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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) June 29, 2010 5 Intended status: Standards Track 6 Expires: December 31, 2010 8 Host Identity Protocol Architecture 9 draft-moskowitz-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 also incorporates 22 lessons learned from the implementations of RFC 5201. 24 Status of this Memo 26 This Internet-Draft is submitted 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). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 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 This Internet-Draft will expire on December 31, 2010. 41 Copyright Notice 43 Copyright (c) 2010 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 This document may contain material from IETF Documents or IETF 57 Contributions published or made publicly available before November 58 10, 2008. The person(s) controlling the copyright in some of this 59 material may not have granted the IETF Trust the right to allow 60 modifications of such material outside the IETF Standards Process. 61 Without obtaining an adequate license from the person(s) controlling 62 the copyright in such materials, this document may not be modified 63 outside the IETF Standards Process, and derivative works of it may 64 not be created outside the IETF Standards Process, except to format 65 it for publication as an RFC or to translate it into languages other 66 than English. 68 Table of Contents 70 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 71 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4 72 2.1. Terms common to other documents . . . . . . . . . . . . . . 5 73 2.2. Terms specific to this and other HIP documents . . . . . . . 5 74 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 7 75 3.1. A desire for a namespace for computing platforms . . . . . . 7 76 4. Host Identity namespace . . . . . . . . . . . . . . . . . . 9 77 4.1. Host Identifiers . . . . . . . . . . . . . . . . . . . . . . 10 78 4.2. Storing Host Identifiers in DNS . . . . . . . . . . . . . . 10 79 4.3. Host Identity Tag (HIT) . . . . . . . . . . . . . . . . . . 11 80 4.4. Host Identity Hash (HIH) . . . . . . . . . . . . . . . . . . 11 81 4.5. Local Scope Identifier (LSI) . . . . . . . . . . . . . . . . 11 82 5. New stack architecture . . . . . . . . . . . . . . . . . . . 12 83 5.1. Transport associations and end-points . . . . . . . . . . . 13 84 6. End-host mobility and multi-homing . . . . . . . . . . . . . 13 85 6.1. Rendezvous mechanism . . . . . . . . . . . . . . . . . . . . 14 86 6.2. Protection against flooding attacks . . . . . . . . . . . . 14 87 7. HIP and IPsec . . . . . . . . . . . . . . . . . . . . . . . 15 88 8. HIP and MAC Security . . . . . . . . . . . . . . . . . . . . 16 89 9. HIP and NATs . . . . . . . . . . . . . . . . . . . . . . . . 16 90 9.1. HIP and TCP checksums . . . . . . . . . . . . . . . . . . . 17 91 10. Multicast . . . . . . . . . . . . . . . . . . . . . . . . . 17 92 11. HIP policies . . . . . . . . . . . . . . . . . . . . . . . . 17 93 12. Benefits of HIP . . . . . . . . . . . . . . . . . . . . . . 18 94 12.1. HIP's answers to NSRG questions . . . . . . . . . . . . . . 19 95 13. Security considerations . . . . . . . . . . . . . . . . . . 21 96 13.1. HITs used in ACLs . . . . . . . . . . . . . . . . . . . . . 22 97 13.2. Non-security considerations . . . . . . . . . . . . . . . . 23 98 14. IANA considerations . . . . . . . . . . . . . . . . . . . . 24 99 15. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 24 100 16. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 101 16.1. Normative References . . . . . . . . . . . . . . . . . . . . 24 102 16.2. Informative references . . . . . . . . . . . . . . . . . . . 25 103 Author's Address . . . . . . . . . . . . . . . . . . . . . . 26 105 1. Introduction 107 The Internet has two important global namespaces: Internet Protocol 108 (IP) addresses and Domain Name Service (DNS) names. These two 109 namespaces have a set of features and abstractions that have powered 110 the Internet to what it is today. They also have a number of 111 weaknesses. Basically, since they are all we have, we try and do too 112 much with them. Semantic overloading and functionality extensions 113 have greatly complicated these namespaces. 115 The proposed Host Identity namespace fills an important gap between 116 the IP and DNS namespaces. The Host Identity namespace consists of 117 Host Identifiers (HI). A Host Identifier is cryptographic in its 118 nature; it is the public key of an asymmetric key-pair. Each host 119 will have at least one Host Identity, but it will typically have more 120 than one. Each Host Identity uniquely identifies a single host, 121 i.e., no two hosts have the same Host Identity. The Host Identity, 122 and the corresponding Host Identifier, can either be public (e.g. 123 published in the DNS), or unpublished. Client systems will tend to 124 have both public and unpublished Identities. 126 There is a subtle but important difference between Host Identities 127 and Host Identifiers. An Identity refers to the abstract entity that 128 is identified. An Identifier, on the other hand, refers to the 129 concrete bit pattern that is used in the identification process. 131 Although the Host Identifiers could be used in many authentication 132 systems, such as IKEv2 [RFC4306], the presented architecture 133 introduces a new protocol, called the Host Identity Protocol (HIP), 134 and a cryptographic exchange, called the HIP base exchange; see also 135 Section 7. The HIP protocols under development provide for limited 136 forms of trust between systems, enhance mobility, multi-homing and 137 dynamic IP renumbering, aid in protocol translation / transition, and 138 reduce certain types of denial-of-service (DoS) attacks. 140 When HIP is used, the actual payload traffic between two HIP hosts is 141 typically, but not necessarily, protected with IPsec. The Host 142 Identities are used to create the needed IPsec Security Associations 143 (SAs) and to authenticate the hosts. When IPsec is used, the actual 144 payload IP packets do not differ in any way from standard IPsec 145 protected IP packets. 147 2. Terminology 148 2.1. Terms common to other documents 150 +---------------+---------------------------------------------------+ 151 | Term | Explanation | 152 +---------------+---------------------------------------------------+ 153 | Public key | The public key of an asymmetric cryptographic key | 154 | | pair. Used as a publicly known identifier for | 155 | | cryptographic identity authentication. | 156 | | | 157 | Private key | The private or secret key of an asymmetric | 158 | | cryptographic key pair. Assumed to be known only | 159 | | to the party identified by the corresponding | 160 | | public key. Used by the identified party to | 161 | | authenticate its identity to other parties. | 162 | | | 163 | Public key | An asymmetric cryptographic key pair consisting | 164 | pair | of public and private keys. For example, | 165 | | Rivest-Shamir-Adelman (RSA) and Digital Signature | 166 | | Algorithm (DSA) key pairs are such key pairs. | 167 | | | 168 | End-point | A communicating entity. For historical reasons, | 169 | | the term 'computing platform' is used in this | 170 | | document as a (rough) synonym for end-point. | 171 +---------------+---------------------------------------------------+ 173 2.2. Terms specific to this and other HIP documents 175 It should be noted that many of the terms defined herein are 176 tautologous, self-referential or defined through circular reference 177 to other terms. This is due to the succinct nature of the 178 definitions. See the text elsewhere in this document for more 179 elaborate explanations. 