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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Moskowitz 3 Internet-Draft Verizon 4 Obsoletes: 4423 (if approved) September 1, 2011 5 Intended status: Standards Track 6 Expires: March 4, 2012 8 Host Identity Protocol Architecture 9 draft-ietf-hip-rfc4423-bis-03 11 Abstract 13 This memo describes a new namespace, the Host Identity namespace, and 14 a new protocol layer, the Host Identity Protocol, between the 15 internetworking and transport layers. Herein are presented the 16 basics of the current namespaces, their strengths and weaknesses, and 17 how a new namespace will add completeness to them. The roles of this 18 new namespace in the protocols are defined. 20 This document obsoletes RFC 4423 and addresses the concerns raised by 21 the IESG, particularly that of crypto agility. It incorporates 22 lessons learned from the implementations of RFC 5201 and goes further 23 to explain how HIP works as a secure signalling channel. 25 Status of this Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on March 4, 2012. 42 Copyright Notice 44 Copyright (c) 2011 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 This document may contain material from IETF Documents or IETF 58 Contributions published or made publicly available before November 59 10, 2008. The person(s) controlling the copyright in some of this 60 material may not have granted the IETF Trust the right to allow 61 modifications of such material outside the IETF Standards Process. 62 Without obtaining an adequate license from the person(s) controlling 63 the copyright in such materials, this document may not be modified 64 outside the IETF Standards Process, and derivative works of it may 65 not be created outside the IETF Standards Process, except to format 66 it for publication as an RFC or to translate it into languages other 67 than English. 69 Table of Contents 71 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 72 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5 73 2.1. Terms common to other documents . . . . . . . . . . . . . . 5 74 2.2. Terms specific to this and other HIP documents . . . . . . . 5 75 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 7 76 3.1. A desire for a namespace for computing platforms . . . . . . 7 77 4. Host Identity namespace . . . . . . . . . . . . . . . . . . 9 78 4.1. Host Identifiers . . . . . . . . . . . . . . . . . . . . . . 10 79 4.2. Host Identity Hash (HIH) . . . . . . . . . . . . . . . . . . 10 80 4.3. Host Identity Tag (HIT) . . . . . . . . . . . . . . . . . . 11 81 4.4. Local Scope Identifier (LSI) . . . . . . . . . . . . . . . . 11 82 4.5. Storing Host Identifiers in Directories . . . . . . . . . . 12 83 5. New stack architecture . . . . . . . . . . . . . . . . . . . 12 84 5.1. Transport associations and end-points . . . . . . . . . . . 13 85 6. End-host mobility and multi-homing . . . . . . . . . . . . . 13 86 6.1. Rendezvous mechanism . . . . . . . . . . . . . . . . . . . . 14 87 6.2. Protection against flooding attacks . . . . . . . . . . . . 14 88 7. HIP and ESP . . . . . . . . . . . . . . . . . . . . . . . . 15 89 8. HIP and MAC Security . . . . . . . . . . . . . . . . . . . . 16 90 9. HIP and NATs . . . . . . . . . . . . . . . . . . . . . . . . 17 91 9.1. HIP and Upper-layer checksums . . . . . . . . . . . . . . . 17 92 10. Multicast . . . . . . . . . . . . . . . . . . . . . . . . . 18 93 11. HIP policies . . . . . . . . . . . . . . . . . . . . . . . . 18 94 12. Benefits of HIP . . . . . . . . . . . . . . . . . . . . . . 18 95 12.1. HIP's answers to NSRG questions . . . . . . . . . . . . . . 19 96 13. Changes from RFC 4423 . . . . . . . . . . . . . . . . . . . 21 97 14. Security considerations . . . . . . . . . . . . . . . . . . 21 98 14.1. HITs used in ACLs . . . . . . . . . . . . . . . . . . . . . 23 99 14.2. Alternative HI considerations . . . . . . . . . . . . . . . 24 100 15. IANA considerations . . . . . . . . . . . . . . . . . . . . 24 101 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 24 102 17. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 103 17.1. Normative References . . . . . . . . . . . . . . . . . . . . 25 104 17.2. Informative references . . . . . . . . . . . . . . . . . . . 26 105 Author's Address . . . . . . . . . . . . . . . . . . . . . . 27 107 1. Introduction 109 The Internet has two important global namespaces: Internet Protocol 110 (IP) addresses and Domain Name Service (DNS) names. These two 111 namespaces have a set of features and abstractions that have powered 112 the Internet to what it is today. They also have a number of 113 weaknesses. Basically, since they are all we have, we try and do too 114 much with them. Semantic overloading and functionality extensions 115 have greatly complicated these namespaces. 117 The proposed Host Identity namespace fills an important gap between 118 the IP and DNS namespaces. A Host Identity conceptually refers to a 119 computing platform, and there may be multiple such Host Identities 120 per computing platform (because the platform may wish to present a 121 different identity to different communicating peers). The Host 122 Identity namespace consists of Host Identifiers (HI). There is 123 exactly one Host Identifier for each Host Identity. While this text 124 later talks about non-cryptographic Host Identifiers, the 125 architecture focuses on the case in which Host Identifiers are 126 cryptographic in nature. Specifically, the Host Identifier is the 127 public key of an asymmetric key-pair. Each Host Identity uniquely 128 identifies a single host, i.e., no two hosts have the same Host 129 Identity. If two or more computing platforms have the same Host 130 Identifier, then they are instantiating a distributed host. The Host 131 Identifier can either be public (e.g. published in the DNS), or 132 unpublished. Client systems will tend to have both public and 133 unpublished Host Identifiers. 135 There is a subtle but important difference between Host Identities 136 and Host Identifiers. An Identity refers to the abstract entity that 137 is identified. An Identifier, on the other hand, refers to the 138 concrete bit pattern that is used in the identification process. 140 Although the Host Identifiers could be used in many authentication 141 systems, such as IKEv2 [RFC4306], the presented architecture 142 introduces a new protocol, called the Host Identity Protocol (HIP), 143 and a cryptographic exchange, called the HIP base exchange; see also 144 Section 7. The HIP protocols provide for limited forms of trust 145 between systems, enhance mobility, multi-homing and dynamic IP 146 renumbering, aid in protocol translation / transition, and reduce 147 certain types of denial-of-service (DoS) attacks. 149 When HIP is used, the actual payload traffic between two HIP hosts is 150 typically, but not necessarily, protected with ESP. The Host 151 Identities are used to create the needed ESP Security Associations 152 (SAs) and to authenticate the hosts. When ESP is used, the actual 153 payload IP packets do not differ in any way from standard ESP 154 protected IP packets. 156 Much has been learned about HIP since [RFC4423] was published. This 157 document expands Host Identities beyond use to enable IP connectivity 158 and security to general interhost secure signalling at any protocol 159 layer. The signal may establish a security association between the 160 hosts, or simply pass information within the channel. 