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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 ICSAlabs 4 Obsoletes: 4423 (if approved) P. Nikander 5 Intended status: Standards Track Ericsson Research Nomadic Lab 6 Expires: July 1, 2010 December 28, 2009 8 Host Identity Protocol Architecture 9 draft-moskowitz-hip-rfc4423-bis-01 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 also incorporates 22 lessons learned from the implementations of RFC 5201. 24 Status of this Memo 26 This Internet-Draft is submitted to IETF in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF), its areas, and its working groups. Note that 31 other groups may also distribute working documents as Internet- 32 Drafts. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 The list of current Internet-Drafts can be accessed at 40 http://www.ietf.org/ietf/1id-abstracts.txt. 42 The list of Internet-Draft Shadow Directories can be accessed at 43 http://www.ietf.org/shadow.html. 45 This Internet-Draft will expire on July 1, 2010. 47 Copyright Notice 48 Copyright (c) 2009 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (http://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the BSD License. 61 This document may contain material from IETF Documents or IETF 62 Contributions published or made publicly available before November 63 10, 2008. The person(s) controlling the copyright in some of this 64 material may not have granted the IETF Trust the right to allow 65 modifications of such material outside the IETF Standards Process. 66 Without obtaining an adequate license from the person(s) controlling 67 the copyright in such materials, this document may not be modified 68 outside the IETF Standards Process, and derivative works of it may 69 not be created outside the IETF Standards Process, except to format 70 it for publication as an RFC or to translate it into languages other 71 than English. 73 Table of Contents 75 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 76 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4 77 2.1. Terms common to other documents . . . . . . . . . . . . . . 5 78 2.2. Terms specific to this and other HIP documents . . . . . . . 5 79 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 7 80 3.1. A desire for a namespace for computing platforms . . . . . . 7 81 4. Host Identity namespace . . . . . . . . . . . . . . . . . . 9 82 4.1. Host Identifiers . . . . . . . . . . . . . . . . . . . . . . 10 83 4.2. Storing Host Identifiers in DNS . . . . . . . . . . . . . . 10 84 4.3. Host Identity Tag (HIT) . . . . . . . . . . . . . . . . . . 11 85 4.4. Host Identity Hash (HIH) . . . . . . . . . . . . . . . . . . 11 86 4.5. Local Scope Identifier (LSI) . . . . . . . . . . . . . . . . 11 87 5. New stack architecture . . . . . . . . . . . . . . . . . . . 12 88 5.1. Transport associations and end-points . . . . . . . . . . . 13 89 6. End-host mobility and multi-homing . . . . . . . . . . . . . 13 90 6.1. Rendezvous mechanism . . . . . . . . . . . . . . . . . . . . 14 91 6.2. Protection against flooding attacks . . . . . . . . . . . . 14 92 7. HIP and IPsec . . . . . . . . . . . . . . . . . . . . . . . 15 93 8. HIP and MAC Security . . . . . . . . . . . . . . . . . . . . 16 94 9. HIP and NATs . . . . . . . . . . . . . . . . . . . . . . . . 16 95 9.1. HIP and TCP checksums . . . . . . . . . . . . . . . . . . . 17 96 10. Multicast . . . . . . . . . . . . . . . . . . . . . . . . . 17 97 11. HIP policies . . . . . . . . . . . . . . . . . . . . . . . . 17 98 12. Benefits of HIP . . . . . . . . . . . . . . . . . . . . . . 18 99 12.1. HIP's answers to NSRG questions . . . . . . . . . . . . . . 19 100 13. Security considerations . . . . . . . . . . . . . . . . . . 21 101 13.1. HITs used in ACLs . . . . . . . . . . . . . . . . . . . . . 22 102 13.2. Non-security considerations . . . . . . . . . . . . . . . . 23 103 14. IANA considerations . . . . . . . . . . . . . . . . . . . . 24 104 15. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 24 105 16. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 106 16.1. Normative References . . . . . . . . . . . . . . . . . . . . 24 107 16.2. Informative references . . . . . . . . . . . . . . . . . . . 25 108 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 26 110 1. Introduction 112 The Internet has two important global namespaces: Internet Protocol 113 (IP) addresses and Domain Name Service (DNS) names. These two 114 namespaces have a set of features and abstractions that have powered 115 the Internet to what it is today. They also have a number of 116 weaknesses. Basically, since they are all we have, we try and do too 117 much with them. Semantic overloading and functionality extensions 118 have greatly complicated these namespaces. 120 The proposed Host Identity namespace fills an important gap between 121 the IP and DNS namespaces. The Host Identity namespace consists of 122 Host Identifiers (HI). A Host Identifier is cryptographic in its 123 nature; it is the public key of an asymmetric key-pair. Each host 124 will have at least one Host Identity, but it will typically have more 125 than one. Each Host Identity uniquely identifies a single host, 126 i.e., no two hosts have the same Host Identity. The Host Identity, 127 and the corresponding Host Identifier, can either be public (e.g. 128 published in the DNS), or unpublished. Client systems will tend to 129 have both public and unpublished Identities. 131 There is a subtle but important difference between Host Identities 132 and Host Identifiers. An Identity refers to the abstract entity that 133 is identified. An Identifier, on the other hand, refers to the 134 concrete bit pattern that is used in the identification process. 136 Although the Host Identifiers could be used in many authentication 137 systems, such as IKEv2 [RFC4306], the presented architecture 138 introduces a new protocol, called the Host Identity Protocol (HIP), 139 and a cryptographic exchange, called the HIP base exchange; see also 140 Section 7. The HIP protocols under development provide for limited 141 forms of trust between systems, enhance mobility, multi-homing and 142 dynamic IP renumbering, aid in protocol translation / transition, and 143 reduce certain types of denial-of-service (DoS) attacks. 145 When HIP is used, the actual payload traffic between two HIP hosts is 146 typically, but not necessarily, protected with IPsec. The Host 147 Identities are used to create the needed IPsec Security Associations 148 (SAs) and to authenticate the hosts. When IPsec is used, the actual 149 payload IP packets do not differ in any way from standard IPsec 150 protected IP packets. 