181 +---------------+---------------------------------------------------+ 182 | Term | Explanation | 183 +---------------+---------------------------------------------------+ 184 | Computing | An entity capable of communicating and computing, | 185 | platform | for example, a computer. See the definition of | 186 | | 'End-point', above. | 187 | | | 188 | HIP base | A cryptographic protocol; see also Section 7. | 189 | exchange | | 190 | | | 191 | HIP packet | An IP packet that carries a 'Host Identity | 192 | | Protocol' message. | 193 | | | 194 | Host Identity | An abstract concept assigned to a 'computing | 195 | | platform'. See 'Host Identifier', below. | 196 | | | 197 | Host Identity | A name space formed by all possible Host | 198 | namespace | Identifiers. | 199 | | | 200 | Host Identity | A protocol used to carry and authenticate Host | 201 | Protocol | Identifiers and other information. | 202 | | | 203 | Host Identity | A 128-bit datum created by taking a cryptographic | 204 | Tag | hash over a Host Identifier. | 205 | | | 206 | Host Identity | The cryptograhic hash used in creating the Host | 207 | Hash | Identity Tag from the Host Identity. | 208 | | | 209 | Host | A public key used as a name for a Host Identity. | 210 | Identifier | | 211 | | | 212 | Local Scope | A 32-bit datum denoting a Host Identity. | 213 | Identifier | | 214 | | | 215 | Public Host | A published or publicly known Host Identfier used | 216 | Identifier | as a public name for a Host Identity, and the | 217 | and Identity | corresponding Identity. | 218 | | | 219 | Unpublished | A Host Identifier that is not placed in any | 220 | Host | public directory, and the corresponding Host | 221 | Identifier | Identity. Unpublished Host Identities are | 222 | and Identity | typically short lived in nature, being often | 223 | | replaced and possibly used just once. | 224 | | | 225 | Rendezvous | A mechanism used to locate mobile hosts based on | 226 | Mechanism | their HIT. | 227 +---------------+---------------------------------------------------+ 229 3. Background 231 The Internet is built from three principal components: computing 232 platforms (end-points), packet transport (i.e., internetworking) 233 infrastructure, and services (applications). The Internet exists to 234 service two principal components: people and robotic services 235 (silicon based people, if you will). All these components need to be 236 named in order to interact in a scalable manner. Here we concentrate 237 on naming computing platforms and packet transport elements. 239 There are two principal namespaces in use in the Internet for these 240 components: IP numbers, and Domain Names. Domain Names provide 241 hierarchically assigned names for some computing platforms and some 242 services. Each hierarchy is delegated from the level above; there is 243 no anonymity in Domain Names. Email, HTTP, and SIP addresses all 244 reference Domain Names. 246 IP numbers are a confounding of two namespaces, the names of a host's 247 networking interfaces and the names of the locations ('confounding' 248 is a term used in statistics to discuss metrics that are merged into 249 one with a gain in indexing, but a loss in informational value). The 250 names of locations should be understood as denoting routing direction 251 vectors, i.e., information that is used to deliver packets to their 252 destinations. 254 IP numbers name networking interfaces, and typically only when the 255 interface is connected to the network. Originally, IP numbers had 256 long-term significance. Today, the vast number of interfaces use 257 ephemeral and/or non-unique IP numbers. That is, every time an 258 interface is connected to the network, it is assigned an IP number. 260 In the current Internet, the transport layers are coupled to the IP 261 addresses. Neither can evolve separately from the other. IPng 262 deliberations were strongly shaped by the decision that a 263 corresponding TCPng would not be created. 265 There are three critical deficiencies with the current namespaces. 266 Firstly, dynamic readdressing cannot be directly managed. Secondly, 267 anonymity is not provided in a consistent, trustable manner. 268 Finally, authentication for systems and datagrams is not provided. 269 All of these deficiencies arise because computing platforms are not 270 well named with the current namespaces. 272 3.1. A desire for a namespace for computing platforms 274 An independent namespace for computing platforms could be used in 275 end-to-end operations independent of the evolution of the 276 internetworking layer and across the many internetworking layers. 278 This could support rapid readdressing of the internetworking layer 279 because of mobility, rehoming, or renumbering. 281 If the namespace for computing platforms is based on public-key 282 cryptography, it can also provide authentication services. If this 283 namespace is locally created without requiring registration, it can 284 provide anonymity. 286 Such a namespace (for computing platforms) and the names in it should 287 have the following characteristics: 289 o The namespace should be applied to the IP 'kernel'. The IP kernel 290 is the 'component' between applications and the packet transport 291 infrastructure. 293 o The namespace should fully decouple the internetworking layer from 294 the higher layers. The names should replace all occurrences of IP 295 addresses within applications (like in the Transport Control 296 Block, TCB). This may require changes to the current APIs. In 297 the long run, it is probable that some new APIs are needed. 299 o The introduction of the namespace should not mandate any 300 administrative infrastructure. Deployment must come from the 301 bottom up, in a pairwise deployment. 303 o The names should have a fixed length representation, for easy 304 inclusion in datagram headers and existing programming interfaces 305 (e.g the TCB). 307 o Using the namespace should be affordable when used in protocols. 308 This is primarily a packet size issue. There is also a 309 computational concern in affordability. 