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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reference: RFC 6833 (Obsoleted by RFC 9301) ** Obsolete normative reference: RFC 6834 (Obsoleted by RFC 9302) == Outdated reference: A later version (-09) exists of draft-ietf-lisp-ddt-02 == Outdated reference: A later version (-22) exists of draft-ietf-lisp-lcaf-07 == Outdated reference: A later version (-29) exists of draft-ietf-lisp-sec-07 == Outdated reference: A later version (-15) exists of draft-ietf-lisp-threats-11 Summary: 3 errors (**), 0 flaws (~~), 5 warnings (==), 1 comment (--).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: July 24, 2015 INRIA 6 January 20, 2015 8 An Architectural Introduction to the Locator/ID Separation Protocol 9 (LISP) 10 draft-ietf-lisp-introduction-10.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 July 24, 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 . . . . . . . . . . . . . . . . . . . . . . 4 58 3.1. Design Principles . . . . . . . . . . . . . . . . . . . . 4 59 3.2. Overview of the Architecture . . . . . . . . . . . . . . 5 60 3.3. Data-Plane . . . . . . . . . . . . . . . . . . . . . . . 8 61 3.3.1. LISP Encapsulation . . . . . . . . . . . . . . . . . 8 62 3.3.2. LISP Forwarding State . . . . . . . . . . . . . . . . 9 63 3.4. Control-Plane . . . . . . . . . . . . . . . . . . . . . . 9 64 3.4.1. LISP Mappings . . . . . . . . . . . . . . . . . . . . 10 65 3.4.2. Mapping System Interface . . . . . . . . . . . . . . 10 66 3.4.3. Mapping System . . . . . . . . . . . . . . . . . . . 11 67 3.5. Internetworking Mechanisms . . . . . . . . . . . . . . . 14 68 4. LISP Operational Mechanisms . . . . . . . . . . . . . . . . . 15 69 4.1. Cache Management . . . . . . . . . . . . . . . . . . . . 15 70 4.2. RLOC Reachability . . . . . . . . . . . . . . . . . . . . 16 71 4.3. ETR Synchronization . . . . . . . . . . . . . . . . . . . 17 72 4.4. MTU Handling . . . . . . . . . . . . . . . . . . . . . . 17 73 5. Mobility . . . . . . . . . . . . . . . . . . . . . . . . . . 18 74 6. Multicast . . . . . . . . . . . . . . . . . . . . . . . . . . 18 75 7. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 19 76 7.1. Traffic Engineering . . . . . . . . . . . . . . . . . . . 19 77 7.2. LISP for IPv6 Co-existence . . . . . . . . . . . . . . . 20 78 7.3. LISP for Virtual Private Networks . . . . . . . . . . . . 20 79 7.4. LISP for Virtual Machine Mobility in Data Centers . . . . 20 80 8. Security Considerations . . . . . . . . . . . . . . . . . . . 21 81 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 82 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22 83 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 84 11.1. Normative References . . . . . . . . . . . . . . . . . . 22 85 11.2. Informative References . . . . . . . . . . . . . . . . . 24 86 Appendix A. A Brief History of Location/Identity Separation . . 25 87 A.1. Old LISP Models . . . . . . . . . . . . . . . . . . . . . 25 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 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. 127 o The LISP edge maps EIDs to RLOCs 129 o Within the underlay network, RLOCs have both locator and 130 identifier semantics 132 o An EID within a LISP site carries both identifier and locator 133 semantics to other nodes within that site 135 o An EID within a LISP site carries identifier and limited locator 136 semantics to nodes at other LISP sites (i.e., enough locator 137 information to tell that the EID is external to the site) 139 The relationship described above is not unique to LISP but it is 140 common to other overlay technologies. 142 The initial motivation in the LISP effort is to be find in the 143 routing scalability problem [RFC4984], where, if LISP is completely 144 deployed, the Internet core is populated with RLOCs while Traffic 145 Engineering mechanisms are pushed to the Mapping System. In such 146 scenario RLOCs are quasi-static (i.e., low churn), hence making the 147 routing system scalable [Quoitin], while EIDs can roam anywhere with 148 no churn to the underlying routing system. [RFC7215] discusses the 149 impact of LISP on the global routing system during the transition 150 period. However, the separation between location and identity that 151 LISP offers makes it suitable for use in additional scenarios such as 152 Traffic Engineering (TE), multihoming, and mobility among others. 154 This document describes the LISP architecture, its main operational 155 mechanisms as its design rationale. It is important to note that 156 this document does not specify or complement the LISP protocol. The 157 interested reader should refer to the main LISP specifications 158 [RFC6830] and the complementary documents [RFC6831], [RFC6832], 159 [RFC6833], [RFC6834], [RFC6835], [RFC6836], [RFC7052] for the 160 protocol specifications along with the LISP deployment guidelines 161 [RFC7215]. 163 2. Definition of Terms 165 This document describes the LISP architecture and does not define or 166 introduce any new term. The reader is referred to [RFC6830], 167 [RFC6831], [RFC6832], [RFC6833], [RFC6834], [RFC6835], [RFC6836], 168 [RFC7052], [RFC7215] for the LISP definition of terms. 170 3. LISP Architecture 172 This section presents the LISP architecture, it first details the 173 design principles of LISP and then it proceeds to describe its main 174 aspects: data-plane, control-plane, and internetworking mechanisms. 176 3.1. Design Principles 178 The LISP architecture is built on top of four basic design 179 principles: 181 o Locator/Identifier split: By decoupling the overloaded semantics 182 of the current IP addresses the Internet core can be assigned 183 identity meaningful addresses and hence, can use aggregation to 184 scale. Devices are assigned with relatively opaque identity 185 meaningful addresses that are independent of their topological 186 location. 188 o Overlay architecture: Overlays route packets over the current 189 Internet, allowing deployment of new protocols without changing 190 the current infrastructure hence, resulting into a low deployment 191 cost. 193 o Decoupled data and control-plane: Separating the data-plane from 194 the control-plane allows them to scale independently and use 195 different architectural approaches. This is important given that 196 they typically have different requirements and allows for other 197 data-planes to be added. While decoupled, data and control-plane 198 are not completely isolated because the LISP data-plane may 199 trigger control-plane activity. 201 o Incremental deployability: This principle ensures that the 202 protocol interoperates with the legacy Internet while providing 203 some of the targeted benefits to early adopters. 