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Checking references for intended status: Informational ---------------------------------------------------------------------------- ** Obsolete normative reference: RFC 6830 (Obsoleted by RFC 9300, RFC 9301) ** Obsolete normative reference: RFC 6833 (Obsoleted by RFC 9301) ** Obsolete normative reference: RFC 6834 (Obsoleted by RFC 9302) == Outdated reference: A later version (-09) exists of draft-ietf-lisp-ddt-02 == Outdated reference: A later version (-22) exists of draft-ietf-lisp-lcaf-07 == Outdated reference: A later version (-29) exists of draft-ietf-lisp-sec-07 == Outdated reference: A later version (-15) exists of draft-ietf-lisp-threats-11 Summary: 3 errors (**), 0 flaws (~~), 5 warnings (==), 1 comment (--).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 A. Cabellos 3 Internet-Draft UPC-BarcelonaTech 4 Intended status: Informational D. Saucez (Ed.) 5 Expires: August 13, 2015 INRIA 6 February 9, 2015 8 An Architectural Introduction to the Locator/ID Separation Protocol 9 (LISP) 10 draft-ietf-lisp-introduction-11.txt 12 Abstract 14 This document describes the architecture of the Locator/ID Separation 15 Protocol (LISP), making it easier to read the rest of the LISP 16 specifications and providing a basis for discussion about the details 17 of the LISP protocols. This document is used for introductory 18 purposes, more details can be found in RFC6830, the protocol 19 specification. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on August 13, 2015. 38 Copyright Notice 40 Copyright (c) 2015 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 56 2. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 4 57 3. LISP Architecture . . . . . . . . . . . . . . . . . . . . . . 5 58 3.1. Design Principles . . . . . . . . . . . . . . . . . . . . 5 59 3.2. Overview of the Architecture . . . . . . . . . . . . . . 6 60 3.3. Data-Plane . . . . . . . . . . . . . . . . . . . . . . . 9 61 3.3.1. LISP Encapsulation . . . . . . . . . . . . . . . . . 9 62 3.3.2. LISP Forwarding State . . . . . . . . . . . . . . . . 10 63 3.4. Control-Plane . . . . . . . . . . . . . . . . . . . . . . 10 64 3.4.1. LISP Mappings . . . . . . . . . . . . . . . . . . . . 11 65 3.4.2. Mapping System Interface . . . . . . . . . . . . . . 11 66 3.4.3. Mapping System . . . . . . . . . . . . . . . . . . . 12 67 3.5. Internetworking Mechanisms . . . . . . . . . . . . . . . 15 68 4. LISP Operational Mechanisms . . . . . . . . . . . . . . . . . 16 69 4.1. Cache Management . . . . . . . . . . . . . . . . . . . . 16 70 4.2. RLOC Reachability . . . . . . . . . . . . . . . . . . . . 17 71 4.3. ETR Synchronization . . . . . . . . . . . . . . . . . . . 18 72 4.4. MTU Handling . . . . . . . . . . . . . . . . . . . . . . 18 73 5. Mobility . . . . . . . . . . . . . . . . . . . . . . . . . . 19 74 6. Multicast . . . . . . . . . . . . . . . . . . . . . . . . . . 19 75 7. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 20 76 7.1. Traffic Engineering . . . . . . . . . . . . . . . . . . . 20 77 7.2. LISP for IPv6 Co-existence . . . . . . . . . . . . . . . 21 78 7.3. LISP for Virtual Private Networks . . . . . . . . . . . . 21 79 7.4. LISP for Virtual Machine Mobility in Data Centers . . . . 21 80 8. Security Considerations . . . . . . . . . . . . . . . . . . . 22 81 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 82 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 23 83 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 84 11.1. Normative References . . . . . . . . . . . . . . . . . . 23 85 11.2. Informative References . . . . . . . . . . . . . . . . . 25 86 Appendix A. A Brief History of Location/Identity Separation . . 26 87 A.1. Old LISP Models . . . . . . . . . . . . . . . . . . . . . 26 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 90 1. Introduction 92 This document introduces the Locator/ID Separation Protocol (LISP) 93 [RFC6830] architecture, its main operational mechanisms and its 94 design rationale. Fundamentally, LISP is built following a well- 95 known architectural idea: decoupling the IP address overloaded 96 semantics. Indeed and as pointed out by the unpublished Internet 97 Draft by Noel Chiappa [Chiappa], currently IP addresses both identify 98 the topological location of a network attachment point as well as the 99 node's identity. However, nodes and routing have fundamentally 100 different requirements, routing systems require that addresses are 101 aggregatable and have topological meaning, while nodes require to be 102 identified independently of their current location [RFC4984]. 104 LISP creates two separate namespaces, EIDs (End-host IDentifiers) and 105 RLOCs (Routing LOCators), both are typically syntactically identical 106 to the current IPv4 and IPv6 addresses. EIDs are used to uniquely 107 identify nodes irrespective of their topological location and are 108 typically routed intra-domain. RLOCs are assigned topologically to 109 network attachment points and are typically routed inter-domain. 110 With LISP, the edge of the Internet (where the nodes are connected) 111 and the core (where inter-domain routing occurs) can be logically 112 separated and interconnected by LISP-capable routers. LISP also 113 introduces a database, called the Mapping System, to store and 114 retrieve mappings between identity and location. LISP-capable 115 routers exchange packets over the Internet core by encapsulating them 116 to the appropriate location. 118 In summary: 120 o RLOCs have meaning only in the underlay network, that is the 121 underlying core routing system. 123 o EIDs have meaning only in the overlay network unless they are 124 leaked into the underlay network. The overlay is the 125 encapsulation relationship between LISP-capable routers. 126 Furthermore EIDs are not assigned from the reserved address 127 blocks. 129 o The LISP edge maps EIDs to RLOCs 131 o Within the underlay network, RLOCs have both locator and 132 identifier semantics 134 o An EID within a LISP site carries both identifier and locator 135 semantics to other nodes within that site 137 o An EID within a LISP site carries identifier and limited locator 138 semantics to nodes at other LISP sites (i.e., enough locator 139 information to tell that the EID is external to the site) 141 The relationship described above is not unique to LISP but it is 142 common to other overlay technologies. 144 The initial motivation in the LISP effort is to be find in the 145 routing scalability problem [RFC4984], where, if LISP is completely 146 deployed, the Internet core is populated with RLOCs while Traffic 147 Engineering mechanisms are pushed to the Mapping System. In such 148 scenario RLOCs are quasi-static (i.e., low churn), hence making the 149 routing system scalable [Quoitin], while EIDs can roam anywhere with 150 no churn to the underlying routing system. [RFC7215] discusses the 151 impact of LISP on the global routing system during the transition 152 period. However, the separation between location and identity that 153 LISP offers makes it suitable for use in additional scenarios such as 154 Traffic Engineering (TE), multihoming, and mobility among others. 