idnits 2.17.1 draft-ietf-lisp-rfc6830bis-14.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (July 17, 2018) is 2111 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-14) exists of draft-ietf-lisp-6834bis-00 == Outdated reference: A later version (-31) exists of draft-ietf-lisp-rfc6833bis-10 == Outdated reference: A later version (-15) exists of draft-ietf-lisp-introduction-13 == Outdated reference: A later version (-12) exists of draft-ietf-lisp-vpn-02 Summary: 0 errors (**), 0 flaws (~~), 5 warnings (==), 1 comment (--). 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 Obsoletes: 6830 (if approved) D. Meyer 5 Intended status: Standards Track D. Lewis 6 Expires: January 18, 2019 Cisco Systems 7 A. Cabellos (Ed.) 8 UPC/BarcelonaTech 9 July 17, 2018 11 The Locator/ID Separation Protocol (LISP) 12 draft-ietf-lisp-rfc6830bis-14 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 This document obsoletes RFC 6830. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at https://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on January 18, 2019. 47 Copyright Notice 49 Copyright (c) 2018 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (https://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 65 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4 66 3. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 4 67 4. Basic Overview . . . . . . . . . . . . . . . . . . . . . . . 8 68 4.1. Packet Flow Sequence . . . . . . . . . . . . . . . . . . 10 69 5. LISP Encapsulation Details . . . . . . . . . . . . . . . . . 12 70 5.1. LISP IPv4-in-IPv4 Header Format . . . . . . . . . . . . . 13 71 5.2. LISP IPv6-in-IPv6 Header Format . . . . . . . . . . . . . 13 72 5.3. Tunnel Header Field Descriptions . . . . . . . . . . . . 15 73 6. LISP EID-to-RLOC Map-Cache . . . . . . . . . . . . . . . . . 19 74 7. Dealing with Large Encapsulated Packets . . . . . . . . . . . 19 75 7.1. A Stateless Solution to MTU Handling . . . . . . . . . . 20 76 7.2. A Stateful Solution to MTU Handling . . . . . . . . . . . 21 77 8. Using Virtualization and Segmentation with LISP . . . . . . . 21 78 9. Routing Locator Selection . . . . . . . . . . . . . . . . . . 22 79 10. Routing Locator Reachability . . . . . . . . . . . . . . . . 24 80 10.1. Echo Nonce Algorithm . . . . . . . . . . . . . . . . . . 25 81 11. EID Reachability within a LISP Site . . . . . . . . . . . . . 26 82 12. Routing Locator Hashing . . . . . . . . . . . . . . . . . . . 27 83 13. Changing the Contents of EID-to-RLOC Mappings . . . . . . . . 28 84 13.1. Database Map-Versioning . . . . . . . . . . . . . . . . 29 85 14. Multicast Considerations . . . . . . . . . . . . . . . . . . 29 86 15. Router Performance Considerations . . . . . . . . . . . . . . 30 87 16. Security Considerations . . . . . . . . . . . . . . . . . . . 31 88 17. Network Management Considerations . . . . . . . . . . . . . . 32 89 18. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 90 18.1. LISP UDP Port Numbers . . . . . . . . . . . . . . . . . 32 91 19. References . . . . . . . . . . . . . . . . . . . . . . . . . 32 92 19.1. Normative References . . . . . . . . . . . . . . . . . . 32 93 19.2. Informative References . . . . . . . . . . . . . . . . . 33 94 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 37 95 Appendix B. Document Change Log . . . . . . . . . . . . . . . . 37 96 B.1. Changes to draft-ietf-lisp-rfc6830bis-14 . . . . . . . . 38 97 B.2. Changes to draft-ietf-lisp-rfc6830bis-13 . . . . . . . . 38 98 B.3. Changes to draft-ietf-lisp-rfc6830bis-12 . . . . . . . . 38 99 B.4. Changes to draft-ietf-lisp-rfc6830bis-11 . . . . . . . . 38 100 B.5. Changes to draft-ietf-lisp-rfc6830bis-10 . . . . . . . . 38 101 B.6. Changes to draft-ietf-lisp-rfc6830bis-09 . . . . . . . . 39 102 B.7. Changes to draft-ietf-lisp-rfc6830bis-08 . . . . . . . . 39 103 B.8. Changes to draft-ietf-lisp-rfc6830bis-07 . . . . . . . . 39 104 B.9. Changes to draft-ietf-lisp-rfc6830bis-06 . . . . . . . . 39 105 B.10. Changes to draft-ietf-lisp-rfc6830bis-05 . . . . . . . . 40 106 B.11. Changes to draft-ietf-lisp-rfc6830bis-04 . . . . . . . . 40 107 B.12. Changes to draft-ietf-lisp-rfc6830bis-03 . . . . . . . . 40 108 B.13. Changes to draft-ietf-lisp-rfc6830bis-02 . . . . . . . . 40 109 B.14. Changes to draft-ietf-lisp-rfc6830bis-01 . . . . . . . . 40 110 B.15. Changes to draft-ietf-lisp-rfc6830bis-00 . . . . . . . . 41 111 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41 113 1. Introduction 115 This document describes the Locator/Identifier Separation Protocol 116 (LISP). LISP is an encapsulation protocol built around the 117 fundamental idea of separating the topological location of a network 118 attachment point from the node's identity [CHIAPPA]. As a result 119 LISP creates two namespaces: Endpoint Identifiers (EIDs), that are 120 used to identify end-hosts (e.g., nodes or Virtual Machines) and 121 routable Routing Locators (RLOCs), used to identify network 122 attachment points. LISP then defines functions for mapping between 123 the two namespaces and for encapsulating traffic originated by 124 devices using non-routable EIDs for transport across a network 125 infrastructure that routes and forwards using RLOCs. LISP 126 encapsulation uses a dynamic form of tunneling where no static 127 provisioning is required or necessary. 129 LISP is an overlay protocol that separates control from Data-Plane, 130 this document specifies the Data-Plane, how LISP-capable routers 131 (Tunnel Routers) exchange packets by encapsulating them to the 132 appropriate location. Tunnel routers are equipped with a cache, 133 called Map-Cache, that contains EID-to-RLOC mappings. The Map-Cache 134 is populated using the LISP Control-Plane protocol 135 [I-D.ietf-lisp-rfc6833bis]. 137 LISP does not require changes to either host protocol stack or to 138 underlay routers. By separating the EID from the RLOC space, LISP 139 offers native Traffic Engineering, multihoming and mobility, among 140 other features. 142 Creation of LISP was initially motivated by discussions during the 143 IAB-sponsored Routing and Addressing Workshop held in Amsterdam in 144 October 2006 (see [RFC4984]). 146 This document specifies the LISP Data-Plane encapsulation and other 147 LISP forwarding node functionality while [I-D.ietf-lisp-rfc6833bis] 148 specifies the LISP control plane. LISP deployment guidelines can be 149 found in [RFC7215] and [RFC6835] describes considerations for network 150 operational management. Finally, [I-D.ietf-lisp-introduction] 151 describes the LISP architecture. 153 This document obsoletes RFC 6830. 155 2. Requirements Notation 157 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 158 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 159 document are to be interpreted as described in [RFC2119]. 161 3. Definition of Terms 163 Address Family Identifier (AFI): AFI is a term used to describe an 164 address encoding in a packet. An address family that pertains to 165 the Data-Plane. See [AFN] and [RFC3232] for details. An AFI 166 value of 0 used in this specification indicates an unspecified 167 encoded address where the length of the address is 0 octets 168 following the 16-bit AFI value of 0. 170 Anycast Address: Anycast Address is a term used in this document to 171 refer to the same IPv4 or IPv6 address configured and used on 172 multiple systems at the same time. An EID or RLOC can be an 173 anycast address in each of their own address spaces. 175 Client-side: Client-side is a term used in this document to indicate 176 a connection initiation attempt by an end-system represented by an 177 EID. 179 Data-Probe: A Data-Probe is a LISP-encapsulated data packet where 180 the inner-header destination address equals the outer-header 181 destination address used to trigger a Map-Reply by a decapsulating 182 ETR. In addition, the original packet is decapsulated and 183 delivered to the destination host if the destination EID is in the 184 EID-Prefix range configured on the ETR. Otherwise, the packet is 185 discarded. A Data-Probe is used in some of the mapping database 186 designs to "probe" or request a Map-Reply from an ETR; in other 187 cases, Map-Requests are used. See each mapping database design 188 for details. When using Data-Probes, by sending Map-Requests on 189 the underlying routing system, EID-Prefixes must be advertised. 191 Egress Tunnel Router (ETR): An ETR is a router that accepts an IP 192 packet where the destination address in the "outer" IP header is 193 one of its own RLOCs. The router strips the "outer" header and 194 forwards the packet based on the next IP header found. In 195 general, an ETR receives LISP-encapsulated IP packets from the 196 Internet on one side and sends decapsulated IP packets to site 197 end-systems on the other side. ETR functionality does not have to 198 be limited to a router device. A server host can be the endpoint 199 of a LISP tunnel as well. 201 EID-to-RLOC Database: The EID-to-RLOC Database is a global 202 distributed database that contains all known EID-Prefix-to-RLOC 203 mappings. Each potential ETR typically contains a small piece of 204 the database: the EID-to-RLOC mappings for the EID-Prefixes 205 "behind" the router. These map to one of the router's own 206 globally visible IP addresses. Note that there MAY be transient 207 conditions when the EID-Prefix for the site and Locator-Set for 208 each EID-Prefix may not be the same on all ETRs. This has no 209 negative implications, since a partial set of Locators can be 210 used. 212 EID-to-RLOC Map-Cache: The EID-to-RLOC Map-Cache is generally 213 short-lived, on-demand table in an ITR that stores, tracks, and is 214 responsible for timing out and otherwise validating EID-to-RLOC 215 mappings. This cache is distinct from the full "database" of EID- 216 to-RLOC mappings; it is dynamic, local to the ITR(s), and 217 relatively small, while the database is distributed, relatively 218 static, and much more global in scope. 220 EID-Prefix: An EID-Prefix is a power-of-two block of EIDs that are 221 allocated to a site by an address allocation authority. EID- 222 Prefixes are associated with a set of RLOC addresses. EID-Prefix 223 allocations can be broken up into smaller blocks when an RLOC set 224 is to be associated with the larger EID-Prefix block. 226 End-System: An end-system is an IPv4 or IPv6 device that originates 227 packets with a single IPv4 or IPv6 header. The end-system 228 supplies an EID value for the destination address field of the IP 229 header when communicating globally (i.e., outside of its routing 230 domain). An end-system can be a host computer, a switch or router 231 device, or any network appliance. 233 Endpoint ID (EID): An EID is a 32-bit (for IPv4) or 128-bit (for 234 IPv6) value used in the source and destination address fields of 235 the first (most inner) LISP header of a packet. The host obtains 236 a destination EID the same way it obtains a destination address 237 today, for example, through a Domain Name System (DNS) [RFC1034] 238 lookup or Session Initiation Protocol (SIP) [RFC3261] exchange. 