205 3.2. Overview of the Architecture 207 LISP splits architecturally the core from the edge of the Internet by 208 creating two separate namespaces: Endpoint Identifiers (EIDs) and 209 Routing LOCators (RLOCs). The edge consists of LISP sites (e.g., an 210 Autonomous System) that use EID addresses. EIDs are typically -but 211 not limited to- IPv4 or IPv6 addresses that uniquely identify 212 communication end-hosts and are assigned and configured by the same 213 mechanisms that exist at the time of this writing. EIDs do not 214 contain inter-domain topological information and because of this, 215 EIDs are usually routable at the edge (within LISP sites) or in the 216 non-LISP Internet. 218 With LISP, LISP sites (edge) and the core of the Internet are 219 interconnected by means of LISP-capable routers (e.g., border 220 routers) using tunnels. When packets originated from a LISP site are 221 flowing towards the core network, they ingress into an encapsulated 222 tunnel via an Ingress Tunnel Router (ITR). When packets flow from 223 the core network to a LISP site, they egress from an encapsulated 224 tunnel to an Egress Tunnel Router (ETR). An xTR is a router which 225 can perform both ITR and ETR operations. In this context ITRs 226 encapsulate packets while ETRs decapsulate them, hence LISP operates 227 as an overlay on top of the current Internet core. 229 /-----------------\ --- 230 | Mapping | | 231 . System | | Control 232 -| |`, | Plane 233 ,' \-----------------/ . | 234 / | --- 235 ,.., - _,....,, | ,.., | 236 / ` ,' ,-` `', | / ` | 237 / \ +-----+ ,' `, +-----+ / \ | 238 | EID |-| xTR |--/ RLOC ,--| xTR |-| EID | | Data 239 | Space |-| |--| Space |--| |-| Space | | Plane 240 \ / +-----+ . / +-----+ \ / | 241 `. .' `. ,' `. .' | 242 `'-` `., ,.' `'-` --- 243 ``'''`` 244 LISP Site (Edge) Core LISP Site (Edge) 246 Figure 1.- A schema of the LISP Architecture 248 With LISP, the core uses RLOCs, an RLOC is typically -but not limited 249 to- an IPv4 or IPv6 address assigned to an Internet-facing network 250 interface of an ITR or ETR. Typically RLOCs are numbered from 251 topologically aggregatable blocks assigned to a site at each point to 252 which it attaches to the global Internet, the topology is defined by 253 the connectivity of networks. 255 A typically distributed database, called the Mapping System, stores 256 mappings between EIDs and RLOCs. Such mappings relate the identity 257 of the devices attached to LISP sites (EIDs) to the set of RLOCs 258 configured at the LISP-capable routers servicing the site. 259 Furthermore, the mappings also include traffic engineering policies 260 and can be configured to achieve multihoming and load balancing. The 261 LISP Mapping System is conceptually similar to the DNS where it is 262 organized as a distributed multi-organization network database. With 263 LISP, ETRs register mappings while ITRs retrieve them. 265 Finally, the LISP architecture emphasizes a cost effective 266 incremental deployment. Given that LISP represents an overlay to the 267 current Internet architecture, endhosts as well as intra and inter- 268 domain routers remain unchanged, and the only required changes to the 269 existing infrastructure are to routers connecting the EID with the 270 RLOC space. Such LISP capable routers, in most cases, only require a 271 software upgrade. Additionally, LISP requires the deployment of an 272 independent Mapping System, such distributed database is a new 273 network entity. 275 The following describes a simplified packet flow sequence between two 276 nodes that are attached to LISP sites. Client HostA wants to send a 277 packet to server HostB. 279 /----------------\ 280 | Mapping | 281 | System | 282 .| |- 283 ` \----------------/ `. 284 ,` \ 285 / `. 286 ,' _,..-..,, ', 287 / -` `-, \ 288 .' ,' \ `, 289 ` ' \ ' 290 +-----+ | | RLOC_B1+-----+ 291 HostA | | | RLOC |-------| | HostB 292 EID_A--|ITR_A|----| Space | |ETR_B|--EID_B 293 | | RLOC_A1 |-------| | 294 +-----+ | | RLOC_B2+-----+ 295 , / 296 \ / 297 `', ,-` 298 ``''-''`` 300 Figure 2.- Packet flow sequence in LISP 302 1. HostA retrieves the EID_B of HostB (typically querying the DNS) 303 and generates an IP packet as in the Internet, the packet has 304 source address EID_A and destination address EID_B. 306 2. The packet is routed towards ITR_A in the LISP site using 307 standard intra-domain mechanisms. 309 3. ITR_A upon receiving the packet queries the Mapping System to 310 retrieve the locator of ETR_B that is servicing HostB's EID_B. 311 In order to do so it uses a LISP control message called Map- 312 Request, the message contains EID_B as the lookup key. In turn 313 it receives another LISP control message called Map-Reply, the 314 message contains two locators: RLOC_B1 and RLOC_B2 along with 315 traffic engineering policies: priority and weight per locator. 316 ITR_A also stores the mapping in a local cache to speed-up 317 forwarding of subsequent packets. 319 4. ITR_A encapsulates the packet towards RLOC_B1 (chosen according 320 to the priorities/weights specified in the mapping). The packet 321 contains two IP headers, the outer header has RLOC_A1 as source 322 and RLOC_B1 as destination, the inner original header has EID_A 323 as source and EID_B as destination. Furthermore ITR_A adds a 324 LISP header, more details about LISP encapsulation can be found 325 in Section 3.3.1. 327 5. The encapsulated packet is forwarded by the Internet core as a 328 normal IP packet, making the EID invisible from the Internet 329 core. 331 6. Upon reception of the encapsulated packet by ETR_B, it 332 decapsulates the packet and forwards it to HostB. 334 3.3. Data-Plane 336 This section provides a high-level description of the LISP data- 337 plane, which is specified in detail in [RFC6830]. The LISP data- 338 plane is responsible for encapsulating and decapsulating data packets 339 and caching the appropriate forwarding state. It includes two main 340 entities, the ITR and the ETR, both are LISP capable routers that 341 connect the EID with the RLOC space (ITR) and vice versa (ETR). 343 3.3.1. LISP Encapsulation 345 ITRs encapsulate data packets towards ETRs. LISP data packets are 346 encapsulated using UDP (port 4341). A particularity of LISP is that 347 UDP packets should include a zero checksum [RFC6935] [RFC6936] that 348 it is not verified in reception, LISP also supports non-zero 349 checksums that may be verified. This decision was made because the 350 typical transport protocols used by the applications already include 351 a checksum, by neglecting the additional UDP encapsulation checksum 352 xTRs can forward packets more efficiently. 