hop Limit | 639 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 640 | | 641 I + + 642 n | | 643 n + Source EID + 644 e | | 645 r + + 646 | | 647 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 648 d | | 649 r + + 650 | | 651 ^ + Destination EID + 652 \ | | 653 \ + + 654 \ | | 655 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 657 5.3. Tunnel Header Field Descriptions 659 Inner Header (IH): The inner header is the header on the 660 datagram received from the originating host [RFC0791] [RFC8200] 661 [RFC2474]. The source and destination IP addresses are EIDs. 663 Outer Header: (OH) The outer header is a new header prepended by an 664 ITR. The address fields contain RLOCs obtained from the ingress 665 router's EID-to-RLOC Cache. The IP protocol number is "UDP (17)" 666 from [RFC0768]. The setting of the Don't Fragment (DF) bit 667 'Flags' field is according to rules listed in Sections 7.1 and 668 7.2. 670 UDP Header: The UDP header contains an ITR selected source port when 671 encapsulating a packet. See Section 12 for details on the hash 672 algorithm used to select a source port based on the 5-tuple of the 673 inner header. The destination port MUST be set to the well-known 674 IANA-assigned port value 4341. 676 UDP Checksum: The 'UDP Checksum' field SHOULD be transmitted as zero 677 by an ITR for either IPv4 [RFC0768] and IPv6 encapsulation 678 [RFC6935] [RFC6936]. When a packet with a zero UDP checksum is 679 received by an ETR, the ETR MUST accept the packet for 680 decapsulation. When an ITR transmits a non-zero value for the UDP 681 checksum, it MUST send a correctly computed value in this field. 682 When an ETR receives a packet with a non-zero UDP checksum, it MAY 683 choose to verify the checksum value. If it chooses to perform 684 such verification, and the verification fails, the packet MUST be 685 silently dropped. If the ETR chooses not to perform the 686 verification, or performs the verification successfully, the 687 packet MUST be accepted for decapsulation. The handling of UDP 688 zero checksums over IPv6 for all tunneling protocols, including 689 LISP, is subject to the applicability statement in [RFC6936]. 691 UDP Length: The 'UDP Length' field is set for an IPv4-encapsulated 692 packet to be the sum of the inner-header IPv4 Total Length plus 693 the UDP and LISP header lengths. For an IPv6-encapsulated packet, 694 the 'UDP Length' field is the sum of the inner-header IPv6 Payload 695 Length, the size of the IPv6 header (40 octets), and the size of 696 the UDP and LISP headers. 698 N: The N-bit is the nonce-present bit. When this bit is set to 1, 699 the low-order 24 bits of the first 32 bits of the LISP header 700 contain a Nonce. See Section 10.1 for details. Both N- and 701 V-bits MUST NOT be set in the same packet. If they are, a 702 decapsulating ETR MUST treat the 'Nonce/Map-Version' field as 703 having a Nonce value present. 705 L: The L-bit is the 'Locator-Status-Bits' field enabled bit. When 706 this bit is set to 1, the Locator-Status-Bits in the second 707 32 bits of the LISP header are in use. 709 x 1 x x 0 x x x 710 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 711 |N|L|E|V|I|R|K|K| Nonce/Map-Version | 712 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 713 | Locator-Status-Bits | 714 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 716 E: The E-bit is the echo-nonce-request bit. This bit MUST be ignored 717 and has no meaning when the N-bit is set to 0. When the N-bit is 718 set to 1 and this bit is set to 1, an ITR is requesting that the 719 nonce value in the 'Nonce' field be echoed back in LISP- 720 encapsulated packets when the ITR is also an ETR. See 721 Section 10.1 for details. 723 V: The V-bit is the Map-Version present bit. When this bit is set to 724 1, the N-bit MUST be 0. Refer to Section 13.1 for more details. 725 This bit indicates that the LISP header is encoded in this 726 case as: 728 0 x 0 1 x x x x 729 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 730 |N|L|E|V|I|R|K|K| Source Map-Version | Dest Map-Version | 731 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 732 | Instance ID/Locator-Status-Bits | 733 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 735 I: The I-bit is the Instance ID bit. See Section 8 for more details. 736 When this bit is set to 1, the 'Locator-Status-Bits' field is 737 reduced to 8 bits and the high-order 24 bits are used as an 738 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 739 are transmitted as zero and ignored on receipt. The format of the 740 LISP header would look like this: 742 x x x x 1 x x x 743 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 744 |N|L|E|V|I|R|K|K| Nonce/Map-Version | 745 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 746 | Instance ID | LSBs | 747 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 749 R: The R-bit is a Reserved bit for future use. It MUST be set to 0 750 on transmit and MUST be ignored on receipt. 752 KK: The KK-bits are a 2-bit field used when encapsulated packets are 753 encrypted. The field is set to 00 when the packet is not 754 encrypted. See [RFC8061] for further information. 756 LISP Nonce: The LISP 'Nonce' field is a 24-bit value that is 757 randomly generated by an ITR when the N-bit is set to 1. Nonce 758 generation algorithms are an implementation matter but are 759 required to generate different nonces when sending to different 760 RLOCs. However, the same nonce can be used for a period of time 761 when encapsulating to the same ETR. The nonce is also used when 762 the E-bit is set to request the nonce value to be echoed by the 763 other side when packets are returned. When the E-bit is clear but 764 the N-bit is set, a remote ITR is either echoing a previously 765 requested echo-nonce or providing a random nonce. See 766 Section 10.1 for more details. 768 LISP Locator-Status-Bits (LSBs): When the L-bit is also set, the 769 'Locator-Status-Bits' field in the LISP header is set by an ITR to 770 indicate to an ETR the up/down status of the Locators in the 771 source site. Each RLOC in a Map-Reply is assigned an ordinal 772 value from 0 to n-1 (when there are n RLOCs in a mapping entry). 773 The Locator-Status-Bits are numbered from 0 to n-1 from the least 774 significant bit of the field. The field is 32 bits when the I-bit 775 is set to 0 and is 8 bits when the I-bit is set to 1. When a 776 Locator-Status-Bit is set to 1, the ITR is indicating to the ETR 777 that the RLOC associated with the bit ordinal has up status. See 778 Section 10 for details on how an ITR can determine the status of 779 the ETRs at the same site. When a site has multiple EID-Prefixes 780 that result in multiple mappings (where each could have a 781 different Locator-Set), the Locator-Status-Bits setting in an 782 encapsulated packet MUST reflect the mapping for the EID-Prefix 783 that the inner-header source EID address matches. If the LSB for 784 an anycast Locator is set to 1, then there is at least one RLOC 785 with that address, and the ETR is considered 'up'. 787 When doing ITR/PITR encapsulation: 789 o The outer-header 'Time to Live' field (or 'Hop Limit' field, in 790 the case of IPv6) SHOULD be copied from the inner-header 'Time to 791 Live' field. 