240 The source EID is obtained via existing mechanisms used to set a 241 host's "local" IP address. An EID used on the public Internet 242 MUST have the same properties as any other IP address used in that 243 manner; this means, among other things, that it MUST be globally 244 unique. An EID is allocated to a host from an EID-Prefix block 245 associated with the site where the host is located. An EID can be 246 used by a host to refer to other hosts. Note that EID blocks MAY 247 be assigned in a hierarchical manner, independent of the network 248 topology, to facilitate scaling of the mapping database. In 249 addition, an EID block assigned to a site MAY have site-local 250 structure (subnetting) for routing within the site; this structure 251 is not visible to the global routing system. In theory, the bit 252 string that represents an EID for one device can represent an RLOC 253 for a different device. When used in discussions with other 254 Locator/ID separation proposals, a LISP EID will be called an 255 "LEID". Throughout this document, any references to "EID" refer 256 to an LEID. 258 Ingress Tunnel Router (ITR): An ITR is a router that resides in a 259 LISP site. Packets sent by sources inside of the LISP site to 260 destinations outside of the site are candidates for encapsulation 261 by the ITR. The ITR treats the IP destination address as an EID 262 and performs an EID-to-RLOC mapping lookup. The router then 263 prepends an "outer" IP header with one of its routable RLOCs (in 264 the RLOC space) in the source address field and the result of the 265 mapping lookup in the destination address field. Note that this 266 destination RLOC MAY be an intermediate, proxy device that has 267 better knowledge of the EID-to-RLOC mapping closer to the 268 destination EID. In general, an ITR receives IP packets from site 269 end-systems on one side and sends LISP-encapsulated IP packets 270 toward the Internet on the other side. 272 Specifically, when a service provider prepends a LISP header for 273 Traffic Engineering purposes, the router that does this is also 274 regarded as an ITR. The outer RLOC the ISP ITR uses can be based 275 on the outer destination address (the originating ITR's supplied 276 RLOC) or the inner destination address (the originating host's 277 supplied EID). 279 LISP Header: LISP header is a term used in this document to refer 280 to the outer IPv4 or IPv6 header, a UDP header, and a LISP- 281 specific 8-octet header that follow the UDP header and that an ITR 282 prepends or an ETR strips. 284 LISP Router: A LISP router is a router that performs the functions 285 of any or all of the following: ITR, ETR, RTR, Proxy-ITR (PITR), 286 or Proxy-ETR (PETR). 288 LISP Site: LISP site is a set of routers in an edge network that are 289 under a single technical administration. LISP routers that reside 290 in the edge network are the demarcation points to separate the 291 edge network from the core network. 293 Locator-Status-Bits (LSBs): Locator-Status-Bits are present in the 294 LISP header. They are used by ITRs to inform ETRs about the up/ 295 down status of all ETRs at the local site. These bits are used as 296 a hint to convey up/down router status and not path reachability 297 status. The LSBs can be verified by use of one of the Locator 298 reachability algorithms described in Section 10. 300 Negative Mapping Entry: A negative mapping entry, also known as a 301 negative cache entry, is an EID-to-RLOC entry where an EID-Prefix 302 is advertised or stored with no RLOCs. That is, the Locator-Set 303 for the EID-to-RLOC entry is empty or has an encoded Locator count 304 of 0. This type of entry could be used to describe a prefix from 305 a non-LISP site, which is explicitly not in the mapping database. 306 There are a set of well-defined actions that are encoded in a 307 Negative Map-Reply. 309 Proxy-ETR (PETR): A PETR is defined and described in [RFC6832]. A 310 PETR acts like an ETR but does so on behalf of LISP sites that 311 send packets to destinations at non-LISP sites. 313 Proxy-ITR (PITR): A PITR is defined and described in [RFC6832]. A 314 PITR acts like an ITR but does so on behalf of non-LISP sites that 315 send packets to destinations at LISP sites. 317 Recursive Tunneling: Recursive Tunneling occurs when a packet has 318 more than one LISP IP header. Additional layers of tunneling MAY 319 be employed to implement Traffic Engineering or other re-routing 320 as needed. When this is done, an additional "outer" LISP header 321 is added, and the original RLOCs are preserved in the "inner" 322 header. 324 Re-Encapsulating Tunneling Router (RTR): An RTR acts like an ETR to 325 remove a LISP header, then acts as an ITR to prepend a new LISP 326 header. This is known as Re-encapsulating Tunneling. Doing this 327 allows a packet to be re-routed by the RTR without adding the 328 overhead of additional tunnel headers. When using multiple 329 mapping database systems, care must be taken to not create re- 330 encapsulation loops through misconfiguration. 332 Route-Returnability: Route-returnability is an assumption that the 333 underlying routing system will deliver packets to the destination. 334 When combined with a nonce that is provided by a sender and 335 returned by a receiver, this limits off-path data insertion. A 336 route-returnability check is verified when a message is sent with 337 a nonce, another message is returned with the same nonce, and the 338 destination of the original message appears as the source of the 339 returned message. 341 Routing Locator (RLOC): An RLOC is an IPv4 [RFC0791] or IPv6 342 [RFC8200] address of an Egress Tunnel Router (ETR). An RLOC is 343 the output of an EID-to-RLOC mapping lookup. An EID maps to zero 344 or more RLOCs. Typically, RLOCs are numbered from blocks that are 345 assigned to a site at each point to which it attaches to the 346 underlay network; where the topology is defined by the 347 connectivity of provider networks. Multiple RLOCs can be assigned 348 to the same ETR device or to multiple ETR devices at a site. 350 Server-side: Server-side is a term used in this document to indicate 351 that a connection initiation attempt is being accepted for a 352 destination EID. 354 TE-ETR: A TE-ETR is an ETR that is deployed in a service provider 355 network that strips an outer LISP header for Traffic Engineering 356 purposes. 358 TE-ITR: A TE-ITR is an ITR that is deployed in a service provider 359 network that prepends an additional LISP header for Traffic 360 Engineering purposes. 362 xTR: An xTR is a reference to an ITR or ETR when direction of data 363 flow is not part of the context description. "xTR" refers to the 364 router that is the tunnel endpoint and is used synonymously with 365 the term "Tunnel Router". For example, "An xTR can be located at 366 the Customer Edge (CE) router" indicates both ITR and ETR 367 functionality at the CE router. 369 4. Basic Overview 371 One key concept of LISP is that end-systems operate the same way they 372 do today. The IP addresses that hosts use for tracking sockets and 373 connections, and for sending and receiving packets, do not change. 374 In LISP terminology, these IP addresses are called Endpoint 375 Identifiers (EIDs). 377 Routers continue to forward packets based on IP destination 378 addresses. When a packet is LISP encapsulated, these addresses are 379 referred to as Routing Locators (RLOCs). Most routers along a path 380 between two hosts will not change; they continue to perform routing/ 381 forwarding lookups on the destination addresses. For routers between 382 the source host and the ITR as well as routers from the ETR to the 383 destination host, the destination address is an EID. For the routers 384 between the ITR and the ETR, the destination address is an RLOC. 386 Another key LISP concept is the "Tunnel Router". A Tunnel Router 387 prepends LISP headers on host-originated packets and strips them 388 prior to final delivery to their destination. The IP addresses in 389 this "outer header" are RLOCs. During end-to-end packet exchange 390 between two Internet hosts, an ITR prepends a new LISP header to each 391 packet, and an ETR strips the new header. The ITR performs EID-to- 392 RLOC lookups to determine the routing path to the ETR, which has the 393 RLOC as one of its IP addresses. 395 Some basic rules governing LISP are: 397 o End-systems only send to addresses that are EIDs. EIDs are 398 typically IP addresses assigned to hosts (other types of EID are 399 supported by LISP, see [RFC8060] for further information). End- 400 systems don't know that addresses are EIDs versus RLOCs but assume 401 that packets get to their intended destinations. In a system 402 where LISP is deployed, LISP routers intercept EID-addressed 403 packets and assist in delivering them across the network core 404 where EIDs cannot be routed. The procedure a host uses to send IP 405 packets does not change. 407 o LISP routers mostly deal with Routing Locator addresses. See 408 details in Section 4.1 to clarify what is meant by "mostly". 410 o RLOCs are always IP addresses assigned to routers, preferably 411 topologically oriented addresses from provider CIDR (Classless 412 Inter-Domain Routing) blocks. 414 o When a router originates packets, it MAY use as a source address 415 either an EID or RLOC. When acting as a host (e.g., when 416 terminating a transport session such as Secure SHell (SSH), 417 TELNET, or the Simple Network Management Protocol (SNMP)), it MAY 418 use an EID that is explicitly assigned for that purpose. An EID 419 that identifies the router as a host MUST NOT be used as an RLOC; 420 an EID is only routable within the scope of a site. A typical BGP 421 configuration might demonstrate this "hybrid" EID/RLOC usage where 422 a router could use its "host-like" EID to terminate iBGP sessions 423 to other routers in a site while at the same time using RLOCs to 424 terminate eBGP sessions to routers outside the site. 426 o Packets with EIDs in them are not expected to be delivered end-to- 427 end in the absence of an EID-to-RLOC mapping operation. They are 428 expected to be used locally for intra-site communication or to be 429 encapsulated for inter-site communication. 431 o EIDs MAY also be structured (subnetted) in a manner suitable for 432 local routing within an Autonomous System (AS). 434 An additional LISP header MAY be prepended to packets by a TE-ITR 435 when re-routing of the path for a packet is desired. A potential 436 use-case for this would be an ISP router that needs to perform 437 Traffic Engineering for packets flowing through its network. In such 438 a situation, termed "Recursive Tunneling", an ISP transit acts as an 439 additional ITR, and the RLOC it uses for the new prepended header 440 would be either a TE-ETR within the ISP (along an intra-ISP traffic 441 engineered path) or a TE-ETR within another ISP (an inter-ISP traffic 442 engineered path, where an agreement to build such a path exists). 