156 This document describes the LISP architecture, its main operational 157 mechanisms as its design rationale. It is important to note that 158 this document does not specify or complement the LISP protocol. The 159 interested reader should refer to the main LISP specifications 160 [RFC6830] and the complementary documents [RFC6831], [RFC6832], 161 [RFC6833], [RFC6834], [RFC6835], [RFC6836], [RFC7052] for the 162 protocol specifications along with the LISP deployment guidelines 163 [RFC7215]. 165 2. Definition of Terms 167 Endpoint IDentifier (EID): EIDs are IPv4 or IPv6 addresses used to 168 uniquely identify nodes irrespective of their topological location 169 and are typically routed intra-domain. 171 Routing LOcator (RLOC): RLOCs are IPv4 or IPv6 addresses assigned 172 topologically to network attachment points and typically routed 173 inter-domain. 175 Ingress Tunnel Router (ITR): A LISP-capable router that encapsulates 176 packets from a LISP site towards the core network. 178 Egress Tunnel Router (ETR): A LISP-capable router that decapsulates 179 packets from the core of the network towards a LISP site. 181 xTR: A router that implements both ITR and ETR functionalities. 183 Map-Request: A LISP signaling message used to request an EID-to-RLOC 184 mapping. 186 Map-Reply: A LISP signaling message sent in response to a Map- 187 Request that contains a resolved EID-to-RLOC mapping. 189 Map-Register: A LISP signaling message used to register an EID-to- 190 RLOC mapping. 192 Map-Notify: A LISP signaling message sent in response of a Map- 193 Register to acknowledge the correct reception of an EID-to-RLOC 194 mapping. 196 This document describes the LISP architecture and does not introduce 197 any new term. The reader is referred to [RFC6830], [RFC6831], 198 [RFC6832], [RFC6833], [RFC6834], [RFC6835], [RFC6836], [RFC7052], 199 [RFC7215] for the complete definition of terms. 201 3. LISP Architecture 203 This section presents the LISP architecture, it first details the 204 design principles of LISP and then it proceeds to describe its main 205 aspects: data-plane, control-plane, and internetworking mechanisms. 207 3.1. Design Principles 209 The LISP architecture is built on top of four basic design 210 principles: 212 o Locator/Identifier split: By decoupling the overloaded semantics 213 of the current IP addresses the Internet core can be assigned 214 identity meaningful addresses and hence, can use aggregation to 215 scale. Devices are assigned with relatively opaque identity 216 meaningful addresses that are independent of their topological 217 location. 219 o Overlay architecture: Overlays route packets over the current 220 Internet, allowing deployment of new protocols without changing 221 the current infrastructure hence, resulting into a low deployment 222 cost. 224 o Decoupled data and control-plane: Separating the data-plane from 225 the control-plane allows them to scale independently and use 226 different architectural approaches. This is important given that 227 they typically have different requirements and allows for other 228 data-planes to be added. While decoupled, data and control-plane 229 are not completely isolated because the LISP data-plane may 230 trigger control-plane activity. 232 o Incremental deployability: This principle ensures that the 233 protocol interoperates with the legacy Internet while providing 234 some of the targeted benefits to early adopters. 236 3.2. Overview of the Architecture 238 LISP splits architecturally the core from the edge of the Internet by 239 creating two separate namespaces: Endpoint Identifiers (EIDs) and 240 Routing LOCators (RLOCs). The edge consists of LISP sites (e.g., an 241 Autonomous System) that use EID addresses. EIDs are typically -but 242 not limited to- IPv4 or IPv6 addresses that uniquely identify 243 communication end-hosts and are assigned and configured by the same 244 mechanisms that exist at the time of this writing. EIDs do not 245 contain inter-domain topological information and because of this, 246 EIDs are usually routable at the edge (within LISP sites) or in the 247 non-LISP Internet. 249 With LISP, LISP sites (edge) and the core of the Internet are 250 interconnected by means of LISP-capable routers (e.g., border 251 routers) using tunnels. When packets originated from a LISP site are 252 flowing towards the core network, they ingress into an encapsulated 253 tunnel via an Ingress Tunnel Router (ITR). When packets flow from 254 the core network to a LISP site, they egress from an encapsulated 255 tunnel to an Egress Tunnel Router (ETR). An xTR is a router which 256 can perform both ITR and ETR operations. In this context ITRs 257 encapsulate packets while ETRs decapsulate them, hence LISP operates 258 as an overlay on top of the current Internet core. 260 /-----------------\ --- 261 | Mapping | | 262 . System | | Control 263 -| |`, | Plane 264 ,' \-----------------/ . | 265 / | --- 266 ,.., - _,....,, | ,.., | 267 / ` ,' ,-` `', | / ` | 268 / \ +-----+ ,' `, +-----+ / \ | 269 | EID |-| xTR |--/ RLOC ,--| xTR |-| EID | | Data 270 | Space |-| |--| Space |--| |-| Space | | Plane 271 \ / +-----+ . / +-----+ \ / | 272 `. .' `. ,' `. .' | 273 `'-` `., ,.' `'-` --- 274 ``'''`` 275 LISP Site (Edge) Core LISP Site (Edge) 277 Figure 1.- A schema of the LISP Architecture 279 With LISP, the core uses RLOCs, an RLOC is typically -but not limited 280 to- an IPv4 or IPv6 address assigned to an Internet-facing network 281 interface of an ITR or ETR. Typically RLOCs are numbered from 282 topologically aggregatable blocks assigned to a site at each point to 283 which it attaches to the global Internet, the topology is defined by 284 the connectivity of networks. 286 A typically distributed database, called the Mapping System, stores 287 mappings between EIDs and RLOCs. Such mappings relate the identity 288 of the devices attached to LISP sites (EIDs) to the set of RLOCs 289 configured at the LISP-capable routers servicing the site. 290 Furthermore, the mappings also include traffic engineering policies 291 and can be configured to achieve multihoming and load balancing. The 292 LISP Mapping System is conceptually similar to the DNS where it is 293 organized as a distributed multi-organization network database. With 294 LISP, ETRs register mappings while ITRs retrieve them. 296 Finally, the LISP architecture emphasizes a cost effective 297 incremental deployment. Given that LISP represents an overlay to the 298 current Internet architecture, endhosts as well as intra and inter- 299 domain routers remain unchanged, and the only required changes to the 300 existing infrastructure are to routers connecting the EID with the 301 RLOC space. Such LISP capable routers, in most cases, only require a 302 software upgrade. Additionally, LISP requires the deployment of an 303 independent Mapping System, such distributed database is a new 304 network entity. 306 The following describes a simplified packet flow sequence between two 307 nodes that are attached to LISP sites. Client HostA wants to send a 308 packet to server HostB. 310 /----------------\ 311 | Mapping | 312 | System | 313 .| |- 314 ` \----------------/ `. 315 ,` \ 316 / `. 317 ,' _,..