793 o The outer-header 'Differentiated Services Code Point' (DSCP) field 794 (or the 'Traffic Class' field, in the case of IPv6) SHOULD be 795 copied from the inner-header DSCP field ('Traffic Class' field, in 796 the case of IPv6) considering the exception listed below. 798 o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 799 of the IPv6 'Traffic Class' field) requires special treatment in 800 order to avoid discarding indications of congestion [RFC3168]. 801 ITR encapsulation MUST copy the 2-bit 'ECN' field from the inner 802 header to the outer header. Re-encapsulation MUST copy the 2-bit 803 'ECN' field from the stripped outer header to the new outer 804 header. 806 When doing ETR/PETR decapsulation: 808 o The inner-header 'Time to Live' field (or 'Hop Limit' field, in 809 the case of IPv6) SHOULD be copied from the outer-header 'Time to 810 Live' field, when the Time to Live value of the outer header is 811 less than the Time to Live value of the inner header. Failing to 812 perform this check can cause the Time to Live of the inner header 813 to increment across encapsulation/decapsulation cycles. This 814 check is also performed when doing initial encapsulation, when a 815 packet comes to an ITR or PITR destined for a LISP site. 817 o The inner-header 'Differentiated Services Code Point' (DSCP) field 818 (or the 'Traffic Class' field, in the case of IPv6) SHOULD be 819 copied from the outer-header DSCP field ('Traffic Class' field, in 820 the case of IPv6) considering the exception listed below. 822 o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 823 of the IPv6 'Traffic Class' field) requires special treatment in 824 order to avoid discarding indications of congestion [RFC3168]. If 825 the 'ECN' field contains a congestion indication codepoint (the 826 value is '11', the Congestion Experienced (CE) codepoint), then 827 ETR decapsulation MUST copy the 2-bit 'ECN' field from the 828 stripped outer header to the surviving inner header that is used 829 to forward the packet beyond the ETR. These requirements preserve 830 CE indications when a packet that uses ECN traverses a LISP tunnel 831 and becomes marked with a CE indication due to congestion between 832 the tunnel endpoints. 834 Note that if an ETR/PETR is also an ITR/PITR and chooses to re- 835 encapsulate after decapsulating, the net effect of this is that the 836 new outer header will carry the same Time to Live as the old outer 837 header minus 1. 839 Copying the Time to Live (TTL) serves two purposes: first, it 840 preserves the distance the host intended the packet to travel; 841 second, and more importantly, it provides for suppression of looping 842 packets in the event there is a loop of concatenated tunnels due to 843 misconfiguration. 845 The Explicit Congestion Notification ('ECN') field occupies bits 6 846 and 7 of both the IPv4 'Type of Service' field and the IPv6 'Traffic 847 Class' field [RFC3168]. The 'ECN' field requires special treatment 848 in order to avoid discarding indications of congestion [RFC3168]. An 849 ITR/PITR encapsulation MUST copy the 2-bit 'ECN' field from the inner 850 header to the outer header. Re-encapsulation MUST copy the 2-bit 851 'ECN' field from the stripped outer header to the new outer header. 852 If the 'ECN' field contains a congestion indication codepoint (the 853 value is '11', the Congestion Experienced (CE) codepoint), then ETR/ 854 PETR decapsulation MUST copy the 2-bit 'ECN' field from the stripped 855 outer header to the surviving inner header that is used to forward 856 the packet beyond the ETR. These requirements preserve CE 857 indications when a packet that uses ECN traverses a LISP tunnel and 858 becomes marked with a CE indication due to congestion between the 859 tunnel endpoints. 861 6. LISP EID-to-RLOC Map-Cache 863 ITRs and PITRs maintain an on-demand cache, referred as LISP EID-to- 864 RLOC Map-Cache, that contains mappings from EID-prefixes to locator 865 sets. The cache is used to encapsulate packets from the EID space to 866 the corresponding RLOC network attachment point. 868 When an ITR/PITR receives a packet from inside of the LISP site to 869 destinations outside of the site a longest-prefix match lookup of the 870 EID is done to the Map-Cache. 872 When the lookup succeeds, the Locator-Set retrieved from the Map- 873 Cache is used to send the packet to the EID's topological location. 875 If the lookup fails, the ITR/PITR needs to retrieve the mapping using 876 the LISP Control-Plane protocol [I-D.ietf-lisp-rfc6833bis]. The 877 mapping is then stored in the local Map-Cache to forward subsequent 878 packets addressed to the same EID-prefix. 880 The Map-Cache is a local cache of mappings, entries are expired based 881 on the associated Time to live. In addition, entries can be updated 882 with more current information, see Section 13 for further information 883 on this. Finally, the Map-Cache also contains reachability 884 information about EIDs and RLOCs, and uses LISP reachability 885 information mechanisms to determine the reachability of RLOCs, see 886 Section 10 for the specific mechanisms. 888 7. Dealing with Large Encapsulated Packets 890 This section proposes two mechanisms to deal with packets that exceed 891 the path MTU between the ITR and ETR. 893 It is left to the implementor to decide if the stateless or stateful 894 mechanism SHOULD be implemented. Both or neither can be used, since 895 it is a local decision in the ITR regarding how to deal with MTU 896 issues, and sites can interoperate with differing mechanisms. 898 Both stateless and stateful mechanisms also apply to Re-encapsulating 899 and Recursive Tunneling, so any actions below referring to an ITR 900 also apply to a TE-ITR. 902 7.1. A Stateless Solution to MTU Handling 904 An ITR stateless solution to handle MTU issues is described as 905 follows: 907 1. Define H to be the size, in octets, of the outer header an ITR 908 prepends to a packet. This includes the UDP and LISP header 909 lengths. 911 2. Define L to be the size, in octets, of the maximum-sized packet 912 an ITR can send to an ETR without the need for the ITR or any 913 intermediate routers to fragment the packet. 915 3. Define an architectural constant S for the maximum size of a 916 packet, in octets, an ITR MUST receive from the source so the 917 effective MTU can be met. That is, L = S + H. 919 When an ITR receives a packet from a site-facing interface and adds H 920 octets worth of encapsulation to yield a packet size greater than L 921 octets (meaning the received packet size was greater than S octets 922 from the source), it resolves the MTU issue by first splitting the 923 original packet into 2 equal-sized fragments. A LISP header is then 924 prepended to each fragment. The size of the encapsulated fragments 925 is then (S/2 + H), which is less than the ITR's estimate of the path 926 MTU between the ITR and its correspondent ETR. 928 When an ETR receives encapsulated fragments, it treats them as two 929 individually encapsulated packets. It strips the LISP headers and 930 then forwards each fragment to the destination host of the 931 destination site. The two fragments are reassembled at the 932 destination host into the single IP datagram that was originated by 933 the source host. Note that reassembly can happen at the ETR if the 934 encapsulated packet was fragmented at or after the ITR. 936 This behavior is performed by the ITR when the source host originates 937 a packet with the 'DF' field of the IP header set to 0. When the 938 'DF' field of the IP header is set to 1, or the packet is an IPv6 939 packet originated by the source host, the ITR will drop the packet 940 when the size is greater than L and send an ICMP Unreachable/ 941 Fragmentation-Needed message to the source with a value of S, where S 942 is (L - H). 