354 LISP-encapsulated packets also include a LISP header (after the UDP 355 header and before the original IP header). The LISP header is 356 prepended by ITRs and striped by ETRs. It carries reachability 357 information (see more details in Section 4.2) and the Instance ID 358 field. The Instance ID field is used to distinguish traffic to/from 359 different tenant address spaces at the LISP site and that may use 360 overlapped but logically separated EID addressing. 362 Overall, LISP works on 4 headers, the inner header the source 363 constructed, and the 3 headers a LISP encapsulator prepends ("outer" 364 to "inner"): 366 1. Outer IP header containing RLOCs as source and destination 367 addresses. This header is originated by ITRs and stripped by 368 ETRs. 370 2. UDP header (port 4341) with zero checksum. This header is 371 originated by ITRs and stripped by ETRs. 373 3. LISP header that contains various forwarding-plane features (such 374 as reachability) and an Instance ID field. This header is 375 originated by ITRs and stripped by ETRs. 377 4. Inner IP header containing EIDs as source and destination 378 addresses. This header is created by the source end-host and is 379 left unchanged by LISP data plane processing on the ITR and ETR. 381 Finally, in some scenarios Recursive and/or Re-encapsulating tunnels 382 can be used for Traffic Engineering and re-routing. Re-encapsulating 383 tunnels are consecutive LISP tunnels and occur when a decapsulator 384 (an ETR action) removes a LISP header and then acts as an encapsultor 385 (an ITR action) to prepend another one. On the other hand, Recursive 386 tunnels are nested tunnels and are implemented by using multiple LISP 387 encapsulations on a packet. Typically such functions are implemented 388 by Reencapsulating Tunnel Routers (RTRs). An RTR can be thought as a 389 router that first acts as an ETR by decapsulating packets and then as 390 an ITR by encapsulating them towards another locator, more 391 information can be found at [RFC6830]. 393 3.3.2. LISP Forwarding State 395 In the LISP architecture, ITRs keep just enough information to route 396 traffic flowing through it. Meaning that, ITRs retrieve from the 397 LISP Mapping System mappings between EID prefixes and RLOCs that are 398 used to encapsulate packets. Such mappings are stored in a local 399 cache called the Map-Cache for subsequent packets addressed to the 400 same EID prefix. Note that, in case of overlapping EID-prefixes, 401 following a single request, the ITR may receive a set of mappings, 402 covering the requested EID-prefix and all more-specifics (cf., 403 Section 6.1.5 [RFC6830]). Mappings include a (Time-to-Live) TTL (set 404 by the ETR). More details about the Map-Cache management can be 405 found in Section 4.1. 407 3.4. Control-Plane 409 The LISP control-plane, specified in [RFC6833], provides a standard 410 interface to register and request mappings. The LISP Mapping System 411 is a database that stores such mappings. The following first 412 describes the mappings, then the standard interface to the Mapping 413 System, and finally its architecture. 415 3.4.1. LISP Mappings 417 Each mapping includes the bindings between EID prefix(es) and set of 418 RLOCs as well as traffic engineering policies, in the form of 419 priorities and weights for the RLOCs. Priorities allow the ETR to 420 configure active/backup policies while weights are used to load- 421 balance traffic among the RLOCs (on a per-flow basis). 423 Typical mappings in LISP bind EIDs in the form of IP prefixes with a 424 set of RLOCs, also in the form of IPs. IPv4 and IPv6 addresses are 425 encoded using the appropriate Address Family Identifier (AFI) 426 [RFC3232]. However LISP can also support more general address 427 encoding by means of the ongoing effort around the LISP Canonical 428 Address Format (LCAF) [I-D.ietf-lisp-lcaf]. 430 With such a general syntax for address encoding in place, LISP aims 431 to provide flexibility to current and future applications. For 432 instance LCAFs could support MAC addresses, geo-coordinates, ASCII 433 names and application specific data. 435 3.4.2. Mapping System Interface 437 LISP defines a standard interface between data and control planes. 438 The interface is specified in [RFC6833] and defines two entities: 440 Map-Server: A network infrastructure component that learns mappings 441 from ETRs and publishes them into the LISP Mapping System. 442 Typically Map-Servers are not authoritative to reply to queries 443 and hence, they forward them to the ETR. However they can also 444 operate in proxy-mode, where the ETRs delegate replying to queries 445 to Map-Servers. This setup is useful when the ETR has limited 446 resources (i.e., CPU or power). 448 Map-Resolver: A network infrastructure component that interfaces 449 ITRs with the Mapping System by proxying queries and in some cases 450 responses. 452 The interface defines four LISP control messages which are sent as 453 UDP datagrams (port 4342): 455 Map-Register: This message is used by ETRs to register mappings in 456 the Mapping System and it is authenticated using a shared key 457 between the ETR and the Map-Server. 459 Map-Notify: When requested by the ETR, this message is sent by the 460 Map-Server in response to a Map-Register to acknowledge the 461 correct reception of the mapping and convey the latest Map-Server 462 state on the EID to RLOC mapping. In some cases a Map-Notify can 463 be sent to the previous RLOCs when an EID is registered by a new 464 set of RLOCs. 466 Map-Request: This message is used by ITRs or Map-Resolvers to 467 resolve the mapping of a given EID. 469 Map-Reply: This message is sent by Map-Servers or ETRs in response 470 to a Map-Request and contains the resolved mapping. Please note 471 that a Map-Reply may contain a negative reply if, for example, the 472 queried EID is not part of the LISP EID space. In such cases the 473 ITR typically forwards the traffic natively (non encapsulated) to 474 the public Internet, this behavior is defined to support 475 incremental deployment of LISP. 477 3.4.3. Mapping System 479 LISP architecturally decouples control and data-plane by means of a 480 standard interface. This interface glues the data-plane, routers 481 responsible for forwarding data-packets, with the LISP Mapping 482 System, a database responsible for storing mappings. 