311 o Name collisions should be avoided as much as possible. The 312 mathematics of the birthday paradox can be used to estimate the 313 chance of a collision in a given population and hash space. In 314 general, for a random hash space of size n bits, we would expect 315 to obtain a collision after approximately 1.2*sqrt(2**n) hashes 316 were obtained. For 64 bits, this number is roughly 4 billion. A 317 hash size of 64 bits may be too small to avoid collisions in a 318 large population; for example, there is a 1% chance of collision 319 in a population of 640M. For 100 bits (or more), we would not 320 expect a collision until approximately 2**50 (1 quadrillion) 321 hashes were generated. 323 o The names should have a localized abstraction so that it can be 324 used in existing protocols and APIs. 326 o It must be possible to create names locally. This can provide 327 anonymity at the cost of making resolvability very difficult. 329 * Sometimes the names may contain a delegation component. This 330 is the cost of resolvability. 332 o The namespace should provide authentication services. 334 o The names should be long lived, but replaceable at any time. This 335 impacts access control lists; short lifetimes will tend to result 336 in tedious list maintenance or require a namespace infrastructure 337 for central control of access lists. 339 In this document, a new namespace approaching these ideas is called 340 the Host Identity namespace. Using Host Identities requires its own 341 protocol layer, the Host Identity Protocol, between the 342 internetworking and transport layers. The names are based on public- 343 key cryptography to supply authentication services. Properly 344 designed, it can deliver all of the above stated requirements. 346 4. Host Identity namespace 348 A name in the Host Identity namespace, a Host Identifier (HI), 349 represents a statistically globally unique name for naming any system 350 with an IP stack. This identity is normally associated with, but not 351 limited to, an IP stack. A system can have multiple identities, some 352 'well known', some unpublished or 'anonymous'. A system may self- 353 assert its own identity, or may use a third-party authenticator like 354 DNSSEC [RFC2535], PGP, or X.509 to 'notarize' the identity assertion. 355 It is expected that the Host Identifiers will initially be 356 authenticated with DNSSEC and that all implementations will support 357 DNSSEC as a minimal baseline. 359 In theory, any name that can claim to be 'statistically globally 360 unique' may serve as a Host Identifier. However, in the authors' 361 opinion, a public key of a 'public key pair' makes the best Host 362 Identifier. As will be specified in the Host Identity Protocol 363 specification, a public-key-based HI can authenticate the HIP packets 364 and protect them for man-in-the-middle attacks. Since authenticated 365 datagrams are mandatory to provide much of HIP's denial-of-service 366 protection, the Diffie-Hellman exchange in HIP has to be 367 authenticated. Thus, only public-key HI and authenticated HIP 368 messages are supported in practice. In this document, the non- 369 cryptographic forms of HI and HIP are presented to complete the 370 theory of HI, but they should not be implemented as they could 371 produce worse denial-of-service attacks than the Internet has without 372 Host Identity. 374 4.1. Host Identifiers 376 Host Identity adds two main features to Internet protocols. The 377 first is a decoupling of the internetworking and transport layers; 378 see Section 5. This decoupling will allow for independent evolution 379 of the two layers. Additionally, it can provide end-to-end services 380 over multiple internetworking realms. The second feature is host 381 authentication. Because the Host Identifier is a public key, this 382 key can be used for authentication in security protocols like IPsec. 384 The only completely defined structure of the Host Identity is that of 385 a public/private key pair. In this case, the Host Identity is 386 referred to by its public component, the public key. Thus, the name 387 representing a Host Identity in the Host Identity namespace, i.e., 388 the Host Identifier, is the public key. In a way, the possession of 389 the private key defines the Identity itself. If the private key is 390 possessed by more than one node, the Identity can be considered to be 391 a distributed one. 393 Architecturally, any other Internet naming convention might form a 394 usable base for Host Identifiers. However, non-cryptographic names 395 should only be used in situations of high trust - low risk. That is 396 any place where host authentication is not needed (no risk of host 397 spoofing) and no use of IPsec. However, at least for interconnected 398 networks spanning several operational domains, the set of 399 environments where the risk of host spoofing allowed by non- 400 cryptographic Host Identifiers is acceptable is the null set. Hence, 401 the current HIP documents do not specify how to use any other types 402 of Host Identifiers but public keys. 404 The actual Host Identities are never directly used in any Internet 405 protocols. The corresponding Host Identifiers (public keys) may be 406 stored in various DNS or LDAP directories as identified elsewhere in 407 this document, and they are passed in the HIP base exchange. A Host 408 Identity Tag (HIT) is used in other protocols to represent the Host 409 Identity. Another representation of the Host Identities, the Local 410 Scope Identifier (LSI), can also be used in protocols and APIs. 412 4.2. Storing Host Identifiers in DNS 414 The public Host Identifiers should be stored in DNS; the unpublished 415 Host Identifiers should not be stored anywhere (besides the 416 communicating hosts themselves). The (public) HI along with the 417 supported HIHs are stored in a new RR type. This RR type is defined 418 in HIP DNS Extension [RFC5205]. 420 Alternatively, or in addition to storing Host Identifiers in the DNS, 421 they may be stored in various kinds of Public Key Infrastructure 422 (PKI). Such a practice may allow them to be used for purposes other 423 than pure host identification. 425 4.3. Host Identity Tag (HIT) 427 A Host Identity Tag is a 128-bit representation for a Host Identity. 428 It is created by taking a cryptographic hash over the corresponding 429 Host Identifier. There are two advantages of using a hash over using 430 the Host Identifier in protocols. Firstly, its fixed length makes 431 for easier protocol coding and also better manages the packet size 432 cost of this technology. Secondly, it presents the identity in a 433 consistent format to the protocol independent of the cryptographic 434 algorithms used. 436 There can be multiple HITs per Host Identifier when multiple hashes 437 are supported. An Initator may have to initially guess which HIT to 438 use for the Responder, typically based on what it perfers, until it 439 learns the appropriate HIT through the HIP exchange. 