162 2. Terminology 164 2.1. Terms common to other documents 166 +---------------+---------------------------------------------------+ 167 | Term | Explanation | 168 +---------------+---------------------------------------------------+ 169 | Public key | The public key of an asymmetric cryptographic key | 170 | | pair. Used as a publicly known identifier for | 171 | | cryptographic identity authentication. | 172 | | | 173 | Private key | The private or secret key of an asymmetric | 174 | | cryptographic key pair. Assumed to be known only | 175 | | to the party identified by the corresponding | 176 | | public key. Used by the identified party to | 177 | | authenticate its identity to other parties. | 178 | | | 179 | Public key | An asymmetric cryptographic key pair consisting | 180 | pair | of public and private keys. For example, | 181 | | Rivest-Shamir-Adelman (RSA) and Digital Signature | 182 | | Algorithm (DSA) key pairs are such key pairs. | 183 | | | 184 | End-point | A communicating entity. For historical reasons, | 185 | | the term 'computing platform' is used in this | 186 | | document as a (rough) synonym for end-point. | 187 +---------------+---------------------------------------------------+ 189 2.2. Terms specific to this and other HIP documents 191 It should be noted that many of the terms defined herein are 192 tautologous, self-referential or defined through circular reference 193 to other terms. This is due to the succinct nature of the 194 definitions. See the text elsewhere in this document and in RFC 5201 195 [RFC5201-bis] for more elaborate explanations. 197 +---------------+---------------------------------------------------+ 198 | Term | Explanation | 199 +---------------+---------------------------------------------------+ 200 | Computing | An entity capable of communicating and computing, | 201 | platform | for example, a computer. See the definition of | 202 | | 'End-point', above. | 203 | | | 204 | HIP base | A cryptographic protocol; see also Section 7. | 205 | exchange | | 206 | | | 207 | HIP packet | An IP packet that carries a 'Host Identity | 208 | | Protocol' message. | 209 | | | 210 | Host Identity | An abstract concept assigned to a 'computing | 211 | | platform'. See 'Host Identifier', below. | 212 | | | 213 | Host Identity | A name space formed by all possible Host | 214 | namespace | Identifiers. | 215 | | | 216 | Host Identity | A protocol used to carry and authenticate Host | 217 | Protocol | Identifiers and other information. | 218 | | | 219 | Host Identity | The cryptograhic hash used in creating the Host | 220 | Hash | Identity Tag from the Host Identity. | 221 | | | 222 | Host Identity | A 128-bit datum created by taking a cryptographic | 223 | Tag | hash over a Host Identifier plus bits to identify | 224 | | which hash used. | 225 | | | 226 | Host | A public key used as a name for a Host Identity. | 227 | Identifier | | 228 | | | 229 | Local Scope | A 32-bit datum denoting a Host Identity. | 230 | Identifier | | 231 | | | 232 | Public Host | A published or publicly known Host Identfier used | 233 | Identifier | as a public name for a Host Identity, and the | 234 | and Identity | corresponding Identity. | 235 | | | 236 | Unpublished | A Host Identifier that is not placed in any | 237 | Host | public directory, and the corresponding Host | 238 | Identifier | Identity. Unpublished Host Identities are | 239 | and Identity | typically short lived in nature, being often | 240 | | replaced and possibly used just once. | 241 | | | 242 | Rendezvous | A mechanism used to locate mobile hosts based on | 243 | Mechanism | their HIT. | 244 +---------------+---------------------------------------------------+ 246 3. Background 248 The Internet is built from three principal components: computing 249 platforms (end-points), packet transport (i.e., internetworking) 250 infrastructure, and services (applications). The Internet exists to 251 service two principal components: people and robotic services 252 (silicon based people, if you will). All these components need to be 253 named in order to interact in a scalable manner. Here we concentrate 254 on naming computing platforms and packet transport elements. 256 There are two principal namespaces in use in the Internet for these 257 components: IP numbers, and Domain Names. Domain Names provide 258 hierarchically assigned names for some computing platforms and some 259 services. Each hierarchy is delegated from the level above; there is 260 no anonymity in Domain Names. Email, HTTP, and SIP addresses all 261 reference Domain Names. 263 The IP addressing namespace has been overloaded to name both 264 interfaces (at layer-3) and endpoints (for the endpoint-specific part 265 of layer-3, and for layer-4). In their role as interface names, IP 266 addresses are sometimes called "locators" and serve as an endpoint 267 within a routing topology. 269 IP numbers name networking interfaces, and typically only when the 270 interface is connected to the network. Originally, IP numbers had 271 long-term significance. Today, the vast number of interfaces use 272 ephemeral and/or non-unique IP numbers. That is, every time an 273 interface is connected to the network, it is assigned an IP number. 275 In the current Internet, the transport layers are coupled to the IP 276 addresses. Neither can evolve separately from the other. IPng 277 deliberations were strongly shaped by the decision that a 278 corresponding TCPng would not be created. 280 There are three critical deficiencies with the current namespaces. 281 Firstly, dynamic readdressing cannot be directly managed. Secondly, 282 anonymity is not provided in a consistent, trustable manner. 283 Finally, authentication for systems and datagrams is not provided. 284 All of these deficiencies arise because computing platforms are not 285 well named with the current namespaces. 287 3.1. A desire for a namespace for computing platforms 289 An independent namespace for computing platforms could be used in 290 end-to-end operations independent of the evolution of the 291 internetworking layer and across the many internetworking layers. 292 This could support rapid readdressing of the internetworking layer 293 because of mobility, rehoming, or renumbering. 295 If the namespace for computing platforms is based on public-key 296 cryptography, it can also provide authentication services. If this 297 namespace is locally created without requiring registration, it can 298 provide anonymity. 300 Such a namespace (for computing platforms) and the names in it should 301 have the following characteristics: 303 o The namespace should be applied to the IP 'kernel' or stack. The 304 IP stack is the 'component' between applications and the packet 305 transport infrastructure. 307 o The namespace should fully decouple the internetworking layer from 308 the higher layers. The names should replace all occurrences of IP 309 addresses within applications (like in the Transport Control 310 Block, TCB). This may require changes to the current APIs. In 311 the long run, it is probable that some new APIs are needed. 313 o The introduction of the namespace should not mandate any 314 administrative infrastructure. Deployment must come from the 315 bottom up, in a pairwise deployment. 317 o The names should have a fixed length representation, for easy 318 inclusion in datagram headers and existing programming interfaces 319 (e.g the TCB). 