484 With this separation in place the data and control-plane can use 485 different architectures if needed and scale independently. Typically 486 the data-plane is optimized to route packets according to 487 hierarchical IP addresses. However the control-plane may have 488 different requirements, for instance and by taking advantage of the 489 LCAFs, the Mapping System may be used to store non-hierarchical keys 490 (such as MAC addresses), requiring different architectural approaches 491 for scalability. Another important difference between the LISP 492 control and data-planes is that, and as a result of the local mapping 493 cache available at ITR, the Mapping System does not need to operate 494 at line-rate. 496 Many of the existing mechanisms to create distributed systems have 497 been explored and considered for the Mapping System architecture: 498 graph-based databases in the form of LISP+ALT [RFC6836], hierarchical 499 databases in the form of LISP-DDT [I-D.ietf-lisp-ddt], monolithic 500 databases in the form of LISP-NERD [RFC6837], flat databases in the 501 form of LISP-DHT [I-D.cheng-lisp-shdht],[Mathy] and, a multicast- 502 based database [I-D.curran-lisp-emacs]. Furthermore it is worth 503 noting that, in some scenarios such as private deployments, the 504 Mapping System can operate as logically centralized. In such cases 505 it is typically composed of a single Map-Server/Map-Resolver. 507 The following focuses on the two mapping systems that have been 508 implemented and deployed (LISP-ALT and LISP+DDT). 510 3.4.3.1. LISP+ALT 512 The LISP Alternative Topology (LISP+ALT) [RFC6836] was the first 513 Mapping System proposed, developed and deployed on the LISP pilot 514 network. It is based on a distributed BGP overlay participated by 515 Map-Servers and Map-Resolvers. The nodes connect to their peers 516 through static tunnels. Each Map-Server involved in the ALT topology 517 advertises the EID-prefixes registered by the serviced ETRs, making 518 the EID routable on the ALT topology. 520 When an ITR needs a mapping it sends a Map-Request to a Map-Resolver 521 that, using the ALT topology, forwards the Map-Request towards the 522 Map-Server responsible for the mapping. Upon reception the Map- 523 Server forwards the request to the ETR that in turn, replies directly 524 to the ITR using the native Internet core. 526 3.4.3.2. LISP-DDT 528 LISP-DDT [I-D.ietf-lisp-ddt] is conceptually similar to the DNS, a 529 hierarchical directory whose internal structure mirrors the 530 hierarchical nature of the EID address space. The DDT hierarchy is 531 composed of DDT nodes forming a tree structure, the leafs of the tree 532 are Map-Servers. On top of the structure there is the DDT root node 533 [DDT-ROOT], which is a particular instance of a DDT node and that 534 matches the entire address space. As in the case of DNS, DDT 535 supports multiple redundant DDT nodes and/or DDT roots. Finally, 536 Map-Resolvers are the clients of the DDT hierarchy and can query 537 either the DDT root and/or other DDT nodes. 539 /---------\ 540 | | 541 | DDT Root| 542 | /0 | 543 ,.\---------/-, 544 ,-'` | `'., 545 -'` | `- 546 /-------\ /-------\ /-------\ 547 | DDT | | DDT | | DDT | 548 | Node | | Node | | Note | ... 549 | 0/8 | | 1/8 | | 2/8 | 550 \-------/ \-------/ \-------/ 551 _. _. . -..,,,_ 552 -` -` \ ````''-- 553 +------------+ +------------+ +------------+ +------------+ 554 | Map-Server | | Map-Server | | Map-Server | | Map-Server | 555 | EID-prefix1| | EID-prefix2| | EID-prefix3| | EID-prefix4| 556 +------------+ +------------+ +------------+ +------------+ 558 Figure 3.- A schematic representation of the DDT tree structure, 559 please note that the prefixes and the structure depicted 560 should be only considered as an example. 562 The DDT structure does not actually index EID-prefixes but eXtended 563 EID-prefixes (XEID). An XEID-prefix is just the concatenation of the 564 following fields (from most significant bit to less significant bit): 565 Database-ID, Instance ID, Address Family Identifier and the actual 566 EID-prefix. The Database-ID is provided for possible future 567 requirements of higher levels in the hierarchy and to enable the 568 creation of multiple and separate database trees. 570 In order to resolve a query LISP-DDT operates in a similar way to the 571 DNS but only supports iterative lookups. DDT clients (usually Map- 572 Resolvers) generate Map-Requests to the DDT root node. In response 573 they receive a newly introduced LISP-control message: a Map-Referral. 574 A Map-Referral provides the list of RLOCs of the set of DDT nodes 575 matching a configured XEID delegation. That is, the information 576 contained in the Map-Referral points to the child of the queried DDT 577 node that has more specific information about the queried XEID- 578 prefix. This process is repeated until the DDT client walks the tree 579 structure (downwards) and discovers the Map-Server servicing the 580 queried XEID. At this point the client sends a Map-Request and 581 receives a Map-Reply containing the mappings. It is important to 582 note that DDT clients can also cache the information contained in 583 Map-Referrals, that is, they cache the DDT structure. This is used 584 to reduce the mapping retrieving latency[Jakab]. 586 The DDT Mapping System relies on manual configuration. That is Map- 587 Resolvers are manually configured with the set of available DDT root 588 nodes while DDT nodes are manually configured with the appropriate 589 XEID delegations. Configuration changes in the DDT nodes are only 590 required when the tree structure changes itself, but it doesn't 591 depend on EID dynamics (RLOC allocation or traffic engineering policy 592 changes). 594 3.5. Internetworking Mechanisms 596 EIDs are typically identical to either IPv4 or IPv6 addresses and 597 they are stored in the LISP Mapping System, however they are usually 598 not announced in the Internet global routing system. As a result 599 LISP requires an internetworking mechanism to allow LISP sites to 600 speak with non-LISP sites and vice versa. LISP internetworking 601 mechanisms are specified in [RFC6832]. 603 LISP defines two entities to provide internetworking: 605 Proxy Ingress Tunnel Router (PITR): PITRs provide connectivity from 606 the legacy Internet to LISP sites. PITRs announce in the global 607 routing system blocks of EID prefixes (aggregating when possible) 608 to attract traffic. For each incoming packet from a source not in 609 a LISP site (a non-EID), the PITR LISP-encapsulates it towards the 610 RLOC(s) of the appropriate LISP site. The impact of PITRs in the 611 routing table size of the Default-Free Zone (DFZ) is, in the 612 worst-case, similar to the case in which LISP is not deployed. 613 EID-prefixes will be aggregated as much as possible both by the 614 PITR and by the global routing system. 