441 In the HIP packets, the HITs identify the sender and recipient of a 442 packet. Consequently, a HIT should be unique in the whole IP 443 universe as long as it is being used. In the extremely rare case of 444 a single HIT mapping to more than one Host Identity, the Host 445 Identifiers (public keys) will make the final difference. If there 446 is more than one public key for a given node, the HIT acts as a hint 447 for the correct public key to use. 449 4.4. Host Identity Hash (HIH) 451 The Host Identity Hash is the cryptographic hash used in producing 452 the HIT from the HI. It is also the hash used through out the HIP 453 protocol for consistancy and simplicity. It is possible to for the 454 two Hosts in the HIP exchange to use different hashes. 456 Multiple HIHs within HIP is needed to address the moving target of 457 creation and eventual compromise of cryptographic hashes. This 458 significantly complicates HIP and offers an attacker an additional 459 downgrade attack that is mitigated in the HIP protocol. 461 4.5. Local Scope Identifier (LSI) 463 An LSI is a 32-bit localized representation for a Host Identity. The 464 purpose of an LSI is to facilitate using Host Identities in existing 465 protocols and APIs. LSI's advantage over HIT is its size; its 466 disadvantage is its local scope. 468 Examples of how LSIs can be used include: as the address in an FTP 469 command and as the address in a socket call. Thus, LSIs act as a 470 bridge for Host Identities into IPv4-based protocols and APIs. LSIs 471 also make it possible for some IPv4 applications to run over an IPv6 472 network. 474 5. New stack architecture 476 One way to characterize Host Identity is to compare the proposed new 477 architecture with the current one. As discussed above, the IP 478 addresses can be seen to be a confounding of routing direction 479 vectors and interface names. Using the terminology from the IRTF 480 Name Space Research Group Report [nsrg-report] and, e.g., the 481 unpublished Internet-Draft Endpoints and Endpoint Names 482 [chiappa-endpoints], the IP addresses currently embody the dual role 483 of locators and end-point identifiers. That is, each IP address 484 names a topological location in the Internet, thereby acting as a 485 routing direction vector, or locator. At the same time, the IP 486 address names the physical network interface currently located at the 487 point-of-attachment, thereby acting as a end-point name. 489 In the HIP architecture, the end-point names and locators are 490 separated from each other. IP addresses continue to act as locators. 491 The Host Identifiers take the role of end-point identifiers. It is 492 important to understand that the end-point names based on Host 493 Identities are slightly different from interface names; a Host 494 Identity can be simultaneously reachable through several interfaces. 496 The difference between the bindings of the logical entities are 497 illustrated in Figure 1. 499 Service ------ Socket Service ------ Socket 500 | | 501 | | 502 | | 503 | | 504 End-point | End-point --- Host Identity 505 \ | | 506 \ | | 507 \ | | 508 \ | | 509 Location --- IP address Location --- IP address 511 Figure 1 513 5.1. Transport associations and end-points 515 Architecturally, HIP provides for a different binding of transport- 516 layer protocols. That is, the transport-layer associations, i.e., 517 TCP connections and UDP associations, are no longer bound to IP 518 addresses but to Host Identities. 520 It is possible that a single physical computer hosts several logical 521 end-points. With HIP, each of these end-points would have a distinct 522 Host Identity. Furthermore, since the transport associations are 523 bound to Host Identities, HIP provides for process migration and 524 clustered servers. That is, if a Host Identity is moved from one 525 physical computer to another, it is also possible to simultaneously 526 move all the transport associations without breaking them. 527 Similarly, if it is possible to distribute the processing of a single 528 Host Identity over several physical computers, HIP provides for 529 cluster based services without any changes at the client end-point. 531 6. End-host mobility and multi-homing 533 HIP decouples the transport from the internetworking layer, and binds 534 the transport associations to the Host Identities (through actually 535 either the HIT or LSI). Consequently, HIP can provide for a degree 536 of internetworking mobility and multi-homing at a low infrastructure 537 cost. HIP mobility includes IP address changes (via any method) to 538 either party. Thus, a system is considered mobile if its IP address 539 can change dynamically for any reason like PPP, DHCP, IPv6 prefix 540 reassignments, or a NAT device remapping its translation. Likewise, 541 a system is considered multi-homed if it has more than one globally 542 routable IP address at the same time. HIP links IP addresses 543 together, when multiple IP addresses correspond to the same Host 544 Identity, and if one address becomes unusable, or a more preferred 545 address becomes available, existing transport associations can easily 546 be moved to another address. 548 When a node moves while communication is already on-going, address 549 changes are rather straightforward. The peer of the mobile node can 550 just accept a HIP or an integrity protected IPsec packet from any 551 address and ignore the source address. However, as discussed in 552 Section 6.2 below, a mobile node must send a HIP readdress packet to 553 inform the peer of the new address(es), and the peer must verify that 554 the mobile node is reachable through these addresses. This is 555 especially helpful for those situations where the peer node is 556 sending data periodically to the mobile node (that is re-starting a 557 connection after the initial connection). 559 6.1. Rendezvous mechanism 561 Making a contact to a mobile node is slightly more involved. In 562 order to start the HIP exchange, the initiator node has to know how 563 to reach the mobile node. Although infrequently moving HIP nodes 564 could use Dynamic DNS [RFC2136] to update their reachability 565 information in the DNS, an alternative to using DNS in this fashion 566 is to use a piece of new static infrastructure to facilitate 567 rendezvous between HIP nodes. 569 The mobile node keeps the rendezvous infrastructure continuously 570 updated with its current IP address(es). The mobile nodes must trust 571 the rendezvous mechanism to properly maintain their HIT and IP 572 address mappings. 574 The rendezvous mechanism is also needed if both of the nodes happen 575 to change their address at the same time, either because they are 576 mobile and happen to move at the same time, because one of them is 577 off-line for a while, or because of some other reason. In such a 578 case, the HIP readdress packets will cross each other in the network 579 and never reach the peer node. 581 The HIP rendezvous mechanism is defined in HIP Rendezvous [RFC5204]. 583 6.2. Protection against flooding attacks 585 Although the idea of informing about address changes by simply 586 sending packets with a new source address appears appealing, it is 587 not secure enough. That is, even if HIP does not rely on the source 588 address for anything (once the base exchange has been completed), it 589 appears to be necessary to check a mobile node's reachability at the 590 new address before actually sending any larger amounts of traffic to 591 the new address. 