321 o Using the namespace should be affordable when used in protocols. 322 This is primarily a packet size issue. There is also a 323 computational concern in affordability. 325 o Name collisions should be avoided as much as possible. The 326 mathematics of the birthday paradox can be used to estimate the 327 chance of a collision in a given population and hash space. In 328 general, for a random hash space of size n bits, we would expect 329 to obtain a collision after approximately 1.2*sqrt(2**n) hashes 330 were obtained. For 64 bits, this number is roughly 4 billion. A 331 hash size of 64 bits may be too small to avoid collisions in a 332 large population; for example, there is a 1% chance of collision 333 in a population of 640M. For 100 bits (or more), we would not 334 expect a collision until approximately 2**50 (1 quadrillion) 335 hashes were generated. 337 o The names should have a localized abstraction so that it can be 338 used in existing protocols and APIs. 340 o It must be possible to create names locally. When such names are 341 not published, this can provide anonymity at the cost of making 342 resolvability very difficult. 344 * Sometimes the names may contain a delegation component. This 345 is the cost of resolvability. 347 o The namespace should provide authentication services. 349 o The names should be long lived, but replaceable at any time. This 350 impacts access control lists; short lifetimes will tend to result 351 in tedious list maintenance or require a namespace infrastructure 352 for central control of access lists. 354 In this document, a new namespace approaching these ideas is called 355 the Host Identity namespace. Using Host Identities requires its own 356 protocol layer, the Host Identity Protocol, between the 357 internetworking and transport layers. The names are based on public- 358 key cryptography to supply authentication services. Properly 359 designed, it can deliver all of the above stated requirements. 361 4. Host Identity namespace 363 A name in the Host Identity namespace, a Host Identifier (HI), 364 represents a statistically globally unique name for naming any system 365 with an IP stack. This identity is normally associated with, but not 366 limited to, an IP stack. A system can have multiple identities, some 367 'well known', some unpublished or 'anonymous'. A system may self- 368 assert its own identity, or may use a third-party authenticator like 369 DNSSEC [RFC2535], PGP, or X.509 to 'notarize' the identity assertion 370 to another namespace. It is expected that the Host Identifiers will 371 initially be authenticated with DNSSEC and that all implementations 372 will support DNSSEC as a minimal baseline. 374 In theory, any name that can claim to be 'statistically globally 375 unique' may serve as a Host Identifier. However, in the authors' 376 opinion, a public key of a 'public key pair' makes the best Host 377 Identifier. As will be specified in the Host Identity Protocol Base 378 EXchange (BEX) [RFC5201-bis] specification, a public-key-based HI can 379 authenticate the HIP packets and protect them for man-in-the-middle 380 attacks. Since authenticated datagrams are mandatory to provide much 381 of HIP's denial-of-service protection, the Diffie-Hellman exchange in 382 HIP BEX has to be authenticated. Thus, only public-key HI and 383 authenticated HIP messages are supported in practice. 385 In this document, the non-cryptographic forms of HI and HIP are 386 presented to complete the theory of HI, but they should not be 387 implemented as they could produce worse denial-of-service attacks 388 than the Internet has without Host Identity. There is on-going 389 research in challenge puzzles to use non-cryptographic HI, like 390 RFIDs, in an HIP exchange tailored to the workings of such 391 challenges. 393 4.1. Host Identifiers 395 Host Identity adds two main features to Internet protocols. The 396 first is a decoupling of the internetworking and transport layers; 397 see Section 5. This decoupling will allow for independent evolution 398 of the two layers. Additionally, it can provide end-to-end services 399 over multiple internetworking realms. The second feature is host 400 authentication. Because the Host Identifier is a public key, this 401 key can be used for authentication in security protocols like ESP. 403 The only completely defined structure of the Host Identity is that of 404 a public/private key pair. In this case, the Host Identity is 405 referred to by its public component, the public key. Thus, the name 406 representing a Host Identity in the Host Identity namespace, i.e., 407 the Host Identifier, is the public key. In a way, the possession of 408 the private key defines the Identity itself. If the private key is 409 possessed by more than one node, the Identity can be considered to be 410 a distributed one. 412 Architecturally, any other Internet naming convention might form a 413 usable base for Host Identifiers. However, non-cryptographic names 414 should only be used in situations of high trust - low risk. That is 415 any place where host authentication is not needed (no risk of host 416 spoofing) and no use of ESP. However, at least for interconnected 417 networks spanning several operational domains, the set of 418 environments where the risk of host spoofing allowed by non- 419 cryptographic Host Identifiers is acceptable is the null set. Hence, 420 the current HIP documents do not specify how to use any other types 421 of Host Identifiers but public keys. 423 The actual Host Identities are never directly used in any Internet 424 protocols. The corresponding Host Identifiers (public keys) may be 425 stored in various DNS or LDAP directories as identified elsewhere in 426 this document, and they are passed in the HIP base exchange. A Host 427 Identity Tag (HIT) is used in other protocols to represent the Host 428 Identity. Another representation of the Host Identities, the Local 429 Scope Identifier (LSI), can also be used in protocols and APIs. 431 4.2. Host Identity Hash (HIH) 433 The Host Identity Hash is the cryptographic hash used in producing 434 the HIT from the HI. It is also the hash used through out the HIP 435 protocol for consistancy and simplicity. It is possible to for the 436 two Hosts in the HIP exchange to use different hashes. 438 Multiple HIHs within HIP are needed to address the moving target of 439 creation and eventual compromise of cryptographic hashes. This 440 significantly complicates HIP and offers an attacker an additional 441 downgrade attack that is mitigated in the HIP protocol. 443 4.3. Host Identity Tag (HIT) 445 A Host Identity Tag is a 128-bit representation for a Host Identity. 446 It is created from an HIH and other information, like an IPv6 prefix 447 and a hash identifier. There are two advantages of using the HIT 448 over using the Host Identifier in protocols. Firstly, its fixed 449 length makes for easier protocol coding and also better manages the 450 packet size cost of this technology. Secondly, it presents the 451 identity in a consistent format to the protocol independent of the 452 cryptographic algorithms used. 454 There can be multiple HITs per Host Identifier when multiple hashes 455 are supported. An Initator may have to initially guess which HIT to 456 use for the Responder, typically based on what it perfers, until it 457 learns the appropriate HIT through the HIP exchange. 