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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) February 25, 2011 5 Intended status: Standards Track 6 Expires: August 29, 2011 8 Host Identity Protocol Architecture 9 draft-ietf-hip-rfc4423-bis-02 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 August 29, 2011. 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. Storing Host Identifiers in DNS . . . . . . . . . . . . . . 10 80 4.3. Host Identity Tag (HIT) . . . . . . . . . . . . . . . . . . 11 81 4.4. Host Identity Hash (HIH) . . . . . . . . . . . . . . . . . . 11 82 4.5. Local Scope Identifier (LSI) . . . . . . . . . . . . . . . . 11 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 IPsec . . . . . . . . . . . . . . . . . . . . . . . 15 89 8. HIP and MAC Security . . . . . . . . . . . . . . . . . . . . 16 90 9. HIP and NATs . . . . . . . . . . . . . . . . . . . . . . . . 16 91 9.1. HIP and Upper-layer checksums . . . . . . . . . . . . . . . 17 92 10. Multicast . . . . . . . . . . . . . . . . . . . . . . . . . 17 93 11. HIP policies . . . . . . . . . . . . . . . . . . . . . . . . 17 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. Non-security considerations . . . . . . . . . . . . . . . . 23 100 15. IANA considerations . . . . . . . . . . . . . . . . . . . . 24 101 16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 24 102 17. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 103 17.1. Normative References . . . . . . . . . . . . . . . . . . . . 25 104 17.2. Informative references . . . . . . . . . . . . . . . . . . . 25 105 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. The Host Identity namespace consists of 119 Host Identifiers (HI). A Host Identifier is cryptographic in its 120 nature; it is the public key of an asymmetric key-pair. Each host 121 will have at least one Host Identity, but it will typically have more 122 than one. Each Host Identity uniquely identifies a single host, 123 i.e., no two hosts have the same Host Identity. The Host Identity, 124 and the corresponding Host Identifier, can either be public (e.g. 125 published in the DNS), or unpublished. Client systems will tend to 126 have both public and unpublished Identities. 128 There is a subtle but important difference between Host Identities 129 and Host Identifiers. An Identity refers to the abstract entity that 130 is identified. An Identifier, on the other hand, refers to the 131 concrete bit pattern that is used in the identification process. 133 Although the Host Identifiers could be used in many authentication 134 systems, such as IKEv2 [RFC4306], the presented architecture 135 introduces a new protocol, called the Host Identity Protocol (HIP), 136 and a cryptographic exchange, called the HIP base exchange; see also 137 Section 7. The HIP protocols provide for limited forms of trust 138 between systems, enhance mobility, multi-homing and dynamic IP 139 renumbering, aid in protocol translation / transition, and reduce 140 certain types of denial-of-service (DoS) attacks. 142 When HIP is used, the actual payload traffic between two HIP hosts is 143 typically, but not necessarily, protected with IPsec. The Host 144 Identities are used to create the needed IPsec Security Associations 145 (SAs) and to authenticate the hosts. When IPsec is used, the actual 146 payload IP packets do not differ in any way from standard IPsec 147 protected IP packets. 149 Much has been learned about HIP since [RFC4423] was published. This 150 document expands Host Identities beyond use to enable IP connectivity 151 and security to general interhost secure signalling at any protocol 152 layer. The signal may establish a security association between the 153 hosts, or simply pass information within the channel. 155 2. Terminology 157 2.1. Terms common to other documents 159 +---------------+---------------------------------------------------+ 160 | Term | Explanation | 161 +---------------+---------------------------------------------------+ 162 | Public key | The public key of an asymmetric cryptographic key | 163 | | pair. Used as a publicly known identifier for | 164 | | cryptographic identity authentication. | 165 | | | 166 | Private key | The private or secret key of an asymmetric | 167 | | cryptographic key pair. Assumed to be known only | 168 | | to the party identified by the corresponding | 169 | | public key. Used by the identified party to | 170 | | authenticate its identity to other parties. | 171 | | | 172 | Public key | An asymmetric cryptographic key pair consisting | 173 | pair | of public and private keys. For example, | 174 | | Rivest-Shamir-Adelman (RSA) and Digital Signature | 175 | | Algorithm (DSA) key pairs are such key pairs. | 176 | | | 177 | End-point | A communicating entity. For historical reasons, | 178 | | the term 'computing platform' is used in this | 179 | | document as a (rough) synonym for end-point. | 180 +---------------+---------------------------------------------------+ 182 2.2. Terms specific to this and other HIP documents 184 It should be noted that many of the terms defined herein are 185 tautologous, self-referential or defined through circular reference 186 to other terms. This is due to the succinct nature of the 187 definitions. See the text elsewhere in this document and in RFC 5201 188 [RFC5201-bis] for more elaborate explanations. 190 +---------------+---------------------------------------------------+ 191 | Term | Explanation | 192 +---------------+---------------------------------------------------+ 193 | Computing | An entity capable of communicating and computing, | 194 | platform | for example, a computer. See the definition of | 195 | | 'End-point', above. | 196 | | | 197 | HIP base | A cryptographic protocol; see also Section 7. | 198 | exchange | | 199 | | | 200 | HIP packet | An IP packet that carries a 'Host Identity | 201 | | Protocol' message. | 202 | | | 203 | Host Identity | An abstract concept assigned to a 'computing | 204 | | platform'. See 'Host Identifier', below. | 205 | | | 206 | Host Identity | A name space formed by all possible Host | 207 | namespace | Identifiers. | 208 | | | 209 | Host Identity | A protocol used to carry and authenticate Host | 210 | Protocol | Identifiers and other information. | 211 | | | 212 | Host Identity | A 128-bit datum created by taking a cryptographic | 213 | Tag | hash over a Host Identifier. | 214 | | | 215 | Host Identity | The cryptograhic hash used in creating the Host | 216 | Hash | Identity Tag from the Host Identity. | 217 | | | 218 | Host | A public key used as a name for a Host Identity. | 219 | Identifier | | 220 | | | 221 | Local Scope | A 32-bit datum denoting a Host Identity. | 222 | Identifier | | 223 | | | 224 | Public Host | A published or publicly known Host Identfier used | 225 | Identifier | as a public name for a Host Identity, and the | 226 | and Identity | corresponding Identity. | 227 | | | 228 | Unpublished | A Host Identifier that is not placed in any | 229 | Host | public directory, and the corresponding Host | 230 | Identifier | Identity. Unpublished Host Identities are | 231 | and Identity | typically short lived in nature, being often | 232 | | replaced and possibly used just once. | 233 | | | 234 | Rendezvous | A mechanism used to locate mobile hosts based on | 235 | Mechanism | their HIT. | 236 +---------------+---------------------------------------------------+ 238 3. Background 240 The Internet is built from three principal components: computing 241 platforms (end-points), packet transport (i.e., internetworking) 242 infrastructure, and services (applications). The Internet exists to 243 service two principal components: people and robotic services 244 (silicon based people, if you will). All these components need to be 245 named in order to interact in a scalable manner. Here we concentrate 246 on naming computing platforms and packet transport elements. 