593 Blindly accepting new addresses would potentially lead to flooding 594 Denial-of-Service attacks against third parties [RFC4225]. In a 595 distributed flooding attack an attacker opens high volume HIP 596 connections with a large number of hosts (using unpublished HIs), and 597 then claims to all of these hosts that it has moved to a target 598 node's IP address. If the peer hosts were to simply accept the move, 599 the result would be a packet flood to the target node's address. To 600 close this attack, HIP includes an address check mechanism where the 601 reachability of a node is separately checked at each address before 602 using the address for larger amounts of traffic. 604 Whenever HIP is used between two hosts that fully trust each other, 605 the hosts may optionally decide to skip the address tests. However, 606 such performance optimization must be restricted to peers that are 607 known to be trustworthy and capable of protecting themselves from 608 malicious software. 610 7. HIP and IPsec 612 The preferred way of implementing HIP is to use IPsec to carry the 613 actual data traffic. As of today, the only completely defined method 614 is to use IPsec Encapsulated Security Payload (ESP) to carry the data 615 packets [RFC5202]. In the future, other ways of transporting payload 616 data may be developed, including ones that do not use cryptographic 617 protection. 619 In practice, the HIP base exchange uses the cryptographic Host 620 Identifiers to set up a pair of ESP Security Associations (SAs) to 621 enable ESP in an end-to-end manner. This is implemented in a way 622 that can span addressing realms. 624 While it would be possible, at least in theory, to use some existing 625 cryptographic protocol, such as IKEv2 together with Host Identifiers, 626 to establish the needed SAs, HIP defines a new protocol. There are a 627 number of historical reasons for this, and there are also a few 628 architectural reasons. First, IKE (and IKEv2) were not designed with 629 middle boxes in mind. As adding a new naming layer allows one to 630 potentially add a new forwarding layer (see Section 9, below), it is 631 very important that the HIP protocols are friendly towards any middle 632 boxes. 634 Second, from a conceptual point of view, the IPsec Security Parameter 635 Index (SPI) in ESP provides a simple compression of the HITs. This 636 does require per-HIT-pair SAs (and SPIs), and a decrease of policy 637 granularity over other Key Management Protocols, such as IKE and 638 IKEv2. In particular, the current thinking is limited to a situation 639 where, conceptually, there is only one pair of SAs between any given 640 pair of HITs. In other words, from an architectural point of view, 641 HIP only supports host-to-host (or endpoint-to-endpoint) Security 642 Associations. If two hosts need more pairs of parallel SAs, they 643 should use separate HITs for that. However, future HIP extensions 644 may provide for more granularity and creation of several ESP SAs 645 between a pair of HITs. 647 Since HIP is designed for host usage, not for gateways or so called 648 Bump-in-the-Wire (BITW) implementations, only ESP transport mode is 649 supported. An ESP SA pair is indexed by the SPIs and the two HITs 650 (both HITs since a system can have more than one HIT). The SAs need 651 not to be bound to IP addresses; all internal control of the SA is by 652 the HITs. Thus, a host can easily change its address using Mobile 653 IP, DHCP, PPP, or IPv6 readdressing and still maintain the SAs. 655 Since the transports are bound to the SA (via an LSI or a HIT), any 656 active transport is also maintained. Thus, real-world conditions 657 like loss of a PPP connection and its re-establishment or a mobile 658 handover will not require a HIP negotiation or disruption of 659 transport services [Bel1998]. 661 Since HIP does not negotiate any SA lifetimes, all lifetimes are 662 local policy. The only lifetimes a HIP implementation must support 663 are sequence number rollover (for replay protection), and SA timeout. 664 An SA times out if no packets are received using that SA. 665 Implementations may support lifetimes for the various ESP transforms. 667 8. HIP and MAC Security 669 The IEEE 802 standards have been defining MAC layered security. Many 670 of these standards use EAP [RFC3748] as a Key Management System (KMS) 671 transport, but some like IEEE 802.15.4 [IEEE.802-15-4.2006] leave the 672 KMS and its transport as "Out of Scope". 674 HIP is well suited as a KMS in these environments. 676 o HIP is independent of IP addressing and can be directly 677 transported over any network protocol. 679 o Master Keys in 802 protocols are strictly pair-based with group 680 keys transported from the group controller using pair-wise keys. 682 o AdHoc 802 networks can be better served by a peer-to-peer KMS than 683 the EAP client/server model. 685 o Some devices are very memory constrained and a common KMS for both 686 MAC and IP security represents a considerable code savings. 688 9. HIP and NATs 690 Passing packets between different IP addressing realms requires 691 changing IP addresses in the packet header. This may happen, for 692 example, when a packet is passed between the public Internet and a 693 private address space, or between IPv4 and IPv6 networks. The 694 address translation is usually implemented as Network Address 695 Translation (NAT) [RFC3022] or NAT Protocol translation (NAT-PT) 696 [RFC2766]. 698 In a network environment where identification is based on the IP 699 addresses, identifying the communicating nodes is difficult when NAT 700 is used. With HIP, the transport-layer end-points are bound to the 701 Host Identities. Thus, a connection between two hosts can traverse 702 many addressing realm boundaries. The IP addresses are used only for 703 routing purposes; they may be changed freely during packet traversal. 705 For a HIP-based flow, a HIP-aware NAT or NAT-PT system tracks the 706 mapping of HITs, and the corresponding IPsec SPIs, to an IP address. 707 The NAT system has to learn mappings both from HITs and from SPIs to 708 IP addresses. Many HITs (and SPIs) can map to a single IP address on 709 a NAT, simplifying connections on address poor NAT interfaces. The 710 NAT can gain much of its knowledge from the HIP packets themselves; 711 however, some NAT configuration may be necessary. 713 NAT systems cannot touch the datagrams within the IPsec envelope, 714 thus application-specific address translation must be done in the end 715 systems. HIP provides for 'Distributed NAT', and uses the HIT or the 716 LSI as a placeholder for embedded IP addresses. 718 HIP and NAT interaction is defined in [RFC5770]. 