-..,, ', 318 / -` `-, \ 319 .' ,' \ `, 320 ` ' \ ' 321 +-----+ | | RLOC_B1+-----+ 322 HostA | | | RLOC |-------| | HostB 323 EID_A--|ITR_A|----| Space | |ETR_B|--EID_B 324 | | RLOC_A1 |-------| | 325 +-----+ | | RLOC_B2+-----+ 326 , / 327 \ / 328 `', ,-` 329 ``''-''`` 331 Figure 2.- Packet flow sequence in LISP 333 1. HostA retrieves the EID_B of HostB, typically querying the DNS 334 and obtaining and A or AAAA record. Then it generates an IP 335 packet as in the Internet, the packet has source address EID_A 336 and destination address EID_B. 338 2. The packet is routed towards ITR_A in the LISP site using 339 standard intra-domain mechanisms. 341 3. ITR_A upon receiving the packet queries the Mapping System to 342 retrieve the locator of ETR_B that is servicing HostB's EID_B. 343 In order to do so it uses a LISP control message called Map- 344 Request, the message contains EID_B as the lookup key. In turn 345 it receives another LISP control message called Map-Reply, the 346 message contains two locators: RLOC_B1 and RLOC_B2 along with 347 traffic engineering policies: priority and weight per locator. 348 Note that a Map-Reply can contain more locators if needed. ITR_A 349 also stores the mapping in a local cache to speed-up forwarding 350 of subsequent packets. 352 4. ITR_A encapsulates the packet towards RLOC_B1 (chosen according 353 to the priorities/weights specified in the mapping). The packet 354 contains two IP headers, the outer header has RLOC_A1 as source 355 and RLOC_B1 as destination, the inner original header has EID_A 356 as source and EID_B as destination. Furthermore ITR_A adds a 357 LISP header, more details about LISP encapsulation can be found 358 in Section 3.3.1. 360 5. The encapsulated packet is forwarded by the Internet core as a 361 normal IP packet, making the EID invisible from the Internet 362 core. 364 6. Upon reception of the encapsulated packet by ETR_B, it 365 decapsulates the packet and forwards it to HostB. 367 3.3. Data-Plane 369 This section provides a high-level description of the LISP data- 370 plane, which is specified in detail in [RFC6830]. The LISP data- 371 plane is responsible for encapsulating and decapsulating data packets 372 and caching the appropriate forwarding state. It includes two main 373 entities, the ITR and the ETR, both are LISP capable routers that 374 connect the EID with the RLOC space (ITR) and vice versa (ETR). 376 3.3.1. LISP Encapsulation 378 ITRs encapsulate data packets towards ETRs. LISP data packets are 379 encapsulated using UDP (port 4341), the source port is selected by 380 the ITR and ignored on reception. A particularity of LISP is that 381 UDP packets should include a zero checksum [RFC6935] [RFC6936] that 382 it is not verified in reception, LISP also supports non-zero 383 checksums that may be verified. This decision was made because the 384 typical transport protocols used by the applications already include 385 a checksum, by neglecting the additional UDP encapsulation checksum 386 xTRs can forward packets more efficiently. 388 LISP-encapsulated packets also include a LISP header (after the UDP 389 header and before the original IP header). The LISP header is 390 prepended by ITRs and striped by ETRs. It carries reachability 391 information (see more details in Section 4.2) and the Instance ID 392 field. The Instance ID field is used to distinguish traffic to/from 393 different tenant address spaces at the LISP site and that may use 394 overlapped but logically separated EID addressing. 396 Overall, LISP works on 4 headers, the inner header the source 397 constructed, and the 3 headers a LISP encapsulator prepends ("outer" 398 to "inner"): 400 1. Outer IP header containing RLOCs as source and destination 401 addresses. This header is originated by ITRs and stripped by 402 ETRs. 404 2. UDP header (port 4341) with zero checksum. This header is 405 originated by ITRs and stripped by ETRs. 407 3. LISP header that contains various forwarding-plane features (such 408 as reachability) and an Instance ID field. This header is 409 originated by ITRs and stripped by ETRs. 411 4. Inner IP header containing EIDs as source and destination 412 addresses. This header is created by the source end-host and is 413 left unchanged by LISP data plane processing on the ITR and ETR. 415 Finally, in some scenarios Recursive and/or Re-encapsulating tunnels 416 can be used for Traffic Engineering and re-routing. Re-encapsulating 417 tunnels are consecutive LISP tunnels and occur when a decapsulator 418 (an ETR action) removes a LISP header and then acts as an encapsultor 419 (an ITR action) to prepend another one. On the other hand, Recursive 420 tunnels are nested tunnels and are implemented by using multiple LISP 421 encapsulations on a packet. Typically such functions are implemented 422 by Reencapsulating Tunnel Routers (RTRs). An RTR can be thought of 423 as a router that first acts as an ETR by decapsulating packets and 424 then as an ITR by encapsulating them towards another locator, more 425 information can be found at [RFC6830]. 427 3.3.2. LISP Forwarding State 429 In the LISP architecture, ITRs keep just enough information to route 430 traffic flowing through it. Meaning that, ITRs retrieve from the 431 LISP Mapping System mappings between EID prefixes and RLOCs that are 432 used to encapsulate packets. Such mappings are stored in a local 433 cache called the Map-Cache for subsequent packets addressed to the 434 same EID prefix. Note that, in case of overlapping EID-prefixes, 435 following a single request, the ITR may receive a set of mappings, 436 covering the requested EID-prefix and all more-specifics (cf., 437 Section 6.1.5 [RFC6830]). Mappings include a (Time-to-Live) TTL (set 438 by the ETR). More details about the Map-Cache management can be 439 found in Section 4.1. 441 3.4. Control-Plane 443 The LISP control-plane, specified in [RFC6833], provides a standard 444 interface to register and request mappings. The LISP Mapping System 445 is a database that stores such mappings. The following first 446 describes the mappings, then the standard interface to the Mapping 447 System, and finally its architecture. 449 3.4.1. LISP Mappings 451 Each mapping includes the bindings between EID prefix(es) and set of 452 RLOCs as well as traffic engineering policies, in the form of 453 priorities and weights for the RLOCs. Priorities allow the ETR to 454 configure active/backup policies while weights are used to load- 455 balance traffic among the RLOCs (on a per-flow basis). 457 Typical mappings in LISP bind EIDs in the form of IP prefixes with a 458 set of RLOCs, also in the form of IPs. IPv4 and IPv6 addresses are 459 encoded using the appropriate Address Family Identifier (AFI) 460 [RFC3232]. However LISP can also support more general address 461 encoding by means of the ongoing effort around the LISP Canonical 462 Address Format (LCAF) [I-D.ietf-lisp-lcaf]. 464 With such a general syntax for address encoding in place, LISP aims 465 to provide flexibility to current and future applications. For 466 instance LCAFs could support MAC addresses, geo-coordinates, ASCII 467 names and application specific data. 469 3.4.2. Mapping System Interface 471 LISP defines a standard interface between data and control planes. 