944 When the outer-header encapsulation uses an IPv4 header, an 945 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 946 can be avoided. An implementation MAY set the DF bit in such headers 947 to 0 if it has good reason to believe there are unresolvable path MTU 948 issues between the sending ITR and the receiving ETR. 950 This specification RECOMMENDS that L be defined as 1500. 952 7.2. A Stateful Solution to MTU Handling 954 An ITR stateful solution to handle MTU issues is described as follows 955 and was first introduced in [OPENLISP]: 957 1. The ITR will keep state of the effective MTU for each Locator per 958 Map-Cache entry. The effective MTU is what the core network can 959 deliver along the path between the ITR and ETR. 961 2. When an IPv6-encapsulated packet, or an IPv4-encapsulated packet 962 with the DF bit set to 1, exceeds what the core network can 963 deliver, one of the intermediate routers on the path will send an 964 ICMP Unreachable/Fragmentation-Needed message to the ITR. The 965 ITR will parse the ICMP message to determine which Locator is 966 affected by the effective MTU change and then record the new 967 effective MTU value in the Map-Cache entry. 969 3. When a packet is received by the ITR from a source inside of the 970 site and the size of the packet is greater than the effective MTU 971 stored with the Map-Cache entry associated with the destination 972 EID the packet is for, the ITR will send an ICMP Unreachable/ 973 Fragmentation-Needed message back to the source. The packet size 974 advertised by the ITR in the ICMP Unreachable/Fragmentation- 975 Needed message is the effective MTU minus the LISP encapsulation 976 length. 978 Even though this mechanism is stateful, it has advantages over the 979 stateless IP fragmentation mechanism, by not involving the 980 destination host with reassembly of ITR fragmented packets. 982 8. Using Virtualization and Segmentation with LISP 984 There are several cases where segregation is needed at the EID level. 985 For instance, this is the case for deployments containing overlapping 986 addresses, traffic isolation policies or multi-tenant virtualization. 987 For these and other scenarios where segregation is needed, Instance 988 IDs are used. 990 An Instance ID can be carried in a LISP-encapsulated packet. An ITR 991 that prepends a LISP header will copy a 24-bit value used by the LISP 992 router to uniquely identify the address space. The value is copied 993 to the 'Instance ID' field of the LISP header, and the I-bit is set 994 to 1. 996 When an ETR decapsulates a packet, the Instance ID from the LISP 997 header is used as a table identifier to locate the forwarding table 998 to use for the inner destination EID lookup. 1000 For example, an 802.1Q VLAN tag or VPN identifier could be used as a 1001 24-bit Instance ID. See [I-D.ietf-lisp-vpn] for LISP VPN use-case 1002 details. 1004 The Instance ID that is stored in the mapping database when LISP-DDT 1005 [RFC8111] is used is 32 bits in length. That means the Control-Plane 1006 can store more instances than a given Data-Plane can use. Multiple 1007 Data-Planes can use the same 32-bit space as long as the low-order 24 1008 bits don't overlap among xTRs. 1010 9. Routing Locator Selection 1012 The Map-Cache contains the state used by ITRs and PITRs to 1013 encapsulate packets. When an ITR/PITR receives a packet from inside 1014 the LISP site to a destination outside of the site a longest-prefix 1015 match lookup of the EID is done to the Map-Cache (see Section 6). 1016 The lookup returns a single Locator-Set containing a list of RLOCs 1017 corresponding to the EID's topological location. Each RLOC in the 1018 Locator-Set is associated with a 'Priority' and 'Weight', this 1019 information is used to select the RLOC to encapsulate. 1021 The RLOC with the lowest 'Priority' is selected. An RLOC with 1022 'Priority' 255 means that MUST NOT be used for forwarding. When 1023 multiple RLOC have the same 'Priority' then the 'Weight' states how 1024 to load balance traffic among them. The value of the 'Weight' 1025 represents the relative weight of the total packets that match the 1026 maping entry. 1028 The following are different scenarios for choosing RLOCs and the 1029 controls that are available: 1031 o The server-side returns one RLOC. The client-side can only use 1032 one RLOC. The server-side has complete control of the selection. 1034 o The server-side returns a list of RLOCs where a subset of the list 1035 has the same best Priority. The client can only use the subset 1036 list according to the weighting assigned by the server-side. In 1037 this case, the server-side controls both the subset list and load- 1038 splitting across its members. The client-side can use RLOCs 1039 outside of the subset list if it determines that the subset list 1040 is unreachable (unless RLOCs are set to a Priority of 255). Some 1041 sharing of control exists: the server-side determines the 1042 destination RLOC list and load distribution while the client-side 1043 has the option of using alternatives to this list if RLOCs in the 1044 list are unreachable. 1046 o The server-side sets a Weight of zero for the RLOC subset list. 1047 In this case, the client-side can choose how the traffic load is 1048 spread across the subset list. Control is shared by the server- 1049 side determining the list and the client-side determining load 1050 distribution. Again, the client can use alternative RLOCs if the 1051 server-provided list of RLOCs is unreachable. 1053 o Either side (more likely the server-side ETR) decides not to send 1054 a Map-Request. For example, if the server-side ETR does not send 1055 Map-Requests, it gleans RLOCs from the client-side ITR, giving the 1056 client-side ITR responsibility for bidirectional RLOC reachability 1057 and preferability. Server-side ETR gleaning of the client-side 1058 ITR RLOC is done by caching the inner-header source EID and the 1059 outer-header source RLOC of received packets. The client-side ITR 1060 controls how traffic is returned and can alternate using an outer- 1061 header source RLOC, which then can be added to the list the 1062 server-side ETR uses to return traffic. Since no Priority or 1063 Weights are provided using this method, the server-side ETR MUST 1064 assume that each client-side ITR RLOC uses the same best Priority 1065 with a Weight of zero. In addition, since EID-Prefix encoding 1066 cannot be conveyed in data packets, the EID-to-RLOC Cache on 1067 Tunnel Routers can grow to be very large. 