616 Proxy Egress Tunnel Router (PETR): PETRs provide connectivity from 617 LISP sites to the legacy Internet. In some scenarios, LISP sites 618 may be unable to send encapsulated packets with a local EID 619 address as a source to the legacy Internet. For instance when 620 Unicast Reverse Path Forwarding (uRPF) is used by Provider Edge 621 routers, or when an intermediate network between a LISP site and a 622 non-LISP site does not support the desired version of IP (IPv4 or 623 IPv6). In both cases the PETR overcomes such limitations by 624 encapsulating packets over the network. There is no specified 625 provision for the distribution of PETR RLOC addresses to the ITRs. 627 Additionally, LISP also defines mechanisms to operate with private 628 EIDs [RFC1918] by means of LISP-NAT [RFC6832]. In this case the xTR 629 replaces a private EID source address with a routable one. At the 630 time of this writing, work is ongoing to define NAT-traversal 631 capabilities, that is xTRs behind a NAT using non-routable RLOCs. 633 4. LISP Operational Mechanisms 635 This section details the main operational mechanisms defined in LISP. 637 4.1. Cache Management 639 LISP's decoupled control and data-plane, where mappings are stored in 640 the control-plane and used for forwarding in the data plane, requires 641 a local cache in ITRs to reduce signaling overhead (Map-Request/Map- 642 Reply) and increase forwarding speed. The local cache available at 643 the ITRs, called Map-Cache, is used by the router to LISP-encapsulate 644 packets. The Map-Cache is indexed by (Instance ID, EID-prefix) and 645 contains basically the set of RLOCs with the associated traffic 646 engineering policies (priorities and weights). 648 The Map-Cache, as any other cache, requires cache coherence 649 mechanisms to maintain up-to-date information. LISP defines three 650 main mechanisms for cache coherence: 652 Time-To-Live (TTL): Each mapping contains a TTL set by the ETR, upon 653 expiration of the TTL the ITR has to refresh the mapping by 654 sending a new Map-Request. Typical values for TTL defined by LISP 655 are 24 hours. 657 Solicit-Map-Request (SMR): SMR is an explicit mechanism to update 658 mapping information. In particular a special type of Map-Request 659 can be sent on demand by ETRs to request refreshing a mapping. 660 Upon reception of a SMR message, the ITR must refresh the bindings 661 by sending a Map-Request to the Mapping System. Further uses of 662 SMRs are documented in [RFC6830]. 664 Map-Versioning: This optional mechanism piggybacks in the LISP 665 header of data-packets the version number of the mappings used by 666 an xTR. This way, when an xTR receives a LISP-encapsulated packet 667 from a remote xTR, it can check whether its own Map-Cache or the 668 one of the remote xTR is outdated. If its Map-Cache is outdated, 669 it sends a Map-Request for the remote EID so to obtain the newest 670 mappings. On the contrary, if it detects that the remote xTR Map- 671 Cache is outdated, it sends a SMR to notify it that a new mapping 672 is available. 674 Finally it is worth noting that in some cases an entry in the map- 675 cache can be proactively refreshed using the mechanisms described in 676 the section below. 678 4.2. RLOC Reachability 680 The LISP architecture is an edge to edge pull architecture, where the 681 network state is stored in the control-plane while the data-plane 682 pulls it on demand. This has consequences concerning the propagation 683 of xTRs reachability/liveness information. On the contrary BGP is a 684 push architecture, where the required network state is pushed by 685 means of BGP UPDATE messages to BGP speakers. In push architectures, 686 reachability information is also pushed to the interested routers. 687 However pull architectures require explicit mechanisms to propagate 688 reachability information. LISP defines a set of mechanisms to inform 689 ITRs and PITRS about the reachability of the cached RLOCs: 691 Locator Status Bits (LSB): LSB is a passive technique, the LSB field 692 is carried by data-packets in the LISP header and can be set by a 693 ETRs to specify which RLOCs of the ETR site are up/down. This 694 information can be used by the ITRs as a hint about the reachability 695 to perform additional checks. Also note that LSB does not provide 696 path reachability status, only hints on the status of RLOCs. 698 Echo-nonce: This is also a passive technique, that can only operate 699 effectively when data flows bi-directionally between two 700 communicating xTRs. Basically, an ITR piggybacks a random number 701 (called nonce) in LISP data packets, if the path and the probed 702 locator are up, the ETR will piggyback the same random number on the 703 next data-packet, if this is not the case the ITR can set the locator 704 as unreachable. When traffic flow is unidirectional or when the ETR 705 receiving the traffic is not the same as the ITR that transmits it 706 back, additional mechanisms are required. 708 RLOC-probing: This is an active probing algorithm where ITRs send 709 probes to specific locators, this effectively probes both the locator 710 and the path. In particular this is done by sending a Map-Request 711 (with certain flags activated) on the data-plane (RLOC space) and 712 waiting in return a Map-Reply, also sent on the data-plane. The 713 active nature of RLOC-probing provides an effective mechanism to 714 determine reachability and, in case of failure, switching to a 715 different locator. Furthermore the mechanism also provides useful 716 RTT estimates of the delay of the path that can be used by other 717 network algorithms. 719 Additionally, LISP also recommends inferring reachability of locators 720 by using information provided by the underlay, in particular: 722 It is worth noting that RLOC probing and Echo-nonce can work 723 together. Specifically if a nonce is not echoed, an ITR could RLOC- 724 probe to determine if the path is up when it cannot tell the 725 difference between a failed bidirectional path or the return path is 726 not used (a unidirectional path). 728 ICMP signaling: The LISP underlay -the current Internet- uses the 729 ICMP protocol to signal unreachability (among other things). LISP 730 can take advantage of this and the reception of a ICMP Network 731 Unreachable or ICMP Host Unreachable message can be seen as a hint 732 that a locator might be unreachable, this should lead to perform 733 additional checks. 735 Underlay routing: Both BGP and IBGP carry reachability information, 736 LISP-capable routers that have access to underlay routing information 737 can use it to determine if a given locator or path are reachable. 739 4.3. ETR Synchronization 741 All the ETRs that are authoritative to a particular EID-prefix must 742 announce the same mapping to the requesters, this means that ETRs 743 must be aware of the status of the RLOCs of the remaining ETRs. This 744 is known as ETR synchronization. 