248 There are two principal namespaces in use in the Internet for these 249 components: IP numbers, and Domain Names. Domain Names provide 250 hierarchically assigned names for some computing platforms and some 251 services. Each hierarchy is delegated from the level above; there is 252 no anonymity in Domain Names. Email, HTTP, and SIP addresses all 253 reference Domain Names. 255 IP numbers are a confounding of two namespaces, the names of a host's 256 networking interfaces and the names of the locations ('confounding' 257 is a term used in statistics to discuss metrics that are merged into 258 one with a gain in indexing, but a loss in informational value). The 259 names of locations should be understood as denoting routing direction 260 vectors, i.e., information that is used to deliver packets to their 261 destinations. 263 IP numbers name networking interfaces, and typically only when the 264 interface is connected to the network. Originally, IP numbers had 265 long-term significance. Today, the vast number of interfaces use 266 ephemeral and/or non-unique IP numbers. That is, every time an 267 interface is connected to the network, it is assigned an IP number. 269 In the current Internet, the transport layers are coupled to the IP 270 addresses. Neither can evolve separately from the other. IPng 271 deliberations were strongly shaped by the decision that a 272 corresponding TCPng would not be created. 274 There are three critical deficiencies with the current namespaces. 275 Firstly, dynamic readdressing cannot be directly managed. Secondly, 276 anonymity is not provided in a consistent, trustable manner. 277 Finally, authentication for systems and datagrams is not provided. 278 All of these deficiencies arise because computing platforms are not 279 well named with the current namespaces. 281 3.1. A desire for a namespace for computing platforms 283 An independent namespace for computing platforms could be used in 284 end-to-end operations independent of the evolution of the 285 internetworking layer and across the many internetworking layers. 287 This could support rapid readdressing of the internetworking layer 288 because of mobility, rehoming, or renumbering. 290 If the namespace for computing platforms is based on public-key 291 cryptography, it can also provide authentication services. If this 292 namespace is locally created without requiring registration, it can 293 provide anonymity. 295 Such a namespace (for computing platforms) and the names in it should 296 have the following characteristics: 298 o The namespace should be applied to the IP 'kernel'. The IP kernel 299 is the 'component' between applications and the packet transport 300 infrastructure. 302 o The namespace should fully decouple the internetworking layer from 303 the higher layers. The names should replace all occurrences of IP 304 addresses within applications (like in the Transport Control 305 Block, TCB). This may require changes to the current APIs. In 306 the long run, it is probable that some new APIs are needed. 308 o The introduction of the namespace should not mandate any 309 administrative infrastructure. Deployment must come from the 310 bottom up, in a pairwise deployment. 312 o The names should have a fixed length representation, for easy 313 inclusion in datagram headers and existing programming interfaces 314 (e.g the TCB). 316 o Using the namespace should be affordable when used in protocols. 317 This is primarily a packet size issue. There is also a 318 computational concern in affordability. 320 o Name collisions should be avoided as much as possible. The 321 mathematics of the birthday paradox can be used to estimate the 322 chance of a collision in a given population and hash space. In 323 general, for a random hash space of size n bits, we would expect 324 to obtain a collision after approximately 1.2*sqrt(2**n) hashes 325 were obtained. For 64 bits, this number is roughly 4 billion. A 326 hash size of 64 bits may be too small to avoid collisions in a 327 large population; for example, there is a 1% chance of collision 328 in a population of 640M. For 100 bits (or more), we would not 329 expect a collision until approximately 2**50 (1 quadrillion) 330 hashes were generated. 332 o The names should have a localized abstraction so that it can be 333 used in existing protocols and APIs. 335 o It must be possible to create names locally. This can provide 336 anonymity at the cost of making resolvability very difficult. 338 * Sometimes the names may contain a delegation component. This 339 is the cost of resolvability. 341 o The namespace should provide authentication services. 343 o The names should be long lived, but replaceable at any time. This 344 impacts access control lists; short lifetimes will tend to result 345 in tedious list maintenance or require a namespace infrastructure 346 for central control of access lists. 348 In this document, a new namespace approaching these ideas is called 349 the Host Identity namespace. Using Host Identities requires its own 350 protocol layer, the Host Identity Protocol, between the 351 internetworking and transport layers. The names are based on public- 352 key cryptography to supply authentication services. Properly 353 designed, it can deliver all of the above stated requirements. 355 4. Host Identity namespace 357 A name in the Host Identity namespace, a Host Identifier (HI), 358 represents a statistically globally unique name for naming any system 359 with an IP stack. This identity is normally associated with, but not 360 limited to, an IP stack. A system can have multiple identities, some 361 'well known', some unpublished or 'anonymous'. A system may self- 362 assert its own identity, or may use a third-party authenticator like 363 DNSSEC [RFC2535], PGP, or X.509 to 'notarize' the identity assertion. 364 It is expected that the Host Identifiers will initially be 365 authenticated with DNSSEC and that all implementations will support 366 DNSSEC as a minimal baseline. 