1069 Alternatively, RLOC information MAY be gleaned from received tunneled 1070 packets or EID-to-RLOC Map-Request messages. A "gleaned" Map-Cache 1071 entry, one learned from the source RLOC of a received encapsulated 1072 packet, is only stored and used for a few seconds, pending 1073 verification. Verification is performed by sending a Map-Request to 1074 the source EID (the inner-header IP source address) of the received 1075 encapsulated packet. A reply to this "verifying Map-Request" is used 1076 to fully populate the Map-Cache entry for the "gleaned" EID and is 1077 stored and used for the time indicated from the 'TTL' field of a 1078 received Map-Reply. When a verified Map-Cache entry is stored, data 1079 gleaning no longer occurs for subsequent packets that have a source 1080 EID that matches the EID-Prefix of the verified entry. This 1081 "gleaning" mechanism is OPTIONAL, refer to Section 16 for security 1082 issues regarding this mechanism. 1084 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1085 reachable when the R-bit for the Locator record is set to 1. When 1086 the R-bit is set to 0, an ITR or PITR MUST NOT encapsulate to the 1087 RLOC. Neither the information contained in a Map-Reply nor that 1088 stored in the mapping database system provides reachability 1089 information for RLOCs. Note that reachability is not part of the 1090 mapping system and is determined using one or more of the Routing 1091 Locator reachability algorithms described in the next section. 1093 10. Routing Locator Reachability 1095 Several Data-Plane mechanisms for determining RLOC reachability are 1096 currently defined. Please note that additional Control-Plane based 1097 reachability mechanisms are defined in [I-D.ietf-lisp-rfc6833bis]. 1099 1. An ETR MAY examine the Locator-Status-Bits in the LISP header of 1100 an encapsulated data packet received from an ITR. If the ETR is 1101 also acting as an ITR and has traffic to return to the original 1102 ITR site, it can use this status information to help select an 1103 RLOC. 1105 2. When an ETR receives an encapsulated packet from an ITR, the 1106 source RLOC from the outer header of the packet is likely up. 1108 3. An ITR/ETR pair can use the 'Echo-Noncing' Locator reachability 1109 algorithms described in this section. 1111 When determining Locator up/down reachability by examining the 1112 Locator-Status-Bits from the LISP-encapsulated data packet, an ETR 1113 will receive up-to-date status from an encapsulating ITR about 1114 reachability for all ETRs at the site. CE-based ITRs at the source 1115 site can determine reachability relative to each other using the site 1116 IGP as follows: 1118 o Under normal circumstances, each ITR will advertise a default 1119 route into the site IGP. 1121 o If an ITR fails or if the upstream link to its PE fails, its 1122 default route will either time out or be withdrawn. 1124 Each ITR can thus observe the presence or lack of a default route 1125 originated by the others to determine the Locator-Status-Bits it sets 1126 for them. 1128 When ITRs at the site are not deployed in CE routers, the IGP can 1129 still be used to determine the reachability of Locators, provided 1130 they are injected into the IGP. This is typically done when a /32 1131 address is configured on a loopback interface. 1133 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1134 Locator-Status-Bits in a LISP-encapsulated packet are numbered from 0 1135 to n-1 starting with the least significant bit. For example, if an 1136 RLOC listed in the 3rd position of the Map-Reply goes down (ordinal 1137 value 2), then all ITRs at the site will clear the 3rd least 1138 significant bit (xxxx x0xx) of the 'Locator-Status-Bits' field for 1139 the packets they encapsulate. 1141 When an ETR decapsulates a packet, it will check for any change in 1142 the 'Locator-Status-Bits' field. When a bit goes from 1 to 0, the 1143 ETR, if acting also as an ITR, will refrain from encapsulating 1144 packets to an RLOC that is indicated as down. It will only resume 1145 using that RLOC if the corresponding Locator-Status-Bit returns to a 1146 value of 1. Locator-Status-Bits are associated with a Locator-Set 1147 per EID-Prefix. Therefore, when a Locator becomes unreachable, the 1148 Locator-Status-Bit that corresponds to that Locator's position in the 1149 list returned by the last Map-Reply will be set to zero for that 1150 particular EID-Prefix. Refer to Section 16 for security related 1151 issues regarding Locator-Status-Bits. 1153 When an ETR decapsulates a packet, it knows that it is reachable from 1154 the encapsulating ITR because that is how the packet arrived. In 1155 most cases, the ETR can also reach the ITR but cannot assume this to 1156 be true, due to the possibility of path asymmetry. In the presence 1157 of unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD 1158 NOT use the lack of return traffic as an indication that the ETR is 1159 unreachable. Instead, it MUST use an alternate mechanism to 1160 determine reachability. 1162 10.1. Echo Nonce Algorithm 1164 When data flows bidirectionally between Locators from different 1165 sites, a Data-Plane mechanism called "nonce echoing" can be used to 1166 determine reachability between an ITR and ETR. When an ITR wants to 1167 solicit a nonce echo, it sets the N- and E-bits and places a 24-bit 1168 nonce [RFC4086] in the LISP header of the next encapsulated data 1169 packet. 1171 When this packet is received by the ETR, the encapsulated packet is 1172 forwarded as normal. When the ETR next sends a data packet to the 1173 ITR, it includes the nonce received earlier with the N-bit set and 1174 E-bit cleared. The ITR sees this "echoed nonce" and knows that the 1175 path to and from the ETR is up. 1177 The ITR will set the E-bit and N-bit for every packet it sends while 1178 in the echo-nonce-request state. The time the ITR waits to process 1179 the echoed nonce before it determines the path is unreachable is 1180 variable and is a choice left for the implementation. 1182 If the ITR is receiving packets from the ETR but does not see the 1183 nonce echoed while being in the echo-nonce-request state, then the 1184 path to the ETR is unreachable. This decision MAY be overridden by 1185 other Locator reachability algorithms. Once the ITR determines that 1186 the path to the ETR is down, it can switch to another Locator for 1187 that EID-Prefix. 1189 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 1190 be implementing both ITR and ETR functionality for the echo nonce 1191 mechanism to operate. 1193 The ITR and ETR MAY both go into the echo-nonce-request state at the 1194 same time. The number of packets sent or the time during which echo 1195 nonce requests are sent is an implementation-specific setting. 1196 However, when an ITR is in the echo-nonce-request state, it can echo 1197 the ETR's nonce in the next set of packets that it encapsulates and 1198 subsequently continue sending echo-nonce-request packets. 1200 This mechanism does not completely solve the forward path 1201 reachability problem, as traffic may be unidirectional. That is, the 1202 ETR receiving traffic at a site MAY not be the same device as an ITR 1203 that transmits traffic from that site, or the site-to-site traffic is 1204 unidirectional so there is no ITR returning traffic. 1206 The echo-nonce algorithm is bilateral. That is, if one side sets the 1207 E-bit and the other side is not enabled for echo-noncing, then the 1208 echoing of the nonce does not occur and the requesting side may 1209 erroneously consider the Locator unreachable. An ITR SHOULD only set 1210 the E-bit in an encapsulated data packet when it knows the ETR is 1211 enabled for echo-noncing. This is conveyed by the E-bit in the RLOC- 1212 probe Map-Reply message. 