746 At the time of this writing LISP does not specify a mechanism to 747 achieve ETR synchronization. Although many well-known techniques 748 could be applied to solve this issue it is still under research, as a 749 result operators must rely on coherent manual configuration 751 4.4. MTU Handling 753 Since LISP encapsulates packets it requires dealing with packets that 754 exceed the MTU of the path between the ITR and the ETR. Specifically 755 LISP defines two mechanisms: 757 Stateless: With this mechanism the effective MTU is assumed from the 758 ITR's perspective. If a payload packet is too big for the 759 effective MTU, and can be fragmented, the payload packet is 760 fragmented on the ITR, such that reassembly is performed at the 761 destination host. 763 Stateful: With this mechanism ITRs keep track of the MTU of the 764 paths towards the destination locators by parsing the ICMP Too Big 765 packets sent by intermediate routers. Additionally ITRs will send 766 ICMP Too Big messages to inform the sources about the effective 767 MTU. 769 In both cases if the packet cannot be fragmented (IPv4 with DF=1 or 770 IPv6) then the ITR drops it and replies with a ICMP Too Big message 771 to the source. 773 5. Mobility 775 The separation between locators and identifiers in LISP was initially 776 proposed for traffic engineering purpose where LISP sites can change 777 their attachment points to the Internet (i.e., RLOCs) without 778 impacting endpoints or the Internet core. In this context, the 779 border routers operate the xTR functionality and endpoints are not 780 aware of the existence of LISP. This functionality is similar to 781 Network Mobility [RFC3963]. However, this mode of operation does not 782 allow seamless mobility of endpoints between different LISP sites as 783 the EID address might not be routable in a visited site. 784 Nevertheless, LISP can be used to enable seamless IP mobility when 785 LISP is directly implemented in the endpoint or when the endpoint 786 roams to an attached xTR. Each endpoint is then an xTR and the EID 787 address is the one presented to the network stack used by 788 applications while the RLOC is the address gathered from the network 789 when it is visited. This functionality is similar to Mobile IP 790 ([RFC5944] and [RFC6275]). 792 Whenever the device changes of RLOC, the xTR updates the RLOC of its 793 local mapping and registers it to its Map-Server, typically with a 794 low TTL value (1min). To avoid the need of a home gateway, the ITR 795 also indicates the RLOC change to all remote devices that have 796 ongoing communications with the device that moved. The combination 797 of both methods ensures the scalability of the system as signaling is 798 strictly limited the Map-Server and to hosts with which 799 communications are ongoing. 801 The decoupled identity and location provided by LISP allows it to 802 operate with other layer 2 and layer 3 mobility solutions. 804 6. Multicast 806 LISP also supports transporting IP multicast packets sent from the 807 EID space, the operational changes required to the multicast 808 protocols are documented in [RFC6831]. 810 In such scenarios, LISP may create multicast state both at the core 811 and at the sites (both source and receiver). When signaling is used 812 to create multicast state at the sites, LISP routers unicast 813 encapsulate PIM Join/Prune messages from receiver to source sites. 814 At the core, ETRs build a new PIM Join/Prune message addressed to the 815 RLOC of the ITR servicing the source. An simplified sequence is 816 shown below 818 1. An end-host willing to join a multicast channel sends an IGMP 819 report. Multicast PIM routers at the LISP site propagate PIM 820 Join/Prune messages (S-EID, G) towards the ETR. 822 2. The join message flows to the ETR, upon reception the ETR builds 823 two join messages, the first one unicast LISP-encapsulates the 824 original join message towards the RLOC of the ITR servicing the 825 source. This message creates (S-EID, G) multicast state at the 826 source site. The second join message contains as destination 827 address the RLOC of the ITR servicing the source (S-RLOC, G) and 828 creates multicast state at the core. 830 3. Multicast data packets originated by the source (S-EID, G) flow 831 from the source to the ITR. The ITR LISP-encapsulates the 832 multicast packets, the outter header includes its own RLOC as the 833 source (S-RLOC) and the original multicast group address (G) as 834 the destination. Please note that multicast group address are 835 logical and are not resolved by the mapping system. Then the 836 multicast packet is transmitted through the core towards the 837 receiving ETRs that decapsulates the packets and sends them using 838 the receiver's site multicast state. 840 LISP [RFC6831] supports all PIM modes, additionally LISP can also 841 support non-PIM mechanisms to maintain multicast state. 843 7. Use Cases 845 7.1. Traffic Engineering 847 BGP is the standard protocol to implement inter-domain routing. With 848 BGP, routing informations are propagated along the network and each 849 autonomous system can implement its own routing policy that will 850 influence the way routing information are propagated. The direct 851 consequence is that an autonomous system cannot precisely control the 852 way the traffic will enter the network. 854 As opposed to BGP, a LISP site can strictly impose via which ETRs the 855 traffic must enter the the LISP site network even though the path 856 followed to reach the ETR is not under the control of the LISP site. 857 This fine control is implemented with the mappings. When a remote 858 site is willing to send traffic to a LISP site, it retrieves the 859 mapping associated to the destination EID via the mapping system. 860 The mapping is sent directly by an authoritative ETR of the EID and 861 is not altered by any intermediate network. 863 A mapping associates a list of RLOCs to an EID prefix. Each RLOC 864 corresponds to an interface of an ETR (or set of ETRs) that is able 865 to correctly forward packets to EIDs in the prefix. Each RLOC is 866 tagged with a priority and a weight in the mapping. The priority is 867 used to indicates which RLOCs should be preferred to send packets 868 (the least preferred ones being provided for backup purpose). The 869 weight permits to balance the load between the RLOCs with the same 870 priority, proportionally to the weight value. 872 As mappings are directly issued by the authoritative ETR of the EID 873 and are not altered while transmitted to the remote site, it offers 874 highly flexible incoming inter-domain traffic engineering with even 875 the possibility for a site to issue a different mapping for each 876 remote site, implementing so precise routing policies. 