444 In order to avoid excessive packet overhead as well as possible 445 encapsulation loops, this document recommends that a maximum of two 446 LISP headers can be prepended to a packet. For initial LISP 447 deployments, it is assumed that two headers is sufficient, where the 448 first prepended header is used at a site for Location/Identity 449 separation and the second prepended header is used inside a service 450 provider for Traffic Engineering purposes. 452 Tunnel Routers can be placed fairly flexibly in a multi-AS topology. 453 For example, the ITR for a particular end-to-end packet exchange 454 might be the first-hop or default router within a site for the source 455 host. Similarly, the ETR might be the last-hop router directly 456 connected to the destination host. Another example, perhaps for a 457 VPN service outsourced to an ISP by a site, the ITR could be the 458 site's border router at the service provider attachment point. 459 Mixing and matching of site-operated, ISP-operated, and other Tunnel 460 Routers is allowed for maximum flexibility. 462 4.1. Packet Flow Sequence 464 This section provides an example of the unicast packet flow, 465 including also Control-Plane information as specified in 466 [I-D.ietf-lisp-rfc6833bis]. The example also assumes the following 467 conditions: 469 o Source host "host1.abc.example.com" is sending a packet to 470 "host2.xyz.example.com", exactly what host1 would do if the site 471 was not using LISP. 473 o Each site is multihomed, so each Tunnel Router has an address 474 (RLOC) assigned from the service provider address block for each 475 provider to which that particular Tunnel Router is attached. 477 o The ITR(s) and ETR(s) are directly connected to the source and 478 destination, respectively, but the source and destination can be 479 located anywhere in the LISP site. 481 o A Map-Request is sent for an external destination when the 482 destination is not found in the forwarding table or matches a 483 default route. Map-Requests are sent to the mapping database 484 system by using the LISP Control-Plane protocol documented in 485 [I-D.ietf-lisp-rfc6833bis]. 487 o Map-Replies are sent on the underlying routing system topology 488 using the [I-D.ietf-lisp-rfc6833bis] Control-Plane protocol. 490 Client host1.abc.example.com wants to communicate with server 491 host2.xyz.example.com: 493 1. host1.abc.example.com wants to open a TCP connection to 494 host2.xyz.example.com. It does a DNS lookup on 495 host2.xyz.example.com. An A/AAAA record is returned. This 496 address is the destination EID. The locally assigned address of 497 host1.abc.example.com is used as the source EID. An IPv4 or IPv6 498 packet is built and forwarded through the LISP site as a normal 499 IP packet until it reaches a LISP ITR. 501 2. The LISP ITR must be able to map the destination EID to an RLOC 502 of one of the ETRs at the destination site. The specific method 503 used to do this is not described in this example. See 504 [I-D.ietf-lisp-rfc6833bis] for further information. 506 3. The ITR sends a LISP Map-Request as specified in 507 [I-D.ietf-lisp-rfc6833bis]. Map-Requests SHOULD be rate-limited. 509 4. The mapping system helps forwarding the Map-Request to the 510 corresponding ETR. When the Map-Request arrives at one of the 511 ETRs at the destination site, it will process the packet as a 512 control message. 514 5. The ETR looks at the destination EID of the Map-Request and 515 matches it against the prefixes in the ETR's configured EID-to- 516 RLOC mapping database. This is the list of EID-Prefixes the ETR 517 is supporting for the site it resides in. If there is no match, 518 the Map-Request is dropped. Otherwise, a LISP Map-Reply is 519 returned to the ITR. 521 6. The ITR receives the Map-Reply message, parses the message (to 522 check for format validity), and stores the mapping information 523 from the packet. This information is stored in the ITR's EID-to- 524 RLOC Map-Cache. Note that the Map-Cache is an on-demand cache. 526 An ITR will manage its Map-Cache in such a way that optimizes for 527 its resource constraints. 529 7. Subsequent packets from host1.abc.example.com to 530 host2.xyz.example.com will have a LISP header prepended by the 531 ITR using the appropriate RLOC as the LISP header destination 532 address learned from the ETR. Note that the packet MAY be sent 533 to a different ETR than the one that returned the Map-Reply due 534 to the source site's hashing policy or the destination site's 535 Locator-Set policy. 537 8. The ETR receives these packets directly (since the destination 538 address is one of its assigned IP addresses), checks the validity 539 of the addresses, strips the LISP header, and forwards packets to 540 the attached destination host. 542 9. In order to defer the need for a mapping lookup in the reverse 543 direction, an ETR can OPTIONALLY create a cache entry that maps 544 the source EID (inner-header source IP address) to the source 545 RLOC (outer-header source IP address) in a received LISP packet. 546 Such a cache entry is termed a "glean mapping" and only contains 547 a single RLOC for the EID in question. More complete information 548 about additional RLOCs SHOULD be verified by sending a LISP Map- 549 Request for that EID. Both the ITR and the ETR MAY also 550 influence the decision the other makes in selecting an RLOC. 552 5. LISP Encapsulation Details 554 Since additional tunnel headers are prepended, the packet becomes 555 larger and can exceed the MTU of any link traversed from the ITR to 556 the ETR. It is RECOMMENDED in IPv4 that packets do not get 557 fragmented as they are encapsulated by the ITR. Instead, the packet 558 is dropped and an ICMP Unreachable/Fragmentation-Needed message is 559 returned to the source. 561 In the case when fragmentation is needed, this specification 562 RECOMMENDS that implementations provide support for one of the 563 proposed fragmentation and reassembly schemes. Two existing schemes 564 are detailed in Section 7. 566 Since IPv4 or IPv6 addresses can be either EIDs or RLOCs, the LISP 567 architecture supports IPv4 EIDs with IPv6 RLOCs (where the inner 568 header is in IPv4 packet format and the outer header is in IPv6 569 packet format) or IPv6 EIDs with IPv4 RLOCs (where the inner header 570 is in IPv6 packet format and the outer header is in IPv4 packet 571 format). The next sub-sections illustrate packet formats for the 572 homogeneous case (IPv4-in-IPv4 and IPv6-in-IPv6), but all 4 573 combinations MUST be supported. Additional types of EIDs are defined 574 in [RFC8060]. 576 5.1. LISP IPv4-in-IPv4 Header Format 578 0 1 2 3 579 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 1 580 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 581 / |Version| IHL | DSCP |ECN| Total Length | 582 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 583 | | Identification |Flags| Fragment Offset | 584 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 585 OH | Time to Live | Protocol = 17 | Header Checksum | 586 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 587 | | Source Routing Locator | 588 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 589 \ | Destination Routing Locator | 590 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 591 / | Source Port = xxxx | Dest Port = 4341 | 592 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 593 \ | UDP Length | UDP Checksum | 594 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 595 L |N|L|E|V|I|R|K|K| Nonce/Map-Version | 596 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 597 S / | Instance ID/Locator-Status-Bits | 598 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 599 / |Version| IHL | DSCP |ECN| Total Length | 600 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 601 | | Identification |Flags| Fragment Offset | 602 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 603 IH | Time to Live | Protocol | Header Checksum | 604 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 605 | | Source EID | 606 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 607 \ | Destination EID | 608 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 610 IHL = IP-Header-Length 612 5.2. LISP IPv6-in-IPv6 Header Format 614 0 1 2 3 615 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 1 616 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 617 / |Version| DSCP |ECN| Flow Label | 618 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 619 | | Payload Length | Next Header=17| Hop Limit | 620 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 621 | | 622 O + + 623 u | | 624 t + Source Routing Locator + 625 e | | 626 r + + 627 | | 628 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 629 d | | 630 r + + 631 | | 632 ^ + Destination Routing Locator + 633 | | | 634 \ + + 635 \ | | 636 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 637 / | Source Port = xxxx | Dest Port = 4341 | 638 UDP +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 639 \ | UDP Length | UDP Checksum | 640 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 641 L |N|L|E|V|I|R|K|K| Nonce/Map-Version | 642 I \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 643 S / | Instance ID/Locator-Status-Bits | 644 P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 645 / |Version| DSCP |ECN| Flow Label | 646 / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 647 / | Payload Length | Next Header | Hop Limit | 648 v +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 649 | | 650 I + + 651 n | | 652 n + Source EID + 653 e | | 654 r + + 655 | | 656 H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 657 d | | 658 r + + 659 | | 660 ^ + Destination EID + 661 \ | | 662 \ + + 663 \ | | 664 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 666 5.3. Tunnel Header Field Descriptions 668 Inner Header (IH): The inner header is the header on the 669 datagram received from the originating host [RFC0791] [RFC8200] 670 [RFC2474]. The source and destination IP addresses are EIDs. 672 Outer Header: (OH) The outer header is a new header prepended by an 673 ITR. The address fields contain RLOCs obtained from the ingress 674 router's EID-to-RLOC Cache. The IP protocol number is "UDP (17)" 675 from [RFC0768]. The setting of the Don't Fragment (DF) bit 676 'Flags' field is according to rules listed in Sections 7.1 and 677 7.2. 679 UDP Header: The UDP header contains an ITR selected source port when 680 encapsulating a packet. See Section 12 for details on the hash 681 algorithm used to select a source port based on the 5-tuple of the 682 inner header. The destination port MUST be set to the well-known 683 IANA-assigned port value 4341. 685 UDP Checksum: The 'UDP Checksum' field SHOULD be transmitted as zero 686 by an ITR for either IPv4 [RFC0768] and IPv6 encapsulation 687 [RFC6935] [RFC6936]. When a packet with a zero UDP checksum is 688 received by an ETR, the ETR MUST accept the packet for 689 decapsulation. When an ITR transmits a non-zero value for the UDP 690 checksum, it MUST send a correctly computed value in this field. 