1214 11. EID Reachability within a LISP Site 1216 A site MAY be multihomed using two or more ETRs. The hosts and 1217 infrastructure within a site will be addressed using one or more EID- 1218 Prefixes that are mapped to the RLOCs of the relevant ETRs in the 1219 mapping system. One possible failure mode is for an ETR to lose 1220 reachability to one or more of the EID-Prefixes within its own site. 1221 When this occurs when the ETR sends Map-Replies, it can clear the 1222 R-bit associated with its own Locator. And when the ETR is also an 1223 ITR, it can clear its Locator-Status-Bit in the encapsulation data 1224 header. 1226 It is recognized that there are no simple solutions to the site 1227 partitioning problem because it is hard to know which part of the 1228 EID-Prefix range is partitioned and which Locators can reach any sub- 1229 ranges of the EID-Prefixes. Note that this is not a new problem 1230 introduced by the LISP architecture. The problem exists today when a 1231 multihomed site uses BGP to advertise its reachability upstream. 1233 12. Routing Locator Hashing 1235 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message 1236 that is stored in the Map-Cache of a requesting ITR, the Locator-Set 1237 for the EID-Prefix MAY contain different Priority and Weight values 1238 for each locator address. When more than one best Priority Locator 1239 exists, the ITR can decide how to load-share traffic against the 1240 corresponding Locators. 1242 The following hash algorithm MAY be used by an ITR to select a 1243 Locator for a packet destined to an EID for the EID-to-RLOC mapping: 1245 1. Either a source and destination address hash or the traditional 1246 5-tuple hash can be used. The traditional 5-tuple hash includes 1247 the source and destination addresses; source and destination TCP, 1248 UDP, or Stream Control Transmission Protocol (SCTP) port numbers; 1249 and the IP protocol number field or IPv6 next-protocol fields of 1250 a packet that a host originates from within a LISP site. When a 1251 packet is not a TCP, UDP, or SCTP packet, the source and 1252 destination addresses only from the header are used to compute 1253 the hash. 1255 2. Take the hash value and divide it by the number of Locators 1256 stored in the Locator-Set for the EID-to-RLOC mapping. 1258 3. The remainder will yield a value of 0 to "number of Locators 1259 minus 1". Use the remainder to select the Locator in the 1260 Locator-Set. 1262 Note that when a packet is LISP encapsulated, the source port number 1263 in the outer UDP header needs to be set. Selecting a hashed value 1264 allows core routers that are attached to Link Aggregation Groups 1265 (LAGs) to load-split the encapsulated packets across member links of 1266 such LAGs. Otherwise, core routers would see a single flow, since 1267 packets have a source address of the ITR, for packets that are 1268 originated by different EIDs at the source site. A suggested setting 1269 for the source port number computed by an ITR is a 5-tuple hash 1270 function on the inner header, as described above. 1272 Many core router implementations use a 5-tuple hash to decide how to 1273 balance packet load across members of a LAG. The 5-tuple hash 1274 includes the source and destination addresses of the packet and the 1275 source and destination ports when the protocol number in the packet 1276 is TCP or UDP. For this reason, UDP encoding is used for LISP 1277 encapsulation. 1279 13. Changing the Contents of EID-to-RLOC Mappings 1281 Since the LISP architecture uses a caching scheme to retrieve and 1282 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 1283 date mapping is to re-request the mapping. However, the ITRs do not 1284 know when the mappings change, and the ETRs do not keep track of 1285 which ITRs requested its mappings. For scalability reasons, it is 1286 desirable to maintain this approach but need to provide a way for 1287 ETRs to change their mappings and inform the sites that are currently 1288 communicating with the ETR site using such mappings. 1290 This section defines a Data-Plane mechanism for updating EID-to-RLOC 1291 mappings. Additionally, the Solicit-Map Request (SMR) Control-Plane 1292 updating mechanism is specified in [I-D.ietf-lisp-rfc6833bis]. 1294 When adding a new Locator record in lexicographic order to the end of 1295 a Locator-Set, it is easy to update mappings. We assume that new 1296 mappings will maintain the same Locator ordering as the old mapping 1297 but will just have new Locators appended to the end of the list. So, 1298 some ITRs can have a new mapping while other ITRs have only an old 1299 mapping that is used until they time out. When an ITR has only an 1300 old mapping but detects bits set in the Locator-Status-Bits that 1301 correspond to Locators beyond the list it has cached, it simply 1302 ignores them. However, this can only happen for locator addresses 1303 that are lexicographically greater than the locator addresses in the 1304 existing Locator-Set. 1306 When a Locator record is inserted in the middle of a Locator-Set, to 1307 maintain lexicographic order, SMR procedure 1308 [I-D.ietf-lisp-rfc6833bis] is used to inform ITRs and PITRs of the 1309 new Locator-Status-Bit mappings. 1311 When a Locator record is removed from a Locator-Set, ITRs that have 1312 the mapping cached will not use the removed Locator because the xTRs 1313 will set the Locator-Status-Bit to 0. So, even if the Locator is in 1314 the list, it will not be used. For new mapping requests, the xTRs 1315 can set the Locator AFI to 0 (indicating an unspecified address), as 1316 well as setting the corresponding Locator-Status-Bit to 0. This 1317 forces ITRs with old or new mappings to avoid using the removed 1318 Locator. 1320 If many changes occur to a mapping over a long period of time, one 1321 will find empty record slots in the middle of the Locator-Set and new 1322 records appended to the Locator-Set. At some point, it would be 1323 useful to compact the Locator-Set so the Locator-Status-Bit settings 1324 can be efficiently packed. 1326 We propose here a Data-Plane mechanism (Map-Versioning) to update the 1327 contents of EID-to-RLOC mappings. Please note that in addition the 1328 Solicit-Map Request (specified in [I-D.ietf-lisp-rfc6833bis]) is a 1329 Control-Plane mechanisms that can be used to update EID-to-RLOC 1330 mappings. 1332 13.1. Database Map-Versioning 1334 When there is unidirectional packet flow between an ITR and ETR, and 1335 the EID-to-RLOC mappings change on the ETR, it needs to inform the 1336 ITR so encapsulation to a removed Locator can stop and can instead be 1337 started to a new Locator in the Locator-Set. 1339 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 1340 Number. This is known as the Destination Map-Version Number. ITRs 1341 include the Destination Map-Version Number in packets they 1342 encapsulate to the site. When an ETR decapsulates a packet and 1343 detects that the Destination Map-Version Number is less than the 1344 current version for its mapping, the SMR procedure described in 1345 [I-D.ietf-lisp-rfc6833bis] occurs. 