368 In theory, any name that can claim to be 'statistically globally 369 unique' may serve as a Host Identifier. However, in the authors' 370 opinion, a public key of a 'public key pair' makes the best Host 371 Identifier. As will be specified in the Host Identity Protocol Base 372 EXchange (BEX) [RFC5201-bis] specification, a public-key-based HI can 373 authenticate the HIP packets and protect them for man-in-the-middle 374 attacks. Since authenticated datagrams are mandatory to provide much 375 of HIP's denial-of-service protection, the Diffie-Hellman exchange in 376 HIP BEX has to be authenticated. Thus, only public-key HI and 377 authenticated HIP messages are supported in practice. 379 In this document, the non-cryptographic forms of HI and HIP are 380 presented to complete the theory of HI, but they should not be 381 implemented as they could produce worse denial-of-service attacks 382 than the Internet has without Host Identity. There is on-going 383 research in challenge puzzles to use non-cryptographic HI, like 384 RFIDs, in an HIP exchange tailored to the workings of such 385 challenges. 387 4.1. Host Identifiers 389 Host Identity adds two main features to Internet protocols. The 390 first is a decoupling of the internetworking and transport layers; 391 see Section 5. This decoupling will allow for independent evolution 392 of the two layers. Additionally, it can provide end-to-end services 393 over multiple internetworking realms. The second feature is host 394 authentication. Because the Host Identifier is a public key, this 395 key can be used for authentication in security protocols like IPsec. 397 The only completely defined structure of the Host Identity is that of 398 a public/private key pair. In this case, the Host Identity is 399 referred to by its public component, the public key. Thus, the name 400 representing a Host Identity in the Host Identity namespace, i.e., 401 the Host Identifier, is the public key. In a way, the possession of 402 the private key defines the Identity itself. If the private key is 403 possessed by more than one node, the Identity can be considered to be 404 a distributed one. 406 Architecturally, any other Internet naming convention might form a 407 usable base for Host Identifiers. However, non-cryptographic names 408 should only be used in situations of high trust - low risk. That is 409 any place where host authentication is not needed (no risk of host 410 spoofing) and no use of IPsec. However, at least for interconnected 411 networks spanning several operational domains, the set of 412 environments where the risk of host spoofing allowed by non- 413 cryptographic Host Identifiers is acceptable is the null set. Hence, 414 the current HIP documents do not specify how to use any other types 415 of Host Identifiers but public keys. 417 The actual Host Identities are never directly used in any Internet 418 protocols. The corresponding Host Identifiers (public keys) may be 419 stored in various DNS or LDAP directories as identified elsewhere in 420 this document, and they are passed in the HIP base exchange. A Host 421 Identity Tag (HIT) is used in other protocols to represent the Host 422 Identity. Another representation of the Host Identities, the Local 423 Scope Identifier (LSI), can also be used in protocols and APIs. 425 4.2. Storing Host Identifiers in DNS 427 The public Host Identifiers should be stored in DNS; the unpublished 428 Host Identifiers should not be stored anywhere (besides the 429 communicating hosts themselves). The (public) HI along with the 430 supported HIHs are stored in a new RR type. This RR type is defined 431 in HIP DNS Extension [I-D.ietf-hip-rfc5205-bis]. 433 Alternatively, or in addition to storing Host Identifiers in the DNS, 434 they may be stored in various kinds of Public Key Infrastructure 435 (PKI). Such a practice may allow them to be used for purposes other 436 than pure host identification. 438 4.3. Host Identity Tag (HIT) 440 A Host Identity Tag is a 128-bit representation for a Host Identity. 441 It is created by taking a cryptographic hash over the corresponding 442 Host Identifier. There are two advantages of using a hash over using 443 the Host Identifier in protocols. Firstly, its fixed length makes 444 for easier protocol coding and also better manages the packet size 445 cost of this technology. Secondly, it presents the identity in a 446 consistent format to the protocol independent of the cryptographic 447 algorithms used. 449 There can be multiple HITs per Host Identifier when multiple hashes 450 are supported. An Initator may have to initially guess which HIT to 451 use for the Responder, typically based on what it perfers, until it 452 learns the appropriate HIT through the HIP exchange. 454 In the HIP packets, the HITs identify the sender and recipient of a 455 packet. Consequently, a HIT should be unique in the whole IP 456 universe as long as it is being used. In the extremely rare case of 457 a single HIT mapping to more than one Host Identity, the Host 458 Identifiers (public keys) will make the final difference. If there 459 is more than one public key for a given node, the HIT acts as a hint 460 for the correct public key to use. 462 4.4. Host Identity Hash (HIH) 464 The Host Identity Hash is the cryptographic hash used in producing 465 the HIT from the HI. It is also the hash used through out the HIP 466 protocol for consistancy and simplicity. It is possible to for the 467 two Hosts in the HIP exchange to use different hashes. 469 Multiple HIHs within HIP are needed to address the moving target of 470 creation and eventual compromise of cryptographic hashes. This 471 significantly complicates HIP and offers an attacker an additional 472 downgrade attack that is mitigated in the HIP protocol. 474 4.5. Local Scope Identifier (LSI) 476 An LSI is a 32-bit localized representation for a Host Identity. The 477 purpose of an LSI is to facilitate using Host Identities in existing 478 protocols and APIs. LSI's advantage over HIT is its size; its 479 disadvantage is its local scope. 481 Examples of how LSIs can be used include: as the address in an FTP 482 command and as the address in a socket call. Thus, LSIs act as a 483 bridge for Host Identities into IPv4-based protocols and APIs. LSIs 484 also make it possible for some IPv4 applications to run over an IPv6 485 network. 