152 2. Terminology 153 2.1. Terms common to other documents 155 +---------------+---------------------------------------------------+ 156 | Term | Explanation | 157 +---------------+---------------------------------------------------+ 158 | Public key | The public key of an asymmetric cryptographic key | 159 | | pair. Used as a publicly known identifier for | 160 | | cryptographic identity authentication. | 161 | | | 162 | Private key | The private or secret key of an asymmetric | 163 | | cryptographic key pair. Assumed to be known only | 164 | | to the party identified by the corresponding | 165 | | public key. Used by the identified party to | 166 | | authenticate its identity to other parties. | 167 | | | 168 | Public key | An asymmetric cryptographic key pair consisting | 169 | pair | of public and private keys. For example, | 170 | | Rivest-Shamir-Adelman (RSA) and Digital Signature | 171 | | Algorithm (DSA) key pairs are such key pairs. | 172 | | | 173 | End-point | A communicating entity. For historical reasons, | 174 | | the term 'computing platform' is used in this | 175 | | document as a (rough) synonym for end-point. | 176 +---------------+---------------------------------------------------+ 178 2.2. Terms specific to this and other HIP documents 180 It should be noted that many of the terms defined herein are 181 tautologous, self-referential or defined through circular reference 182 to other terms. This is due to the succinct nature of the 183 definitions. See the text elsewhere in this document for more 184 elaborate explanations. 186 +---------------+---------------------------------------------------+ 187 | Term | Explanation | 188 +---------------+---------------------------------------------------+ 189 | Computing | An entity capable of communicating and computing, | 190 | platform | for example, a computer. See the definition of | 191 | | 'End-point', above. | 192 | | | 193 | HIP base | A cryptographic protocol; see also Section 7. | 194 | exchange | | 195 | | | 196 | HIP packet | An IP packet that carries a 'Host Identity | 197 | | Protocol' message. | 198 | | | 199 | Host Identity | An abstract concept assigned to a 'computing | 200 | | platform'. See 'Host Identifier', below. | 201 | | | 202 | Host Identity | A name space formed by all possible Host | 203 | namespace | Identifiers. | 204 | | | 205 | Host Identity | A protocol used to carry and authenticate Host | 206 | Protocol | Identifiers and other information. | 207 | | | 208 | Host Identity | A 128-bit datum created by taking a cryptographic | 209 | Tag | hash over a Host Identifier. | 210 | | | 211 | Host Identity | The cryptograhic hash used in creating the Host | 212 | Hash | Identity Tag from the Host Identity. | 213 | | | 214 | Host | A public key used as a name for a Host Identity. | 215 | Identifier | | 216 | | | 217 | Local Scope | A 32-bit datum denoting a Host Identity. | 218 | Identifier | | 219 | | | 220 | Public Host | A published or publicly known Host Identfier used | 221 | Identifier | as a public name for a Host Identity, and the | 222 | and Identity | corresponding Identity. | 223 | | | 224 | Unpublished | A Host Identifier that is not placed in any | 225 | Host | public directory, and the corresponding Host | 226 | Identifier | Identity. Unpublished Host Identities are | 227 | and Identity | typically short lived in nature, being often | 228 | | replaced and possibly used just once. | 229 | | | 230 | Rendezvous | A mechanism used to locate mobile hosts based on | 231 | Mechanism | their HIT. | 232 +---------------+---------------------------------------------------+ 234 3. Background 236 The Internet is built from three principal components: computing 237 platforms (end-points), packet transport (i.e., internetworking) 238 infrastructure, and services (applications). The Internet exists to 239 service two principal components: people and robotic services 240 (silicon based people, if you will). All these components need to be 241 named in order to interact in a scalable manner. Here we concentrate 242 on naming computing platforms and packet transport elements. 244 There are two principal namespaces in use in the Internet for these 245 components: IP numbers, and Domain Names. Domain Names provide 246 hierarchically assigned names for some computing platforms and some 247 services. Each hierarchy is delegated from the level above; there is 248 no anonymity in Domain Names. Email, HTTP, and SIP addresses all 249 reference Domain Names. 251 IP numbers are a confounding of two namespaces, the names of a host's 252 networking interfaces and the names of the locations ('confounding' 253 is a term used in statistics to discuss metrics that are merged into 254 one with a gain in indexing, but a loss in informational value). The 255 names of locations should be understood as denoting routing direction 256 vectors, i.e., information that is used to deliver packets to their 257 destinations. 259 IP numbers name networking interfaces, and typically only when the 260 interface is connected to the network. Originally, IP numbers had 261 long-term significance. Today, the vast number of interfaces use 262 ephemeral and/or non-unique IP numbers. That is, every time an 263 interface is connected to the network, it is assigned an IP number. 265 In the current Internet, the transport layers are coupled to the IP 266 addresses. Neither can evolve separately from the other. IPng 267 deliberations were strongly shaped by the decision that a 268 corresponding TCPng would not be created. 270 There are three critical deficiencies with the current namespaces. 271 Firstly, dynamic readdressing cannot be directly managed. Secondly, 272 anonymity is not provided in a consistent, trustable manner. 273 Finally, authentication for systems and datagrams is not provided. 274 All of these deficiencies arise because computing platforms are not 275 well named with the current namespaces. 277 3.1. A desire for a namespace for computing platforms 279 An independent namespace for computing platforms could be used in 280 end-to-end operations independent of the evolution of the 281 internetworking layer and across the many internetworking layers. 283 This could support rapid readdressing of the internetworking layer 284 because of mobility, rehoming, or renumbering. 286 If the namespace for computing platforms is based on public-key 287 cryptography, it can also provide authentication services. If this 288 namespace is locally created without requiring registration, it can 289 provide anonymity. 291 Such a namespace (for computing platforms) and the names in it should 292 have the following characteristics: 294 o The namespace should be applied to the IP 'kernel'. The IP kernel 295 is the 'component' between applications and the packet transport 296 infrastructure. 298 o The namespace should fully decouple the internetworking layer from 299 the higher layers. The names should replace all occurrences of IP 300 addresses within applications (like in the Transport Control 301 Block, TCB). This may require changes to the current APIs. In 302 the long run, it is probable that some new APIs are needed. 304 o The introduction of the namespace should not mandate any 305 administrative infrastructure. Deployment must come from the 306 bottom up, in a pairwise deployment. 308 o The names should have a fixed length representation, for easy 309 inclusion in datagram headers and existing programming interfaces 310 (e.g the TCB). 312 o Using the namespace should be affordable when used in protocols. 313 This is primarily a packet size issue. There is also a 314 computational concern in affordability. 