720 9.1. HIP and TCP checksums 722 There is no way for a host to know if any of the IP addresses in an 723 IP header are the addresses used to calculate the TCP checksum. That 724 is, it is not feasible to calculate the TCP checksum using the actual 725 IP addresses in the pseudo header; the addresses received in the 726 incoming packet are not necessarily the same as they were on the 727 sending host. Furthermore, it is not possible to recompute the 728 upper-layer checksums in the NAT/NAT-PT system, since the traffic is 729 IPsec protected. Consequently, the TCP and UDP checksums are 730 calculated using the HITs in the place of the IP addresses in the 731 pseudo header. Furthermore, only the IPv6 pseudo header format is 732 used. This provides for IPv4 / IPv6 protocol translation. 734 10. Multicast 736 There was little if any concrete thoughts about how HIP might affect 737 IP-layer or application-layer multicast. 739 11. HIP policies 741 There are a number of variables that will influence the HIP exchanges 742 that each host must support. All HIP implementations should support 743 at least 2 HIs, one to publish in DNS and an unpublished one for 744 anonymous usage. Although unpublished HIs will be rarely used as 745 responder HIs, they are likely be common for initiators. Support for 746 multiple HIs is recommended. 748 Many initiators would want to use a different HI for different 749 responders. The implementations should provide for a policy of 750 initiator HIT to responder HIT. This policy should also include 751 preferred transforms and local lifetimes. 753 Responders would need a similar policy, describing the hosts allowed 754 to participate in HIP exchanges, and the preferred transforms and 755 local lifetimes. 757 12. Benefits of HIP 759 In the beginning, the network layer protocol (i.e., IP) had the 760 following four "classic" invariants: 762 o Non-mutable: The address sent is the address received. 764 o Non-mobile: The address doesn't change during the course of an 765 "association". 767 o Reversible: A return header can always be formed by reversing the 768 source and destination addresses. 770 o Omniscient: Each host knows what address a partner host can use to 771 send packets to it. 773 Actually, the fourth can be inferred from 1 and 3, but it is worth 774 mentioning for reasons that will be obvious soon if not already. 776 In the current "post-classic" world, we are intentionally trying to 777 get rid of the second invariant (both for mobility and for multi- 778 homing), and we have been forced to give up the first and the fourth. 779 Realm Specific IP [RFC3102] is an attempt to reinstate the fourth 780 invariant without the first invariant. IPv6 is an attempt to 781 reinstate the first invariant. 783 Few systems on the Internet have DNS names that are meaningful. That 784 is, if they have a Fully Qualified Domain Name (FQDN), that name 785 typically belongs to a NAT device or a dial-up server, and does not 786 really identify the system itself but its current connectivity. 787 FQDNs (and their extensions as email names) are application-layer 788 names; more frequently naming services than a particular system. 789 This is why many systems on the Internet are not registered in the 790 DNS; they do not have services of interest to other Internet hosts. 792 DNS names are references to IP addresses. This only demonstrates the 793 interrelationship of the networking and application layers. DNS, as 794 the Internet's only deployed, distributed database is also the 795 repository of other namespaces, due in part to DNSSEC and application 796 specific key records. Although each namespace can be stretched (IP 797 with v6, DNS with KEY records), neither can adequately provide for 798 host authentication or act as a separation between internetworking 799 and transport layers. 801 The Host Identity (HI) namespace fills an important gap between the 802 IP and DNS namespaces. An interesting thing about the HI is that it 803 actually allows one to give up all but the 3rd network-layer 804 invariant. That is to say, as long as the source and destination 805 addresses in the network-layer protocol are reversible, then things 806 work ok because HIP takes care of host identification, and 807 reversibility allows one to get a packet back to one's partner host. 808 You do not care if the network-layer address changes in transit 809 (mutable) and you don't care what network-layer address the partner 810 is using (non-omniscient). 812 12.1. HIP's answers to NSRG questions 814 The IRTF Name Space Research Group has posed a number of evaluating 815 questions in their report [nsrg-report]. In this section, we provide 816 answers to these questions. 818 1. How would a stack name improve the overall functionality of the 819 Internet? 821 HIP decouples the internetworking layer from the transport 822 layer, allowing each to evolve separately. The decoupling 823 makes end-host mobility and multi-homing easier, also across 824 IPv4 and IPv6 networks. HIs make network renumbering easier, 825 and they also make process migration and clustered servers 826 easier to implement. Furthermore, being cryptographic in 827 nature, they provide the basis for solving the security 828 problems related to end-host mobility and multi-homing. 830 2. What does a stack name look like? 832 A HI is a cryptographic public key. However, instead of using 833 the keys directly, most protocols use a fixed size hash of the 834 public key. 836 3. What is its lifetime? 838 HIP provides both stable and temporary Host Identifiers. 839 Stable HIs are typically long lived, with a lifetime of years 840 or more. The lifetime of temporary HIs depends on how long 841 the upper-layer connections and applications need them, and 842 can range from a few seconds to years. 844 4. Where does it live in the stack? 846 The HIs live between the transport and internetworking layers. 848 5. How is it used on the end points 850 The Host Identifiers may be used directly or indirectly (in 851 the form of HITs or LSIs) by applications when they access 852 network services. Additionally, the Host Identifiers, as 853 public keys, are used in the built in key agreement protocol, 854 called the HIP base exchange, to authenticate the hosts to 855 each other. 857 6. What administrative infrastructure is needed to support it? 859 In some environments, it is possible to use HIP 860 opportunistically, without any infrastructure. However, to 861 gain full benefit from HIP, the HIs must be stored in the DNS 862 or a PKI, and a new rendezvous mechanism is needed [RFC5205]. 864 7. If we add an additional layer would it make the address list in 865 SCTP unnecessary? 867 Yes 869 8. What additional security benefits would a new naming scheme 870 offer? 872 HIP reduces dependency on IP addresses, making the so called 873 address ownership [Nik2001] problems easier to solve. In 874 practice, HIP provides security for end-host mobility and 875 multi-homing. Furthermore, since HIP Host Identifiers are 876 public keys, standard public key certificate infrastructures 877 can be applied on the top of HIP. 879 9. What would the resolution mechanisms be, or what characteristics 880 of a resolution mechanisms would be required? 