691 When an ETR receives a packet with a non-zero UDP checksum, it MAY 692 choose to verify the checksum value. If it chooses to perform 693 such verification, and the verification fails, the packet MUST be 694 silently dropped. If the ETR chooses not to perform the 695 verification, or performs the verification successfully, the 696 packet MUST be accepted for decapsulation. The handling of UDP 697 zero checksums over IPv6 for all tunneling protocols, including 698 LISP, is subject to the applicability statement in [RFC6936]. 700 UDP Length: The 'UDP Length' field is set for an IPv4-encapsulated 701 packet to be the sum of the inner-header IPv4 Total Length plus 702 the UDP and LISP header lengths. For an IPv6-encapsulated packet, 703 the 'UDP Length' field is the sum of the inner-header IPv6 Payload 704 Length, the size of the IPv6 header (40 octets), and the size of 705 the UDP and LISP headers. 707 N: The N-bit is the nonce-present bit. When this bit is set to 1, 708 the low-order 24 bits of the first 32 bits of the LISP header 709 contain a Nonce. See Section 10.1 for details. Both N- and 710 V-bits MUST NOT be set in the same packet. If they are, a 711 decapsulating ETR MUST treat the 'Nonce/Map-Version' field as 712 having a Nonce value present. 714 L: The L-bit is the 'Locator-Status-Bits' field enabled bit. When 715 this bit is set to 1, the Locator-Status-Bits in the second 716 32 bits of the LISP header are in use. 718 x 1 x x 0 x x x 719 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 720 |N|L|E|V|I|R|K|K| Nonce/Map-Version | 721 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 722 | Locator-Status-Bits | 723 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 725 E: The E-bit is the echo-nonce-request bit. This bit MUST be ignored 726 and has no meaning when the N-bit is set to 0. When the N-bit is 727 set to 1 and this bit is set to 1, an ITR is requesting that the 728 nonce value in the 'Nonce' field be echoed back in LISP- 729 encapsulated packets when the ITR is also an ETR. See 730 Section 10.1 for details. 732 V: The V-bit is the Map-Version present bit. When this bit is set to 733 1, the N-bit MUST be 0. Refer to Section 13.1 for more details. 734 This bit indicates that the LISP header is encoded in this 735 case as: 737 0 x 0 1 x x x x 738 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 739 |N|L|E|V|I|R|K|K| Source Map-Version | Dest Map-Version | 740 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 741 | Instance ID/Locator-Status-Bits | 742 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 744 I: The I-bit is the Instance ID bit. See Section 8 for more details. 745 When this bit is set to 1, the 'Locator-Status-Bits' field is 746 reduced to 8 bits and the high-order 24 bits are used as an 747 Instance ID. If the L-bit is set to 0, then the low-order 8 bits 748 are transmitted as zero and ignored on receipt. The format of the 749 LISP header would look like this: 751 x x x x 1 x x x 752 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 753 |N|L|E|V|I|R|K|K| Nonce/Map-Version | 754 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 755 | Instance ID | LSBs | 756 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 758 R: The R-bit is a Reserved bit for future use. It MUST be set to 0 759 on transmit and MUST be ignored on receipt. 761 KK: The KK-bits are a 2-bit field used when encapsulated packets are 762 encrypted. The field is set to 00 when the packet is not 763 encrypted. See [RFC8061] for further information. 765 LISP Nonce: The LISP 'Nonce' field is a 24-bit value that is 766 randomly generated by an ITR when the N-bit is set to 1. Nonce 767 generation algorithms are an implementation matter but are 768 required to generate different nonces when sending to different 769 RLOCs. However, the same nonce can be used for a period of time 770 when encapsulating to the same ETR. The nonce is also used when 771 the E-bit is set to request the nonce value to be echoed by the 772 other side when packets are returned. When the E-bit is clear but 773 the N-bit is set, a remote ITR is either echoing a previously 774 requested echo-nonce or providing a random nonce. See 775 Section 10.1 for more details. 777 LISP Locator-Status-Bits (LSBs): When the L-bit is also set, the 778 'Locator-Status-Bits' field in the LISP header is set by an ITR to 779 indicate to an ETR the up/down status of the Locators in the 780 source site. Each RLOC in a Map-Reply is assigned an ordinal 781 value from 0 to n-1 (when there are n RLOCs in a mapping entry). 782 The Locator-Status-Bits are numbered from 0 to n-1 from the least 783 significant bit of the field. The field is 32 bits when the I-bit 784 is set to 0 and is 8 bits when the I-bit is set to 1. When a 785 Locator-Status-Bit is set to 1, the ITR is indicating to the ETR 786 that the RLOC associated with the bit ordinal has up status. See 787 Section 10 for details on how an ITR can determine the status of 788 the ETRs at the same site. When a site has multiple EID-Prefixes 789 that result in multiple mappings (where each could have a 790 different Locator-Set), the Locator-Status-Bits setting in an 791 encapsulated packet MUST reflect the mapping for the EID-Prefix 792 that the inner-header source EID address matches. If the LSB for 793 an anycast Locator is set to 1, then there is at least one RLOC 794 with that address, and the ETR is considered 'up'. 796 When doing ITR/PITR encapsulation: 798 o The outer-header 'Time to Live' field (or 'Hop Limit' field, in 799 the case of IPv6) SHOULD be copied from the inner-header 'Time to 800 Live' field. 802 o The outer-header 'Differentiated Services Code Point' (DSCP) field 803 (or the 'Traffic Class' field, in the case of IPv6) SHOULD be 804 copied from the inner-header DSCP field ('Traffic Class' field, in 805 the case of IPv6) considering the exception listed below. 807 o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 808 of the IPv6 'Traffic Class' field) requires special treatment in 809 order to avoid discarding indications of congestion [RFC3168]. 810 ITR encapsulation MUST copy the 2-bit 'ECN' field from the inner 811 header to the outer header. Re-encapsulation MUST copy the 2-bit 812 'ECN' field from the stripped outer header to the new outer 813 header. 815 When doing ETR/PETR decapsulation: 817 o The inner-header 'Time to Live' field (or 'Hop Limit' field, in 818 the case of IPv6) SHOULD be copied from the outer-header 'Time to 819 Live' field, when the Time to Live value of the outer header is 820 less than the Time to Live value of the inner header. Failing to 821 perform this check can cause the Time to Live of the inner header 822 to increment across encapsulation/decapsulation cycles. This 823 check is also performed when doing initial encapsulation, when a 824 packet comes to an ITR or PITR destined for a LISP site. 826 o The inner-header 'Differentiated Services Code Point' (DSCP) field 827 (or the 'Traffic Class' field, in the case of IPv6) SHOULD be 828 copied from the outer-header DSCP field ('Traffic Class' field, in 829 the case of IPv6) considering the exception listed below. 831 o The 'Explicit Congestion Notification' (ECN) field (bits 6 and 7 832 of the IPv6 'Traffic Class' field) requires special treatment in 833 order to avoid discarding indications of congestion [RFC3168]. If 834 the 'ECN' field contains a congestion indication codepoint (the 835 value is '11', the Congestion Experienced (CE) codepoint), then 836 ETR decapsulation MUST copy the 2-bit 'ECN' field from the 837 stripped outer header to the surviving inner header that is used 838 to forward the packet beyond the ETR. These requirements preserve 839 CE indications when a packet that uses ECN traverses a LISP tunnel 840 and becomes marked with a CE indication due to congestion between 841 the tunnel endpoints. 843 Note that if an ETR/PETR is also an ITR/PITR and chooses to re- 844 encapsulate after decapsulating, the net effect of this is that the 845 new outer header will carry the same Time to Live as the old outer 846 header minus 1. 848 Copying the Time to Live (TTL) serves two purposes: first, it 849 preserves the distance the host intended the packet to travel; 850 second, and more importantly, it provides for suppression of looping 851 packets in the event there is a loop of concatenated tunnels due to 852 misconfiguration. 854 The Explicit Congestion Notification ('ECN') field occupies bits 6 855 and 7 of both the IPv4 'Type of Service' field and the IPv6 'Traffic 856 Class' field [RFC3168]. The 'ECN' field requires special treatment 857 in order to avoid discarding indications of congestion [RFC3168]. An 858 ITR/PITR encapsulation MUST copy the 2-bit 'ECN' field from the inner 859 header to the outer header. Re-encapsulation MUST copy the 2-bit 860 'ECN' field from the stripped outer header to the new outer header. 861 If the 'ECN' field contains a congestion indication codepoint (the 862 value is '11', the Congestion Experienced (CE) codepoint), then ETR/ 863 PETR decapsulation MUST copy the 2-bit 'ECN' field from the stripped 864 outer header to the surviving inner header that is used to forward 865 the packet beyond the ETR. These requirements preserve CE 866 indications when a packet that uses ECN traverses a LISP tunnel and 867 becomes marked with a CE indication due to congestion between the 868 tunnel endpoints. 870 6. LISP EID-to-RLOC Map-Cache 872 ITRs and PITRs maintain an on-demand cache, referred as LISP EID-to- 873 RLOC Map-Cache, that contains mappings from EID-prefixes to locator 874 sets. The cache is used to encapsulate packets from the EID space to 875 the corresponding RLOC network attachment point. 877 When an ITR/PITR receives a packet from inside of the LISP site to 878 destinations outside of the site a longest-prefix match lookup of the 879 EID is done to the Map-Cache. 881 When the lookup succeeds, the Locator-Set retrieved from the Map- 882 Cache is used to send the packet to the EID's topological location. 884 If the lookup fails, the ITR/PITR needs to retrieve the mapping using 885 the LISP Control-Plane protocol [I-D.ietf-lisp-rfc6833bis]. The 886 mapping is then stored in the local Map-Cache to forward subsequent 887 packets addressed to the same EID-prefix. 889 The Map-Cache is a local cache of mappings, entries are expired based 890 on the associated Time to live. In addition, entries can be updated 891 with more current information, see Section 13 for further information 892 on this. Finally, the Map-Cache also contains reachability 893 information about EIDs and RLOCs, and uses LISP reachability 894 information mechanisms to determine the reachability of RLOCs, see 895 Section 10 for the specific mechanisms. 897 7. Dealing with Large Encapsulated Packets 899 This section proposes two mechanisms to deal with packets that exceed 900 the path MTU between the ITR and ETR. 902 It is left to the implementor to decide if the stateless or stateful 903 mechanism SHOULD be implemented. Both or neither can be used, since 904 it is a local decision in the ITR regarding how to deal with MTU 905 issues, and sites can interoperate with differing mechanisms. 