1347 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 1348 Version Number. This is known as the Source Map-Version Number. 1349 When an ETR decapsulates a packet and detects that the Source Map- 1350 Version Number is greater than the last Map-Version Number sent in a 1351 Map-Reply from the ITR's site, the ETR will send a Map-Request to one 1352 of the ETRs for the source site. 1354 A Map-Version Number is used as a sequence number per EID-Prefix, so 1355 values that are greater are considered to be more recent. A value of 1356 0 for the Source Map-Version Number or the Destination Map-Version 1357 Number conveys no versioning information, and an ITR does no 1358 comparison with previously received Map-Version Numbers. 1360 A Map-Version Number can be included in Map-Register messages as 1361 well. This is a good way for the Map-Server to assure that all ETRs 1362 for a site registering to it will be synchronized according to Map- 1363 Version Number. 1365 See [RFC6834] for a more detailed analysis and description of 1366 Database Map-Versioning. 1368 14. Multicast Considerations 1370 A multicast group address, as defined in the original Internet 1371 architecture, is an identifier of a grouping of topologically 1372 independent receiver host locations. The address encoding itself 1373 does not determine the location of the receiver(s). The multicast 1374 routing protocol, and the network-based state the protocol creates, 1375 determine where the receivers are located. 1377 In the context of LISP, a multicast group address is both an EID and 1378 a Routing Locator. Therefore, no specific semantic or action needs 1379 to be taken for a destination address, as it would appear in an IP 1380 header. Therefore, a group address that appears in an inner IP 1381 header built by a source host will be used as the destination EID. 1382 The outer IP header (the destination Routing Locator address), 1383 prepended by a LISP router, can use the same group address as the 1384 destination Routing Locator, use a multicast or unicast Routing 1385 Locator obtained from a Mapping System lookup, or use other means to 1386 determine the group address mapping. 1388 With respect to the source Routing Locator address, the ITR prepends 1389 its own IP address as the source address of the outer IP header. 1390 Just like it would if the destination EID was a unicast address. 1391 This source Routing Locator address, like any other Routing Locator 1392 address, MUST be globally routable. 1394 There are two approaches for LISP-Multicast, one that uses native 1395 multicast routing in the underlay with no support from the Mapping 1396 System and the other that uses only unicast routing in the underlay 1397 with support from the Mapping System. See [RFC6831] and 1398 [I-D.ietf-lisp-signal-free-multicast], respectively, for details. 1399 Details for LISP-Multicast and interworking with non-LISP sites are 1400 described in [RFC6831] and [RFC6832]. 1402 15. Router Performance Considerations 1404 LISP is designed to be very "hardware-based forwarding friendly". A 1405 few implementation techniques can be used to incrementally implement 1406 LISP: 1408 o When a tunnel-encapsulated packet is received by an ETR, the outer 1409 destination address may not be the address of the router. This 1410 makes it challenging for the control plane to get packets from the 1411 hardware. This may be mitigated by creating special Forwarding 1412 Information Base (FIB) entries for the EID-Prefixes of EIDs served 1413 by the ETR (those for which the router provides an RLOC 1414 translation). These FIB entries are marked with a flag indicating 1415 that Control-Plane processing SHOULD be performed. The forwarding 1416 logic of testing for particular IP protocol number values is not 1417 necessary. There are a few proven cases where no changes to 1418 existing deployed hardware were needed to support the LISP Data- 1419 Plane. 1421 o On an ITR, prepending a new IP header consists of adding more 1422 octets to a MAC rewrite string and prepending the string as part 1423 of the outgoing encapsulation procedure. Routers that support 1424 Generic Routing Encapsulation (GRE) tunneling [RFC2784] or 6to4 1425 tunneling [RFC3056] may already support this action. 1427 o A packet's source address or interface the packet was received on 1428 can be used to select VRF (Virtual Routing/Forwarding). The VRF's 1429 routing table can be used to find EID-to-RLOC mappings. 1431 For performance issues related to Map-Cache management, see 1432 Section 16. 1434 16. Security Considerations 1436 Security considerations for LISP are discussed in [RFC7833]. 1438 A complete LISP threat analysis can be found in [RFC7835], in what 1439 follows we provide a summary. 1441 The optional mechanisms of gleaning is offered to directly obtain a 1442 mapping from the LISP encapsulated packets. Specifically, an xTR can 1443 learn the EID-to-RLOC mapping by inspecting the source RLOC and 1444 source EID of an encapsulated packet, and insert this new mapping 1445 into its Map-Cache. An off-path attacker can spoof the source EID 1446 address to divert the traffic sent to the victim's spoofed EID. If 1447 the attacker spoofs the source RLOC, it can mount a DoS attack by 1448 redirecting traffic to the spoofed victim's RLOC, potentially 1449 overloading it. 1451 The LISP Data-Plane defines several mechanisms to monitor RLOC Data- 1452 Plane reachability, in this context Locator-Status Bits, Nonce- 1453 Present and Echo-Nonce bits of the LISP encapsulation header can be 1454 manipulated by an attacker to mount a DoS attack. An off-path 1455 attacker able to spoof the RLOC of a victim's xTR can manipulate such 1456 mechanisms to declare a set of RLOCs unreachable. This can be used 1457 also, for instance, to declare only one RLOC reachable with the aim 1458 of overload it. 1460 Map-Versioning is a Data-Plane mechanism used to signal a peering xTR 1461 that a local EID-to-RLOC mapping has been updated, so that the 1462 peering xTR uses LISP Control-Plane signaling message to retrieve a 1463 fresh mapping. This can be used by an attacker to forge the map- 1464 versioning field of a LISP encapsulated header and force an excessive 1465 amount of signaling between xTRs that may overload them. 1467 Most of the attack vectors can be mitigated with careful deployment 1468 and configuration, information learned opportunistically (such as LSB 1469 or gleaning) SHOULD be verified with other reachability mechanisms. 1470 In addition, systematic rate-limitation and filtering is an effective 1471 technique to mitigate attacks that aim to overload the Control-Plane. 1473 17. Network Management Considerations 1475 Considerations for network management tools exist so the LISP 1476 protocol suite can be operationally managed. These mechanisms can be 1477 found in [RFC7052] and [RFC6835]. 1479 18. IANA Considerations 1481 This section provides guidance to the Internet Assigned Numbers 1482 Authority (IANA) regarding registration of values related to this 1483 Data-Plane LISP specification, in accordance with BCP 26 [RFC8126]. 