459 In the HIP packets, the HITs identify the sender and recipient of a 460 packet. Consequently, a HIT should be unique in the whole IP 461 universe as long as it is being used. In the extremely rare case of 462 a single HIT mapping to more than one Host Identity, the Host 463 Identifiers (public keys) will make the final difference. If there 464 is more than one public key for a given node, the HIT acts as a hint 465 for the correct public key to use. 467 4.4. Local Scope Identifier (LSI) 469 An LSI is a 32-bit localized representation for a Host Identity. The 470 purpose of an LSI is to facilitate using Host Identities in existing 471 protocols and APIs. LSI's advantage over HIT is its size; its 472 disadvantage is its local scope. 474 Examples of how LSIs can be used include: as the address in an FTP 475 command and as the address in a socket call. Thus, LSIs act as a 476 bridge for Host Identities into IPv4-based protocols and APIs. LSIs 477 also make it possible for some IPv4 applications to run over an IPv6 478 network. 480 4.5. Storing Host Identifiers in Directories 482 The public Host Identifiers should be stored in DNS; the unpublished 483 Host Identifiers should not be stored anywhere (besides the 484 communicating hosts themselves). The (public) HI along with the 485 supported HIHs are stored in a new RR type. This RR type is defined 486 in HIP DNS Extension [I-D.ietf-hip-rfc5205-bis]. 488 Alternatively, or in addition to storing Host Identifiers in the DNS, 489 they may be stored in various other directories (e.g. LDAP, DHT) or 490 in a Public Key Infrastructure (PKI). Such a practice may allow them 491 to be used for purposes other than pure host identification. 493 5. New stack architecture 495 One way to characterize Host Identity is to compare the proposed new 496 architecture with the current one. As discussed above, the IP 497 addresses can be seen to be a confounding of routing direction 498 vectors and interface names. Using the terminology from the IRTF 499 Name Space Research Group Report [nsrg-report] and, e.g., the 500 unpublished Internet-Draft Endpoints and Endpoint Names 501 [chiappa-endpoints], the IP addresses currently embody the dual role 502 of locators and end-point identifiers. That is, each IP address 503 names a topological location in the Internet, thereby acting as a 504 routing direction vector, or locator. At the same time, the IP 505 address names the physical network interface currently located at the 506 point-of-attachment, thereby acting as a end-point name. 508 In the HIP architecture, the end-point names and locators are 509 separated from each other. IP addresses continue to act as locators. 510 The Host Identifiers take the role of end-point identifiers. It is 511 important to understand that the end-point names based on Host 512 Identities are slightly different from interface names; a Host 513 Identity can be simultaneously reachable through several interfaces. 515 The difference between the bindings of the logical entities are 516 illustrated in Figure 1. 518 Transport ---- Socket Transport ------ Socket 519 association | association | 520 | | 521 | | 522 | | 523 End-point | End-point --- Host Identity 524 \ | | 525 \ | | 526 \ | | 527 \ | | 528 Location --- IP address Location --- IP address 530 Figure 1 532 5.1. Transport associations and end-points 534 Architecturally, HIP provides for a different binding of transport- 535 layer protocols. That is, the transport-layer associations, i.e., 536 TCP connections and UDP associations, are no longer bound to IP 537 addresses but to Host Identities. 539 It is possible that a single physical computer hosts several logical 540 end-points. With HIP, each of these end-points would have a distinct 541 Host Identity. Furthermore, since the transport associations are 542 bound to Host Identities, HIP provides for process migration and 543 clustered servers. That is, if a Host Identity is moved from one 544 physical computer to another, it is also possible to simultaneously 545 move all the transport associations without breaking them. 546 Similarly, if it is possible to distribute the processing of a single 547 Host Identity over several physical computers, HIP provides for 548 cluster based services without any changes at the client end-point. 550 6. End-host mobility and multi-homing 552 HIP decouples the transport from the internetworking layer, and binds 553 the transport associations to the Host Identities (through actually 554 either the HIT or LSI). Consequently, HIP can provide for a degree 555 of internetworking mobility and multi-homing at a low infrastructure 556 cost. HIP mobility includes IP address changes (via any method) to 557 either party. Thus, a system is considered mobile if its IP address 558 can change dynamically for any reason like PPP, DHCP, IPv6 prefix 559 reassignments, or a NAT device remapping its translation. Likewise, 560 a system is considered multi-homed if it has more than one globally 561 routable IP address at the same time. HIP links IP addresses 562 together, when multiple IP addresses correspond to the same Host 563 Identity, and if one address becomes unusable, or a more preferred 564 address becomes available, existing transport associations can easily 565 be moved to another address. 567 When a node moves while communication is already on-going, address 568 changes are rather straightforward. The peer of the mobile node can 569 just accept a HIP or an integrity protected ESP packet from any 570 address and ignore the source address. However, as discussed in 571 Section 6.2 below, a mobile node must send a HIP readdress packet to 572 inform the peer of the new address(es), and the peer must verify that 573 the mobile node is reachable through these addresses. This is 574 especially helpful for those situations where the peer node is 575 sending data periodically to the mobile node (that is re-starting a 576 connection after the initial connection). 578 6.1. Rendezvous mechanism 580 Making a contact to a mobile node is slightly more involved. In 581 order to start the HIP exchange, the initiator node has to know how 582 to reach the mobile node. Although infrequently moving HIP nodes 583 could use Dynamic DNS [RFC2136] to update their reachability 584 information in the DNS, an alternative to using DNS in this fashion 585 is to use a piece of new static infrastructure to facilitate 586 rendezvous between HIP nodes. 588 The mobile node keeps the rendezvous infrastructure continuously 589 updated with its current IP address(es). The mobile nodes must trust 590 the rendezvous mechanism to properly maintain their HIT and IP 591 address mappings. 593 The rendezvous mechanism is also needed if both of the nodes happen 594 to change their address at the same time, either because they are 595 mobile and happen to move at the same time, because one of them is 596 off-line for a while, or because of some other reason. In such a 597 case, the HIP UPDATE packets will cross each other in the network and 598 never reach the peer node. 600 The HIP rendezvous mechanism is defined in HIP Rendezvous 601 [I-D.ietf-hip-rfc5204-bis]. 