882 For most purposes, an approach where DNS names are resolved 883 simultaneously to HIs and IP addresses is sufficient. 884 However, if it becomes necessary to resolve HIs into IP 885 addresses or back to DNS names, a flat resolution 886 infrastructure is needed. Such an infrastructure could be 887 based on the ideas of Distributed Hash Tables, but would 888 require significant new development and deployment. 890 13. Security considerations 892 HIP takes advantage of the new Host Identity paradigm to provide 893 secure authentication of hosts and to provide a fast key exchange for 894 IPsec. HIP also attempts to limit the exposure of the host to 895 various denial-of-service (DoS) and man-in-the-middle (MitM) attacks. 896 In so doing, HIP itself is subject to its own DoS and MitM attacks 897 that potentially could be more damaging to a host's ability to 898 conduct business as usual. 900 Resource exhausting denial-of-service attacks take advantage of the 901 cost of setting up a state for a protocol on the responder compared 902 to the 'cheapness' on the initiator. HIP allows a responder to 903 increase the cost of the start of state on the initiator and makes an 904 effort to reduce the cost to the responder. This is done by having 905 the responder start the authenticated Diffie-Hellman exchange instead 906 of the initiator, making the HIP base exchange 4 packets long. There 907 are more details on this process in the Host Identity Protocol under 908 development. 910 HIP optionally supports opportunistic negotiation. That is, if a 911 host receives a start of transport without a HIP negotiation, it can 912 attempt to force a HIP exchange before accepting the connection. 913 This has the potential for DoS attacks against both hosts. If the 914 method to force the start of HIP is expensive on either host, the 915 attacker need only spoof a TCP SYN. This would put both systems into 916 the expensive operations. HIP avoids this attack by having the 917 responder send a simple HIP packet that it can pre-build. Since this 918 packet is fixed and easily replayed, the initiator only reacts to it 919 if it has just started a connection to the responder. 921 Man-in-the-middle attacks are difficult to defend against, without 922 third-party authentication. A skillful MitM could easily handle all 923 parts of the HIP base exchange, but HIP indirectly provides the 924 following protection from a MitM attack. If the responder's HI is 925 retrieved from a signed DNS zone or secured by some other means, the 926 initiator can use this to authenticate the signed HIP packets. 927 Likewise, if the initiator's HI is in a secure DNS zone, the 928 responder can retrieve it and validate the signed HIP packets. 929 However, since an initiator may choose to use an unpublished HI, it 930 knowingly risks a MitM attack. The responder may choose not to 931 accept a HIP exchange with an initiator using an unknown HI. 933 The need to support multiple hashes for generating the HIT from the 934 HI affords the MitM a potentially powerful downgrade attack due to 935 the a-priori need of the HIT in the HIP base exchange. The base 936 exchange has been augmented to deal with such an attack by restarting 937 on detecting the attack. At worst this would only lead to a 938 situation in which the base exchange would never finish (or would be 939 aborted after some retries). As a drawback, this leads to an 6-way 940 base exchange which may seem bad at first. However, since this only 941 happens in an attack scenario and since the attack can be handled (so 942 it is not interesting to mount anymore), we assume the additional 943 messages are not a problem at all. Since the MitM cannot be 944 successful with a downgrade attack, these sorts of attacks will only 945 occur as 'nuisance' attacks. So, the base exchange would still be 946 usually just four packets even though implementations must be 947 prepared to protect themselves against the downgrade attack. 949 In HIP, the Security Association for IPsec is indexed by the SPI; the 950 source address is always ignored, and the destination address may be 951 ignored as well. Therefore, HIP-enabled IPsec Encapsulated Security 952 Payload (ESP) is IP address independent. This might seem to make it 953 easier for an attacker, but ESP with replay protection is already as 954 well protected as possible, and the removal of the IP address as a 955 check should not increase the exposure of IPsec ESP to DoS attacks. 957 Since not all hosts will ever support HIP, ICMPv4 'Destination 958 Unreachable, Protocol Unreachable' and ICMPv6 'Parameter Problem, 959 Unrecognized Next Header' messages are to be expected and present a 960 DoS attack. Against an initiator, the attack would look like the 961 responder does not support HIP, but shortly after receiving the ICMP 962 message, the initiator would receive a valid HIP packet. Thus, to 963 protect against this attack, an initiator should not react to an ICMP 964 message until a reasonable time has passed, allowing it to get the 965 real responder's HIP packet. A similar attack against the responder 966 is more involved. 968 Another MitM attack is simulating a responder's administrative 969 rejection of a HIP initiation. This is a simple ICMP 'Destination 970 Unreachable, Administratively Prohibited' message. A HIP packet is 971 not used because it would either have to have unique content, and 972 thus difficult to generate, resulting in yet another DoS attack, or 973 just as spoofable as the ICMP message. Like in the previous case, 974 the defense against this attack is for the initiator to wait a 975 reasonable time period to get a valid HIP packet. If one does not 976 come, then the initiator has to assume that the ICMP message is 977 valid. Since this is the only point in the HIP base exchange where 978 this ICMP message is appropriate, it can be ignored at any other 979 point in the exchange. 981 13.1. HITs used in ACLs 983 It is expected that HITs will be used in ACLs. Future firewalls can 984 use HITs to control egress and ingress to networks, with an assurance 985 level difficult to achieve today. As discussed above in Section 7, 986 once a HIP session has been established, the SPI value in an IPsec 987 packet may be used as an index, indicating the HITs. In practice, 988 firewalls can inspect HIP packets to learn of the bindings between 989 HITs, SPI values, and IP addresses. They can even explicitly control 990 IPsec usage, dynamically opening IPsec ESP only for specific SPI 991 values and IP addresses. The signatures in HIP packets allow a 992 capable firewall to ensure that the HIP exchange is indeed happening 993 between two known hosts. This may increase firewall security. 995 There has been considerable bad experience with distributed ACLs that 996 contain public key related material, for example, with SSH. If the 997 owner of a key needs to revoke it for any reason, the task of finding 998 all locations where the key is held in an ACL may be impossible. If 999 the reason for the revocation is due to private key theft, this could 1000 be a serious issue. 