1485 18.1. LISP UDP Port Numbers 1487 The IANA registry has allocated UDP port number 4341 for the LISP 1488 Data-Plane. IANA has updated the description for UDP port 4341 as 1489 follows: 1491 lisp-data 4341 udp LISP Data Packets 1493 19. References 1495 19.1. Normative References 1497 [I-D.ietf-lisp-rfc6833bis] 1498 Fuller, V., Farinacci, D., and A. Cabellos-Aparicio, 1499 "Locator/ID Separation Protocol (LISP) Control-Plane", 1500 draft-ietf-lisp-rfc6833bis-09 (work in progress), March 1501 2018. 1503 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 1504 DOI 10.17487/RFC0768, August 1980, 1505 . 1507 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 1508 DOI 10.17487/RFC0791, September 1981, 1509 . 1511 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1512 "Definition of the Differentiated Services Field (DS 1513 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1514 DOI 10.17487/RFC2474, December 1998, 1515 . 1517 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 1518 of Explicit Congestion Notification (ECN) to IP", 1519 RFC 3168, DOI 10.17487/RFC3168, September 2001, 1520 . 1522 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1523 (IPv6) Specification", STD 86, RFC 8200, 1524 DOI 10.17487/RFC8200, July 2017, 1525 . 1527 19.2. Informative References 1529 [AFN] IANA, "Address Family Numbers", August 2016, 1530 . 1532 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed", 1533 1999, 1534 . 1536 [I-D.ietf-lisp-eid-mobility] 1537 Portoles-Comeras, M., Ashtaputre, V., Moreno, V., Maino, 1538 F., and D. Farinacci, "LISP L2/L3 EID Mobility Using a 1539 Unified Control Plane", draft-ietf-lisp-eid-mobility-01 1540 (work in progress), November 2017. 1542 [I-D.ietf-lisp-introduction] 1543 Cabellos-Aparicio, A. and D. Saucez, "An Architectural 1544 Introduction to the Locator/ID Separation Protocol 1545 (LISP)", draft-ietf-lisp-introduction-13 (work in 1546 progress), April 2015. 1548 [I-D.ietf-lisp-mn] 1549 Farinacci, D., Lewis, D., Meyer, D., and C. White, "LISP 1550 Mobile Node", draft-ietf-lisp-mn-01 (work in progress), 1551 October 2017. 1553 [I-D.ietf-lisp-predictive-rlocs] 1554 Farinacci, D. and P. Pillay-Esnault, "LISP Predictive 1555 RLOCs", draft-ietf-lisp-predictive-rlocs-01 (work in 1556 progress), November 2017. 1558 [I-D.ietf-lisp-sec] 1559 Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D. 1560 Saucez, "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-14 1561 (work in progress), October 2017. 1563 [I-D.ietf-lisp-signal-free-multicast] 1564 Moreno, V. and D. Farinacci, "Signal-Free LISP Multicast", 1565 draft-ietf-lisp-signal-free-multicast-09 (work in 1566 progress), March 2018. 1568 [I-D.ietf-lisp-vpn] 1569 Moreno, V. and D. Farinacci, "LISP Virtual Private 1570 Networks (VPNs)", draft-ietf-lisp-vpn-01 (work in 1571 progress), November 2017. 1573 [LISA96] Lear, E., Tharp, D., Katinsky, J., and J. Coffin, 1574 "Renumbering: Threat or Menace?", Usenix Tenth System 1575 Administration Conference (LISA 96), October 1996. 1577 [OPENLISP] 1578 Iannone, L., Saucez, D., and O. Bonaventure, "OpenLISP 1579 Implementation Report", Work in Progress, July 2008. 1581 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 1582 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 1583 . 1585 [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G., 1586 and E. Lear, "Address Allocation for Private Internets", 1587 BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996, 1588 . 1590 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1591 Requirement Levels", BCP 14, RFC 2119, 1592 DOI 10.17487/RFC2119, March 1997, 1593 . 1595 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 1596 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 1597 DOI 10.17487/RFC2784, March 2000, 1598 . 1600 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 1601 via IPv4 Clouds", RFC 3056, DOI 10.17487/RFC3056, February 1602 2001, . 1604 [RFC3232] Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced 1605 by an On-line Database", RFC 3232, DOI 10.17487/RFC3232, 1606 January 2002, . 1608 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 1609 A., Peterson, J., Sparks, R., Handley, M., and E. 1610 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 1611 DOI 10.17487/RFC3261, June 2002, 1612 . 1614 [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, 1615 "Randomness Requirements for Security", BCP 106, RFC 4086, 1616 DOI 10.17487/RFC4086, June 2005, 1617 . 1619 [RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for 1620 Renumbering an IPv6 Network without a Flag Day", RFC 4192, 1621 DOI 10.17487/RFC4192, September 2005, 1622 . 1624 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 1625 (CIDR): The Internet Address Assignment and Aggregation 1626 Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August 1627 2006, . 1629 [RFC4866] Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route 1630 Optimization for Mobile IPv6", RFC 4866, 1631 DOI 10.17487/RFC4866, May 2007, 1632 . 1634 [RFC4984] Meyer, D., Ed., Zhang, L., Ed., and K. Fall, Ed., "Report 1635 from the IAB Workshop on Routing and Addressing", 1636 RFC 4984, DOI 10.17487/RFC4984, September 2007, 1637 . 1639 [RFC5944] Perkins, C., Ed., "IP Mobility Support for IPv4, Revised", 1640 RFC 5944, DOI 10.17487/RFC5944, November 2010, 1641 . 1643 [RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility 1644 Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July 1645 2011, . 1647 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 1648 Locator/ID Separation Protocol (LISP) for Multicast 1649 Environments", RFC 6831, DOI 10.17487/RFC6831, January 1650 2013, . 1652 [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 1653 "Interworking between Locator/ID Separation Protocol 1654 (LISP) and Non-LISP Sites", RFC 6832, 1655 DOI 10.17487/RFC6832, January 2013, 1656 . 1658 [RFC6834] Iannone, L., Saucez, D., and O. Bonaventure, "Locator/ID 1659 Separation Protocol (LISP) Map-Versioning", RFC 6834, 1660 DOI 10.17487/RFC6834, January 2013, 1661 . 1663 [RFC6835] Farinacci, D. and D. Meyer, "The Locator/ID Separation 1664 Protocol Internet Groper (LIG)", RFC 6835, 1665 DOI 10.17487/RFC6835, January 2013, 1666 . 1668 [RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and 1669 UDP Checksums for Tunneled Packets", RFC 6935, 1670 DOI 10.17487/RFC6935, April 2013, 1671 . 1673 [RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement 1674 for the Use of IPv6 UDP Datagrams with Zero Checksums", 1675 RFC 6936, DOI 10.17487/RFC6936, April 2013, 1676 . 1678 [RFC7052] Schudel, G., Jain, A., and V. Moreno, "Locator/ID 1679 Separation Protocol (LISP) MIB", RFC 7052, 1680 DOI 10.17487/RFC7052, October 2013, 1681 . 1683 [RFC7215] Jakab, L., Cabellos-Aparicio, A., Coras, F., Domingo- 1684 Pascual, J., and D. Lewis, "Locator/Identifier Separation 1685 Protocol (LISP) Network Element Deployment 1686 Considerations", RFC 7215, DOI 10.17487/RFC7215, April 1687 2014, . 1689 [RFC7833] Howlett, J., Hartman, S., and A. Perez-Mendez, Ed., "A 1690 RADIUS Attribute, Binding, Profiles, Name Identifier 1691 Format, and Confirmation Methods for the Security 1692 Assertion Markup Language (SAML)", RFC 7833, 1693 DOI 10.17487/RFC7833, May 2016, 1694 . 1696 [RFC7835] Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID 1697 Separation Protocol (LISP) Threat Analysis", RFC 7835, 1698 DOI 10.17487/RFC7835, April 2016, 1699 . 1701 [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 1702 Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, 1703 February 2017, . 