472 The interface is specified in [RFC6833] and defines two entities: 474 Map-Server: A network infrastructure component that learns mappings 475 from ETRs and publishes them into the LISP Mapping System. 476 Typically Map-Servers are not authoritative to reply to queries 477 and hence, they forward them to the ETR. However they can also 478 operate in proxy-mode, where the ETRs delegate replying to queries 479 to Map-Servers. This setup is useful when the ETR has limited 480 resources (i.e., CPU or power). 482 Map-Resolver: A network infrastructure component that interfaces 483 ITRs with the Mapping System by proxying queries and in some cases 484 responses. 486 The interface defines four LISP control messages which are sent as 487 UDP datagrams (port 4342): 489 Map-Register: This message is used by ETRs to register mappings in 490 the Mapping System and it is authenticated using a shared key 491 between the ETR and the Map-Server. 493 Map-Notify: When requested by the ETR, this message is sent by the 494 Map-Server in response to a Map-Register to acknowledge the 495 correct reception of the mapping and convey the latest Map-Server 496 state on the EID to RLOC mapping. In some cases a Map-Notify can 497 be sent to the previous RLOCs when an EID is registered by a new 498 set of RLOCs. 500 Map-Request: This message is used by ITRs or Map-Resolvers to 501 resolve the mapping of a given EID. 503 Map-Reply: This message is sent by Map-Servers or ETRs in response 504 to a Map-Request and contains the resolved mapping. Please note 505 that a Map-Reply may contain a negative reply if, for example, the 506 queried EID is not part of the LISP EID space. In such cases the 507 ITR typically forwards the traffic natively (non encapsulated) to 508 the public Internet, this behavior is defined to support 509 incremental deployment of LISP. 511 3.4.3. Mapping System 513 LISP architecturally decouples control and data-plane by means of a 514 standard interface. This interface glues the data-plane, routers 515 responsible for forwarding data-packets, with the LISP Mapping 516 System, a database responsible for storing mappings. 518 With this separation in place the data and control-plane can use 519 different architectures if needed and scale independently. Typically 520 the data-plane is optimized to route packets according to 521 hierarchical IP addresses. However the control-plane may have 522 different requirements, for instance and by taking advantage of the 523 LCAFs, the Mapping System may be used to store non-hierarchical keys 524 (such as MAC addresses), requiring different architectural approaches 525 for scalability. Another important difference between the LISP 526 control and data-planes is that, and as a result of the local mapping 527 cache available at ITR, the Mapping System does not need to operate 528 at line-rate. 530 Many of the existing mechanisms to create distributed systems have 531 been explored and considered for the Mapping System architecture: 532 graph-based databases in the form of LISP+ALT [RFC6836], hierarchical 533 databases in the form of LISP-DDT [I-D.ietf-lisp-ddt], monolithic 534 databases in the form of LISP-NERD [RFC6837], flat databases in the 535 form of LISP-DHT [I-D.cheng-lisp-shdht],[Mathy] and, a multicast- 536 based database [I-D.curran-lisp-emacs]. Furthermore it is worth 537 noting that, in some scenarios such as private deployments, the 538 Mapping System can operate as logically centralized. In such cases 539 it is typically composed of a single Map-Server/Map-Resolver. 541 The following focuses on the two mapping systems that have been 542 implemented and deployed (LISP-ALT and LISP+DDT). 544 3.4.3.1. LISP+ALT 546 The LISP Alternative Topology (LISP+ALT) [RFC6836] was the first 547 Mapping System proposed, developed and deployed on the LISP pilot 548 network. It is based on a distributed BGP overlay participated by 549 Map-Servers and Map-Resolvers. The nodes connect to their peers 550 through static tunnels. Each Map-Server involved in the ALT topology 551 advertises the EID-prefixes registered by the serviced ETRs, making 552 the EID routable on the ALT topology. 554 When an ITR needs a mapping it sends a Map-Request to a Map-Resolver 555 that, using the ALT topology, forwards the Map-Request towards the 556 Map-Server responsible for the mapping. Upon reception the Map- 557 Server forwards the request to the ETR that in turn, replies directly 558 to the ITR using the native Internet core. 560 3.4.3.2. LISP-DDT 562 LISP-DDT [I-D.ietf-lisp-ddt] is conceptually similar to the DNS, a 563 hierarchical directory whose internal structure mirrors the 564 hierarchical nature of the EID address space. The DDT hierarchy is 565 composed of DDT nodes forming a tree structure, the leafs of the tree 566 are Map-Servers. On top of the structure there is the DDT root node 567 [DDT-ROOT], which is a particular instance of a DDT node and that 568 matches the entire address space. As in the case of DNS, DDT 569 supports multiple redundant DDT nodes and/or DDT roots. Finally, 570 Map-Resolvers are the clients of the DDT hierarchy and can query 571 either the DDT root and/or other DDT nodes. 573 /---------\ 574 | | 575 | DDT Root| 576 | /0 | 577 ,.\---------/-, 578 ,-'` | `'., 579 -'` | `- 580 /-------\ /-------\ /-------\ 581 | DDT | | DDT | | DDT | 582 | Node | | Node | | Note | ... 583 | 0/8 | | 1/8 | | 2/8 | 584 \-------/ \-------/ \-------/ 585 _. _. . -..,,,_ 586 -` -` \ ````''-- 587 +------------+ +------------+ +------------+ +------------+ 588 | Map-Server | | Map-Server | | Map-Server | | Map-Server | 589 | EID-prefix1| | EID-prefix2| | EID-prefix3| | EID-prefix4| 590 +------------+ +------------+ +------------+ +------------+ 592 Figure 3.- A schematic representation of the DDT tree structure, 593 please note that the prefixes and the structure depicted 594 should be only considered as an example. 596 The DDT structure does not actually index EID-prefixes but eXtended 597 EID-prefixes (XEID). An XEID-prefix is just the concatenation of the 598 following fields (from most significant bit to less significant bit): 599 Database-ID, Instance ID, Address Family Identifier and the actual 600 EID-prefix. The Database-ID is provided for possible future 601 requirements of higher levels in the hierarchy and to enable the 602 creation of multiple and separate database trees. 604 In order to resolve a query LISP-DDT operates in a similar way to the 605 DNS but only supports iterative lookups. DDT clients (usually Map- 606 Resolvers) generate Map-Requests to the DDT root node. In response 607 they receive a newly introduced LISP-control message: a Map-Referral. 608 A Map-Referral provides the list of RLOCs of the set of DDT nodes 609 matching a configured XEID delegation. That is, the information 610 contained in the Map-Referral points to the child of the queried DDT 611 node that has more specific information about the queried XEID- 612 prefix. This process is repeated until the DDT client walks the tree 613 structure (downwards) and discovers the Map-Server servicing the 614 queried XEID. At this point the client sends a Map-Request and 615 receives a Map-Reply containing the mappings. It is important to 616 note that DDT clients can also cache the information contained in 617 Map-Referrals, that is, they cache the DDT structure. This is used 618 to reduce the mapping retrieving latency[Jakab]. 