316 o Name collisions should be avoided as much as possible. The 317 mathematics of the birthday paradox can be used to estimate the 318 chance of a collision in a given population and hash space. In 319 general, for a random hash space of size n bits, we would expect 320 to obtain a collision after approximately 1.2*sqrt(2**n) hashes 321 were obtained. For 64 bits, this number is roughly 4 billion. A 322 hash size of 64 bits may be too small to avoid collisions in a 323 large population; for example, there is a 1% chance of collision 324 in a population of 640M. For 100 bits (or more), we would not 325 expect a collision until approximately 2**50 (1 quadrillion) 326 hashes were generated. 328 o The names should have a localized abstraction so that it can be 329 used in existing protocols and APIs. 331 o It must be possible to create names locally. This can provide 332 anonymity at the cost of making resolvability very difficult. 334 * Sometimes the names may contain a delegation component. This 335 is the cost of resolvability. 337 o The namespace should provide authentication services. 339 o The names should be long lived, but replaceable at any time. This 340 impacts access control lists; short lifetimes will tend to result 341 in tedious list maintenance or require a namespace infrastructure 342 for central control of access lists. 344 In this document, a new namespace approaching these ideas is called 345 the Host Identity namespace. Using Host Identities requires its own 346 protocol layer, the Host Identity Protocol, between the 347 internetworking and transport layers. The names are based on public- 348 key cryptography to supply authentication services. Properly 349 designed, it can deliver all of the above stated requirements. 351 4. Host Identity namespace 353 A name in the Host Identity namespace, a Host Identifier (HI), 354 represents a statistically globally unique name for naming any system 355 with an IP stack. This identity is normally associated with, but not 356 limited to, an IP stack. A system can have multiple identities, some 357 'well known', some unpublished or 'anonymous'. A system may self- 358 assert its own identity, or may use a third-party authenticator like 359 DNSSEC [RFC2535], PGP, or X.509 to 'notarize' the identity assertion. 360 It is expected that the Host Identifiers will initially be 361 authenticated with DNSSEC and that all implementations will support 362 DNSSEC as a minimal baseline. 364 In theory, any name that can claim to be 'statistically globally 365 unique' may serve as a Host Identifier. However, in the authors' 366 opinion, a public key of a 'public key pair' makes the best Host 367 Identifier. As will be specified in the Host Identity Protocol 368 specification, a public-key-based HI can authenticate the HIP packets 369 and protect them for man-in-the-middle attacks. Since authenticated 370 datagrams are mandatory to provide much of HIP's denial-of-service 371 protection, the Diffie-Hellman exchange in HIP has to be 372 authenticated. Thus, only public-key HI and authenticated HIP 373 messages are supported in practice. In this document, the non- 374 cryptographic forms of HI and HIP are presented to complete the 375 theory of HI, but they should not be implemented as they could 376 produce worse denial-of-service attacks than the Internet has without 377 Host Identity. 379 4.1. Host Identifiers 381 Host Identity adds two main features to Internet protocols. The 382 first is a decoupling of the internetworking and transport layers; 383 see Section 5. This decoupling will allow for independent evolution 384 of the two layers. Additionally, it can provide end-to-end services 385 over multiple internetworking realms. The second feature is host 386 authentication. Because the Host Identifier is a public key, this 387 key can be used for authentication in security protocols like IPsec. 389 The only completely defined structure of the Host Identity is that of 390 a public/private key pair. In this case, the Host Identity is 391 referred to by its public component, the public key. Thus, the name 392 representing a Host Identity in the Host Identity namespace, i.e., 393 the Host Identifier, is the public key. In a way, the possession of 394 the private key defines the Identity itself. If the private key is 395 possessed by more than one node, the Identity can be considered to be 396 a distributed one. 398 Architecturally, any other Internet naming convention might form a 399 usable base for Host Identifiers. However, non-cryptographic names 400 should only be used in situations of high trust - low risk. That is 401 any place where host authentication is not needed (no risk of host 402 spoofing) and no use of IPsec. However, at least for interconnected 403 networks spanning several operational domains, the set of 404 environments where the risk of host spoofing allowed by non- 405 cryptographic Host Identifiers is acceptable is the null set. Hence, 406 the current HIP documents do not specify how to use any other types 407 of Host Identifiers but public keys. 409 The actual Host Identities are never directly used in any Internet 410 protocols. The corresponding Host Identifiers (public keys) may be 411 stored in various DNS or LDAP directories as identified elsewhere in 412 this document, and they are passed in the HIP base exchange. A Host 413 Identity Tag (HIT) is used in other protocols to represent the Host 414 Identity. Another representation of the Host Identities, the Local 415 Scope Identifier (LSI), can also be used in protocols and APIs. 417 4.2. Storing Host Identifiers in DNS 419 The public Host Identifiers should be stored in DNS; the unpublished 420 Host Identifiers should not be stored anywhere (besides the 421 communicating hosts themselves). The (public) HI along with the 422 supported HIHs are stored in a new RR type. This RR type is defined 423 in HIP DNS Extension [RFC5205]. 425 Alternatively, or in addition to storing Host Identifiers in the DNS, 426 they may be stored in various kinds of Public Key Infrastructure 427 (PKI). Such a practice may allow them to be used for purposes other 428 than pure host identification. 430 4.3. Host Identity Tag (HIT) 432 A Host Identity Tag is a 128-bit representation for a Host Identity. 433 It is created by taking a cryptographic hash over the corresponding 434 Host Identifier. There are two advantages of using a hash over using 435 the Host Identifier in protocols. Firstly, its fixed length makes 436 for easier protocol coding and also better manages the packet size 437 cost of this technology. Secondly, it presents the identity in a 438 consistent format to the protocol independent of the cryptographic 439 algorithms used. 441 There can be multiple HITs per Host Identifier when multiple hashes 442 are supported. An Initator may have to initially guess which HIT to 443 use for the Responder, typically based on what it perfers, until it 444 learns the appropriate HIT through the HIP exchange. 