878 7.2. LISP for IPv6 Co-existence 880 LISP encapsulations allows to transport packets using EIDs from a 881 given address family (e.g., IPv6) with packets from other address 882 families (e.g., IPv4). The absence of correlation between the 883 address family of RLOCs and EIDs makes LISP a candidate to allow, 884 e.g., IPv6 to be deployed when all of the core network may not have 885 IPv6 enabled. 887 For example, two IPv6-only data centers could be interconnected via 888 the legacy IPv4 Internet. If their border routers are LISP capable, 889 sending packets between the data center is done without any form of 890 translation as the native IPv6 packets (in the EID space) will be 891 LISP encapsulated and transmitted over the IPv4 legacy Internet by 892 the mean of IPv4 RLOCs. 894 7.3. LISP for Virtual Private Networks 896 It is common to operate several virtual networks over the same 897 physical infrastructure. In such virtual private networks, it is 898 essential to distinguish which virtual network a packet belongs and 899 tags or labels are used for that purpose. When using LISP, the 900 distinction can be made with the Instance ID field. When an ITR 901 encapsulates a packet from a particular virtual network (e.g., known 902 via the VRF or VLAN), it tags the encapsulated packet with the 903 Instance ID corresponding to the virtual network of the packet. When 904 an ETR receives a packet tagged with an Instance ID it uses the 905 Instance ID to determine how to treat the packet. 907 The main usage of LISP for virtual private networks does not 908 introduce additional requirements on the underlying network, as long 909 as it is running IP. 911 7.4. LISP for Virtual Machine Mobility in Data Centers 913 A way to enable seamless virtual machine mobility in data center is 914 to conceive the datacenter backbone as the RLOC space and the subnet 915 where servers are hosted as forming the EID space. A LISP router is 916 placed at the border between the backbone and each subnet. When a 917 virtual machine is moved to another subnet, it can keep (temporarily) 918 the address it had before the move so to continue without a transport 919 layer connection reset. When an xTR detects a source address 920 received on a subnet to be an address not assigned to the subnet, it 921 registers the address to the Mapping System. 923 To inform the other LISP routers that the machine moved and where, 924 and then to avoid detours via the initial subnetwork, mechanisms such 925 as the Solicit-Map-Request messages are used. 927 8. Security Considerations 929 This section describes the security considerations associated to the 930 LISP protocol. 932 LISP uses a pull architecture to learn mappings. While in a push 933 system, the state necessary to forward packets is learned 934 independently of the traffic itself, with a pull architecture, the 935 system becomes reactive and data-plane events (e.g., the arrival of a 936 packet for an unknown destination) may trigger control-plane events. 937 This on-demand learning of mappings provides many advantages as 938 discussed above but may also affect the way security is enforced. 940 Usually, the data-plane is implemented in the fast path of routers to 941 provide high performance forwarding capabilities while the control- 942 plane features are implemented in the slow path to offer high 943 flexibility and a performance gap of several order of magnitude can 944 be observed between the slow and the fast paths. As a consequence, 945 the way data-plane events are notified to the control-plane must be 946 thought carefully so to not overload the slow path and rate limiting 947 should be used as specified in [RFC6830]. 949 Care must also be taken so to not overload the mapping system (i.e., 950 the control plane infrastructure) as the operations to be performed 951 by the mapping system may be more complex than those on the data- 952 plane, for that reason [RFC6830] recommends to rate limit the sending 953 of messages to the mapping system. 955 To improve resiliency and reduce the overall number of messages 956 exchanged, LISP offers the possibility to leak information, such as 957 reachabilty of locators, directly into data plane packets. In 958 environments that are not fully trusted, control informations gleaned 959 from data-plane packets should be verified before using them. 961 Mappings are the centrepiece of LISP and all precautions must be 962 taken to avoid them to be manipulated or misused by malicious 963 entities. Using trustable Map-Servers that strictly respect 964 [RFC6833] and the lightweight authentication mechanism proposed by 965 LISP-Sec [I-D.ietf-lisp-sec] reduces the risk of attacks to the 966 mapping integrity. In more critical environments, secure measures 967 may be needed. 969 As with any other tunneling mechanism, middleboxes on the path 970 between an ITR (or PITR) and an ETR (or PETR) must implement 971 mechanisms to strip the LISP encapsulation to correctly inspect the 972 content of LISP encapsulated packets. 974 Like other map-and-encap mechanisms, LISP enables triangular routing 975 (i.e., packets of a flow cross different border routers depending on 976 their direction). This means that intermediate boxes may have 977 incomplete view on the traffic they inspect or manipulate. 979 More details about security implications of LISP are discussed in 980 [I-D.ietf-lisp-threats]. 982 9. IANA Considerations 984 This memo includes no request to IANA. 986 10. Acknowledgements 988 This document was initiated by Noel Chiappa and much of the core 989 philosophy came from him. The authors acknowledge the important 990 contributions he has made to this work and thank him for his past 991 efforts. 993 The authors would also like to thank Dino Farinacci, Fabio Maino, 994 Luigi Iannone, Sharon Barakai, Isidoros Kouvelas, Christian Cassar, 995 Florin Coras, Marc Binderberger, Alberto Rodriguez-Natal, Ronald 996 Bonica, Chad Hintz, Robert Raszuk, Joel M. Halpern, Darrel Lewis, as 997 well as every people acknowledged in [RFC6830]. 999 11. References 1001 11.1. Normative References 1003 [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and 1004 E. Lear, "Address Allocation for Private Internets", BCP 1005 5, RFC 1918, February 1996. 1007 [RFC3232] Reynolds, J., "Assigned Numbers: RFC 1700 is Replaced by 1008 an On-line Database", RFC 3232, January 2002. 1010 [RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. 1011 Thubert, "Network Mobility (NEMO) Basic Support Protocol", 1012 RFC 3963, January 2005. 1014 [RFC4984] Meyer, D., Zhang, L., and K. Fall, "Report from the IAB 1015 Workshop on Routing and Addressing", RFC 4984, September 1016 2007. 1018 [RFC5944] Perkins, C., "IP Mobility Support for IPv4, Revised", RFC 1019 5944, November 2010. 1021 [RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support 1022 in IPv6", RFC 6275, July 2011. 