620 The DDT Mapping System relies on manual configuration. That is Map- 621 Resolvers are manually configured with the set of available DDT root 622 nodes while DDT nodes are manually configured with the appropriate 623 XEID delegations. Configuration changes in the DDT nodes are only 624 required when the tree structure changes itself, but it doesn't 625 depend on EID dynamics (RLOC allocation or traffic engineering policy 626 changes). 628 3.5. Internetworking Mechanisms 630 EIDs are typically identical to either IPv4 or IPv6 addresses and 631 they are stored in the LISP Mapping System, however they are usually 632 not announced in the Internet global routing system. As a result 633 LISP requires an internetworking mechanism to allow LISP sites to 634 speak with non-LISP sites and vice versa. LISP internetworking 635 mechanisms are specified in [RFC6832]. 637 LISP defines two entities to provide internetworking: 639 Proxy Ingress Tunnel Router (PITR): PITRs provide connectivity from 640 the legacy Internet to LISP sites. PITRs announce in the global 641 routing system blocks of EID prefixes (aggregating when possible) 642 to attract traffic. For each incoming packet from a source not in 643 a LISP site (a non-EID), the PITR LISP-encapsulates it towards the 644 RLOC(s) of the appropriate LISP site. The impact of PITRs in the 645 routing table size of the Default-Free Zone (DFZ) is, in the 646 worst-case, similar to the case in which LISP is not deployed. 647 EID-prefixes will be aggregated as much as possible both by the 648 PITR and by the global routing system. 650 Proxy Egress Tunnel Router (PETR): PETRs provide connectivity from 651 LISP sites to the legacy Internet. In some scenarios, LISP sites 652 may be unable to send encapsulated packets with a local EID 653 address as a source to the legacy Internet. For instance when 654 Unicast Reverse Path Forwarding (uRPF) is used by Provider Edge 655 routers, or when an intermediate network between a LISP site and a 656 non-LISP site does not support the desired version of IP (IPv4 or 657 IPv6). In both cases the PETR overcomes such limitations by 658 encapsulating packets over the network. There is no specified 659 provision for the distribution of PETR RLOC addresses to the ITRs. 661 Additionally, LISP also defines mechanisms to operate with private 662 EIDs [RFC1918] by means of LISP-NAT [RFC6832]. In this case the xTR 663 replaces a private EID source address with a routable one. At the 664 time of this writing, work is ongoing to define NAT-traversal 665 capabilities, that is xTRs behind a NAT using non-routable RLOCs. 667 4. LISP Operational Mechanisms 669 This section details the main operational mechanisms defined in LISP. 671 4.1. Cache Management 673 LISP's decoupled control and data-plane, where mappings are stored in 674 the control-plane and used for forwarding in the data plane, requires 675 a local cache in ITRs to reduce signaling overhead (Map-Request/Map- 676 Reply) and increase forwarding speed. The local cache available at 677 the ITRs, called Map-Cache, is used by the router to LISP-encapsulate 678 packets. The Map-Cache is indexed by (Instance ID, EID-prefix) and 679 contains basically the set of RLOCs with the associated traffic 680 engineering policies (priorities and weights). 682 The Map-Cache, as any other cache, requires cache coherence 683 mechanisms to maintain up-to-date information. LISP defines three 684 main mechanisms for cache coherence: 686 Time-To-Live (TTL): Each mapping contains a TTL set by the ETR, upon 687 expiration of the TTL the ITR has to refresh the mapping by 688 sending a new Map-Request. Typical values for TTL defined by LISP 689 are 24 hours. 691 Solicit-Map-Request (SMR): SMR is an explicit mechanism to update 692 mapping information. In particular a special type of Map-Request 693 can be sent on demand by ETRs to request refreshing a mapping. 694 Upon reception of a SMR message, the ITR must refresh the bindings 695 by sending a Map-Request to the Mapping System. Further uses of 696 SMRs are documented in [RFC6830]. 698 Map-Versioning: This optional mechanism piggybacks in the LISP 699 header of data-packets the version number of the mappings used by 700 an xTR. This way, when an xTR receives a LISP-encapsulated packet 701 from a remote xTR, it can check whether its own Map-Cache or the 702 one of the remote xTR is outdated. If its Map-Cache is outdated, 703 it sends a Map-Request for the remote EID so to obtain the newest 704 mappings. On the contrary, if it detects that the remote xTR Map- 705 Cache is outdated, it sends a SMR to notify it that a new mapping 706 is available. 708 Finally it is worth noting that in some cases an entry in the map- 709 cache can be proactively refreshed using the mechanisms described in 710 the section below. 712 4.2. RLOC Reachability 714 The LISP architecture is an edge to edge pull architecture, where the 715 network state is stored in the control-plane while the data-plane 716 pulls it on demand. This has consequences concerning the propagation 717 of xTRs reachability/liveness information. On the contrary BGP is a 718 push architecture, where the required network state is pushed by 719 means of BGP UPDATE messages to BGP speakers. In push architectures, 720 reachability information is also pushed to the interested routers. 721 However pull architectures require explicit mechanisms to propagate 722 reachability information. LISP defines a set of mechanisms to inform 723 ITRs and PITRS about the reachability of the cached RLOCs: 725 Locator Status Bits (LSB): LSB is a passive technique, the LSB field 726 is carried by data-packets in the LISP header and can be set by a 727 ETRs to specify which RLOCs of the ETR site are up/down. This 728 information can be used by the ITRs as a hint about the reachability 729 to perform additional checks. Also note that LSB does not provide 730 path reachability status, only hints on the status of RLOCs. 732 Echo-nonce: This is also a passive technique, that can only operate 733 effectively when data flows bi-directionally between two 734 communicating xTRs. Basically, an ITR piggybacks a random number 735 (called nonce) in LISP data packets, if the path and the probed 736 locator are up, the ETR will piggyback the same random number on the 737 next data-packet, if this is not the case the ITR can set the locator 738 as unreachable. When traffic flow is unidirectional or when the ETR 739 receiving the traffic is not the same as the ITR that transmits it 740 back, additional mechanisms are required. 742 RLOC-probing: This is an active probing algorithm where ITRs send 743 probes to specific locators, this effectively probes both the locator 744 and the path. In particular this is done by sending a Map-Request 745 (with certain flags activated) on the data-plane (RLOC space) and 746 waiting in return a Map-Reply, also sent on the data-plane. The 747 active nature of RLOC-probing provides an effective mechanism to 748 determine reachability and, in case of failure, switching to a 749 different locator. Furthermore the mechanism also provides useful 750 RTT estimates of the delay of the path that can be used by other 751 network algorithms. 