446 In the HIP packets, the HITs identify the sender and recipient of a 447 packet. Consequently, a HIT should be unique in the whole IP 448 universe as long as it is being used. In the extremely rare case of 449 a single HIT mapping to more than one Host Identity, the Host 450 Identifiers (public keys) will make the final difference. If there 451 is more than one public key for a given node, the HIT acts as a hint 452 for the correct public key to use. 454 4.4. Host Identity Hash (HIH) 456 The Host Identity Hash is the cryptographic hash used in producing 457 the HIT from the HI. It is also the hash used through out the HIP 458 protocol for consistancy and simplicity. It is possible to for the 459 two Hosts in the HIP exchange to use different hashes. 461 Multiple HIHs within HIP is needed to address the moving target of 462 creation and eventual compromise of cryptographic hashes. This 463 significantly complicates HIP and offers an attacker an additional 464 downgrade attack that is mitigated in the HIP protocol. 466 4.5. Local Scope Identifier (LSI) 468 An LSI is a 32-bit localized representation for a Host Identity. The 469 purpose of an LSI is to facilitate using Host Identities in existing 470 protocols and APIs. LSI's advantage over HIT is its size; its 471 disadvantage is its local scope. 473 Examples of how LSIs can be used include: as the address in an FTP 474 command and as the address in a socket call. Thus, LSIs act as a 475 bridge for Host Identities into IPv4-based protocols and APIs. LSIs 476 also make it possible for some IPv4 applications to run over an IPv6 477 network. 479 5. New stack architecture 481 One way to characterize Host Identity is to compare the proposed new 482 architecture with the current one. As discussed above, the IP 483 addresses can be seen to be a confounding of routing direction 484 vectors and interface names. Using the terminology from the IRTF 485 Name Space Research Group Report [nsrg-report] and, e.g., the 486 unpublished Internet-Draft Endpoints and Endpoint Names 487 [chiappa-endpoints], the IP addresses currently embody the dual role 488 of locators and end-point identifiers. That is, each IP address 489 names a topological location in the Internet, thereby acting as a 490 routing direction vector, or locator. At the same time, the IP 491 address names the physical network interface currently located at the 492 point-of-attachment, thereby acting as a end-point name. 494 In the HIP architecture, the end-point names and locators are 495 separated from each other. IP addresses continue to act as locators. 496 The Host Identifiers take the role of end-point identifiers. It is 497 important to understand that the end-point names based on Host 498 Identities are slightly different from interface names; a Host 499 Identity can be simultaneously reachable through several interfaces. 501 The difference between the bindings of the logical entities are 502 illustrated in Figure 1. 504 Service ------ Socket Service ------ Socket 505 | | 506 | | 507 | | 508 | | 509 End-point | End-point --- Host Identity 510 \ | | 511 \ | | 512 \ | | 513 \ | | 514 Location --- IP address Location --- IP address 516 Figure 1 518 5.1. Transport associations and end-points 520 Architecturally, HIP provides for a different binding of transport- 521 layer protocols. That is, the transport-layer associations, i.e., 522 TCP connections and UDP associations, are no longer bound to IP 523 addresses but to Host Identities. 525 It is possible that a single physical computer hosts several logical 526 end-points. With HIP, each of these end-points would have a distinct 527 Host Identity. Furthermore, since the transport associations are 528 bound to Host Identities, HIP provides for process migration and 529 clustered servers. That is, if a Host Identity is moved from one 530 physical computer to another, it is also possible to simultaneously 531 move all the transport associations without breaking them. 532 Similarly, if it is possible to distribute the processing of a single 533 Host Identity over several physical computers, HIP provides for 534 cluster based services without any changes at the client end-point. 536 6. End-host mobility and multi-homing 538 HIP decouples the transport from the internetworking layer, and binds 539 the transport associations to the Host Identities (through actually 540 either the HIT or LSI). Consequently, HIP can provide for a degree 541 of internetworking mobility and multi-homing at a low infrastructure 542 cost. HIP mobility includes IP address changes (via any method) to 543 either party. Thus, a system is considered mobile if its IP address 544 can change dynamically for any reason like PPP, DHCP, IPv6 prefix 545 reassignments, or a NAT device remapping its translation. Likewise, 546 a system is considered multi-homed if it has more than one globally 547 routable IP address at the same time. HIP links IP addresses 548 together, when multiple IP addresses correspond to the same Host 549 Identity, and if one address becomes unusable, or a more preferred 550 address becomes available, existing transport associations can easily 551 be moved to another address. 553 When a node moves while communication is already on-going, address 554 changes are rather straightforward. The peer of the mobile node can 555 just accept a HIP or an integrity protected IPsec packet from any 556 address and ignore the source address. However, as discussed in 557 Section 6.2 below, a mobile node must send a HIP readdress packet to 558 inform the peer of the new address(es), and the peer must verify that 559 the mobile node is reachable through these addresses. This is 560 especially helpful for those situations where the peer node is 561 sending data periodically to the mobile node (that is re-starting a 562 connection after the initial connection). 564 6.1. Rendezvous mechanism 566 Making a contact to a mobile node is slightly more involved. In 567 order to start the HIP exchange, the initiator node has to know how 568 to reach the mobile node. Although infrequently moving HIP nodes 569 could use Dynamic DNS [RFC2136] to update their reachability 570 information in the DNS, an alternative to using DNS in this fashion 571 is to use a piece of new static infrastructure to facilitate 572 rendezvous between HIP nodes. 574 The mobile node keeps the rendezvous infrastructure continuously 575 updated with its current IP address(es). The mobile nodes must trust 576 the rendezvous mechanism to properly maintain their HIT and IP 577 address mappings. 579 The rendezvous mechanism is also needed if both of the nodes happen 580 to change their address at the same time, either because they are 581 mobile and happen to move at the same time, because one of them is 582 off-line for a while, or because of some other reason. In such a 583 case, the HIP readdress packets will cross each other in the network 584 and never reach the peer node. 586 The HIP rendezvous mechanism is defined in HIP Rendezvous [RFC5204]. 