603 6.2. Protection against flooding attacks 605 Although the idea of informing about address changes by simply 606 sending packets with a new source address appears appealing, it is 607 not secure enough. That is, even if HIP does not rely on the source 608 address for anything (once the base exchange has been completed), it 609 appears to be necessary to check a mobile node's reachability at the 610 new address before actually sending any larger amounts of traffic to 611 the new address. 613 Blindly accepting new addresses would potentially lead to flooding 614 Denial-of-Service attacks against third parties [RFC4225]. In a 615 distributed flooding attack an attacker opens high volume HIP 616 connections with a large number of hosts (using unpublished HIs), and 617 then claims to all of these hosts that it has moved to a target 618 node's IP address. If the peer hosts were to simply accept the move, 619 the result would be a packet flood to the target node's address. To 620 prevent this type of attack, HIP includes an address check mechanism 621 where the reachability of a node is separately checked at each 622 address before using the address for larger amounts of traffic. 624 A credit-based authorization approach Host Mobility with the Host 625 Identity Protocol [I-D.ietf-hip-rfc5206-bis] can be used between 626 hosts for sending data prior to completing the address tests. 627 Otherwise, if HIP is used between two hosts that fully trust each 628 other, the hosts may optionally decide to skip the address tests. 629 However, such performance optimization must be restricted to peers 630 that are known to be trustworthy and capable of protecting themselves 631 from malicious software. 633 7. HIP and ESP 635 The preferred way of implementing HIP is to use ESP to carry the 636 actual data traffic. As of today, the only completely defined method 637 is to use ESP Encapsulated Security Payload (ESP) to carry the data 638 packets [I-D.ietf-hip-rfc5202-bis]. In the future, other ways of 639 transporting payload data may be developed, including ones that do 640 not use cryptographic protection. 642 In practice, the HIP base exchange uses the cryptographic Host 643 Identifiers to set up a pair of ESP Security Associations (SAs) to 644 enable ESP in an end-to-end manner. This is implemented in a way 645 that can span addressing realms. 647 While it would be possible, at least in theory, to use some existing 648 cryptographic protocol, such as IKEv2 together with Host Identifiers, 649 to establish the needed SAs, HIP defines a new protocol. There are a 650 number of historical reasons for this, and there are also a few 651 architectural reasons. First, IKE (and IKEv2) were not designed with 652 middle boxes in mind. As adding a new naming layer allows one to 653 potentially add a new forwarding layer (see Section 9, below), it is 654 very important that the HIP provides mechanisms for middlebox 655 authentication. 657 Second, from a conceptual point of view, the IPsec Security Parameter 658 Index (SPI) in ESP provides a simple compression of the HITs. This 659 does require per-HIT-pair SAs (and SPIs), and a decrease of policy 660 granularity over other Key Management Protocols, such as IKE and 661 IKEv2. In other words, from an architectural point of view, HIP only 662 supports host-to-host (or endpoint-to-endpoint) Security 663 Associations. 665 Originally, as HIP is designed for host usage, not for gateways or so 666 called Bump-in-the-Wire (BITW) implementations, only ESP transport 667 mode is supported. An ESP SA pair is indexed by the SPIs and the two 668 HITs (both HITs since a system can have more than one HIT). The SAs 669 need not to be bound to IP addresses; all internal control of the SA 670 is by the HITs. Thus, a host can easily change its address using 671 Mobile IP, DHCP, PPP, or IPv6 readdressing and still maintain the 672 SAs. Since the transports are bound to the SA (via an LSI or a HIT), 673 any active transport is also maintained. Thus, real-world conditions 674 like loss of a PPP connection and its re-establishment or a mobile 675 handover will not require a HIP negotiation or disruption of 676 transport services [Bel1998]. 678 It should be noted that there are already BITW implementations. This 679 is still consistant to the SA bindings above. 681 Since HIP does not negotiate any SA lifetimes, all lifetimes are 682 local policy. The only lifetimes a HIP implementation must support 683 are sequence number rollover (for replay protection), and SA timeout. 684 An SA times out if no packets are received using that SA. 685 Implementations may support lifetimes for the various ESP transforms. 687 8. HIP and MAC Security 689 The IEEE 802 standards have been defining MAC layered security. Many 690 of these standards use EAP [RFC3748] as a Key Management System (KMS) 691 transport, but some like IEEE 802.15.4 [IEEE.802-15-4.2006] leave the 692 KMS and its transport as "Out of Scope". 694 HIP is well suited as a KMS in these environments. 696 o HIP is independent of IP addressing and can be directly 697 transported over any network protocol. 699 o Master Keys in 802 protocols are strictly pair-based with group 700 keys transported from the group controller using pair-wise keys. 702 o AdHoc 802 networks can be better served by a peer-to-peer KMS than 703 the EAP client/server model. 705 o Some devices are very memory constrained and a common KMS for both 706 MAC and IP security represents a considerable code savings. 708 9. HIP and NATs 710 Passing packets between different IP addressing realms requires 711 changing IP addresses in the packet header. This may happen, for 712 example, when a packet is passed between the public Internet and a 713 private address space, or between IPv4 and IPv6 networks. The 714 address translation is usually implemented as Network Address 715 Translation (NAT) [RFC3022] or NAT Protocol translation (NAT-PT) 716 [RFC2766]. 718 In a network environment where identification is based on the IP 719 addresses, identifying the communicating nodes is difficult when NAT 720 is used. With HIP, the transport-layer end-points are bound to the 721 Host Identities. Thus, a connection between two hosts can traverse 722 many addressing realm boundaries. The IP addresses are used only for 723 routing purposes; they may be changed freely during packet traversal. 725 For a HIP-based flow, a HIP-aware NAT or NAT-PT system tracks the 726 mapping of HITs, and the corresponding ESP SPIs, to an IP address. 727 The NAT system has to learn mappings both from HITs and from SPIs to 728 IP addresses. Many HITs (and SPIs) can map to a single IP address on 729 a NAT, simplifying connections on address poor NAT interfaces. The 730 NAT can gain much of its knowledge from the HIP packets themselves; 731 however, some NAT configuration may be necessary. 733 NAT systems cannot touch the datagrams within the ESP envelope, thus 734 application-specific address translation must be done in the end 735 systems. HIP provides for 'Distributed NAT', and uses the HIT or the 736 LSI as a placeholder for embedded IP addresses. 738 An experimental HIP and NAT traversal is defined in [RFC5770]. 740 9.1. HIP and Upper-layer checksums 742 There is no way for a host to know if any of the IP addresses in an 743 IP header are the addresses used to calculate the TCP checksum. That 744 is, it is not feasible to calculate the TCP checksum using the actual 745 IP addresses in the pseudo header; the addresses received in the 746 incoming packet are not necessarily the same as they were on the 747 sending host. Furthermore, it is not possible to recompute the 748 upper-layer checksums in the NAT/NAT-PT system, since the traffic is 749 ESP protected. Consequently, the TCP and UDP checksums are 750 calculated using the HITs in the place of the IP addresses in the 751 pseudo header. Furthermore, only the IPv6 pseudo header format is 752 used. This provides for IPv4 / IPv6 protocol translation. 