907 Both stateless and stateful mechanisms also apply to Re-encapsulating 908 and Recursive Tunneling, so any actions below referring to an ITR 909 also apply to a TE-ITR. 911 7.1. A Stateless Solution to MTU Handling 913 An ITR stateless solution to handle MTU issues is described as 914 follows: 916 1. Define H to be the size, in octets, of the outer header an ITR 917 prepends to a packet. This includes the UDP and LISP header 918 lengths. 920 2. Define L to be the size, in octets, of the maximum-sized packet 921 an ITR can send to an ETR without the need for the ITR or any 922 intermediate routers to fragment the packet. 924 3. Define an architectural constant S for the maximum size of a 925 packet, in octets, an ITR MUST receive from the source so the 926 effective MTU can be met. That is, L = S + H. 928 When an ITR receives a packet from a site-facing interface and adds H 929 octets worth of encapsulation to yield a packet size greater than L 930 octets (meaning the received packet size was greater than S octets 931 from the source), it resolves the MTU issue by first splitting the 932 original packet into 2 equal-sized fragments. A LISP header is then 933 prepended to each fragment. The size of the encapsulated fragments 934 is then (S/2 + H), which is less than the ITR's estimate of the path 935 MTU between the ITR and its correspondent ETR. 937 When an ETR receives encapsulated fragments, it treats them as two 938 individually encapsulated packets. It strips the LISP headers and 939 then forwards each fragment to the destination host of the 940 destination site. The two fragments are reassembled at the 941 destination host into the single IP datagram that was originated by 942 the source host. Note that reassembly can happen at the ETR if the 943 encapsulated packet was fragmented at or after the ITR. 945 This behavior is performed by the ITR when the source host originates 946 a packet with the 'DF' field of the IP header set to 0. When the 947 'DF' field of the IP header is set to 1, or the packet is an IPv6 948 packet originated by the source host, the ITR will drop the packet 949 when the size is greater than L and send an ICMP Unreachable/ 950 Fragmentation-Needed message to the source with a value of S, where S 951 is (L - H). 953 When the outer-header encapsulation uses an IPv4 header, an 954 implementation SHOULD set the DF bit to 1 so ETR fragment reassembly 955 can be avoided. An implementation MAY set the DF bit in such headers 956 to 0 if it has good reason to believe there are unresolvable path MTU 957 issues between the sending ITR and the receiving ETR. 959 This specification RECOMMENDS that L be defined as 1500. 961 7.2. A Stateful Solution to MTU Handling 963 An ITR stateful solution to handle MTU issues is described as follows 964 and was first introduced in [OPENLISP]: 966 1. The ITR will keep state of the effective MTU for each Locator per 967 Map-Cache entry. The effective MTU is what the core network can 968 deliver along the path between the ITR and ETR. 970 2. When an IPv6-encapsulated packet, or an IPv4-encapsulated packet 971 with the DF bit set to 1, exceeds what the core network can 972 deliver, one of the intermediate routers on the path will send an 973 ICMP Unreachable/Fragmentation-Needed message to the ITR. The 974 ITR will parse the ICMP message to determine which Locator is 975 affected by the effective MTU change and then record the new 976 effective MTU value in the Map-Cache entry. 978 3. When a packet is received by the ITR from a source inside of the 979 site and the size of the packet is greater than the effective MTU 980 stored with the Map-Cache entry associated with the destination 981 EID the packet is for, the ITR will send an ICMP Unreachable/ 982 Fragmentation-Needed message back to the source. The packet size 983 advertised by the ITR in the ICMP Unreachable/Fragmentation- 984 Needed message is the effective MTU minus the LISP encapsulation 985 length. 987 Even though this mechanism is stateful, it has advantages over the 988 stateless IP fragmentation mechanism, by not involving the 989 destination host with reassembly of ITR fragmented packets. 991 8. Using Virtualization and Segmentation with LISP 993 There are several cases where segregation is needed at the EID level. 994 For instance, this is the case for deployments containing overlapping 995 addresses, traffic isolation policies or multi-tenant virtualization. 996 For these and other scenarios where segregation is needed, Instance 997 IDs are used. 999 An Instance ID can be carried in a LISP-encapsulated packet. An ITR 1000 that prepends a LISP header will copy a 24-bit value used by the LISP 1001 router to uniquely identify the address space. The value is copied 1002 to the 'Instance ID' field of the LISP header, and the I-bit is set 1003 to 1. 1005 When an ETR decapsulates a packet, the Instance ID from the LISP 1006 header is used as a table identifier to locate the forwarding table 1007 to use for the inner destination EID lookup. 1009 For example, an 802.1Q VLAN tag or VPN identifier could be used as a 1010 24-bit Instance ID. See [I-D.ietf-lisp-vpn] for LISP VPN use-case 1011 details. 1013 The Instance ID that is stored in the mapping database when LISP-DDT 1014 [RFC8111] is used is 32 bits in length. That means the Control-Plane 1015 can store more instances than a given Data-Plane can use. Multiple 1016 Data-Planes can use the same 32-bit space as long as the low-order 24 1017 bits don't overlap among xTRs. 1019 9. Routing Locator Selection 1021 The Map-Cache contains the state used by ITRs and PITRs to 1022 encapsulate packets. When an ITR/PITR receives a packet from inside 1023 the LISP site to a destination outside of the site a longest-prefix 1024 match lookup of the EID is done to the Map-Cache (see Section 6). 1025 The lookup returns a single Locator-Set containing a list of RLOCs 1026 corresponding to the EID's topological location. Each RLOC in the 1027 Locator-Set is associated with a 'Priority' and 'Weight', this 1028 information is used to select the RLOC to encapsulate. 1030 The RLOC with the lowest 'Priority' is selected. An RLOC with 1031 'Priority' 255 means that MUST NOT be used for forwarding. When 1032 multiple RLOC have the same 'Priority' then the 'Weight' states how 1033 to load balance traffic among them. The value of the 'Weight' 1034 represents the relative weight of the total packets that match the 1035 maping entry. 1037 The following are different scenarios for choosing RLOCs and the 1038 controls that are available: 1040 o The server-side returns one RLOC. The client-side can only use 1041 one RLOC. The server-side has complete control of the selection. 1043 o The server-side returns a list of RLOCs where a subset of the list 1044 has the same best Priority. The client can only use the subset 1045 list according to the weighting assigned by the server-side. In 1046 this case, the server-side controls both the subset list and load- 1047 splitting across its members. The client-side can use RLOCs 1048 outside of the subset list if it determines that the subset list 1049 is unreachable (unless RLOCs are set to a Priority of 255). Some 1050 sharing of control exists: the server-side determines the 1051 destination RLOC list and load distribution while the client-side 1052 has the option of using alternatives to this list if RLOCs in the 1053 list are unreachable. 1055 o The server-side sets a Weight of zero for the RLOC subset list. 1056 In this case, the client-side can choose how the traffic load is 1057 spread across the subset list. Control is shared by the server- 1058 side determining the list and the client-side determining load 1059 distribution. Again, the client can use alternative RLOCs if the 1060 server-provided list of RLOCs is unreachable. 1062 o Either side (more likely the server-side ETR) decides not to send 1063 a Map-Request. For example, if the server-side ETR does not send 1064 Map-Requests, it gleans RLOCs from the client-side ITR, giving the 1065 client-side ITR responsibility for bidirectional RLOC reachability 1066 and preferability. Server-side ETR gleaning of the client-side 1067 ITR RLOC is done by caching the inner-header source EID and the 1068 outer-header source RLOC of received packets. The client-side ITR 1069 controls how traffic is returned and can alternate using an outer- 1070 header source RLOC, which then can be added to the list the 1071 server-side ETR uses to return traffic. Since no Priority or 1072 Weights are provided using this method, the server-side ETR MUST 1073 assume that each client-side ITR RLOC uses the same best Priority 1074 with a Weight of zero. In addition, since EID-Prefix encoding 1075 cannot be conveyed in data packets, the EID-to-RLOC Cache on 1076 Tunnel Routers can grow to be very large. 1078 Alternatively, RLOC information MAY be gleaned from received tunneled 1079 packets or EID-to-RLOC Map-Request messages. A "gleaned" Map-Cache 1080 entry, one learned from the source RLOC of a received encapsulated 1081 packet, is only stored and used for a few seconds, pending 1082 verification. Verification is performed by sending a Map-Request to 1083 the source EID (the inner-header IP source address) of the received 1084 encapsulated packet. A reply to this "verifying Map-Request" is used 1085 to fully populate the Map-Cache entry for the "gleaned" EID and is 1086 stored and used for the time indicated from the 'TTL' field of a 1087 received Map-Reply. When a verified Map-Cache entry is stored, data 1088 gleaning no longer occurs for subsequent packets that have a source 1089 EID that matches the EID-Prefix of the verified entry. This 1090 "gleaning" mechanism is OPTIONAL, refer to Section 16 for security 1091 issues regarding this mechanism. 1093 RLOCs that appear in EID-to-RLOC Map-Reply messages are assumed to be 1094 reachable when the R-bit for the Locator record is set to 1. When 1095 the R-bit is set to 0, an ITR or PITR MUST NOT encapsulate to the 1096 RLOC. Neither the information contained in a Map-Reply nor that 1097 stored in the mapping database system provides reachability 1098 information for RLOCs. Note that reachability is not part of the 1099 mapping system and is determined using one or more of the Routing 1100 Locator reachability algorithms described in the next section. 1102 10. Routing Locator Reachability 1104 Several Data-Plane mechanisms for determining RLOC reachability are 1105 currently defined. Please note that additional Control-Plane based 1106 reachability mechanisms are defined in [I-D.ietf-lisp-rfc6833bis]. 1108 1. An ETR MAY examine the Locator-Status-Bits in the LISP header of 1109 an encapsulated data packet received from an ITR. If the ETR is 1110 also acting as an ITR and has traffic to return to the original 1111 ITR site, it can use this status information to help select an 1112 RLOC. 1114 2. When an ETR receives an encapsulated packet from an ITR, the 1115 source RLOC from the outer header of the packet is likely up. 1117 3. An ITR/ETR pair can use the 'Echo-Noncing' Locator reachability 1118 algorithms described in this section. 