753 Additionally, LISP also recommends inferring reachability of locators 754 by using information provided by the underlay, in particular: 756 It is worth noting that RLOC probing and Echo-nonce can work 757 together. Specifically if a nonce is not echoed, an ITR could RLOC- 758 probe to determine if the path is up when it cannot tell the 759 difference between a failed bidirectional path or the return path is 760 not used (a unidirectional path). 762 ICMP signaling: The LISP underlay -the current Internet- uses the 763 ICMP protocol to signal unreachability (among other things). LISP 764 can take advantage of this and the reception of a ICMP Network 765 Unreachable or ICMP Host Unreachable message can be seen as a hint 766 that a locator might be unreachable, this should lead to perform 767 additional checks. 769 Underlay routing: Both BGP and IBGP carry reachability information, 770 LISP-capable routers that have access to underlay routing information 771 can use it to determine if a given locator or path are reachable. 773 4.3. ETR Synchronization 775 All the ETRs that are authoritative to a particular EID-prefix must 776 announce the same mapping to the requesters, this means that ETRs 777 must be aware of the status of the RLOCs of the remaining ETRs. This 778 is known as ETR synchronization. 780 At the time of this writing LISP does not specify a mechanism to 781 achieve ETR synchronization. Although many well-known techniques 782 could be applied to solve this issue it is still under research, as a 783 result operators must rely on coherent manual configuration 785 4.4. MTU Handling 787 Since LISP encapsulates packets it requires dealing with packets that 788 exceed the MTU of the path between the ITR and the ETR. Specifically 789 LISP defines two mechanisms: 791 Stateless: With this mechanism the effective MTU is assumed from the 792 ITR's perspective. If a payload packet is too big for the 793 effective MTU, and can be fragmented, the payload packet is 794 fragmented on the ITR, such that reassembly is performed at the 795 destination host. 797 Stateful: With this mechanism ITRs keep track of the MTU of the 798 paths towards the destination locators by parsing the ICMP Too Big 799 packets sent by intermediate routers. Additionally ITRs will send 800 ICMP Too Big messages to inform the sources about the effective 801 MTU. 803 In both cases if the packet cannot be fragmented (IPv4 with DF=1 or 804 IPv6) then the ITR drops it and replies with a ICMP Too Big message 805 to the source. 807 5. Mobility 809 The separation between locators and identifiers in LISP was initially 810 proposed for traffic engineering purpose where LISP sites can change 811 their attachment points to the Internet (i.e., RLOCs) without 812 impacting endpoints or the Internet core. In this context, the 813 border routers operate the xTR functionality and endpoints are not 814 aware of the existence of LISP. This functionality is similar to 815 Network Mobility [RFC3963]. However, this mode of operation does not 816 allow seamless mobility of endpoints between different LISP sites as 817 the EID address might not be routable in a visited site. 818 Nevertheless, LISP can be used to enable seamless IP mobility when 819 LISP is directly implemented in the endpoint or when the endpoint 820 roams to an attached xTR. Each endpoint is then an xTR and the EID 821 address is the one presented to the network stack used by 822 applications while the RLOC is the address gathered from the network 823 when it is visited. This functionality is similar to Mobile IP 824 ([RFC5944] and [RFC6275]). 826 Whenever the device changes of RLOC, the xTR updates the RLOC of its 827 local mapping and registers it to its Map-Server, typically with a 828 low TTL value (1min). To avoid the need of a home gateway, the ITR 829 also indicates the RLOC change to all remote devices that have 830 ongoing communications with the device that moved. The combination 831 of both methods ensures the scalability of the system as signaling is 832 strictly limited the Map-Server and to hosts with which 833 communications are ongoing. 835 The decoupled identity and location provided by LISP allows it to 836 operate with other layer 2 and layer 3 mobility solutions. 838 6. Multicast 840 LISP also supports transporting IP multicast packets sent from the 841 EID space, the operational changes required to the multicast 842 protocols are documented in [RFC6831]. 844 In such scenarios, LISP may create multicast state both at the core 845 and at the sites (both source and receiver). When signaling is used 846 to create multicast state at the sites, LISP routers unicast 847 encapsulate PIM Join/Prune messages from receiver to source sites. 848 At the core, ETRs build a new PIM Join/Prune message addressed to the 849 RLOC of the ITR servicing the source. An simplified sequence is 850 shown below 852 1. An end-host willing to join a multicast channel sends an IGMP 853 report. Multicast PIM routers at the LISP site propagate PIM 854 Join/Prune messages (S-EID, G) towards the ETR. 856 2. The join message flows to the ETR, upon reception the ETR builds 857 two join messages, the first one unicast LISP-encapsulates the 858 original join message towards the RLOC of the ITR servicing the 859 source. This message creates (S-EID, G) multicast state at the 860 source site. The second join message contains as destination 861 address the RLOC of the ITR servicing the source (S-RLOC, G) and 862 creates multicast state at the core. 864 3. Multicast data packets originated by the source (S-EID, G) flow 865 from the source to the ITR. The ITR LISP-encapsulates the 866 multicast packets, the outter header includes its own RLOC as the 867 source (S-RLOC) and the original multicast group address (G) as 868 the destination. Please note that multicast group address are 869 logical and are not resolved by the mapping system. Then the 870 multicast packet is transmitted through the core towards the 871 receiving ETRs that decapsulates the packets and sends them using 872 the receiver's site multicast state. 874 LISP [RFC6831] supports all PIM modes, additionally LISP can also 875 support non-PIM mechanisms to maintain multicast state. 877 7. Use Cases 879 7.1. Traffic Engineering 881 BGP is the standard protocol to implement inter-domain routing. With 882 BGP, routing information are propagated along the network and each 883 autonomous system can implement its own routing policy that will 884 influence the way routing information are propagated. The direct 885 consequence is that an autonomous system cannot precisely control the 886 way the traffic will enter the network. 888 As opposed to BGP, a LISP site can strictly impose via which ETRs the 889 traffic must enter the the LISP site network even though the path 890 followed to reach the ETR is not under the control of the LISP site. 891 This fine control is implemented with the mappings. When a remote 892 site is willing to send traffic to a LISP site, it retrieves the 893 mapping associated to the destination EID via the mapping system. 894 The mapping is sent directly by an authoritative ETR of the EID and 895 is not altered by any intermediate network. 