1024 [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The 1025 Locator/ID Separation Protocol (LISP)", RFC 6830, January 1026 2013. 1028 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The 1029 Locator/ID Separation Protocol (LISP) for Multicast 1030 Environments", RFC 6831, January 2013. 1032 [RFC6832] Lewis, D., Meyer, D., Farinacci, D., and V. Fuller, 1033 "Interworking between Locator/ID Separation Protocol 1034 (LISP) and Non-LISP Sites", RFC 6832, January 2013. 1036 [RFC6833] Fuller, V. and D. Farinacci, "Locator/ID Separation 1037 Protocol (LISP) Map-Server Interface", RFC 6833, January 1038 2013. 1040 [RFC6834] Iannone, L., Saucez, D., and O. Bonaventure, "Locator/ID 1041 Separation Protocol (LISP) Map-Versioning", RFC 6834, 1042 January 2013. 1044 [RFC6835] Farinacci, D. and D. Meyer, "The Locator/ID Separation 1045 Protocol Internet Groper (LIG)", RFC 6835, January 2013. 1047 [RFC6836] Fuller, V., Farinacci, D., Meyer, D., and D. Lewis, 1048 "Locator/ID Separation Protocol Alternative Logical 1049 Topology (LISP+ALT)", RFC 6836, January 2013. 1051 [RFC6837] Lear, E., "NERD: A Not-so-novel Endpoint ID (EID) to 1052 Routing Locator (RLOC) Database", RFC 6837, January 2013. 1054 [RFC6935] Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and 1055 UDP Checksums for Tunneled Packets", RFC 6935, April 2013. 1057 [RFC6936] Fairhurst, G. and M. Westerlund, "Applicability Statement 1058 for the Use of IPv6 UDP Datagrams with Zero Checksums", 1059 RFC 6936, April 2013. 1061 [RFC7052] Schudel, G., Jain, A., and V. Moreno, "Locator/ID 1062 Separation Protocol (LISP) MIB", RFC 7052, October 2013. 1064 [RFC7215] Jakab, L., Cabellos-Aparicio, A., Coras, F., Domingo- 1065 Pascual, J., and D. Lewis, "Locator/Identifier Separation 1066 Protocol (LISP) Network Element Deployment 1067 Considerations", RFC 7215, April 2014. 1069 11.2. Informative References 1071 [Chiappa] Chiappa, J., "Endpoints and Endpoint names: A Propose 1072 Enhancement to the Internet Architecture, 1073 http://mercury.lcs.mit.edu/~jnc/tech/endpoints.txt", 1999. 1075 [DDT-ROOT] 1076 LISP DDT ROOT, , "http://ddt-root.org/", August 2013. 1078 [I-D.cheng-lisp-shdht] 1079 Cheng, L. and J. Wang, "LISP Single-Hop DHT Mapping 1080 Overlay", draft-cheng-lisp-shdht-04 (work in progress), 1081 July 2013. 1083 [I-D.curran-lisp-emacs] 1084 Brim, S., Farinacci, D., Meyer, D., and J. Curran, "EID 1085 Mappings Multicast Across Cooperating Systems for LISP", 1086 draft-curran-lisp-emacs-00 (work in progress), November 1087 2007. 1089 [I-D.ietf-lisp-ddt] 1090 Fuller, V., Lewis, D., Ermagan, V., and A. Jain, "LISP 1091 Delegated Database Tree", draft-ietf-lisp-ddt-02 (work in 1092 progress), October 2014. 1094 [I-D.ietf-lisp-lcaf] 1095 Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical 1096 Address Format (LCAF)", draft-ietf-lisp-lcaf-07 (work in 1097 progress), December 2014. 1099 [I-D.ietf-lisp-sec] 1100 Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D. 1101 Saucez, "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-07 1102 (work in progress), October 2014. 1104 [I-D.ietf-lisp-threats] 1105 Saucez, D., Iannone, L., and O. Bonaventure, "LISP Threats 1106 Analysis", draft-ietf-lisp-threats-11 (work in progress), 1107 December 2014. 1109 [Jakab] Jakab, L., Cabellos, A., Saucez, D., and O. Bonaventure, 1110 "LISP-TREE: A DNS Hierarchy to Support the LISP Mapping 1111 System, IEEE Journal on Selected Areas in Communications, 1112 vol. 28, no. 8, pp. 1332-1343", October 2010. 1114 [Mathy] Mathy, L., Iannone, L., and O. Bonaventure, "LISP-DHT: 1115 Towards a DHT to map identifiers onto locators. The ACM 1116 ReArch, Re-Architecting the Internet. Madrid (Spain)", 1117 December 2008. 1119 [Quoitin] Quoitin, B., Iannone, L., Launois, C., and O. Bonaventure, 1120 ""Evaluating the Benefits of the Locator/Identifier 1121 Separation" in Proceedings of 2Nd ACM/IEEE International 1122 Workshop on Mobility in the Evolving Internet 1123 Architecture", 2007. 1125 Appendix A. A Brief History of Location/Identity Separation 1127 The LISP system for separation of location and identity resulted from 1128 the discussions of this topic at the Amsterdam IAB Routing and 1129 Addressing Workshop, which took place in October 2006 [RFC4984]. 1131 A small group of like-minded personnel from various scattered 1132 locations within Cisco, spontaneously formed immediately after that 1133 workshop, to work on an idea that came out of informal discussions at 1134 the workshop and on various mailing lists. The first Internet-Draft 1135 on LISP appeared in January, 2007. 1137 Trial implementations started at that time, with initial trial 1138 deployments underway since June 2007; the results of early experience 1139 have been fed back into the design in a continuous, ongoing process 1140 over several years. LISP at this point represents a moderately 1141 mature system, having undergone a long organic series of changes and 1142 updates. 1144 LISP transitioned from an IRTF activity to an IETF WG in March 2009, 1145 and after numerous revisions, the basic specifications moved to 1146 becoming RFCs at the start of 2013 (although work to expand and 1147 improve it, and find new uses for it, continues, and undoubtly will 1148 for a long time to come). 1150 A.1. Old LISP Models 1152 LISP, as initially conceived, had a number of potential operating 1153 modes, named 'models'. Although they are note used anymore, one 1154 occasionally sees mention of them, so they are briefly described 1155 here. 1157 LISP 1: EIDs all appear in the normal routing and forwarding tables 1158 of the network (i.e. they are 'routable');this property is used to 1159 'bootstrap' operation, by using this to load EID->RLOC mappings. 1160 Packets were sent with the EID as the destination in the outer 1161 wrapper; when an ETR saw such a packet, it would send a Map-Reply 1162 to the source ITR, giving the full mapping. 1164 LISP 1.5: Similar to LISP 1, but the routability of EIDs happens on 1165 a separate network. 1167 LISP 2: EIDs are not routable; EID->RLOC mappings are available from 1168 the DNS. 1170 LISP 3: EIDs are not routable; and have to be looked up in in a new 1171 EID->RLOC mapping database (in the initial concept, a system using 1172 Distributed Hash Tables). Two variants were possible: a 'push' 1173 system, in which all mappings were distributed to all ITRs, and a 1174 'pull' system in which ITRs load the mappings they need, as 1175 needed. 1177 Authors' Addresses 1179 Albert Cabellos 1180 UPC-BarcelonaTech 1181 c/ Jordi Girona 1-3 1182 Barcelona, Catalonia 08034 1183 Spain 1185 Email: acabello@ac.upc.edu 1187 Damien Saucez (Ed.) 1188 INRIA 1189 2004 route des Lucioles BP 93 1190 Sophia Antipolis Cedex 06902 1191 France 1193 Email: damien.saucez@inria.fr