588 6.2. Protection against flooding attacks 590 Although the idea of informing about address changes by simply 591 sending packets with a new source address appears appealing, it is 592 not secure enough. That is, even if HIP does not rely on the source 593 address for anything (once the base exchange has been completed), it 594 appears to be necessary to check a mobile node's reachability at the 595 new address before actually sending any larger amounts of traffic to 596 the new address. 598 Blindly accepting new addresses would potentially lead to flooding 599 Denial-of-Service attacks against third parties [RFC4225]. In a 600 distributed flooding attack an attacker opens high volume HIP 601 connections with a large number of hosts (using unpublished HIs), and 602 then claims to all of these hosts that it has moved to a target 603 node's IP address. If the peer hosts were to simply accept the move, 604 the result would be a packet flood to the target node's address. To 605 close this attack, HIP includes an address check mechanism where the 606 reachability of a node is separately checked at each address before 607 using the address for larger amounts of traffic. 609 Whenever HIP is used between two hosts that fully trust each other, 610 the hosts may optionally decide to skip the address tests. However, 611 such performance optimization must be restricted to peers that are 612 known to be trustworthy and capable of protecting themselves from 613 malicious software. 615 7. HIP and IPsec 617 The preferred way of implementing HIP is to use IPsec to carry the 618 actual data traffic. As of today, the only completely defined method 619 is to use IPsec Encapsulated Security Payload (ESP) to carry the data 620 packets [RFC5202]. In the future, other ways of transporting payload 621 data may be developed, including ones that do not use cryptographic 622 protection. 624 In practice, the HIP base exchange uses the cryptographic Host 625 Identifiers to set up a pair of ESP Security Associations (SAs) to 626 enable ESP in an end-to-end manner. This is implemented in a way 627 that can span addressing realms. 629 While it would be possible, at least in theory, to use some existing 630 cryptographic protocol, such as IKEv2 together with Host Identifiers, 631 to establish the needed SAs, HIP defines a new protocol. There are a 632 number of historical reasons for this, and there are also a few 633 architectural reasons. First, IKE (and IKEv2) were not designed with 634 middle boxes in mind. As adding a new naming layer allows one to 635 potentially add a new forwarding layer (see Section 9, below), it is 636 very important that the HIP protocols are friendly towards any middle 637 boxes. 639 Second, from a conceptual point of view, the IPsec Security Parameter 640 Index (SPI) in ESP provides a simple compression of the HITs. This 641 does require per-HIT-pair SAs (and SPIs), and a decrease of policy 642 granularity over other Key Management Protocols, such as IKE and 643 IKEv2. In particular, the current thinking is limited to a situation 644 where, conceptually, there is only one pair of SAs between any given 645 pair of HITs. In other words, from an architectural point of view, 646 HIP only supports host-to-host (or endpoint-to-endpoint) Security 647 Associations. If two hosts need more pairs of parallel SAs, they 648 should use separate HITs for that. However, future HIP extensions 649 may provide for more granularity and creation of several ESP SAs 650 between a pair of HITs. 652 Since HIP is designed for host usage, not for gateways or so called 653 Bump-in-the-Wire (BITW) implementations, only ESP transport mode is 654 supported. An ESP SA pair is indexed by the SPIs and the two HITs 655 (both HITs since a system can have more than one HIT). The SAs need 656 not to be bound to IP addresses; all internal control of the SA is by 657 the HITs. Thus, a host can easily change its address using Mobile 658 IP, DHCP, PPP, or IPv6 readdressing and still maintain the SAs. 660 Since the transports are bound to the SA (via an LSI or a HIT), any 661 active transport is also maintained. Thus, real-world conditions 662 like loss of a PPP connection and its re-establishment or a mobile 663 handover will not require a HIP negotiation or disruption of 664 transport services [Bel1998]. 666 Since HIP does not negotiate any SA lifetimes, all lifetimes are 667 local policy. The only lifetimes a HIP implementation must support 668 are sequence number rollover (for replay protection), and SA timeout. 669 An SA times out if no packets are received using that SA. 670 Implementations may support lifetimes for the various ESP transforms. 672 8. HIP and MAC Security 674 The IEEE 802 standards have been defining MAC layered security. Many 675 of these standards use EAP [RFC3748] as a Key Management System (KMS) 676 transport, but some like IEEE 802.15.4 [IEEE.802-15-4.2006] leave the 677 KMS and its transport as "Out of Scope". 679 HIP is well suited as a KMS in these environments. 681 o HIP is independent of IP addressing and can be directly 682 transported over any network protocol. 684 o Master Keys in 802 protocols are strictly pair-based with group 685 keys transported from the group controller using pair-wise keys. 687 o AdHoc 802 networks can be better served by a peer-to-peer KMS than 688 the EAP client/server model. 690 o Some devices are very memory constrained and a common KMS for both 691 MAC and IP security represents a considerable code savings. 693 9. HIP and NATs 695 Passing packets between different IP addressing realms requires 696 changing IP addresses in the packet header. This may happen, for 697 example, when a packet is passed between the public Internet and a 698 private address space, or between IPv4 and IPv6 networks. The 699 address translation is usually implemented as Network Address 700 Translation (NAT) [RFC3022] or NAT Protocol translation (NAT-PT) 701 [RFC2766]. 703 In a network environment where identification is based on the IP 704 addresses, identifying the communicating nodes is difficult when NAT 705 is used. With HIP, the transport-layer end-points are bound to the 706 Host Identities. Thus, a connection between two hosts can traverse 707 many addressing realm boundaries. The IP addresses are used only for 708 routing purposes; they may be changed freely during packet traversal. 710 For a HIP-based flow, a HIP-aware NAT or NAT-PT system tracks the 711 mapping of HITs, and the corresponding IPsec SPIs, to an IP address. 712 The NAT system has to learn mappings both from HITs and from SPIs to 713 IP addresses. Many HITs (and SPIs) can map to a single IP address on 714 a NAT, simplifying connections on address poor NAT interfaces. The 715 NAT can gain much of its knowledge from the HIP packets themselves; 716 however, some NAT configuration may be necessary. 718 NAT systems cannot touch the datagrams within the IPsec envelope, 719 thus application-specific address translation must be done in the end 720 systems. HIP provides for 'Distributed NAT', and uses the HIT or the 721 LSI as a placeholder for embedded IP addresses. 723 HIP and NAT interaction is defined in [hip-nat-traversal]. 