1002 A host can keep track of all of its partners that might use its HIT 1003 in an ACL by logging all remote HITs. It should only be necessary to 1004 log responder hosts. With this information, the host can notify the 1005 various hosts about the change to the HIT. There has been no attempt 1006 to develop a secure method to issue the HIT revocation notice. 1008 HIP-aware NATs, however, are transparent to the HIP aware systems by 1009 design. Thus, the host may find it difficult to notify any NAT that 1010 is using a HIT in an ACL. Since most systems will know of the NATs 1011 for their network, there should be a process by which they can notify 1012 these NATs of the change of the HIT. This is mandatory for systems 1013 that function as responders behind a NAT. In a similar vein, if a 1014 host is notified of a change in a HIT of an initiator, it should 1015 notify its NAT of the change. In this manner, NATs will get updated 1016 with the HIT change. 1018 13.2. Non-security considerations 1020 The definition of the Host Identifier states that the HI need not be 1021 a public key. It implies that the HI could be any value; for example 1022 a FQDN. This document does not describe how to support such a non- 1023 cryptographic HI. A non-cryptographic HI would still offer the 1024 services of the HIT or LSI for NAT traversal. It would be possible 1025 to carry HITs in HIP packets that had neither privacy nor 1026 authentication. Since such a mode would offer so little additional 1027 functionality for so much addition to the IP kernel, it has not been 1028 defined. Given how little public key cryptography HIP requires, HIP 1029 should only be implemented using public key Host Identities. 1031 If it is desirable to use HIP in a low security situation where 1032 public key computations are considered expensive, HIP can be used 1033 with very short Diffie-Hellman and Host Identity keys. Such use 1034 makes the participating hosts vulnerable to MitM and connection 1035 hijacking attacks. However, it does not cause flooding dangers, 1036 since the address check mechanism relies on the routing system and 1037 not on cryptographic strength. 1039 14. IANA considerations 1041 This document has no actions for IANA. 1043 15. Acknowledgments 1045 For the people historically involved in the early stages of HIP, see 1046 the Acknowledgements section in the Host Identity Protocol 1047 specification. 1049 During the later stages of this document, when the editing baton was 1050 transfered to Pekka Nikander, the comments from the early 1051 implementors and others, including Jari Arkko, Tom Henderson, Petri 1052 Jokela, Miika Komu, Mika Kousa, Andrew McGregor, Jan Melen, Tim 1053 Shepard, Jukka Ylitalo, and Jorma Wall, were invaluable. Finally, 1054 Lars Eggert, Spencer Dawkins and Dave Crocker provided valuable input 1055 during the final stages of publication, most of which was 1056 incorporated but some of which the authors decided to ignore in order 1057 to get this document published in the first place. 1059 The authors want to express their special thanks to Tom Henderson, 1060 who took the burden of editing the document in response to IESG 1061 comments at the time when both of the authors were busy doing other 1062 things. Without his perseverance original document might have never 1063 made it as RFC4423. 1065 This latest effort to update and move HIP forward within the IETF 1066 process owes its impetuous to the three HIP development teams: 1067 Boeing, HIIT (Helsinki Institute for Information Technology), and 1068 NomadicLab of Ericsson. Without their collective efforts HIP would 1069 have withered as on the IETF vine as a nice concept. 1071 16. References 1073 16.1. Normative References 1075 [RFC5202] Jokela, P., Moskowitz, R., and P. Nikander, "Using the 1076 Encapsulating Security Payload (ESP) Transport Format with 1077 the Host Identity Protocol (HIP)", RFC 5202, April 2008. 1079 [RFC5204] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) 1080 Rendezvous Extension", RFC 5204, April 2008. 1082 [RFC5205] Nikander, P. and J. Laganier, "Host Identity Protocol 1083 (HIP) Domain Name System (DNS) Extensions", RFC 5205, 1084 April 2008. 1086 16.2. Informative references 1088 [RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound, 1089 "Dynamic Updates in the Domain Name System (DNS UPDATE)", 1090 RFC 2136, April 1997. 1092 [RFC2535] Eastlake, D., "Domain Name System Security Extensions", 1093 RFC 2535, March 1999. 1095 [RFC2766] Tsirtsis, G. and P. Srisuresh, "Network Address 1096 Translation - Protocol Translation (NAT-PT)", RFC 2766, 1097 February 2000. 1099 [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network 1100 Address Translator (Traditional NAT)", RFC 3022, 1101 January 2001. 1103 [RFC3102] Borella, M., Lo, J., Grabelsky, D., and G. Montenegro, 1104 "Realm Specific IP: Framework", RFC 3102, October 2001. 1106 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 1107 Levkowetz, "Extensible Authentication Protocol (EAP)", 1108 RFC 3748, June 2004. 1110 [RFC4025] Richardson, M., "A Method for Storing IPsec Keying 1111 Material in DNS", RFC 4025, March 2005. 1113 [RFC4225] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E. 1114 Nordmark, "Mobile IP Version 6 Route Optimization Security 1115 Design Background", RFC 4225, December 2005. 1117 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", 1118 RFC 4306, December 2005. 1120 [RFC5770] Komu, M., Henderson, T., Tschofenig, H., Melen, J., and A. 1121 Keranen, "Basic Host Identity Protocol (HIP) Extensions 1122 for Traversal of Network Address Translators", RFC 5770, 1123 April 2010. 1125 [nsrg-report] 1126 Lear, E. and R. Droms, "What's In A Name:Thoughts from the 1127 NSRG", draft-irtf-nsrg-report-10 (work in progress), 1128 September 2003. 1130 [IEEE.802-15-4.2006] 1131 "Information technology - Telecommunications and 1132 information exchange between systems - Local and 1133 metropolitan area networks - Specific requirements - Part 1134 15.4: Wireless Medium Access Control (MAC) and Physical 1135 Layer (PHY) Specifications for Low-Rate Wireless Personal 1136 Area Networks (WPANs)", IEEE Standard 802.15.4, 1137 September 2006, . 1140 [chiappa-endpoints] 1141 Chiappa, J., "Endpoints and Endpoint Names: A Proposed 1142 Enhancement to the Internet Architecture", 1143 URL http://www.chiappa.net/~jnc/tech/endpoints.txt, 1999. 1145 [Nik2001] Nikander, P., "Denial-of-Service, Address Ownership, and 1146 Early Authentication in the IPv6 World", in Proceesings 1147 of Security Protocols, 9th International Workshop, 1148 Cambridge, UK, April 25-27 2001, LNCS 2467, pp. 12-26, 1149 Springer, 2002. 1151 [Bel1998] Bellovin, S., "EIDs, IPsec, and HostNAT", in Proceedings 1152 of 41th IETF, Los Angeles, CA, 1153 URL http://www1.cs.columbia.edu/~smb/talks/hostnat.pdf, 1154 March 1998. 1156 Author's Address 1158 Robert Moskowitz 1159 ICSA labs, An Independent Division of Verizon Business 1160 1000 Bent Creek Blvd, Suite 200 1161 Mechanicsburg, PA 1162 USA 1164 Email: robert.moskowitz@icsalabs.com