487 5. New stack architecture 489 One way to characterize Host Identity is to compare the proposed new 490 architecture with the current one. As discussed above, the IP 491 addresses can be seen to be a confounding of routing direction 492 vectors and interface names. Using the terminology from the IRTF 493 Name Space Research Group Report [nsrg-report] and, e.g., the 494 unpublished Internet-Draft Endpoints and Endpoint Names 495 [chiappa-endpoints], the IP addresses currently embody the dual role 496 of locators and end-point identifiers. That is, each IP address 497 names a topological location in the Internet, thereby acting as a 498 routing direction vector, or locator. At the same time, the IP 499 address names the physical network interface currently located at the 500 point-of-attachment, thereby acting as a end-point name. 502 In the HIP architecture, the end-point names and locators are 503 separated from each other. IP addresses continue to act as locators. 504 The Host Identifiers take the role of end-point identifiers. It is 505 important to understand that the end-point names based on Host 506 Identities are slightly different from interface names; a Host 507 Identity can be simultaneously reachable through several interfaces. 509 The difference between the bindings of the logical entities are 510 illustrated in Figure 1. 512 Service ------ Socket Service ------ Socket 513 | | 514 | | 515 | | 516 | | 517 End-point | End-point --- Host Identity 518 \ | | 519 \ | | 520 \ | | 521 \ | | 522 Location --- IP address Location --- IP address 523 Figure 1 525 5.1. Transport associations and end-points 527 Architecturally, HIP provides for a different binding of transport- 528 layer protocols. That is, the transport-layer associations, i.e., 529 TCP connections and UDP associations, are no longer bound to IP 530 addresses but to Host Identities. 532 It is possible that a single physical computer hosts several logical 533 end-points. With HIP, each of these end-points would have a distinct 534 Host Identity. Furthermore, since the transport associations are 535 bound to Host Identities, HIP provides for process migration and 536 clustered servers. That is, if a Host Identity is moved from one 537 physical computer to another, it is also possible to simultaneously 538 move all the transport associations without breaking them. 539 Similarly, if it is possible to distribute the processing of a single 540 Host Identity over several physical computers, HIP provides for 541 cluster based services without any changes at the client end-point. 543 6. End-host mobility and multi-homing 545 HIP decouples the transport from the internetworking layer, and binds 546 the transport associations to the Host Identities (through actually 547 either the HIT or LSI). Consequently, HIP can provide for a degree 548 of internetworking mobility and multi-homing at a low infrastructure 549 cost. HIP mobility includes IP address changes (via any method) to 550 either party. Thus, a system is considered mobile if its IP address 551 can change dynamically for any reason like PPP, DHCP, IPv6 prefix 552 reassignments, or a NAT device remapping its translation. Likewise, 553 a system is considered multi-homed if it has more than one globally 554 routable IP address at the same time. HIP links IP addresses 555 together, when multiple IP addresses correspond to the same Host 556 Identity, and if one address becomes unusable, or a more preferred 557 address becomes available, existing transport associations can easily 558 be moved to another address. 560 When a node moves while communication is already on-going, address 561 changes are rather straightforward. The peer of the mobile node can 562 just accept a HIP or an integrity protected IPsec packet from any 563 address and ignore the source address. However, as discussed in 564 Section 6.2 below, a mobile node must send a HIP readdress packet to 565 inform the peer of the new address(es), and the peer must verify that 566 the mobile node is reachable through these addresses. This is 567 especially helpful for those situations where the peer node is 568 sending data periodically to the mobile node (that is re-starting a 569 connection after the initial connection). 571 6.1. Rendezvous mechanism 573 Making a contact to a mobile node is slightly more involved. In 574 order to start the HIP exchange, the initiator node has to know how 575 to reach the mobile node. Although infrequently moving HIP nodes 576 could use Dynamic DNS [RFC2136] to update their reachability 577 information in the DNS, an alternative to using DNS in this fashion 578 is to use a piece of new static infrastructure to facilitate 579 rendezvous between HIP nodes. 581 The mobile node keeps the rendezvous infrastructure continuously 582 updated with its current IP address(es). The mobile nodes must trust 583 the rendezvous mechanism to properly maintain their HIT and IP 584 address mappings. 586 The rendezvous mechanism is also needed if both of the nodes happen 587 to change their address at the same time, either because they are 588 mobile and happen to move at the same time, because one of them is 589 off-line for a while, or because of some other reason. In such a 590 case, the HIP UPDATE packets will cross each other in the network and 591 never reach the peer node. 593 The HIP rendezvous mechanism is defined in HIP Rendezvous 594 [I-D.ietf-hip-rfc5204-bis]. 596 6.2. Protection against flooding attacks 598 Although the idea of informing about address changes by simply 599 sending packets with a new source address appears appealing, it is 600 not secure enough. That is, even if HIP does not rely on the source 601 address for anything (once the base exchange has been completed), it 602 appears to be necessary to check a mobile node's reachability at the 603 new address before actually sending any larger amounts of traffic to 604 the new address. 606 Blindly accepting new addresses would potentially lead to flooding 607 Denial-of-Service attacks against third parties [RFC4225]. In a 608 distributed flooding attack an attacker opens high volume HIP 609 connections with a large number of hosts (using unpublished HIs), and 610 then claims to all of these hosts that it has moved to a target 611 node's IP address. If the peer hosts were to simply accept the move, 612 the result would be a packet flood to the target node's address. To 613 prevent this type of attack, HIP includes an address check mechanism 614 where the reachability of a node is separately checked at each 615 address before using the address for larger amounts of traffic. 617 A credit-based authorization approach Host Mobility with the Host 618 Identity Protocol [I-D.ietf-hip-rfc5206-bis] can be used between 619 hosts for sending data prior to completing the address tests. 620 Otherwise, if HIP is used between two hosts that fully trust each 621 other, the hosts may optionally decide to skip the address tests. 622 However, such performance optimization must be restricted to peers 623 that are known to be trustworthy and capable of protecting themselves 624 from malicious software. 626 7. HIP and IPsec 628 The preferred way of implementing HIP is to use IPsec to carry the 629 actual data traffic. As of today, the only completely defined method 630 is to use IPsec Encapsulated Security Payload (ESP) to carry the data 631 packets [I-D.ietf-hip-rfc5202-bis]. In the future, other ways of 632 transporting payload data may be developed, including ones that do 633 not use cryptographic protection. 