725 9.1. HIP and TCP checksums 727 There is no way for a host to know if any of the IP addresses in an 728 IP header are the addresses used to calculate the TCP checksum. That 729 is, it is not feasible to calculate the TCP checksum using the actual 730 IP addresses in the pseudo header; the addresses received in the 731 incoming packet are not necessarily the same as they were on the 732 sending host. Furthermore, it is not possible to recompute the 733 upper-layer checksums in the NAT/NAT-PT system, since the traffic is 734 IPsec protected. Consequently, the TCP and UDP checksums are 735 calculated using the HITs in the place of the IP addresses in the 736 pseudo header. Furthermore, only the IPv6 pseudo header format is 737 used. This provides for IPv4 / IPv6 protocol translation. 739 10. Multicast 741 There was little if any concrete thoughts about how HIP might affect 742 IP-layer or application-layer multicast. 744 11. HIP policies 746 There are a number of variables that will influence the HIP exchanges 747 that each host must support. All HIP implementations should support 748 at least 2 HIs, one to publish in DNS and an unpublished one for 749 anonymous usage. Although unpublished HIs will be rarely used as 750 responder HIs, they are likely be common for initiators. Support for 751 multiple HIs is recommended. 753 Many initiators would want to use a different HI for different 754 responders. The implementations should provide for a policy of 755 initiator HIT to responder HIT. This policy should also include 756 preferred transforms and local lifetimes. 758 Responders would need a similar policy, describing the hosts allowed 759 to participate in HIP exchanges, and the preferred transforms and 760 local lifetimes. 762 12. Benefits of HIP 764 In the beginning, the network layer protocol (i.e., IP) had the 765 following four "classic" invariants: 767 o Non-mutable: The address sent is the address received. 769 o Non-mobile: The address doesn't change during the course of an 770 "association". 772 o Reversible: A return header can always be formed by reversing the 773 source and destination addresses. 775 o Omniscient: Each host knows what address a partner host can use to 776 send packets to it. 778 Actually, the fourth can be inferred from 1 and 3, but it is worth 779 mentioning for reasons that will be obvious soon if not already. 781 In the current "post-classic" world, we are intentionally trying to 782 get rid of the second invariant (both for mobility and for multi- 783 homing), and we have been forced to give up the first and the fourth. 784 Realm Specific IP [RFC3102] is an attempt to reinstate the fourth 785 invariant without the first invariant. IPv6 is an attempt to 786 reinstate the first invariant. 788 Few systems on the Internet have DNS names that are meaningful. That 789 is, if they have a Fully Qualified Domain Name (FQDN), that name 790 typically belongs to a NAT device or a dial-up server, and does not 791 really identify the system itself but its current connectivity. 792 FQDNs (and their extensions as email names) are application-layer 793 names; more frequently naming services than a particular system. 794 This is why many systems on the Internet are not registered in the 795 DNS; they do not have services of interest to other Internet hosts. 797 DNS names are references to IP addresses. This only demonstrates the 798 interrelationship of the networking and application layers. DNS, as 799 the Internet's only deployed, distributed database is also the 800 repository of other namespaces, due in part to DNSSEC and application 801 specific key records. Although each namespace can be stretched (IP 802 with v6, DNS with KEY records), neither can adequately provide for 803 host authentication or act as a separation between internetworking 804 and transport layers. 806 The Host Identity (HI) namespace fills an important gap between the 807 IP and DNS namespaces. An interesting thing about the HI is that it 808 actually allows one to give up all but the 3rd network-layer 809 invariant. That is to say, as long as the source and destination 810 addresses in the network-layer protocol are reversible, then things 811 work ok because HIP takes care of host identification, and 812 reversibility allows one to get a packet back to one's partner host. 813 You do not care if the network-layer address changes in transit 814 (mutable) and you don't care what network-layer address the partner 815 is using (non-omniscient). 817 12.1. HIP's answers to NSRG questions 819 The IRTF Name Space Research Group has posed a number of evaluating 820 questions in their report [nsrg-report]. In this section, we provide 821 answers to these questions. 823 1. How would a stack name improve the overall functionality of the 824 Internet? 826 HIP decouples the internetworking layer from the transport 827 layer, allowing each to evolve separately. The decoupling 828 makes end-host mobility and multi-homing easier, also across 829 IPv4 and IPv6 networks. HIs make network renumbering easier, 830 and they also make process migration and clustered servers 831 easier to implement. Furthermore, being cryptographic in 832 nature, they provide the basis for solving the security 833 problems related to end-host mobility and multi-homing. 835 2. What does a stack name look like? 837 A HI is a cryptographic public key. However, instead of using 838 the keys directly, most protocols use a fixed size hash of the 839 public key. 841 3. What is its lifetime? 843 HIP provides both stable and temporary Host Identifiers. 844 Stable HIs are typically long lived, with a lifetime of years 845 or more. The lifetime of temporary HIs depends on how long 846 the upper-layer connections and applications need them, and 847 can range from a few seconds to years. 849 4. Where does it live in the stack? 851 The HIs live between the transport and internetworking layers. 853 5. How is it used on the end points 855 The Host Identifiers may be used directly or indirectly (in 856 the form of HITs or LSIs) by applications when they access 857 network services. Additionally, the Host Identifiers, as 858 public keys, are used in the built in key agreement protocol, 859 called the HIP base exchange, to authenticate the hosts to 860 each other. 862 6. What administrative infrastructure is needed to support it? 864 In some environments, it is possible to use HIP 865 opportunistically, without any infrastructure. However, to 866 gain full benefit from HIP, the HIs must be stored in the DNS 867 or a PKI, and a new rendezvous mechanism is needed [RFC5205]. 869 7. If we add an additional layer would it make the address list in 870 SCTP unnecessary? 872 Yes 874 8. What additional security benefits would a new naming scheme 875 offer? 877 HIP reduces dependency on IP addresses, making the so called 878 address ownership [Nik2001] problems easier to solve. In 879 practice, HIP provides security for end-host mobility and 880 multi-homing. Furthermore, since HIP Host Identifiers are 881 public keys, standard public key certificate infrastructures 882 can be applied on the top of HIP. 884 9. What would the resolution mechanisms be, or what characteristics 885 of a resolution mechanisms would be required? 887 For most purposes, an approach where DNS names are resolved 888 simultaneously to HIs and IP addresses is sufficient. 