897 A mapping associates a list of RLOCs to an EID prefix. Each RLOC 898 corresponds to an interface of an ETR (or set of ETRs) that is able 899 to correctly forward packets to EIDs in the prefix. Each RLOC is 900 tagged with a priority and a weight in the mapping. The priority is 901 used to indicates which RLOCs should be preferred to send packets 902 (the least preferred ones being provided for backup purpose). The 903 weight permits to balance the load between the RLOCs with the same 904 priority, proportionally to the weight value. 906 As mappings are directly issued by the authoritative ETR of the EID 907 and are not altered while transmitted to the remote site, it offers 908 highly flexible incoming inter-domain traffic engineering with even 909 the possibility for a site to issue a different mapping for each 910 remote site, implementing so precise routing policies. 912 7.2. LISP for IPv6 Co-existence 914 LISP encapsulations allows to transport packets using EIDs from a 915 given address family (e.g., IPv6) with packets from other address 916 families (e.g., IPv4). The absence of correlation between the 917 address family of RLOCs and EIDs makes LISP a candidate to allow, 918 e.g., IPv6 to be deployed when all of the core network may not have 919 IPv6 enabled. 921 For example, two IPv6-only data centers could be interconnected via 922 the legacy IPv4 Internet. If their border routers are LISP capable, 923 sending packets between the data center is done without any form of 924 translation as the native IPv6 packets (in the EID space) will be 925 LISP encapsulated and transmitted over the IPv4 legacy Internet by 926 the mean of IPv4 RLOCs. 928 7.3. LISP for Virtual Private Networks 930 It is common to operate several virtual networks over the same 931 physical infrastructure. In such virtual private networks, it is 932 essential to distinguish which virtual network a packet belongs and 933 tags or labels are used for that purpose. When using LISP, the 934 distinction can be made with the Instance ID field. When an ITR 935 encapsulates a packet from a particular virtual network (e.g., known 936 via the VRF or VLAN), it tags the encapsulated packet with the 937 Instance ID corresponding to the virtual network of the packet. When 938 an ETR receives a packet tagged with an Instance ID it uses the 939 Instance ID to determine how to treat the packet. 941 The main usage of LISP for virtual private networks does not 942 introduce additional requirements on the underlying network, as long 943 as it is running IP. 945 7.4. LISP for Virtual Machine Mobility in Data Centers 947 A way to enable seamless virtual machine mobility in data center is 948 to conceive the datacenter backbone as the RLOC space and the subnet 949 where servers are hosted as forming the EID space. A LISP router is 950 placed at the border between the backbone and each subnet. When a 951 virtual machine is moved to another subnet, it can keep (temporarily) 952 the address it had before the move so to continue without a transport 953 layer connection reset. When an xTR detects a source address 954 received on a subnet to be an address not assigned to the subnet, it 955 registers the address to the Mapping System. 957 To inform the other LISP routers that the machine moved and where, 958 and then to avoid detours via the initial subnetwork, mechanisms such 959 as the Solicit-Map-Request messages are used. 961 8. Security Considerations 963 This section describes the security considerations associated to the 964 LISP protocol. 966 LISP uses a pull architecture to learn mappings. While in a push 967 system, the state necessary to forward packets is learned 968 independently of the traffic itself, with a pull architecture, the 969 system becomes reactive and data-plane events (e.g., the arrival of a 970 packet for an unknown destination) may trigger control-plane events. 971 This on-demand learning of mappings provides many advantages as 972 discussed above but may also affect the way security is enforced. 974 Usually, the data-plane is implemented in the fast path of routers to 975 provide high performance forwarding capabilities while the control- 976 plane features are implemented in the slow path to offer high 977 flexibility and a performance gap of several order of magnitude can 978 be observed between the slow and the fast paths. As a consequence, 979 the way data-plane events are notified to the control-plane must be 980 thought carefully so to not overload the slow path and rate limiting 981 should be used as specified in [RFC6830]. 983 Care must also be taken so to not overload the mapping system (i.e., 984 the control plane infrastructure) as the operations to be performed 985 by the mapping system may be more complex than those on the data- 986 plane, for that reason [RFC6830] recommends to rate limit the sending 987 of messages to the mapping system. 989 To improve resiliency and reduce the overall number of messages 990 exchanged, LISP offers the possibility to leak information, such as 991 reachabilty of locators, directly into data plane packets. In 992 environments that are not fully trusted, control information gleaned 993 from data-plane packets should be verified before using them. 995 Mappings are the centrepiece of LISP and all precautions must be 996 taken to avoid them to be manipulated or misused by malicious 997 entities. Using trustable Map-Servers that strictly respect 998 [RFC6833] and the lightweight authentication mechanism proposed by 999 LISP-Sec [I-D.ietf-lisp-sec] reduces the risk of attacks to the 1000 mapping integrity. In more critical environments, secure measures 1001 may be needed. 1003 As with any other tunneling mechanism, middleboxes on the path 1004 between an ITR (or PITR) and an ETR (or PETR) must implement 1005 mechanisms to strip the LISP encapsulation to correctly inspect the 1006 content of LISP encapsulated packets. 1008 Like other map-and-encap mechanisms, LISP enables triangular routing 1009 (i.e., packets of a flow cross different border routers depending on 1010 their direction). This means that intermediate boxes may have 1011 incomplete view on the traffic they inspect or manipulate. 1013 More details about security implications of LISP are discussed in 1014 [I-D.ietf-lisp-threats]. 1016 9. IANA Considerations 1018 This memo includes no request to IANA. 1020 10. Acknowledgements 1022 This document was initiated by Noel Chiappa and much of the core 1023 philosophy came from him. The authors acknowledge the important 1024 contributions he has made to this work and thank him for his past 1025 efforts. 1027 The authors would also like to thank Dino Farinacci, Fabio Maino, 1028 Luigi Iannone, Sharon Barakai, Isidoros Kouvelas, Christian Cassar, 1029 Florin Coras, Marc Binderberger, Alberto Rodriguez-Natal, Ronald 1030 Bonica, Chad Hintz, Robert Raszuk, Joel M. Halpern, Darrel Lewis, as 1031 well as every people acknowledged in [RFC6830]. 1033 11. References 1035 11.1. Normative References 1037 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 1038 E. Lear, "Address Allocation for Private Internets", BCP 1039 5, RFC 1918, February 1996. 1041 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by 1042 an On-line Database", RFC 3232, January 2002. 