1120 When determining Locator up/down reachability by examining the 1121 Locator-Status-Bits from the LISP-encapsulated data packet, an ETR 1122 will receive up-to-date status from an encapsulating ITR about 1123 reachability for all ETRs at the site. CE-based ITRs at the source 1124 site can determine reachability relative to each other using the site 1125 IGP as follows: 1127 o Under normal circumstances, each ITR will advertise a default 1128 route into the site IGP. 1130 o If an ITR fails or if the upstream link to its PE fails, its 1131 default route will either time out or be withdrawn. 1133 Each ITR can thus observe the presence or lack of a default route 1134 originated by the others to determine the Locator-Status-Bits it sets 1135 for them. 1137 When ITRs at the site are not deployed in CE routers, the IGP can 1138 still be used to determine the reachability of Locators, provided 1139 they are injected into the IGP. This is typically done when a /32 1140 address is configured on a loopback interface. 1142 RLOCs listed in a Map-Reply are numbered with ordinals 0 to n-1. The 1143 Locator-Status-Bits in a LISP-encapsulated packet are numbered from 0 1144 to n-1 starting with the least significant bit. For example, if an 1145 RLOC listed in the 3rd position of the Map-Reply goes down (ordinal 1146 value 2), then all ITRs at the site will clear the 3rd least 1147 significant bit (xxxx x0xx) of the 'Locator-Status-Bits' field for 1148 the packets they encapsulate. 1150 When an ETR decapsulates a packet, it will check for any change in 1151 the 'Locator-Status-Bits' field. When a bit goes from 1 to 0, the 1152 ETR, if acting also as an ITR, will refrain from encapsulating 1153 packets to an RLOC that is indicated as down. It will only resume 1154 using that RLOC if the corresponding Locator-Status-Bit returns to a 1155 value of 1. Locator-Status-Bits are associated with a Locator-Set 1156 per EID-Prefix. Therefore, when a Locator becomes unreachable, the 1157 Locator-Status-Bit that corresponds to that Locator's position in the 1158 list returned by the last Map-Reply will be set to zero for that 1159 particular EID-Prefix. Refer to Section 16 for security related 1160 issues regarding Locator-Status-Bits. 1162 When an ETR decapsulates a packet, it knows that it is reachable from 1163 the encapsulating ITR because that is how the packet arrived. In 1164 most cases, the ETR can also reach the ITR but cannot assume this to 1165 be true, due to the possibility of path asymmetry. In the presence 1166 of unidirectional traffic flow from an ITR to an ETR, the ITR SHOULD 1167 NOT use the lack of return traffic as an indication that the ETR is 1168 unreachable. Instead, it MUST use an alternate mechanism to 1169 determine reachability. 1171 10.1. Echo Nonce Algorithm 1173 When data flows bidirectionally between Locators from different 1174 sites, a Data-Plane mechanism called "nonce echoing" can be used to 1175 determine reachability between an ITR and ETR. When an ITR wants to 1176 solicit a nonce echo, it sets the N- and E-bits and places a 24-bit 1177 nonce [RFC4086] in the LISP header of the next encapsulated data 1178 packet. 1180 When this packet is received by the ETR, the encapsulated packet is 1181 forwarded as normal. When the ETR next sends a data packet to the 1182 ITR, it includes the nonce received earlier with the N-bit set and 1183 E-bit cleared. The ITR sees this "echoed nonce" and knows that the 1184 path to and from the ETR is up. 1186 The ITR will set the E-bit and N-bit for every packet it sends while 1187 in the echo-nonce-request state. The time the ITR waits to process 1188 the echoed nonce before it determines the path is unreachable is 1189 variable and is a choice left for the implementation. 1191 If the ITR is receiving packets from the ETR but does not see the 1192 nonce echoed while being in the echo-nonce-request state, then the 1193 path to the ETR is unreachable. This decision MAY be overridden by 1194 other Locator reachability algorithms. Once the ITR determines that 1195 the path to the ETR is down, it can switch to another Locator for 1196 that EID-Prefix. 1198 Note that "ITR" and "ETR" are relative terms here. Both devices MUST 1199 be implementing both ITR and ETR functionality for the echo nonce 1200 mechanism to operate. 1202 The ITR and ETR MAY both go into the echo-nonce-request state at the 1203 same time. The number of packets sent or the time during which echo 1204 nonce requests are sent is an implementation-specific setting. 1205 However, when an ITR is in the echo-nonce-request state, it can echo 1206 the ETR's nonce in the next set of packets that it encapsulates and 1207 subsequently continue sending echo-nonce-request packets. 1209 This mechanism does not completely solve the forward path 1210 reachability problem, as traffic may be unidirectional. That is, the 1211 ETR receiving traffic at a site MAY not be the same device as an ITR 1212 that transmits traffic from that site, or the site-to-site traffic is 1213 unidirectional so there is no ITR returning traffic. 1215 The echo-nonce algorithm is bilateral. That is, if one side sets the 1216 E-bit and the other side is not enabled for echo-noncing, then the 1217 echoing of the nonce does not occur and the requesting side may 1218 erroneously consider the Locator unreachable. An ITR SHOULD only set 1219 the E-bit in an encapsulated data packet when it knows the ETR is 1220 enabled for echo-noncing. This is conveyed by the E-bit in the RLOC- 1221 probe Map-Reply message. 1223 11. EID Reachability within a LISP Site 1225 A site MAY be multihomed using two or more ETRs. The hosts and 1226 infrastructure within a site will be addressed using one or more EID- 1227 Prefixes that are mapped to the RLOCs of the relevant ETRs in the 1228 mapping system. One possible failure mode is for an ETR to lose 1229 reachability to one or more of the EID-Prefixes within its own site. 1230 When this occurs when the ETR sends Map-Replies, it can clear the 1231 R-bit associated with its own Locator. And when the ETR is also an 1232 ITR, it can clear its Locator-Status-Bit in the encapsulation data 1233 header. 1235 It is recognized that there are no simple solutions to the site 1236 partitioning problem because it is hard to know which part of the 1237 EID-Prefix range is partitioned and which Locators can reach any sub- 1238 ranges of the EID-Prefixes. Note that this is not a new problem 1239 introduced by the LISP architecture. The problem exists today when a 1240 multihomed site uses BGP to advertise its reachability upstream. 1242 12. Routing Locator Hashing 1244 When an ETR provides an EID-to-RLOC mapping in a Map-Reply message 1245 that is stored in the Map-Cache of a requesting ITR, the Locator-Set 1246 for the EID-Prefix MAY contain different Priority and Weight values 1247 for each locator address. When more than one best Priority Locator 1248 exists, the ITR can decide how to load-share traffic against the 1249 corresponding Locators. 1251 The following hash algorithm MAY be used by an ITR to select a 1252 Locator for a packet destined to an EID for the EID-to-RLOC mapping: 1254 1. Either a source and destination address hash or the traditional 1255 5-tuple hash can be used. The traditional 5-tuple hash includes 1256 the source and destination addresses; source and destination TCP, 1257 UDP, or Stream Control Transmission Protocol (SCTP) port numbers; 1258 and the IP protocol number field or IPv6 next-protocol fields of 1259 a packet that a host originates from within a LISP site. When a 1260 packet is not a TCP, UDP, or SCTP packet, the source and 1261 destination addresses only from the header are used to compute 1262 the hash. 1264 2. Take the hash value and divide it by the number of Locators 1265 stored in the Locator-Set for the EID-to-RLOC mapping. 1267 3. The remainder will yield a value of 0 to "number of Locators 1268 minus 1". Use the remainder to select the Locator in the 1269 Locator-Set. 1271 Note that when a packet is LISP encapsulated, the source port number 1272 in the outer UDP header needs to be set. Selecting a hashed value 1273 allows core routers that are attached to Link Aggregation Groups 1274 (LAGs) to load-split the encapsulated packets across member links of 1275 such LAGs. Otherwise, core routers would see a single flow, since 1276 packets have a source address of the ITR, for packets that are 1277 originated by different EIDs at the source site. A suggested setting 1278 for the source port number computed by an ITR is a 5-tuple hash 1279 function on the inner header, as described above. 1281 Many core router implementations use a 5-tuple hash to decide how to 1282 balance packet load across members of a LAG. The 5-tuple hash 1283 includes the source and destination addresses of the packet and the 1284 source and destination ports when the protocol number in the packet 1285 is TCP or UDP. For this reason, UDP encoding is used for LISP 1286 encapsulation. 1288 13. Changing the Contents of EID-to-RLOC Mappings 1290 Since the LISP architecture uses a caching scheme to retrieve and 1291 store EID-to-RLOC mappings, the only way an ITR can get a more up-to- 1292 date mapping is to re-request the mapping. However, the ITRs do not 1293 know when the mappings change, and the ETRs do not keep track of 1294 which ITRs requested its mappings. For scalability reasons, it is 1295 desirable to maintain this approach but need to provide a way for 1296 ETRs to change their mappings and inform the sites that are currently 1297 communicating with the ETR site using such mappings. 1299 This section defines a Data-Plane mechanism for updating EID-to-RLOC 1300 mappings. Additionally, the Solicit-Map Request (SMR) Control-Plane 1301 updating mechanism is specified in [I-D.ietf-lisp-rfc6833bis]. 1303 When adding a new Locator record in lexicographic order to the end of 1304 a Locator-Set, it is easy to update mappings. We assume that new 1305 mappings will maintain the same Locator ordering as the old mapping 1306 but will just have new Locators appended to the end of the list. So, 1307 some ITRs can have a new mapping while other ITRs have only an old 1308 mapping that is used until they time out. When an ITR has only an 1309 old mapping but detects bits set in the Locator-Status-Bits that 1310 correspond to Locators beyond the list it has cached, it simply 1311 ignores them. However, this can only happen for locator addresses 1312 that are lexicographically greater than the locator addresses in the 1313 existing Locator-Set. 1315 When a Locator record is inserted in the middle of a Locator-Set, to 1316 maintain lexicographic order, SMR procedure 1317 [I-D.ietf-lisp-rfc6833bis] is used to inform ITRs and PITRs of the 1318 new Locator-Status-Bit mappings. 1320 When a Locator record is removed from a Locator-Set, ITRs that have 1321 the mapping cached will not use the removed Locator because the xTRs 1322 will set the Locator-Status-Bit to 0. So, even if the Locator is in 1323 the list, it will not be used. For new mapping requests, the xTRs 1324 can set the Locator AFI to 0 (indicating an unspecified address), as 1325 well as setting the corresponding Locator-Status-Bit to 0. This 1326 forces ITRs with old or new mappings to avoid using the removed 1327 Locator. 