889 However, if it becomes necessary to resolve HIs into IP 890 addresses or back to DNS names, a flat resolution 891 infrastructure is needed. Such an infrastructure could be 892 based on the ideas of Distributed Hash Tables, but would 893 require significant new development and deployment. 895 13. Security considerations 897 HIP takes advantage of the new Host Identity paradigm to provide 898 secure authentication of hosts and to provide a fast key exchange for 899 IPsec. HIP also attempts to limit the exposure of the host to 900 various denial-of-service (DoS) and man-in-the-middle (MitM) attacks. 901 In so doing, HIP itself is subject to its own DoS and MitM attacks 902 that potentially could be more damaging to a host's ability to 903 conduct business as usual. 905 Resource exhausting denial-of-service attacks take advantage of the 906 cost of setting up a state for a protocol on the responder compared 907 to the 'cheapness' on the initiator. HIP allows a responder to 908 increase the cost of the start of state on the initiator and makes an 909 effort to reduce the cost to the responder. This is done by having 910 the responder start the authenticated Diffie-Hellman exchange instead 911 of the initiator, making the HIP base exchange 4 packets long. There 912 are more details on this process in the Host Identity Protocol under 913 development. 915 HIP optionally supports opportunistic negotiation. That is, if a 916 host receives a start of transport without a HIP negotiation, it can 917 attempt to force a HIP exchange before accepting the connection. 918 This has the potential for DoS attacks against both hosts. If the 919 method to force the start of HIP is expensive on either host, the 920 attacker need only spoof a TCP SYN. This would put both systems into 921 the expensive operations. HIP avoids this attack by having the 922 responder send a simple HIP packet that it can pre-build. Since this 923 packet is fixed and easily replayed, the initiator only reacts to it 924 if it has just started a connection to the responder. 926 Man-in-the-middle attacks are difficult to defend against, without 927 third-party authentication. A skillful MitM could easily handle all 928 parts of the HIP base exchange, but HIP indirectly provides the 929 following protection from a MitM attack. If the responder's HI is 930 retrieved from a signed DNS zone or secured by some other means, the 931 initiator can use this to authenticate the signed HIP packets. 932 Likewise, if the initiator's HI is in a secure DNS zone, the 933 responder can retrieve it and validate the signed HIP packets. 934 However, since an initiator may choose to use an unpublished HI, it 935 knowingly risks a MitM attack. The responder may choose not to 936 accept a HIP exchange with an initiator using an unknown HI. 938 The need to support multiple hashes for generating the HIT from the 939 HI affords the MitM a potentially powerful downgrade attack due to 940 the a-priori need of the HIT in the HIP base exchange. The base 941 exchange has been augmented to deal with such an attack by restarting 942 on detecting the attack. At worst this would only lead to a 943 situation in which the base exchange would never finish (or would be 944 aborted after some retries). As a drawback, this leads to an 6-way 945 base exchange which may seem bad at first. However, since this only 946 happens in an attack scenario and since the attack can be handled (so 947 it is not interesting to mount anymore), we assume the additional 948 messages are not a problem at all. Since the MitM cannot be 949 successful with a downgrade attack, these sorts of attacks will only 950 occur as 'nuisance' attacks. So, the base exchange would still be 951 usually just four packets even though implementations must be 952 prepared to protect themselves against the downgrade attack. 954 In HIP, the Security Association for IPsec is indexed by the SPI; the 955 source address is always ignored, and the destination address may be 956 ignored as well. Therefore, HIP-enabled IPsec Encapsulated Security 957 Payload (ESP) is IP address independent. This might seem to make it 958 easier for an attacker, but ESP with replay protection is already as 959 well protected as possible, and the removal of the IP address as a 960 check should not increase the exposure of IPsec ESP to DoS attacks. 962 Since not all hosts will ever support HIP, ICMPv4 'Destination 963 Unreachable, Protocol Unreachable' and ICMPv6 'Parameter Problem, 964 Unrecognized Next Header' messages are to be expected and present a 965 DoS attack. Against an initiator, the attack would look like the 966 responder does not support HIP, but shortly after receiving the ICMP 967 message, the initiator would receive a valid HIP packet. Thus, to 968 protect against this attack, an initiator should not react to an ICMP 969 message until a reasonable time has passed, allowing it to get the 970 real responder's HIP packet. A similar attack against the responder 971 is more involved. 973 Another MitM attack is simulating a responder's administrative 974 rejection of a HIP initiation. This is a simple ICMP 'Destination 975 Unreachable, Administratively Prohibited' message. A HIP packet is 976 not used because it would either have to have unique content, and 977 thus difficult to generate, resulting in yet another DoS attack, or 978 just as spoofable as the ICMP message. Like in the previous case, 979 the defense against this attack is for the initiator to wait a 980 reasonable time period to get a valid HIP packet. If one does not 981 come, then the initiator has to assume that the ICMP message is 982 valid. Since this is the only point in the HIP base exchange where 983 this ICMP message is appropriate, it can be ignored at any other 984 point in the exchange. 986 13.1. HITs used in ACLs 988 It is expected that HITs will be used in ACLs. Future firewalls can 989 use HITs to control egress and ingress to networks, with an assurance 990 level difficult to achieve today. As discussed above in Section 7, 991 once a HIP session has been established, the SPI value in an IPsec 992 packet may be used as an index, indicating the HITs. In practice, 993 firewalls can inspect HIP packets to learn of the bindings between 994 HITs, SPI values, and IP addresses. They can even explicitly control 995 IPsec usage, dynamically opening IPsec ESP only for specific SPI 996 values and IP addresses. The signatures in HIP packets allow a 997 capable firewall to ensure that the HIP exchange is indeed happening 998 between two known hosts. This may increase firewall security. 1000 There has been considerable bad experience with distributed ACLs that 1001 contain public key related material, for example, with SSH. If the 1002 owner of a key needs to revoke it for any reason, the task of finding 1003 all locations where the key is held in an ACL may be impossible. If 1004 the reason for the revocation is due to private key theft, this could 1005 be a serious issue. 