635 In practice, the HIP base exchange uses the cryptographic Host 636 Identifiers to set up a pair of ESP Security Associations (SAs) to 637 enable ESP in an end-to-end manner. This is implemented in a way 638 that can span addressing realms. 640 While it would be possible, at least in theory, to use some existing 641 cryptographic protocol, such as IKEv2 together with Host Identifiers, 642 to establish the needed SAs, HIP defines a new protocol. There are a 643 number of historical reasons for this, and there are also a few 644 architectural reasons. First, IKE (and IKEv2) were not designed with 645 middle boxes in mind. As adding a new naming layer allows one to 646 potentially add a new forwarding layer (see Section 9, below), it is 647 very important that the HIP protocols are friendly towards any middle 648 boxes. 650 Second, from a conceptual point of view, the IPsec Security Parameter 651 Index (SPI) in ESP provides a simple compression of the HITs. This 652 does require per-HIT-pair SAs (and SPIs), and a decrease of policy 653 granularity over other Key Management Protocols, such as IKE and 654 IKEv2. In particular, the current thinking is limited to a situation 655 where, conceptually, there is only one pair of SAs between any given 656 pair of HITs. In other words, from an architectural point of view, 657 HIP only supports host-to-host (or endpoint-to-endpoint) Security 658 Associations. If two hosts need more pairs of parallel SAs, they 659 should use separate HITs for that. However, future HIP extensions 660 may provide for more granularity and creation of several ESP SAs 661 between a pair of HITs. 663 Since HIP is designed for host usage, not for gateways or so called 664 Bump-in-the-Wire (BITW) implementations, only ESP transport mode is 665 supported. An ESP SA pair is indexed by the SPIs and the two HITs 666 (both HITs since a system can have more than one HIT). The SAs need 667 not to be bound to IP addresses; all internal control of the SA is by 668 the HITs. Thus, a host can easily change its address using Mobile 669 IP, DHCP, PPP, or IPv6 readdressing and still maintain the SAs. 670 Since the transports are bound to the SA (via an LSI or a HIT), any 671 active transport is also maintained. Thus, real-world conditions 672 like loss of a PPP connection and its re-establishment or a mobile 673 handover will not require a HIP negotiation or disruption of 674 transport services [Bel1998]. 676 Since HIP does not negotiate any SA lifetimes, all lifetimes are 677 local policy. The only lifetimes a HIP implementation must support 678 are sequence number rollover (for replay protection), and SA timeout. 679 An SA times out if no packets are received using that SA. 680 Implementations may support lifetimes for the various ESP transforms. 682 8. HIP and MAC Security 684 The IEEE 802 standards have been defining MAC layered security. Many 685 of these standards use EAP [RFC3748] as a Key Management System (KMS) 686 transport, but some like IEEE 802.15.4 [IEEE.802-15-4.2006] leave the 687 KMS and its transport as "Out of Scope". 689 HIP is well suited as a KMS in these environments. 691 o HIP is independent of IP addressing and can be directly 692 transported over any network protocol. 694 o Master Keys in 802 protocols are strictly pair-based with group 695 keys transported from the group controller using pair-wise keys. 697 o AdHoc 802 networks can be better served by a peer-to-peer KMS than 698 the EAP client/server model. 700 o Some devices are very memory constrained and a common KMS for both 701 MAC and IP security represents a considerable code savings. 703 9. HIP and NATs 705 Passing packets between different IP addressing realms requires 706 changing IP addresses in the packet header. This may happen, for 707 example, when a packet is passed between the public Internet and a 708 private address space, or between IPv4 and IPv6 networks. The 709 address translation is usually implemented as Network Address 710 Translation (NAT) [RFC3022] or NAT Protocol translation (NAT-PT) 711 [RFC2766]. 713 In a network environment where identification is based on the IP 714 addresses, identifying the communicating nodes is difficult when NAT 715 is used. With HIP, the transport-layer end-points are bound to the 716 Host Identities. Thus, a connection between two hosts can traverse 717 many addressing realm boundaries. The IP addresses are used only for 718 routing purposes; they may be changed freely during packet traversal. 720 For a HIP-based flow, a HIP-aware NAT or NAT-PT system tracks the 721 mapping of HITs, and the corresponding IPsec SPIs, to an IP address. 722 The NAT system has to learn mappings both from HITs and from SPIs to 723 IP addresses. Many HITs (and SPIs) can map to a single IP address on 724 a NAT, simplifying connections on address poor NAT interfaces. The 725 NAT can gain much of its knowledge from the HIP packets themselves; 726 however, some NAT configuration may be necessary. 728 NAT systems cannot touch the datagrams within the IPsec envelope, 729 thus application-specific address translation must be done in the end 730 systems. HIP provides for 'Distributed NAT', and uses the HIT or the 731 LSI as a placeholder for embedded IP addresses. 733 HIP and NAT interaction is defined in [RFC5770]. 735 9.1. HIP and Upper-layer checksums 737 There is no way for a host to know if any of the IP addresses in an 738 IP header are the addresses used to calculate the TCP checksum. That 739 is, it is not feasible to calculate the TCP checksum using the actual 740 IP addresses in the pseudo header; the addresses received in the 741 incoming packet are not necessarily the same as they were on the 742 sending host. Furthermore, it is not possible to recompute the 743 upper-layer checksums in the NAT/NAT-PT system, since the traffic is 744 IPsec protected. Consequently, the TCP and UDP checksums are 745 calculated using the HITs in the place of the IP addresses in the 746 pseudo header. Furthermore, only the IPv6 pseudo header format is 747 used. This provides for IPv4 / IPv6 protocol translation. 749 10. Multicast 751 Few concrete thoughts exist about how HIP might affect IP-layer or 752 application-layer multicast. 754 11. HIP policies 756 There are a number of variables that will influence the HIP exchanges 757 that each host must support. All HIP implementations should support 758 at least 2 HIs, one to publish in DNS and an unpublished one for 759 anonymous usage. Although unpublished HIs will be rarely used as 760 responder HIs, they are likely be common for initiators. Support for 761 multiple HIs is recommended. 763 Many initiators would want to use a different HI for different 764 responders. The implementations should provide for a policy of 765 initiator HIT to responder HIT. This policy should also include 766 preferred transforms and local lifetimes. 