1329 If many changes occur to a mapping over a long period of time, one 1330 will find empty record slots in the middle of the Locator-Set and new 1331 records appended to the Locator-Set. At some point, it would be 1332 useful to compact the Locator-Set so the Locator-Status-Bit settings 1333 can be efficiently packed. 1335 We propose here a Data-Plane mechanism (Map-Versioning) to update the 1336 contents of EID-to-RLOC mappings. Please note that in addition the 1337 Solicit-Map Request (specified in [I-D.ietf-lisp-rfc6833bis]) is a 1338 Control-Plane mechanisms that can be used to update EID-to-RLOC 1339 mappings. 1341 13.1. Database Map-Versioning 1343 When there is unidirectional packet flow between an ITR and ETR, and 1344 the EID-to-RLOC mappings change on the ETR, it needs to inform the 1345 ITR so encapsulation to a removed Locator can stop and can instead be 1346 started to a new Locator in the Locator-Set. 1348 An ETR, when it sends Map-Reply messages, conveys its own Map-Version 1349 Number. This is known as the Destination Map-Version Number. ITRs 1350 include the Destination Map-Version Number in packets they 1351 encapsulate to the site. When an ETR decapsulates a packet and 1352 detects that the Destination Map-Version Number is less than the 1353 current version for its mapping, the SMR procedure described in 1354 [I-D.ietf-lisp-rfc6833bis] occurs. 1356 An ITR, when it encapsulates packets to ETRs, can convey its own Map- 1357 Version Number. This is known as the Source Map-Version Number. 1358 When an ETR decapsulates a packet and detects that the Source Map- 1359 Version Number is greater than the last Map-Version Number sent in a 1360 Map-Reply from the ITR's site, the ETR will send a Map-Request to one 1361 of the ETRs for the source site. 1363 A Map-Version Number is used as a sequence number per EID-Prefix, so 1364 values that are greater are considered to be more recent. A value of 1365 0 for the Source Map-Version Number or the Destination Map-Version 1366 Number conveys no versioning information, and an ITR does no 1367 comparison with previously received Map-Version Numbers. 1369 A Map-Version Number can be included in Map-Register messages as 1370 well. This is a good way for the Map-Server to assure that all ETRs 1371 for a site registering to it will be synchronized according to Map- 1372 Version Number. 1374 See [I-D.ietf-lisp-6834bis] for a more detailed analysis and 1375 description of Database Map-Versioning. 1377 14. Multicast Considerations 1379 A multicast group address, as defined in the original Internet 1380 architecture, is an identifier of a grouping of topologically 1381 independent receiver host locations. The address encoding itself 1382 does not determine the location of the receiver(s). The multicast 1383 routing protocol, and the network-based state the protocol creates, 1384 determine where the receivers are located. 1386 In the context of LISP, a multicast group address is both an EID and 1387 a Routing Locator. Therefore, no specific semantic or action needs 1388 to be taken for a destination address, as it would appear in an IP 1389 header. Therefore, a group address that appears in an inner IP 1390 header built by a source host will be used as the destination EID. 1391 The outer IP header (the destination Routing Locator address), 1392 prepended by a LISP router, can use the same group address as the 1393 destination Routing Locator, use a multicast or unicast Routing 1394 Locator obtained from a Mapping System lookup, or use other means to 1395 determine the group address mapping. 1397 With respect to the source Routing Locator address, the ITR prepends 1398 its own IP address as the source address of the outer IP header. 1399 Just like it would if the destination EID was a unicast address. 1400 This source Routing Locator address, like any other Routing Locator 1401 address, MUST be globally routable. 1403 There are two approaches for LISP-Multicast, one that uses native 1404 multicast routing in the underlay with no support from the Mapping 1405 System and the other that uses only unicast routing in the underlay 1406 with support from the Mapping System. See [RFC6831] and [RFC8378], 1407 respectively, for details. Details for LISP-Multicast and 1408 interworking with non-LISP sites are described in [RFC6831] and 1409 [RFC6832]. 1411 15. Router Performance Considerations 1413 LISP is designed to be very "hardware-based forwarding friendly". A 1414 few implementation techniques can be used to incrementally implement 1415 LISP: 1417 o When a tunnel-encapsulated packet is received by an ETR, the outer 1418 destination address may not be the address of the router. This 1419 makes it challenging for the control plane to get packets from the 1420 hardware. This may be mitigated by creating special Forwarding 1421 Information Base (FIB) entries for the EID-Prefixes of EIDs served 1422 by the ETR (those for which the router provides an RLOC 1423 translation). These FIB entries are marked with a flag indicating 1424 that Control-Plane processing SHOULD be performed. The forwarding 1425 logic of testing for particular IP protocol number values is not 1426 necessary. There are a few proven cases where no changes to 1427 existing deployed hardware were needed to support the LISP Data- 1428 Plane. 1430 o On an ITR, prepending a new IP header consists of adding more 1431 octets to a MAC rewrite string and prepending the string as part 1432 of the outgoing encapsulation procedure. Routers that support 1433 Generic Routing Encapsulation (GRE) tunneling [RFC2784] or 6to4 1434 tunneling [RFC3056] may already support this action. 1436 o A packet's source address or interface the packet was received on 1437 can be used to select VRF (Virtual Routing/Forwarding). The VRF's 1438 routing table can be used to find EID-to-RLOC mappings. 1440 For performance issues related to Map-Cache management, see 1441 Section 16. 1443 16. Security Considerations 1445 Security considerations for LISP are discussed in [RFC7833]. 1447 A complete LISP threat analysis can be found in [RFC7835], in what 1448 follows we provide a summary. 1450 The optional mechanisms of gleaning is offered to directly obtain a 1451 mapping from the LISP encapsulated packets. Specifically, an xTR can 1452 learn the EID-to-RLOC mapping by inspecting the source RLOC and 1453 source EID of an encapsulated packet, and insert this new mapping 1454 into its Map-Cache. An off-path attacker can spoof the source EID 1455 address to divert the traffic sent to the victim's spoofed EID. If 1456 the attacker spoofs the source RLOC, it can mount a DoS attack by 1457 redirecting traffic to the spoofed victim's RLOC, potentially 1458 overloading it. 1460 The LISP Data-Plane defines several mechanisms to monitor RLOC Data- 1461 Plane reachability, in this context Locator-Status Bits, Nonce- 1462 Present and Echo-Nonce bits of the LISP encapsulation header can be 1463 manipulated by an attacker to mount a DoS attack. An off-path 1464 attacker able to spoof the RLOC of a victim's xTR can manipulate such 1465 mechanisms to declare a set of RLOCs unreachable. This can be used 1466 also, for instance, to declare only one RLOC reachable with the aim 1467 of overload it. 1469 Map-Versioning is a Data-Plane mechanism used to signal a peering xTR 1470 that a local EID-to-RLOC mapping has been updated, so that the 1471 peering xTR uses LISP Control-Plane signaling message to retrieve a 1472 fresh mapping. This can be used by an attacker to forge the map- 1473 versioning field of a LISP encapsulated header and force an excessive 1474 amount of signaling between xTRs that may overload them. 1476 Most of the attack vectors can be mitigated with careful deployment 1477 and configuration, information learned opportunistically (such as LSB 1478 or gleaning) SHOULD be verified with other reachability mechanisms. 1479 In addition, systematic rate-limitation and filtering is an effective 1480 technique to mitigate attacks that aim to overload the Control-Plane. 1482 17. Network Management Considerations 1484 Considerations for network management tools exist so the LISP 1485 protocol suite can be operationally managed. These mechanisms can be 1486 found in [RFC7052] and [RFC6835]. 1488 18. IANA Considerations 1490 This section provides guidance to the Internet Assigned Numbers 1491 Authority (IANA) regarding registration of values related to this 1492 Data-Plane LISP specification, in accordance with BCP 26 [RFC8126]. 1494 18.1. LISP UDP Port Numbers 1496 The IANA registry has allocated UDP port number 4341 for the LISP 1497 Data-Plane. IANA has updated the description for UDP port 4341 as 1498 follows: 1500 lisp-data 4341 udp LISP Data Packets 1502 19. References 1504 19.1. Normative References 1506 [I-D.ietf-lisp-6834bis] 1507 Iannone, L., Saucez, D., and O. Bonaventure, "Locator/ID 1508 Separation Protocol (LISP) Map-Versioning", draft-ietf- 1509 lisp-6834bis-00 (work in progress), July 2018. 1511 [I-D.ietf-lisp-rfc6833bis] 1512 Fuller, V., Farinacci, D., and A. Cabellos-Aparicio, 1513 "Locator/ID Separation Protocol (LISP) Control-Plane", 1514 draft-ietf-lisp-rfc6833bis-10 (work in progress), March 1515 2018. 1517 [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, 1518 DOI 10.17487/RFC0768, August 1980, 1519 . 1521 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 1522 DOI 10.17487/RFC0791, September 1981, 1523 . 1525 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 1526 "Definition of the Differentiated Services Field (DS 1527 Field) in the IPv4 and IPv6 Headers", RFC 2474, 1528 DOI 10.17487/RFC2474, December 1998, 1529 . 1531 [RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition 1532 of Explicit Congestion Notification (ECN) to IP", 1533 RFC 3168, DOI 10.17487/RFC3168, September 2001, 1534 . 1536 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 1537 (IPv6) Specification", STD 86, RFC 8200, 1538 DOI 10.17487/RFC8200, July 2017, 1539 . 1541 19.2. Informative References 1543 [AFN] IANA, "Address Family Numbers", August 2016, 1544 . 1546 [CHIAPPA] Chiappa, J., "Endpoints and Endpoint names: A Proposed", 1547 1999, 1548 . 1550 [I-D.ietf-lisp-introduction] 1551 Cabellos-Aparicio, A. and D. Saucez, "An Architectural 1552 Introduction to the Locator/ID Separation Protocol 1553 (LISP)", draft-ietf-lisp-introduction-13 (work in 1554 progress), April 2015. 1556 [I-D.ietf-lisp-vpn] 1557 Moreno, V. and D. Farinacci, "LISP Virtual Private 1558 Networks (VPNs)", draft-ietf-lisp-vpn-02 (work in 1559 progress), May 2018. 1561 [OPENLISP] 1562 Iannone, L., Saucez, D., and O. Bonaventure, "OpenLISP 1563 Implementation Report", Work in Progress, July 2008. 1565 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 1566 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 1567 . 1569 [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G., 1570 and E. Lear, "Address Allocation for Private Internets", 1571 BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996, 1572 . 