1705 [RFC8061] Farinacci, D. and B. Weis, "Locator/ID Separation Protocol 1706 (LISP) Data-Plane Confidentiality", RFC 8061, 1707 DOI 10.17487/RFC8061, February 2017, 1708 . 1710 [RFC8111] Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A. 1711 Smirnov, "Locator/ID Separation Protocol Delegated 1712 Database Tree (LISP-DDT)", RFC 8111, DOI 10.17487/RFC8111, 1713 May 2017, . 1715 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1716 Writing an IANA Considerations Section in RFCs", BCP 26, 1717 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1718 . 1720 Appendix A. Acknowledgments 1722 An initial thank you goes to Dave Oran for planting the seeds for the 1723 initial ideas for LISP. His consultation continues to provide value 1724 to the LISP authors. 1726 A special and appreciative thank you goes to Noel Chiappa for 1727 providing architectural impetus over the past decades on separation 1728 of location and identity, as well as detailed reviews of the LISP 1729 architecture and documents, coupled with enthusiasm for making LISP a 1730 practical and incremental transition for the Internet. 1732 The authors would like to gratefully acknowledge many people who have 1733 contributed discussions and ideas to the making of this proposal. 1734 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 1735 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 1736 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 1737 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 1738 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 1739 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 1740 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 1741 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 1742 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 1743 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 1744 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 1745 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 1746 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 1747 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 1748 Ermagan, Fabio Maino, Victor Moreno, Chris White, Clarence Filsfils, 1749 Alia Atlas, Florin Coras and Alberto Rodriguez. 1751 This work originated in the Routing Research Group (RRG) of the IRTF. 1752 An individual submission was converted into the IETF LISP working 1753 group document that became this RFC. 1755 The LISP working group would like to give a special thanks to Jari 1756 Arkko, the Internet Area AD at the time that the set of LISP 1757 documents were being prepared for IESG last call, and for his 1758 meticulous reviews and detailed commentaries on the 7 working group 1759 last call documents progressing toward standards-track RFCs. 1761 Appendix B. Document Change Log 1763 [RFC Editor: Please delete this section on publication as RFC.] 1765 B.1. Changes to draft-ietf-lisp-rfc6830bis-12 1767 o Posted March IETF Week 2018. 1769 o Clarified that a new nonce is required per RLOC. 1771 o Removed 'Clock Sweep' section. This text must be placed in a new 1772 OAM document. 1774 o Some references changed from normative to informative 1776 B.2. Changes to draft-ietf-lisp-rfc6830bis-11 1778 o Posted March 2018. 1780 o Removed sections 16, 17 and 18 (Mobility, Deployment and 1781 Traceroute considerations). This text must be placed in a new OAM 1782 document. 1784 B.3. Changes to draft-ietf-lisp-rfc6830bis-10 1786 o Posted March 2018. 1788 o Updated section 'Router Locator Selection' stating that the Data- 1789 Plane MUST follow what's stored in the Map-Cache (priorities and 1790 weights). 1792 o Section 'Routing Locator Reachability': Removed bullet point 2 1793 (ICMP Network/Host Unreachable),3 (hints from BGP),4 (ICMP Port 1794 Unreachable),5 (receive a Map-Reply as a response) and RLOC 1795 probing 1797 o Removed 'Solicit-Map Request'. 1799 B.4. Changes to draft-ietf-lisp-rfc6830bis-09 1801 o Posted January 2018. 1803 o Add more details in section 5.3 about DSCP processing during 1804 encapsulation and decapsulation. 1806 o Added clarity to definitions in the Definition of Terms section 1807 from various commenters. 1809 o Removed PA and PI definitions from Definition of Terms section. 1811 o More editorial changes. 1813 o Removed 4342 from IANA section and move to RFC6833 IANA section. 1815 B.5. Changes to draft-ietf-lisp-rfc6830bis-08 1817 o Posted January 2018. 1819 o Remove references to research work for any protocol mechanisms. 1821 o Document scanned to make sure it is RFC 2119 compliant. 1823 o Made changes to reflect comments from document WG shepherd Luigi 1824 Iannone. 1826 o Ran IDNITs on the document. 1828 B.6. Changes to draft-ietf-lisp-rfc6830bis-07 1830 o Posted November 2017. 1832 o Rephrase how Instance-IDs are used and don't refer to [RFC1918] 1833 addresses. 1835 B.7. Changes to draft-ietf-lisp-rfc6830bis-06 1837 o Posted October 2017. 1839 o Put RTR definition before it is used. 1841 o Rename references that are now working group drafts. 1843 o Remove "EIDs MUST NOT be used as used by a host to refer to other 1844 hosts. Note that EID blocks MAY LISP RLOCs". 1846 o Indicate what address-family can appear in data packets. 1848 o ETRs may, rather than will, be the ones to send Map-Replies. 1850 o Recommend, rather than mandate, max encapsulation headers to 2. 1852 o Reference VPN draft when introducing Instance-ID. 1854 o Indicate that SMRs can be sent when ITR/ETR are in the same node. 1856 o Clarify when private addreses can be used. 1858 B.8. Changes to draft-ietf-lisp-rfc6830bis-05 1860 o Posted August 2017. 1862 o Make it clear that a Reencapsulating Tunnel Router is an RTR. 1864 B.9. Changes to draft-ietf-lisp-rfc6830bis-04 1866 o Posted July 2017. 1868 o Changed reference of IPv6 RFC2460 to RFC8200. 1870 o Indicate that the applicability statement for UDP zero checksums 1871 over IPv6 adheres to RFC6936. 1873 B.10. Changes to draft-ietf-lisp-rfc6830bis-03 1875 o Posted May 2017. 1877 o Move the control-plane related codepoints in the IANA 1878 Considerations section to RFC6833bis. 1880 B.11. Changes to draft-ietf-lisp-rfc6830bis-02 1882 o Posted April 2017. 1884 o Reflect some editorial comments from Damien Sausez. 1886 B.12. Changes to draft-ietf-lisp-rfc6830bis-01 1888 o Posted March 2017. 1890 o Include references to new RFCs published. 1892 o Change references from RFC6833 to RFC6833bis. 1894 o Clarified LCAF text in the IANA section. 1896 o Remove references to "experimental". 1898 B.13. Changes to draft-ietf-lisp-rfc6830bis-00 1900 o Posted December 2016. 1902 o Created working group document from draft-farinacci-lisp 1903 -rfc6830-00 individual submission. No other changes made. 1905 Authors' Addresses 1907 Dino Farinacci 1908 Cisco Systems 1909 Tasman Drive 1910 San Jose, CA 95134 1911 USA 1913 EMail: farinacci@gmail.com 1915 Vince Fuller 1916 Cisco Systems 1917 Tasman Drive 1918 San Jose, CA 95134 1919 USA 1921 EMail: vince.fuller@gmail.com 1923 Dave Meyer 1924 Cisco Systems 1925 170 Tasman Drive 1926 San Jose, CA 1927 USA 1929 EMail: dmm@1-4-5.net 1931 Darrel Lewis 1932 Cisco Systems 1933 170 Tasman Drive 1934 San Jose, CA 1935 USA 1937 EMail: darlewis@cisco.com 1939 Albert Cabellos 1940 UPC/BarcelonaTech 1941 Campus Nord, C. Jordi Girona 1-3 1942 Barcelona, Catalunya 1943 Spain 1945 EMail: acabello@ac.upc.edu