768 Responders would need a similar policy, describing the hosts allowed 769 to participate in HIP exchanges, and the preferred transforms and 770 local lifetimes. 772 12. Benefits of HIP 774 In the beginning, the network layer protocol (i.e., IP) had the 775 following four "classic" invariants: 777 o Non-mutable: The address sent is the address received. 779 o Non-mobile: The address doesn't change during the course of an 780 "association". 782 o Reversible: A return header can always be formed by reversing the 783 source and destination addresses. 785 o Omniscient: Each host knows what address a partner host can use to 786 send packets to it. 788 Actually, the fourth can be inferred from 1 and 3, but it is worth 789 mentioning for reasons that will be obvious soon if not already. 791 In the current "post-classic" world, we are intentionally trying to 792 get rid of the second invariant (both for mobility and for multi- 793 homing), and we have been forced to give up the first and the fourth. 794 Realm Specific IP [RFC3102] is an attempt to reinstate the fourth 795 invariant without the first invariant. IPv6 is an attempt to 796 reinstate the first invariant. 798 Few systems on the Internet have DNS names that are meaningful. That 799 is, if they have a Fully Qualified Domain Name (FQDN), that name 800 typically belongs to a NAT device or a dial-up server, and does not 801 really identify the system itself but its current connectivity. 802 FQDNs (and their extensions as email names) are application-layer 803 names; more frequently naming services than a particular system. 804 This is why many systems on the Internet are not registered in the 805 DNS; they do not have services of interest to other Internet hosts. 807 DNS names are references to IP addresses. This only demonstrates the 808 interrelationship of the networking and application layers. DNS, as 809 the Internet's only deployed, distributed database is also the 810 repository of other namespaces, due in part to DNSSEC and application 811 specific key records. Although each namespace can be stretched (IP 812 with v6, DNS with KEY records), neither can adequately provide for 813 host authentication or act as a separation between internetworking 814 and transport layers. 816 The Host Identity (HI) namespace fills an important gap between the 817 IP and DNS namespaces. An interesting thing about the HI is that it 818 actually allows one to give up all but the 3rd network-layer 819 invariant. That is to say, as long as the source and destination 820 addresses in the network-layer protocol are reversible, then things 821 work ok because HIP takes care of host identification, and 822 reversibility allows one to get a packet back to one's partner host. 823 You do not care if the network-layer address changes in transit 824 (mutable) and you don't care what network-layer address the partner 825 is using (non-omniscient). 827 12.1. HIP's answers to NSRG questions 829 The IRTF Name Space Research Group has posed a number of evaluating 830 questions in their report [nsrg-report]. In this section, we provide 831 answers to these questions. 833 1. How would a stack name improve the overall functionality of the 834 Internet? 836 HIP decouples the internetworking layer from the transport 837 layer, allowing each to evolve separately. The decoupling 838 makes end-host mobility and multi-homing easier, also across 839 IPv4 and IPv6 networks. HIs make network renumbering easier, 840 and they also make process migration and clustered servers 841 easier to implement. Furthermore, being cryptographic in 842 nature, they provide the basis for solving the security 843 problems related to end-host mobility and multi-homing. 845 2. What does a stack name look like? 847 A HI is a cryptographic public key. However, instead of using 848 the keys directly, most protocols use a fixed size hash of the 849 public key. 851 3. What is its lifetime? 853 HIP provides both stable and temporary Host Identifiers. 854 Stable HIs are typically long lived, with a lifetime of years 855 or more. The lifetime of temporary HIs depends on how long 856 the upper-layer connections and applications need them, and 857 can range from a few seconds to years. 859 4. Where does it live in the stack? 861 The HIs live between the transport and internetworking layers. 863 5. How is it used on the end points? 865 The Host Identifiers may be used directly or indirectly (in 866 the form of HITs or LSIs) by applications when they access 867 network services. Additionally, the Host Identifiers, as 868 public keys, are used in the built in key agreement protocol, 869 called the HIP base exchange, to authenticate the hosts to 870 each other. 872 6. What administrative infrastructure is needed to support it? 874 In some environments, it is possible to use HIP 875 opportunistically, without any infrastructure. However, to 876 gain full benefit from HIP, the HIs must be stored in the DNS 877 or a PKI, and a new rendezvous mechanism is needed 878 [I-D.ietf-hip-rfc5205-bis]. 880 7. If we add an additional layer would it make the address list in 881 SCTP unnecessary? 883 Yes 885 8. What additional security benefits would a new naming scheme 886 offer? 888 HIP reduces dependency on IP addresses, making the so called 889 address ownership [Nik2001] problems easier to solve. In 890 practice, HIP provides security for end-host mobility and 891 multi-homing. Furthermore, since HIP Host Identifiers are 892 public keys, standard public key certificate infrastructures 893 can be applied on the top of HIP. 895 9. What would the resolution mechanisms be, or what characteristics 896 of a resolution mechanisms would be required? 898 For most purposes, an approach where DNS names are resolved 899 simultaneously to HIs and IP addresses is sufficient. 900 However, if it becomes necessary to resolve HIs into IP 901 addresses or back to DNS names, a flat resolution 902 infrastructure is needed. Such an infrastructure could be 903 based on the ideas of Distributed Hash Tables, but would 904 require significant new development and deployment. 906 13. Changes from RFC 4423 908 This section summarizes the changes made from [RFC4423]. 910 14. Security considerations 912 HIP takes advantage of the new Host Identity paradigm to provide 913 secure authentication of hosts and to provide a fast key exchange for 914 IPsec. HIP also attempts to limit the exposure of the host to 915 various denial-of-service (DoS) and man-in-the-middle (MitM) attacks. 916 In so doing, HIP itself is subject to its own DoS and MitM attacks 917 that potentially could be more damaging to a host's ability to 918 conduct business as usual. 