754 10. Multicast 756 Since its inception, a few studies have looked at how HIP might 757 affect IP-layer or application-layer multicast. 759 11. HIP policies 761 There are a number of variables that will influence the HIP exchanges 762 that each host must support. All HIP implementations should support 763 at least 2 HIs, one to publish in DNS or similar directory service 764 and an unpublished one for anonymous usage. Although unpublished HIs 765 will be rarely used as responder HIs, they are likely be common for 766 initiators. Support for multiple HIs is recommended. This provides 767 new challenges for systems or users to decide which type of HI to 768 expose when they start a new session. 770 Opportunistic mode (where the initator starts a HIP exchange without 771 prior knowledge of the responder's HI) presents a policy tradeoff. 772 It provides some security benefits but may be subject to MITM. 774 Many initiators would want to use a different HI for different 775 responders. The implementations should provide for a policy of 776 initiator HIT to responder HIT. This policy should also include 777 preferred transforms and local lifetimes. 779 Responders would need a similar policy, describing the hosts allowed 780 to participate in HIP exchanges, and the preferred transforms and 781 local lifetimes. 783 12. Benefits of HIP 785 In the beginning, the network layer protocol (i.e., IP) had the 786 following four "classic" invariants: 788 o Non-mutable: The address sent is the address received. 790 o Non-mobile: The address doesn't change during the course of an 791 "association". 793 o Reversible: A return header can always be formed by reversing the 794 source and destination addresses. 796 o Omniscient: Each host knows what address a partner host can use to 797 send packets to it. 799 Actually, the fourth can be inferred from 1 and 3, but it is worth 800 mentioning for reasons that will be obvious soon if not already. 802 In the current "post-classic" world, we are intentionally trying to 803 get rid of the second invariant (both for mobility and for multi- 804 homing), and we have been forced to give up the first and the fourth. 805 Realm Specific IP [RFC3102] is an attempt to reinstate the fourth 806 invariant without the first invariant. IPv6 is an attempt to 807 reinstate the first invariant. 809 Few systems on the Internet have DNS names that are meaningful. That 810 is, if they have a Fully Qualified Domain Name (FQDN), that name 811 typically belongs to a NAT device or a dial-up server, and does not 812 really identify the system itself but its current connectivity. 813 FQDNs (and their extensions as email names) are application-layer 814 names; more frequently naming services than a particular system. 815 This is why many systems on the Internet are not registered in the 816 DNS; they do not have services of interest to other Internet hosts. 818 DNS names are references to IP addresses. This only demonstrates the 819 interrelationship of the networking and application layers. DNS, as 820 the Internet's only deployed, distributed database is also the 821 repository of other namespaces, due in part to DNSSEC and application 822 specific key records. Although each namespace can be stretched (IP 823 with v6, DNS with KEY records), neither can adequately provide for 824 host authentication or act as a separation between internetworking 825 and transport layers. 827 The Host Identity (HI) namespace fills an important gap between the 828 IP and DNS namespaces. An interesting thing about the HI is that it 829 actually allows one to give up all but the 3rd network-layer 830 invariant. That is to say, as long as the source and destination 831 addresses in the network-layer protocol are reversible, then things 832 work ok because HIP takes care of host identification, and 833 reversibility allows one to get a packet back to one's partner host. 834 You do not care if the network-layer address changes in transit 835 (mutable) and you don't care what network-layer address the partner 836 is using (non-omniscient). 838 12.1. HIP's answers to NSRG questions 840 The IRTF Name Space Research Group has posed a number of evaluating 841 questions in their report [nsrg-report]. In this section, we provide 842 answers to these questions. 844 1. How would a stack name improve the overall functionality of the 845 Internet? 846 HIP decouples the internetworking layer from the transport 847 layer, allowing each to evolve separately. The decoupling 848 makes end-host mobility and multi-homing easier, also across 849 IPv4 and IPv6 networks. HIs make network renumbering easier, 850 and they also make process migration and clustered servers 851 easier to implement. Furthermore, being cryptographic in 852 nature, they provide the basis for solving the security 853 problems related to end-host mobility and multi-homing. 855 2. What does a stack name look like? 857 A HI is a cryptographic public key. However, instead of using 858 the keys directly, most protocols use a fixed size hash of the 859 public key. 861 3. What is its lifetime? 863 HIP provides both stable and temporary Host Identifiers. 864 Stable HIs are typically long lived, with a lifetime of years 865 or more. The lifetime of temporary HIs depends on how long 866 the upper-layer connections and applications need them, and 867 can range from a few seconds to years. 869 4. Where does it live in the stack? 871 The HIs live between the transport and internetworking layers. 873 5. How is it used on the end points? 875 The Host Identifiers may be used directly or indirectly (in 876 the form of HITs or LSIs) by applications when they access 877 network services. Additionally, the Host Identifiers, as 878 public keys, are used in the built in key agreement protocol, 879 called the HIP base exchange, to authenticate the hosts to 880 each other. 882 6. What administrative infrastructure is needed to support it? 884 In some environments, it is possible to use HIP 885 opportunistically, without any infrastructure. However, to 886 gain full benefit from HIP, the HIs must be stored in the DNS 887 or a PKI, and a new rendezvous mechanism is needed 888 [I-D.ietf-hip-rfc5205-bis]. 890 7. If we add an additional layer would it make the address list in 891 SCTP unnecessary? 892 Yes 894 8. What additional security benefits would a new naming scheme 895 offer? 897 HIP reduces dependency on IP addresses, making the so called 898 address ownership [Nik2001] problems easier to solve. In 899 practice, HIP provides security for end-host mobility and 900 multi-homing. Furthermore, since HIP Host Identifiers are 901 public keys, standard public key certificate infrastructures 902 can be applied on the top of HIP. 904 9. What would the resolution mechanisms be, or what characteristics 905 of a resolution mechanisms would be required? 907 For most purposes, an approach where DNS names are resolved 908 simultaneously to HIs and IP addresses is sufficient. 