1007 A host can keep track of all of its partners that might use its HIT 1008 in an ACL by logging all remote HITs. It should only be necessary to 1009 log responder hosts. With this information, the host can notify the 1010 various hosts about the change to the HIT. There has been no attempt 1011 to develop a secure method to issue the HIT revocation notice. 1013 HIP-aware NATs, however, are transparent to the HIP aware systems by 1014 design. Thus, the host may find it difficult to notify any NAT that 1015 is using a HIT in an ACL. Since most systems will know of the NATs 1016 for their network, there should be a process by which they can notify 1017 these NATs of the change of the HIT. This is mandatory for systems 1018 that function as responders behind a NAT. In a similar vein, if a 1019 host is notified of a change in a HIT of an initiator, it should 1020 notify its NAT of the change. In this manner, NATs will get updated 1021 with the HIT change. 1023 13.2. Non-security considerations 1025 The definition of the Host Identifier states that the HI need not be 1026 a public key. It implies that the HI could be any value; for example 1027 a FQDN. This document does not describe how to support such a non- 1028 cryptographic HI. A non-cryptographic HI would still offer the 1029 services of the HIT or LSI for NAT traversal. It would be possible 1030 to carry HITs in HIP packets that had neither privacy nor 1031 authentication. Since such a mode would offer so little additional 1032 functionality for so much addition to the IP kernel, it has not been 1033 defined. Given how little public key cryptography HIP requires, HIP 1034 should only be implemented using public key Host Identities. 1036 If it is desirable to use HIP in a low security situation where 1037 public key computations are considered expensive, HIP can be used 1038 with very short Diffie-Hellman and Host Identity keys. Such use 1039 makes the participating hosts vulnerable to MitM and connection 1040 hijacking attacks. However, it does not cause flooding dangers, 1041 since the address check mechanism relies on the routing system and 1042 not on cryptographic strength. 1044 14. IANA considerations 1046 This document has no actions for IANA. 1048 15. Acknowledgments 1050 For the people historically involved in the early stages of HIP, see 1051 the Acknowledgements section in the Host Identity Protocol 1052 specification. 1054 During the later stages of this document, when the editing baton was 1055 transfered to Pekka Nikander, the comments from the early 1056 implementors and others, including Jari Arkko, Tom Henderson, Petri 1057 Jokela, Miika Komu, Mika Kousa, Andrew McGregor, Jan Melen, Tim 1058 Shepard, Jukka Ylitalo, and Jorma Wall, were invaluable. Finally, 1059 Lars Eggert, Spencer Dawkins and Dave Crocker provided valuable input 1060 during the final stages of publication, most of which was 1061 incorporated but some of which the authors decided to ignore in order 1062 to get this document published in the first place. 1064 The authors want to express their special thanks to Tom Henderson, 1065 who took the burden of editing the document in response to IESG 1066 comments at the time when both of the authors were busy doing other 1067 things. Without his perseverance original document might have never 1068 made it as RFC4423. 1070 This latest effort to update and move HIP forward within the IETF 1071 process owes its impetuous to the three HIP development teams: 1072 Boeing, HIIT (Helsinki Institute for Information Technology), and 1073 NomadicLab of Ericsson. Without their collective efforts HIP would 1074 have withered as on the IETF vine as a nice concept. 1076 16. References 1078 16.1. Normative References 1080 [RFC5202] Jokela, P., Moskowitz, R., and P. Nikander, "Using the 1081 Encapsulating Security Payload (ESP) Transport Format with 1082 the Host Identity Protocol (HIP)", RFC 5202, April 2008. 1084 [RFC5204] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) 1085 Rendezvous Extension", RFC 5204, April 2008. 1087 [RFC5205] Nikander, P. and J. Laganier, "Host Identity Protocol 1088 (HIP) Domain Name System (DNS) Extensions", RFC 5205, 1089 April 2008. 1091 16.2. Informative references 1093 [RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound, 1094 "Dynamic Updates in the Domain Name System (DNS UPDATE)", 1095 RFC 2136, April 1997. 1097 [RFC2535] Eastlake, D., "Domain Name System Security Extensions", 1098 RFC 2535, March 1999. 1100 [RFC2766] Tsirtsis, G. and P. Srisuresh, "Network Address 1101 Translation - Protocol Translation (NAT-PT)", RFC 2766, 1102 February 2000. 1104 [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network 1105 Address Translator (Traditional NAT)", RFC 3022, 1106 January 2001. 1108 [RFC3102] Borella, M., Lo, J., Grabelsky, D., and G. Montenegro, 1109 "Realm Specific IP: Framework", RFC 3102, October 2001. 1111 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 1112 Levkowetz, "Extensible Authentication Protocol (EAP)", 1113 RFC 3748, June 2004. 1115 [RFC4025] Richardson, M., "A Method for Storing IPsec Keying 1116 Material in DNS", RFC 4025, March 2005. 1118 [RFC4225] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E. 1119 Nordmark, "Mobile IP Version 6 Route Optimization Security 1120 Design Background", RFC 4225, December 2005. 1122 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", 1123 RFC 4306, December 2005. 1125 [hip-nat-traversal] 1126 Komu, M., Henderson, T., Tschofenig, H., Melen, J., and A. 1127 Keranen, "Basic HIP Extensions for Traversal of Network 1128 Address Translators", draft-ietf-hip-nat-traversal-09 1129 (work in progress), October 2009. 1131 [nsrg-report] 1132 Lear, E. and R. Droms, "What's In A Name:Thoughts from the 1133 NSRG", draft-irtf-nsrg-report-10 (work in progress), 1134 September 2003. 1136 [IEEE.802-15-4.2006] 1137 "Information technology - Telecommunications and 1138 information exchange between systems - Local and 1139 metropolitan area networks - Specific requirements - Part 1140 15.4: Wireless Medium Access Control (MAC) and Physical 1141 Layer (PHY) Specifications for Low-Rate Wireless Personal 1142 Area Networks (WPANs)", IEEE Standard 802.15.4, 1143 September 2006, . 1146 [chiappa-endpoints] 1147 Chiappa, J., "Endpoints and Endpoint Names: A Proposed 1148 Enhancement to the Internet Architecture", 1149 URL http://www.chiappa.net/~jnc/tech/endpoints.txt, 1999. 1151 [Nik2001] Nikander, P., "Denial-of-Service, Address Ownership, and 1152 Early Authentication in the IPv6 World", in Proceesings 1153 of Security Protocols, 9th International Workshop, 1154 Cambridge, UK, April 25-27 2001, LNCS 2467, pp. 12-26, 1155 Springer, 2002. 1157 [Bel1998] Bellovin, S., "EIDs, IPsec, and HostNAT", in Proceedings 1158 of 41th IETF, Los Angeles, CA, 1159 URL http://www1.cs.columbia.edu/~smb/talks/hostnat.pdf, 1160 March 1998. 1162 Authors' Addresses 1164 Robert Moskowitz 1165 ICSAlabs, An Independent Division of Verizon Business Systems 1166 1000 Bent Creek Blvd, Suite 200 1167 Mechanicsburg, PA 1168 USA 1170 Email: robert.moskowitz@icsalabs.com 1171 Pekka Nikander 1172 Ericsson Research Nomadic Lab 1173 JORVAS FIN-02420 1174 FINLAND 1176 Phone: +358 9 299 1 1177 Email: pekka.nikander@nomadiclab.com