1574 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1575 Requirement Levels", BCP 14, RFC 2119, 1576 DOI 10.17487/RFC2119, March 1997, 1577 . 1579 [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. 1580 Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, 1581 DOI 10.17487/RFC2784, March 2000, 1582 . 1584 [RFC3056] Carpenter, B. and K. Moore, "Connection of IPv6 Domains 1585 via IPv4 Clouds", RFC 3056, DOI 10.17487/RFC3056, February 1586 2001, . 1588 [RFC3232] Reynolds, J., Ed., "Assigned Numbers: RFC 1700 is Replaced 1589 by an On-line Database", RFC 3232, DOI 10.17487/RFC3232, 1590 January 2002, . 1592 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 1593 A., Peterson, J., Sparks, R., Handley, M., and E. 1594 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 1595 DOI 10.17487/RFC3261, June 2002, 1596 . 1598 [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, 1599 "Randomness Requirements for Security", BCP 106, RFC 4086, 1600 DOI 10.17487/RFC4086, June 2005, 1601 . 1603 [RFC4984] Meyer, D., Ed., Zhang, L., Ed., and K. Fall, Ed., "Report 1604 from the IAB Workshop on Routing and Addressing", 1605 RFC 4984, DOI 10.17487/RFC4984, September 2007, 1606 . 1608 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 1609 Locator/ID Separation Protocol (LISP) for Multicast 1610 Environments", RFC 6831, DOI 10.17487/RFC6831, January 1611 2013, . 1613 [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 1614 "Interworking between Locator/ID Separation Protocol 1615 (LISP) and Non-LISP Sites", RFC 6832, 1616 DOI 10.17487/RFC6832, January 2013, 1617 . 1619 [RFC6835] Farinacci, D. and D. Meyer, "The Locator/ID Separation 1620 Protocol Internet Groper (LIG)", RFC 6835, 1621 DOI 10.17487/RFC6835, January 2013, 1622 . 1624 [RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and 1625 UDP Checksums for Tunneled Packets", RFC 6935, 1626 DOI 10.17487/RFC6935, April 2013, 1627 . 1629 [RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement 1630 for the Use of IPv6 UDP Datagrams with Zero Checksums", 1631 RFC 6936, DOI 10.17487/RFC6936, April 2013, 1632 . 1634 [RFC7052] Schudel, G., Jain, A., and V. Moreno, "Locator/ID 1635 Separation Protocol (LISP) MIB", RFC 7052, 1636 DOI 10.17487/RFC7052, October 2013, 1637 . 1639 [RFC7215] Jakab, L., Cabellos-Aparicio, A., Coras, F., Domingo- 1640 Pascual, J., and D. Lewis, "Locator/Identifier Separation 1641 Protocol (LISP) Network Element Deployment 1642 Considerations", RFC 7215, DOI 10.17487/RFC7215, April 1643 2014, . 1645 [RFC7833] Howlett, J., Hartman, S., and A. Perez-Mendez, Ed., "A 1646 RADIUS Attribute, Binding, Profiles, Name Identifier 1647 Format, and Confirmation Methods for the Security 1648 Assertion Markup Language (SAML)", RFC 7833, 1649 DOI 10.17487/RFC7833, May 2016, 1650 . 1652 [RFC7835] Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID 1653 Separation Protocol (LISP) Threat Analysis", RFC 7835, 1654 DOI 10.17487/RFC7835, April 2016, 1655 . 1657 [RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 1658 Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060, 1659 February 2017, . 1661 [RFC8061] Farinacci, D. and B. Weis, "Locator/ID Separation Protocol 1662 (LISP) Data-Plane Confidentiality", RFC 8061, 1663 DOI 10.17487/RFC8061, February 2017, 1664 . 1666 [RFC8111] Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A. 1667 Smirnov, "Locator/ID Separation Protocol Delegated 1668 Database Tree (LISP-DDT)", RFC 8111, DOI 10.17487/RFC8111, 1669 May 2017, . 1671 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1672 Writing an IANA Considerations Section in RFCs", BCP 26, 1673 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1674 . 1676 [RFC8378] Moreno, V. and D. Farinacci, "Signal-Free Locator/ID 1677 Separation Protocol (LISP) Multicast", RFC 8378, 1678 DOI 10.17487/RFC8378, May 2018, 1679 . 1681 Appendix A. Acknowledgments 1683 An initial thank you goes to Dave Oran for planting the seeds for the 1684 initial ideas for LISP. His consultation continues to provide value 1685 to the LISP authors. 1687 A special and appreciative thank you goes to Noel Chiappa for 1688 providing architectural impetus over the past decades on separation 1689 of location and identity, as well as detailed reviews of the LISP 1690 architecture and documents, coupled with enthusiasm for making LISP a 1691 practical and incremental transition for the Internet. 1693 The authors would like to gratefully acknowledge many people who have 1694 contributed discussions and ideas to the making of this proposal. 1695 They include Scott Brim, Andrew Partan, John Zwiebel, Jason Schiller, 1696 Lixia Zhang, Dorian Kim, Peter Schoenmaker, Vijay Gill, Geoff Huston, 1697 David Conrad, Mark Handley, Ron Bonica, Ted Seely, Mark Townsley, 1698 Chris Morrow, Brian Weis, Dave McGrew, Peter Lothberg, Dave Thaler, 1699 Eliot Lear, Shane Amante, Ved Kafle, Olivier Bonaventure, Luigi 1700 Iannone, Robin Whittle, Brian Carpenter, Joel Halpern, Terry 1701 Manderson, Roger Jorgensen, Ran Atkinson, Stig Venaas, Iljitsch van 1702 Beijnum, Roland Bless, Dana Blair, Bill Lynch, Marc Woolward, Damien 1703 Saucez, Damian Lezama, Attilla De Groot, Parantap Lahiri, David 1704 Black, Roque Gagliano, Isidor Kouvelas, Jesper Skriver, Fred Templin, 1705 Margaret Wasserman, Sam Hartman, Michael Hofling, Pedro Marques, Jari 1706 Arkko, Gregg Schudel, Srinivas Subramanian, Amit Jain, Xu Xiaohu, 1707 Dhirendra Trivedi, Yakov Rekhter, John Scudder, John Drake, Dimitri 1708 Papadimitriou, Ross Callon, Selina Heimlich, Job Snijders, Vina 1709 Ermagan, Fabio Maino, Victor Moreno, Chris White, Clarence Filsfils, 1710 Alia Atlas, Florin Coras and Alberto Rodriguez. 1712 This work originated in the Routing Research Group (RRG) of the IRTF. 1713 An individual submission was converted into the IETF LISP working 1714 group document that became this RFC. 1716 The LISP working group would like to give a special thanks to Jari 1717 Arkko, the Internet Area AD at the time that the set of LISP 1718 documents were being prepared for IESG last call, and for his 1719 meticulous reviews and detailed commentaries on the 7 working group 1720 last call documents progressing toward standards-track RFCs. 1722 Appendix B. Document Change Log 1724 [RFC Editor: Please delete this section on publication as RFC.] 1726 B.1. Changes to draft-ietf-lisp-rfc6830bis-14 1728 o Posted July 2018 IETF week. 1730 o Put obsolete of RFC 6830 in Intro section in addition to abstract. 1732 B.2. Changes to draft-ietf-lisp-rfc6830bis-13 1734 o Posted July 2018. 1736 o Fixed Luigi editorial comments to ready draft for RFC status. 1738 B.3. Changes to draft-ietf-lisp-rfc6830bis-12 1740 o Posted March IETF Week 2018. 1742 o Clarified that a new nonce is required per RLOC. 1744 o Removed 'Clock Sweep' section. This text must be placed in a new 1745 OAM document. 1747 o Some references changed from normative to informative 1749 B.4. Changes to draft-ietf-lisp-rfc6830bis-11 1751 o Posted March 2018. 1753 o Removed sections 16, 17 and 18 (Mobility, Deployment and 1754 Traceroute considerations). This text must be placed in a new OAM 1755 document. 1757 B.5. Changes to draft-ietf-lisp-rfc6830bis-10 1759 o Posted March 2018. 1761 o Updated section 'Router Locator Selection' stating that the Data- 1762 Plane MUST follow what's stored in the Map-Cache (priorities and 1763 weights). 1765 o Section 'Routing Locator Reachability': Removed bullet point 2 1766 (ICMP Network/Host Unreachable),3 (hints from BGP),4 (ICMP Port 1767 Unreachable),5 (receive a Map-Reply as a response) and RLOC 1768 probing 1770 o Removed 'Solicit-Map Request'. 1772 B.6. Changes to draft-ietf-lisp-rfc6830bis-09 1774 o Posted January 2018. 1776 o Add more details in section 5.3 about DSCP processing during 1777 encapsulation and decapsulation. 1779 o Added clarity to definitions in the Definition of Terms section 1780 from various commenters. 1782 o Removed PA and PI definitions from Definition of Terms section. 1784 o More editorial changes. 1786 o Removed 4342 from IANA section and move to RFC6833 IANA section. 1788 B.7. Changes to draft-ietf-lisp-rfc6830bis-08 1790 o Posted January 2018. 1792 o Remove references to research work for any protocol mechanisms. 1794 o Document scanned to make sure it is RFC 2119 compliant. 1796 o Made changes to reflect comments from document WG shepherd Luigi 1797 Iannone. 1799 o Ran IDNITs on the document. 1801 B.8. Changes to draft-ietf-lisp-rfc6830bis-07 1803 o Posted November 2017. 1805 o Rephrase how Instance-IDs are used and don't refer to [RFC1918] 1806 addresses. 1808 B.9. Changes to draft-ietf-lisp-rfc6830bis-06 1810 o Posted October 2017. 1812 o Put RTR definition before it is used. 1814 o Rename references that are now working group drafts. 1816 o Remove "EIDs MUST NOT be used as used by a host to refer to other 1817 hosts. Note that EID blocks MAY LISP RLOCs". 1819 o Indicate what address-family can appear in data packets. 1821 o ETRs may, rather than will, be the ones to send Map-Replies. 1823 o Recommend, rather than mandate, max encapsulation headers to 2. 1825 o Reference VPN draft when introducing Instance-ID. 1827 o Indicate that SMRs can be sent when ITR/ETR are in the same node. 1829 o Clarify when private addreses can be used. 1831 B.10. Changes to draft-ietf-lisp-rfc6830bis-05 1833 o Posted August 2017. 1835 o Make it clear that a Reencapsulating Tunnel Router is an RTR. 1837 B.11. Changes to draft-ietf-lisp-rfc6830bis-04 1839 o Posted July 2017. 1841 o Changed reference of IPv6 RFC2460 to RFC8200. 1843 o Indicate that the applicability statement for UDP zero checksums 1844 over IPv6 adheres to RFC6936. 1846 B.12. Changes to draft-ietf-lisp-rfc6830bis-03 1848 o Posted May 2017. 1850 o Move the control-plane related codepoints in the IANA 1851 Considerations section to RFC6833bis. 1853 B.13. Changes to draft-ietf-lisp-rfc6830bis-02 1855 o Posted April 2017. 1857 o Reflect some editorial comments from Damien Sausez. 1859 B.14. Changes to draft-ietf-lisp-rfc6830bis-01 1861 o Posted March 2017. 1863 o Include references to new RFCs published. 1865 o Change references from RFC6833 to RFC6833bis. 1867 o Clarified LCAF text in the IANA section. 1869 o Remove references to "experimental". 1871 B.15. Changes to draft-ietf-lisp-rfc6830bis-00 1873 o Posted December 2016. 1875 o Created working group document from draft-farinacci-lisp 1876 -rfc6830-00 individual submission. No other changes made. 1878 Authors' Addresses 1880 Dino Farinacci 1881 Cisco Systems 1882 Tasman Drive 1883 San Jose, CA 95134 1884 USA 1886 EMail: farinacci@gmail.com 1888 Vince Fuller 1889 Cisco Systems 1890 Tasman Drive 1891 San Jose, CA 95134 1892 USA 1894 EMail: vince.fuller@gmail.com 1896 Dave Meyer 1897 Cisco Systems 1898 170 Tasman Drive 1899 San Jose, CA 1900 USA 1902 EMail: dmm@1-4-5.net 1904 Darrel Lewis 1905 Cisco Systems 1906 170 Tasman Drive 1907 San Jose, CA 1908 USA 1910 EMail: darlewis@cisco.com 1911 Albert Cabellos 1912 UPC/BarcelonaTech 1913 Campus Nord, C. Jordi Girona 1-3 1914 Barcelona, Catalunya 1915 Spain 1917 EMail: acabello@ac.upc.edu