920 Resource exhausting denial-of-service attacks take advantage of the 921 cost of setting up a state for a protocol on the responder compared 922 to the 'cheapness' on the initiator. HIP allows a responder to 923 increase the cost of the start of state on the initiator and makes an 924 effort to reduce the cost to the responder. This is done by having 925 the responder start the authenticated Diffie-Hellman exchange instead 926 of the initiator, making the HIP base exchange 4 packets long. There 927 are more details on this process in the Host Identity Protocol under 928 development. 930 HIP optionally supports opportunistic negotiation. That is, if a 931 host receives a start of transport without a HIP negotiation, it can 932 attempt to force a HIP exchange before accepting the connection. 933 This has the potential for DoS attacks against both hosts. If the 934 method to force the start of HIP is expensive on either host, the 935 attacker need only spoof a TCP SYN. This would put both systems into 936 the expensive operations. HIP avoids this attack by having the 937 responder send a simple HIP packet that it can pre-build. Since this 938 packet is fixed and easily replayed, the initiator only reacts to it 939 if it has just started a connection to the responder. 941 Man-in-the-middle attacks are difficult to defend against, without 942 third-party authentication. A skillful MitM could easily handle all 943 parts of the HIP base exchange, but HIP indirectly provides the 944 following protection from a MitM attack. If the responder's HI is 945 retrieved from a signed DNS zone or secured by some other means, the 946 initiator can use this to authenticate the signed HIP packets. 947 Likewise, if the initiator's HI is in a secure DNS zone, the 948 responder can retrieve it and validate the signed HIP packets. 950 However, since an initiator may choose to use an unpublished HI, it 951 knowingly risks a MitM attack. The responder may choose not to 952 accept a HIP exchange with an initiator using an unknown HI. 954 The need to support multiple hashes for generating the HIT from the 955 HI affords the MitM a potentially powerful downgrade attack due to 956 the a-priori need of the HIT in the HIP base exchange. The base 957 exchange has been augmented to deal with such an attack by restarting 958 on detecting the attack. At worst this would only lead to a 959 situation in which the base exchange would never finish (or would be 960 aborted after some retries). As a drawback, this leads to an 6-way 961 base exchange which may seem bad at first. However, since this only 962 happens in an attack scenario and since the attack can be handled (so 963 it is not interesting to mount anymore), we assume the additional 964 messages are not a problem at all. Since the MitM cannot be 965 successful with a downgrade attack, these sorts of attacks will only 966 occur as 'nuisance' attacks. So, the base exchange would still be 967 usually just four packets even though implementations must be 968 prepared to protect themselves against the downgrade attack. 970 In HIP, the Security Association for IPsec is indexed by the SPI; the 971 source address is always ignored, and the destination address may be 972 ignored as well. Therefore, HIP-enabled IPsec Encapsulated Security 973 Payload (ESP) is IP address independent. This might seem to make it 974 easier for an attacker, but ESP with replay protection is already as 975 well protected as possible, and the removal of the IP address as a 976 check should not increase the exposure of IPsec ESP to DoS attacks. 978 Since not all hosts will ever support HIP, ICMPv4 'Destination 979 Unreachable, Protocol Unreachable' and ICMPv6 'Parameter Problem, 980 Unrecognized Next Header' messages are to be expected and present a 981 DoS attack. Against an initiator, the attack would look like the 982 responder does not support HIP, but shortly after receiving the ICMP 983 message, the initiator would receive a valid HIP packet. Thus, to 984 protect against this attack, an initiator should not react to an ICMP 985 message until a reasonable time has passed, allowing it to get the 986 real responder's HIP packet. A similar attack against the responder 987 is more involved. 989 Another MitM attack is simulating a responder's administrative 990 rejection of a HIP initiation. This is a simple ICMP 'Destination 991 Unreachable, Administratively Prohibited' message. A HIP packet is 992 not used because it would either have to have unique content, and 993 thus difficult to generate, resulting in yet another DoS attack, or 994 just as spoofable as the ICMP message. Like in the previous case, 995 the defense against this attack is for the initiator to wait a 996 reasonable time period to get a valid HIP packet. If one does not 997 come, then the initiator has to assume that the ICMP message is 998 valid. Since this is the only point in the HIP base exchange where 999 this ICMP message is appropriate, it can be ignored at any other 1000 point in the exchange. 1002 14.1. HITs used in ACLs 1004 It is expected that HITs will be used in ACLs. Future firewalls can 1005 use HITs to control egress and ingress to networks, with an assurance 1006 level difficult to achieve today. As discussed above in Section 7, 1007 once a HIP session has been established, the SPI value in an IPsec 1008 packet may be used as an index, indicating the HITs. In practice, 1009 firewalls can inspect HIP packets to learn of the bindings between 1010 HITs, SPI values, and IP addresses. They can even explicitly control 1011 IPsec usage, dynamically opening IPsec ESP only for specific SPI 1012 values and IP addresses. The signatures in HIP packets allow a 1013 capable firewall to ensure that the HIP exchange is indeed happening 1014 between two known hosts. This may increase firewall security. 1016 There has been considerable bad experience with distributed ACLs that 1017 contain public key related material, for example, with SSH. If the 1018 owner of a key needs to revoke it for any reason, the task of finding 1019 all locations where the key is held in an ACL may be impossible. If 1020 the reason for the revocation is due to private key theft, this could 1021 be a serious issue. 1023 A host can keep track of all of its partners that might use its HIT 1024 in an ACL by logging all remote HITs. It should only be necessary to 1025 log responder hosts. With this information, the host can notify the 1026 various hosts about the change to the HIT. There has been no attempt 1027 to develop a secure method to issue the HIT revocation notice. 1029 HIP-aware NATs, however, are transparent to the HIP aware systems by 1030 design. Thus, the host may find it difficult to notify any NAT that 1031 is using a HIT in an ACL. Since most systems will know of the NATs 1032 for their network, there should be a process by which they can notify 1033 these NATs of the change of the HIT. This is mandatory for systems 1034 that function as responders behind a NAT. In a similar vein, if a 1035 host is notified of a change in a HIT of an initiator, it should 1036 notify its NAT of the change. In this manner, NATs will get updated 1037 with the HIT change. 