909 However, if it becomes necessary to resolve HIs into IP 910 addresses or back to DNS names, a flat resolution 911 infrastructure is needed. Such an infrastructure could be 912 based on the ideas of Distributed Hash Tables, but would 913 require significant new development and deployment. 915 13. Changes from RFC 4423 917 This section summarizes the changes made from [RFC4423]. 919 14. Security considerations 921 HIP takes advantage of the new Host Identity paradigm to provide 922 secure authentication of hosts and to provide a fast key exchange for 923 ESP. HIP also attempts to limit the exposure of the host to various 924 denial-of-service (DoS) and man-in-the-middle (MitM) attacks. In so 925 doing, HIP itself is subject to its own DoS and MitM attacks that 926 potentially could be more damaging to a host's ability to conduct 927 business as usual. 929 Resource exhausting denial-of-service attacks take advantage of the 930 cost of setting up a state for a protocol on the responder compared 931 to the 'cheapness' on the initiator. HIP allows a responder to 932 increase the cost of the start of state on the initiator and makes an 933 effort to reduce the cost to the responder. This is done by having 934 the responder start the authenticated Diffie-Hellman exchange instead 935 of the initiator, making the HIP base exchange 4 packets long. There 936 are more details on this process in the Host Identity Protocol under 937 development. 939 HIP optionally supports opportunistic negotiation. That is, if a 940 host receives a start of transport without a HIP negotiation, it can 941 attempt to force a HIP exchange before accepting the connection. 942 This has the potential for DoS attacks against both hosts. If the 943 method to force the start of HIP is expensive on either host, the 944 attacker need only spoof a TCP SYN. This would put both systems into 945 the expensive operations. HIP avoids this attack by having the 946 responder send a simple HIP packet that it can pre-build. Since this 947 packet is fixed and easily replayed, the initiator only reacts to it 948 if it has just started a connection to the responder. 950 Man-in-the-middle attacks are difficult to defend against, without 951 third-party authentication. A skillful MitM could easily handle all 952 parts of the HIP base exchange, but HIP indirectly provides the 953 following protection from a MitM attack. If the responder's HI is 954 retrieved from a signed DNS zone or secured by some other means, the 955 initiator can use this to authenticate the signed HIP packets. 956 Likewise, if the initiator's HI is in a secure DNS zone, the 957 responder can retrieve it and validate the signed HIP packets. 958 However, since an initiator may choose to use an unpublished HI, it 959 knowingly risks a MitM attack. The responder may choose not to 960 accept a HIP exchange with an initiator using an unknown HI. 962 The need to support multiple hashes for generating the HIT from the 963 HI affords the MitM a potentially powerful downgrade attack due to 964 the a-priori need of the HIT in the HIP base exchange. The base 965 exchange has been augmented to deal with such an attack by restarting 966 on detecting the attack. At worst this would only lead to a 967 situation in which the base exchange would never finish (or would be 968 aborted after some retries). As a drawback, this leads to an 6-way 969 base exchange which may seem bad at first. However, since this only 970 happens in an attack scenario and since the attack can be handled (so 971 it is not interesting to mount anymore), we assume the additional 972 messages are not a problem at all. Since the MitM cannot be 973 successful with a downgrade attack, these sorts of attacks will only 974 occur as 'nuisance' attacks. So, the base exchange would still be 975 usually just four packets even though implementations must be 976 prepared to protect themselves against the downgrade attack. 978 In HIP, the Security Association for ESP is indexed by the SPI; the 979 source address is always ignored, and the destination address may be 980 ignored as well. Therefore, HIP-enabled Encapsulated Security 981 Payload (ESP) is IP address independent. This might seem to make it 982 easier for an attacker, but ESP with replay protection is already as 983 well protected as possible, and the removal of the IP address as a 984 check should not increase the exposure of ESP to DoS attacks. 986 Since not all hosts will ever support HIP, ICMPv4 'Destination 987 Unreachable, Protocol Unreachable' and ICMPv6 'Parameter Problem, 988 Unrecognized Next Header' messages are to be expected and present a 989 DoS attack. Against an initiator, the attack would look like the 990 responder does not support HIP, but shortly after receiving the ICMP 991 message, the initiator would receive a valid HIP packet. Thus, to 992 protect against this attack, an initiator should not react to an ICMP 993 message until a reasonable time has passed, allowing it to get the 994 real responder's HIP packet. A similar attack against the responder 995 is more involved. 997 Another MitM attack is simulating a responder's administrative 998 rejection of a HIP initiation. This is a simple ICMP 'Destination 999 Unreachable, Administratively Prohibited' message. A HIP packet is 1000 not used because it would either have to have unique content, and 1001 thus difficult to generate, resulting in yet another DoS attack, or 1002 just as spoofable as the ICMP message. Like in the previous case, 1003 the defense against this attack is for the initiator to wait a 1004 reasonable time period to get a valid HIP packet. If one does not 1005 come, then the initiator has to assume that the ICMP message is 1006 valid. Since this is the only point in the HIP base exchange where 1007 this ICMP message is appropriate, it can be ignored at any other 1008 point in the exchange. 1010 14.1. HITs used in ACLs 1012 It is expected that HITs will be used in ACLs. Future firewalls can 1013 use HITs to control egress and ingress to networks, with an assurance 1014 level difficult to achieve today. As discussed above in Section 7, 1015 once a HIP session has been established, the SPI value in an ESP 1016 packet may be used as an index, indicating the HITs. In practice, 1017 firewalls can inspect HIP packets to learn of the bindings between 1018 HITs, SPI values, and IP addresses. They can even explicitly control 1019 ESP usage, dynamically opening ESP only for specific SPI values and 1020 IP addresses. The signatures in HIP packets allow a capable firewall 1021 to ensure that the HIP exchange is indeed happening between two known 1022 hosts. This may increase firewall security. 1024 A potential of HITs in ACLs is their 'flatness' means they cannot be 1025 aggregated and this could result in large table searches 1027 There has been considerable bad experience with distributed ACLs that 1028 contain public key related material, for example, with SSH. If the 1029 owner of a key needs to revoke it for any reason, the task of finding 1030 all locations where the key is held in an ACL may be impossible. If 1031 the reason for the revocation is due to private key theft, this could 1032 be a serious issue. 1034 A host can keep track of all of its partners that might use its HIT 1035 in an ACL by logging all remote HITs. It should only be necessary to 1036 log responder hosts. With this information, the host can notify the 1037 various hosts about the change to the HIT. There has been no attempt 1038 to develop a secure method to issue the HIT revocation notice. 