1044 [RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. 1045 Thubert, "Network Mobility (NEMO) Basic Support Protocol", 1046 RFC 3963, January 2005. 1048 [RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB 1049 Workshop on Routing and Addressing", RFC 4984, September 1050 2007. 1052 [RFC5944] Perkins, C., "IP Mobility Support for IPv4, Revised", RFC 1053 5944, November 2010. 1055 [RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support 1056 in IPv6", RFC 6275, July 2011. 1058 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 1059 Locator/ID Separation Protocol (LISP)", RFC 6830, January 1060 2013. 1062 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 1063 Locator/ID Separation Protocol (LISP) for Multicast 1064 Environments", RFC 6831, January 2013. 1066 [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 1067 "Interworking between Locator/ID Separation Protocol 1068 (LISP) and Non-LISP Sites", RFC 6832, January 2013. 1070 [RFC6833] Fuller, V. and D. Farinacci, "Locator/ID Separation 1071 Protocol (LISP) Map-Server Interface", RFC 6833, January 1072 2013. 1074 [RFC6834] Iannone, L., Saucez, D., and O. Bonaventure, "Locator/ID 1075 Separation Protocol (LISP) Map-Versioning", RFC 6834, 1076 January 2013. 1078 [RFC6835] Farinacci, D. and D. Meyer, "The Locator/ID Separation 1079 Protocol Internet Groper (LIG)", RFC 6835, January 2013. 1081 [RFC6836] Fuller, V., Farinacci, D., Meyer, D., and D. Lewis, 1082 "Locator/ID Separation Protocol Alternative Logical 1083 Topology (LISP+ALT)", RFC 6836, January 2013. 1085 [RFC6837] Lear, E., "NERD: A Not-so-novel Endpoint ID (EID) to 1086 Routing Locator (RLOC) Database", RFC 6837, January 2013. 1088 [RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and 1089 UDP Checksums for Tunneled Packets", RFC 6935, April 2013. 1091 [RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement 1092 for the Use of IPv6 UDP Datagrams with Zero Checksums", 1093 RFC 6936, April 2013. 1095 [RFC7052] Schudel, G., Jain, A., and V. Moreno, "Locator/ID 1096 Separation Protocol (LISP) MIB", RFC 7052, October 2013. 1098 [RFC7215] Jakab, L., Cabellos-Aparicio, A., Coras, F., Domingo- 1099 Pascual, J., and D. Lewis, "Locator/Identifier Separation 1100 Protocol (LISP) Network Element Deployment 1101 Considerations", RFC 7215, April 2014. 1103 11.2. Informative References 1105 [Chiappa] Chiappa, J., "Endpoints and Endpoint names: A Propose 1106 Enhancement to the Internet Architecture, 1107 http://mercury.lcs.mit.edu/~jnc/tech/endpoints.txt", 1999. 1109 [DDT-ROOT] 1110 LISP DDT ROOT, , "http://ddt-root.org/", August 2013. 1112 [I-D.cheng-lisp-shdht] 1113 Cheng, L. and J. Wang, "LISP Single-Hop DHT Mapping 1114 Overlay", draft-cheng-lisp-shdht-04 (work in progress), 1115 July 2013. 1117 [I-D.curran-lisp-emacs] 1118 Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID 1119 Mappings Multicast Across Cooperating Systems for LISP", 1120 draft-curran-lisp-emacs-00 (work in progress), November 1121 2007. 1123 [I-D.ietf-lisp-ddt] 1124 Fuller, V., Lewis, D., Ermagan, V., and A. Jain, "LISP 1125 Delegated Database Tree", draft-ietf-lisp-ddt-02 (work in 1126 progress), October 2014. 1128 [I-D.ietf-lisp-lcaf] 1129 Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 1130 Address Format (LCAF)", draft-ietf-lisp-lcaf-07 (work in 1131 progress), December 2014. 1133 [I-D.ietf-lisp-sec] 1134 Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D. 1135 Saucez, "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-07 1136 (work in progress), October 2014. 1138 [I-D.ietf-lisp-threats] 1139 Saucez, D., Iannone, L., and O. Bonaventure, "LISP Threats 1140 Analysis", draft-ietf-lisp-threats-11 (work in progress), 1141 December 2014. 1143 [Jakab] Jakab, L., Cabellos, A., Saucez, D., and O. Bonaventure, 1144 "LISP-TREE: A DNS Hierarchy to Support the LISP Mapping 1145 System, IEEE Journal on Selected Areas in Communications, 1146 vol. 28, no. 8, pp. 1332-1343", October 2010. 1148 [Mathy] Mathy, L., Iannone, L., and O. Bonaventure, "LISP-DHT: 1149 Towards a DHT to map identifiers onto locators. The ACM 1150 ReArch, Re-Architecting the Internet. Madrid (Spain)", 1151 December 2008. 1153 [Quoitin] Quoitin, B., Iannone, L., Launois, C., and O. Bonaventure, 1154 ""Evaluating the Benefits of the Locator/Identifier 1155 Separation" in Proceedings of 2Nd ACM/IEEE International 1156 Workshop on Mobility in the Evolving Internet 1157 Architecture", 2007. 1159 Appendix A. A Brief History of Location/Identity Separation 1161 The LISP system for separation of location and identity resulted from 1162 the discussions of this topic at the Amsterdam IAB Routing and 1163 Addressing Workshop, which took place in October 2006 [RFC4984]. 1165 A small group of like-minded personnel from various scattered 1166 locations within Cisco, spontaneously formed immediately after that 1167 workshop, to work on an idea that came out of informal discussions at 1168 the workshop and on various mailing lists. The first Internet-Draft 1169 on LISP appeared in January, 2007. 1171 Trial implementations started at that time, with initial trial 1172 deployments underway since June 2007; the results of early experience 1173 have been fed back into the design in a continuous, ongoing process 1174 over several years. LISP at this point represents a moderately 1175 mature system, having undergone a long organic series of changes and 1176 updates. 1178 LISP transitioned from an IRTF activity to an IETF WG in March 2009, 1179 and after numerous revisions, the basic specifications moved to 1180 becoming RFCs at the start of 2013 (although work to expand and 1181 improve it, and find new uses for it, continues, and undoubtly will 1182 for a long time to come). 1184 A.1. Old LISP Models 1186 LISP, as initially conceived, had a number of potential operating 1187 modes, named 'models'. Although they are not used anymore, one 1188 occasionally sees mention of them, so they are briefly described 1189 here. 1191 LISP 1: EIDs all appear in the normal routing and forwarding tables 1192 of the network (i.e. they are 'routable');this property is used to 1193 'bootstrap' operation, by using this to load EID->RLOC mappings. 1194 Packets were sent with the EID as the destination in the outer 1195 wrapper; when an ETR saw such a packet, it would send a Map-Reply 1196 to the source ITR, giving the full mapping. 1198 LISP 1.5: Similar to LISP 1, but the routability of EIDs happens on 1199 a separate network. 1201 LISP 2: EIDs are not routable; EID->RLOC mappings are available from 1202 the DNS. 1204 LISP 3: EIDs are not routable; and have to be looked up in in a new 1205 EID->RLOC mapping database (in the initial concept, a system using 1206 Distributed Hash Tables). Two variants were possible: a 'push' 1207 system, in which all mappings were distributed to all ITRs, and a 1208 'pull' system in which ITRs load the mappings they need, as 1209 needed. 1211 Authors' Addresses 1213 Albert Cabellos 1214 UPC-BarcelonaTech 1215 c/ Jordi Girona 1-3 1216 Barcelona, Catalonia 08034 1217 Spain 1219 Email: acabello@ac.upc.edu 1221 Damien Saucez (Ed.) 1222 INRIA 1223 2004 route des Lucioles BP 93 1224 Sophia Antipolis Cedex 06902 1225 France 1227 Email: damien.saucez@inria.fr