1039 14.2. Non-security considerations 1041 The definition of the Host Identifier states that the HI need not be 1042 a public key. It implies that the HI could be any value; for example 1043 a FQDN. This document does not describe how to support such a non- 1044 cryptographic HI. A non-cryptographic HI would still offer the 1045 services of the HIT or LSI for NAT traversal. It would be possible 1046 to carry HITs in HIP packets that had neither privacy nor 1047 authentication. Since such a mode would offer so little additional 1048 functionality for so much addition to the IP kernel, it has not been 1049 defined. Given how little public key cryptography HIP requires, HIP 1050 should only be implemented using public key Host Identities. 1052 If it is desirable to use HIP in a low security situation where 1053 public key computations are considered expensive, HIP can be used 1054 with very short Diffie-Hellman and Host Identity keys. Such use 1055 makes the participating hosts vulnerable to MitM and connection 1056 hijacking attacks. However, it does not cause flooding dangers, 1057 since the address check mechanism relies on the routing system and 1058 not on cryptographic strength. 1060 15. IANA considerations 1062 This document has no actions for IANA. 1064 16. Acknowledgments 1066 For the people historically involved in the early stages of HIP, see 1067 the Acknowledgements section in the Host Identity Protocol 1068 specification. 1070 During the later stages of this document, when the editing baton was 1071 transfered to Pekka Nikander, the comments from the early 1072 implementors and others, including Jari Arkko, Tom Henderson, Petri 1073 Jokela, Miika Komu, Mika Kousa, Andrew McGregor, Jan Melen, Tim 1074 Shepard, Jukka Ylitalo, and Jorma Wall, were invaluable. Finally, 1075 Lars Eggert, Spencer Dawkins and Dave Crocker provided valuable input 1076 during the final stages of publication, most of which was 1077 incorporated but some of which the authors decided to ignore in order 1078 to get this document published in the first place. 1080 The authors want to express their special thanks to Tom Henderson, 1081 who took the burden of editing the document in response to IESG 1082 comments at the time when both of the authors were busy doing other 1083 things. Without his perseverance original document might have never 1084 made it as RFC4423. 1086 This latest effort to update and move HIP forward within the IETF 1087 process owes its impetuous to the three HIP development teams: 1088 Boeing, HIIT (Helsinki Institute for Information Technology), and 1089 NomadicLab of Ericsson. Without their collective efforts HIP would 1090 have withered as on the IETF vine as a nice concept. 1092 17. References 1094 17.1. Normative References 1096 [RFC5201-bis] 1097 Moskowitz, R., Jokela, P., Henderson, T., and T. Heer, 1098 "Host Identity Protocol", draft-ietf-hip-rfc5201-bis-04 1099 (work in progress), January 2011. 1101 [I-D.ietf-hip-rfc5202-bis] 1102 Jokela, P., Moskowitz, R., Nikander, P., and J. Melen, 1103 "Using the Encapsulating Security Payload (ESP) Transport 1104 Format with the Host Identity Protocol (HIP)", 1105 draft-ietf-hip-rfc5202-bis-00 (work in progress), 1106 September 2010. 1108 [I-D.ietf-hip-rfc5204-bis] 1109 Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) 1110 Rendezvous Extension", draft-ietf-hip-rfc5204-bis-00 (work 1111 in progress), August 2010. 1113 [I-D.ietf-hip-rfc5205-bis] 1114 Laganier, J., "Host Identity Protocol (HIP) Domain Name 1115 System (DNS) Extension", draft-ietf-hip-rfc5205-bis-00 1116 (work in progress), August 2010. 1118 [I-D.ietf-hip-rfc5206-bis] 1119 Nikander, P., Henderson, T., Vogt, C., and J. Arkko, "Host 1120 Mobility with the Host Identity Protocol", 1121 draft-ietf-hip-rfc5206-bis-01 (work in progress), 1122 October 2010. 1124 17.2. Informative references 1126 [RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound, 1127 "Dynamic Updates in the Domain Name System (DNS UPDATE)", 1128 RFC 2136, April 1997. 1130 [RFC2535] Eastlake, D., "Domain Name System Security Extensions", 1131 RFC 2535, March 1999. 1133 [RFC2766] Tsirtsis, G. and P. Srisuresh, "Network Address 1134 Translation - Protocol Translation (NAT-PT)", RFC 2766, 1135 February 2000. 1137 [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network 1138 Address Translator (Traditional NAT)", RFC 3022, 1139 January 2001. 1141 [RFC3102] Borella, M., Lo, J., Grabelsky, D., and G. Montenegro, 1142 "Realm Specific IP: Framework", RFC 3102, October 2001. 1144 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 1145 Levkowetz, "Extensible Authentication Protocol (EAP)", 1146 RFC 3748, June 2004. 1148 [RFC4025] Richardson, M., "A Method for Storing IPsec Keying 1149 Material in DNS", RFC 4025, March 2005. 1151 [RFC4225] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E. 1152 Nordmark, "Mobile IP Version 6 Route Optimization Security 1153 Design Background", RFC 4225, December 2005. 1155 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", 1156 RFC 4306, December 2005. 1158 [RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol 1159 (HIP) Architecture", RFC 4423, May 2006. 1161 [RFC5770] Komu, M., Henderson, T., Tschofenig, H., Melen, J., and A. 1162 Keranen, "Basic Host Identity Protocol (HIP) Extensions 1163 for Traversal of Network Address Translators", RFC 5770, 1164 April 2010. 1166 [nsrg-report] 1167 Lear, E. and R. Droms, "What's In A Name:Thoughts from the 1168 NSRG", draft-irtf-nsrg-report-10 (work in progress), 1169 September 2003. 1171 [IEEE.802-15-4.2006] 1172 "Information technology - Telecommunications and 1173 information exchange between systems - Local and 1174 metropolitan area networks - Specific requirements - Part 1175 15.4: Wireless Medium Access Control (MAC) and Physical 1176 Layer (PHY) Specifications for Low-Rate Wireless Personal 1177 Area Networks (WPANs)", IEEE Standard 802.15.4, 1178 September 2006, . 1181 [chiappa-endpoints] 1182 Chiappa, J., "Endpoints and Endpoint Names: A Proposed 1183 Enhancement to the Internet Architecture", 1184 URL http://www.chiappa.net/~jnc/tech/endpoints.txt, 1999. 1186 [Nik2001] Nikander, P., "Denial-of-Service, Address Ownership, and 1187 Early Authentication in the IPv6 World", in Proceesings 1188 of Security Protocols, 9th International Workshop, 1189 Cambridge, UK, April 25-27 2001, LNCS 2467, pp. 12-26, 1190 Springer, 2002. 1192 [Bel1998] Bellovin, S., "EIDs, IPsec, and HostNAT", in Proceedings 1193 of 41th IETF, Los Angeles, CA, 1194 URL http://www1.cs.columbia.edu/~smb/talks/hostnat.pdf, 1195 March 1998. 1197 Author's Address 1199 Robert Moskowitz 1200 Verizon Telcom and Business 1201 1000 Bent Creek Blvd, Suite 200 1202 Mechanicsburg, PA 1203 USA 1205 Email: robert.moskowitz@verizonbusiness.com