1040 HIP-aware NATs, however, are transparent to the HIP aware systems by 1041 design. Thus, the host may find it difficult to notify any NAT that 1042 is using a HIT in an ACL. Since most systems will know of the NATs 1043 for their network, there should be a process by which they can notify 1044 these NATs of the change of the HIT. This is mandatory for systems 1045 that function as responders behind a NAT. In a similar vein, if a 1046 host is notified of a change in a HIT of an initiator, it should 1047 notify its NAT of the change. In this manner, NATs will get updated 1048 with the HIT change. 1050 14.2. Alternative HI considerations 1052 The definition of the Host Identifier states that the HI need not be 1053 a public key. It implies that the HI could be any value; for example 1054 a FQDN. This document does not describe how to support such a non- 1055 cryptographic HI. A non-cryptographic HI would still offer the 1056 services of the HIT or LSI for NAT traversal. It would be possible 1057 to carry HITs in HIP packets that had neither privacy nor 1058 authentication. Since such a mode would offer so little additional 1059 functionality for so much addition to the IP kernel, it has not been 1060 defined. Given how little public key cryptography HIP requires, HIP 1061 should only be implemented using public key Host Identities. 1063 If it is desirable to use HIP in a low security situation where 1064 public key computations are considered expensive, HIP can be used 1065 with very short Diffie-Hellman and Host Identity keys. Such use 1066 makes the participating hosts vulnerable to MitM and connection 1067 hijacking attacks. However, it does not cause flooding dangers, 1068 since the address check mechanism relies on the routing system and 1069 not on cryptographic strength. 1071 15. IANA considerations 1073 This document has no actions for IANA. 1075 16. Acknowledgments 1077 For the people historically involved in the early stages of HIP, see 1078 the Acknowledgements section in the Host Identity Protocol 1079 specification. 1081 During the later stages of this document, when the editing baton was 1082 transfered to Pekka Nikander, the comments from the early 1083 implementors and others, including Jari Arkko, Tom Henderson, Petri 1084 Jokela, Miika Komu, Mika Kousa, Andrew McGregor, Jan Melen, Tim 1085 Shepard, Jukka Ylitalo, and Jorma Wall, were invaluable. Finally, 1086 Lars Eggert, Spencer Dawkins and Dave Crocker provided valuable input 1087 during the final stages of publication, most of which was 1088 incorporated but some of which the authors decided to ignore in order 1089 to get this document published in the first place. 1091 The authors want to express their special thanks to Tom Henderson, 1092 who took the burden of editing the document in response to IESG 1093 comments at the time when both of the authors were busy doing other 1094 things. Without his perseverance original document might have never 1095 made it as RFC4423. 1097 This latest effort to update and move HIP forward within the IETF 1098 process owes its impetuous to the three HIP development teams: 1099 Boeing, HIIT (Helsinki Institute for Information Technology), and 1100 NomadicLab of Ericsson. Without their collective efforts HIP would 1101 have withered as on the IETF vine as a nice concept. 1103 17. References 1105 17.1. Normative References 1107 [RFC5201-bis] 1108 Moskowitz, R., Heer, T., Jokela, P., and T. Henderson, 1109 "Host Identity Protocol Version 2 (HIPv2)", 1110 draft-ietf-hip-rfc5201-bis-05 (work in progress), 1111 March 2011. 1113 [I-D.ietf-hip-rfc5202-bis] 1114 Jokela, P., Moskowitz, R., Nikander, P., and J. Melen, 1115 "Using the Encapsulating Security Payload (ESP) Transport 1116 Format with the Host Identity Protocol (HIP)", 1117 draft-ietf-hip-rfc5202-bis-00 (work in progress), 1118 September 2010. 1120 [I-D.ietf-hip-rfc5204-bis] 1121 Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) 1122 Rendezvous Extension", draft-ietf-hip-rfc5204-bis-01 (work 1123 in progress), March 2011. 1125 [I-D.ietf-hip-rfc5205-bis] 1126 Laganier, J., "Host Identity Protocol (HIP) Domain Name 1127 System (DNS) Extension", draft-ietf-hip-rfc5205-bis-01 1128 (work in progress), March 2011. 1130 [I-D.ietf-hip-rfc5206-bis] 1131 Nikander, P., Henderson, T., Vogt, C., and J. Arkko, "Host 1132 Mobility with the Host Identity Protocol", 1133 draft-ietf-hip-rfc5206-bis-02 (work in progress), 1134 March 2011. 1136 17.2. Informative references 1138 [RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound, 1139 "Dynamic Updates in the Domain Name System (DNS UPDATE)", 1140 RFC 2136, April 1997. 1142 [RFC2535] Eastlake, D., "Domain Name System Security Extensions", 1143 RFC 2535, March 1999. 1145 [RFC2766] Tsirtsis, G. and P. Srisuresh, "Network Address 1146 Translation - Protocol Translation (NAT-PT)", RFC 2766, 1147 February 2000. 1149 [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network 1150 Address Translator (Traditional NAT)", RFC 3022, 1151 January 2001. 1153 [RFC3102] Borella, M., Lo, J., Grabelsky, D., and G. Montenegro, 1154 "Realm Specific IP: Framework", RFC 3102, October 2001. 1156 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 1157 Levkowetz, "Extensible Authentication Protocol (EAP)", 1158 RFC 3748, June 2004. 1160 [RFC4025] Richardson, M., "A Method for Storing IPsec Keying 1161 Material in DNS", RFC 4025, March 2005. 1163 [RFC4225] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E. 1164 Nordmark, "Mobile IP Version 6 Route Optimization Security 1165 Design Background", RFC 4225, December 2005. 1167 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", 1168 RFC 4306, December 2005. 1170 [RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol 1171 (HIP) Architecture", RFC 4423, May 2006. 1173 [RFC5770] Komu, M., Henderson, T., Tschofenig, H., Melen, J., and A. 1174 Keranen, "Basic Host Identity Protocol (HIP) Extensions 1175 for Traversal of Network Address Translators", RFC 5770, 1176 April 2010. 1178 [nsrg-report] 1179 Lear, E. and R. Droms, "What's In A Name:Thoughts from the 1180 NSRG", draft-irtf-nsrg-report-10 (work in progress), 1181 September 2003. 1183 [IEEE.802-15-4.2006] 1184 "Information technology - Telecommunications and 1185 information exchange between systems - Local and 1186 metropolitan area networks - Specific requirements - Part 1187 15.4: Wireless Medium Access Control (MAC) and Physical 1188 Layer (PHY) Specifications for Low-Rate Wireless Personal 1189 Area Networks (WPANs)", IEEE Standard 802.15.4, 1190 September 2006, . 1193 [chiappa-endpoints] 1194 Chiappa, J., "Endpoints and Endpoint Names: A Proposed 1195 Enhancement to the Internet Architecture", 1196 URL http://www.chiappa.net/~jnc/tech/endpoints.txt, 1999. 1198 [Nik2001] Nikander, P., "Denial-of-Service, Address Ownership, and 1199 Early Authentication in the IPv6 World", in Proceesings 1200 of Security Protocols, 9th International Workshop, 1201 Cambridge, UK, April 25-27 2001, LNCS 2467, pp. 12-26, 1202 Springer, 2002. 1204 [Bel1998] Bellovin, S., "EIDs, IPsec, and HostNAT", in Proceedings 1205 of 41th IETF, Los Angeles, CA, 1206 URL http://www1.cs.columbia.edu/~smb/talks/hostnat.pdf, 1207 March 1998. 1209 Author's Address 1211 Robert Moskowitz 1212 Verizon 1213 1000 Bent Creek Blvd, Suite 200 1214 Mechanicsburg, PA 1215 USA 1217 Email: robert.moskowitz@verizon.com