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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Moskowitz, Ed. 3 Internet-Draft Verizon 4 Obsoletes: 4423 (if approved) M. Komu 5 Intended status: Informational Aalto 6 Expires: October 26, 2014 April 24, 2014 8 Host Identity Protocol Architecture 9 draft-ietf-hip-rfc4423-bis-08 11 Abstract 13 This memo describes a new namespace, the Host Identity namespace, and 14 a new protocol layer, the Host Identity Protocol, between the 15 internetworking and transport layers. Herein are presented the 16 basics of the current namespaces, their strengths and weaknesses, and 17 how a new namespace will add completeness to them. The roles of this 18 new namespace in the protocols are defined. 20 This document obsoletes RFC 4423 and addresses the concerns raised by 21 the IESG, particularly that of crypto agility. It incorporates 22 lessons learned from the implementations of RFC 5201 and goes further 23 to explain how HIP works as a secure signaling channel. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on October 26, 2014. 42 Copyright Notice 44 Copyright (c) 2014 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 This document may contain material from IETF Documents or IETF 58 Contributions published or made publicly available before November 59 10, 2008. The person(s) controlling the copyright in some of this 60 material may not have granted the IETF Trust the right to allow 61 modifications of such material outside the IETF Standards Process. 62 Without obtaining an adequate license from the person(s) controlling 63 the copyright in such materials, this document may not be modified 64 outside the IETF Standards Process, and derivative works of it may 65 not be created outside the IETF Standards Process, except to format 66 it for publication as an RFC or to translate it into languages other 67 than English. 69 Table of Contents 71 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 72 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 73 2.1. Terms common to other documents . . . . . . . . . . . . . . 4 74 2.2. Terms specific to this and other HIP documents . . . . . . 5 75 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . 6 76 3.1. A desire for a namespace for computing platforms . . . . . 6 77 4. Host Identity namespace . . . . . . . . . . . . . . . . . . . 8 78 4.1. Host Identifiers . . . . . . . . . . . . . . . . . . . . . 9 79 4.2. Host Identity Hash (HIH) . . . . . . . . . . . . . . . . . 10 80 4.3. Host Identity Tag (HIT) . . . . . . . . . . . . . . . . . . 10 81 4.4. Local Scope Identifier (LSI) . . . . . . . . . . . . . . . 11 82 4.5. Storing Host Identifiers in directories . . . . . . . . . . 12 83 5. New stack architecture . . . . . . . . . . . . . . . . . . . 12 84 5.1. On the multiplicity of identities . . . . . . . . . . . . . 13 85 6. Control plane . . . . . . . . . . . . . . . . . . . . . . . . 14 86 6.1. Base exchange . . . . . . . . . . . . . . . . . . . . . . . 14 87 6.2. End-host mobility and multi-homing . . . . . . . . . . . . 15 88 6.3. Rendezvous mechanism . . . . . . . . . . . . . . . . . . . 16 89 6.4. Relay mechanism . . . . . . . . . . . . . . . . . . . . . . 16 90 6.5. Termination of the control plane . . . . . . . . . . . . . 16 91 7. Data plane . . . . . . . . . . . . . . . . . . . . . . . . . 16 92 8. HIP and NATs . . . . . . . . . . . . . . . . . . . . . . . . 17 93 8.1. HIP and Upper-layer checksums . . . . . . . . . . . . . . . 18 94 9. Multicast . . . . . . . . . . . . . . . . . . . . . . . . . . 18 95 10. HIP policies . . . . . . . . . . . . . . . . . . . . . . . . 18 96 11. Design considerations . . . . . . . . . . . . . . . . . . . . 19 97 11.1. Benefits of HIP . . . . . . . . . . . . . . . . . . . . . 19 98 11.2. Drawbacks of HIP . . . . . . . . . . . . . . . . . . . . . 22 99 11.3. Deployment and adoption considerations . . . . . . . . . . 23 100 11.3.1. Deployment analysis . . . . . . . . . . . . . . . . . . 23 101 11.3.2. HIP in 802.15.4 networks . . . . . . . . . . . . . . . . 24 102 11.4. Answers to NSRG questions . . . . . . . . . . . . . . . . 25 103 12. Security considerations . . . . . . . . . . . . . . . . . . . 27 104 12.1. MiTM Attacks . . . . . . . . . . . . . . . . . . . . . . . 27 105 12.2. Protection against flooding attacks . . . . . . . . . . . 28 106 12.3. HITs used in ACLs . . . . . . . . . . . . . . . . . . . . 29 107 12.4. Alternative HI considerations . . . . . . . . . . . . . . 30 108 13. IANA considerations . . . . . . . . . . . . . . . . . . . . . 31 109 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 31 110 15. Changes from RFC 4423 . . . . . . . . . . . . . . . . . . . . 31 111 16. References . . . . . . . . . . . . . . . . . . . . . . . . . 31 112 16.1. Normative References . . . . . . . . . . . . . . . . . . . 32 113 16.2. Informative references . . . . . . . . . . . . . . . . . . 33 114 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39 116 1. Introduction 118 The Internet has two important global namespaces: Internet Protocol 119 (IP) addresses and Domain Name Service (DNS) names. These two 120 namespaces have a set of features and abstractions that have powered 121 the Internet to what it is today. They also have a number of 122 weaknesses. Basically, since they are all we have, we try and do too 123 much with them. Semantic overloading and functionality extensions 124 have greatly complicated these namespaces. 126 The proposed Host Identity namespace fills an important gap between 127 the IP and DNS namespaces. A Host Identity conceptually refers to a 128 computing platform, and there may be multiple such Host Identities 129 per computing platform (because the platform may wish to present a 130 different identity to different communicating peers). The Host 131 Identity namespace consists of Host Identifiers (HI). There is 132 exactly one Host Identifier for each Host Identity (although there 133 may be transient periods of time such as key replacement when more 134 than one identifier may be active). While this text later talks 135 about non-cryptographic Host Identifiers, the architecture focuses on 136 the case in which Host Identifiers are cryptographic in nature. 137 Specifically, the Host Identifier is the public key of an asymmetric 138 key-pair. Each Host Identity uniquely identifies a single host, 139 i.e., no two hosts have the same Host Identity. If two or more 140 computing platforms have the same Host Identifier, then they are 141 instantiating a distributed host. The Host Identifier can either be 142 public (e.g. published in the DNS), or unpublished. Client systems 143 will tend to have both public and unpublished Host Identifiers. 145 There is a subtle but important difference between Host Identities 146 and Host Identifiers. An Identity refers to the abstract entity that 147 is identified. An Identifier, on the other hand, refers to the 148 concrete bit pattern that is used in the identification process. 150 Although the Host Identifiers could be used in many authentication 151 systems, such as IKEv2 [RFC4306], the presented architecture 152 introduces a new protocol, called the Host Identity Protocol (HIP), 153 and a cryptographic exchange, called the HIP base exchange; see also 154 Section 6. HIP provides for limited forms of trust between systems, 155 enhance mobility, multi-homing and dynamic IP renumbering, aid in 156 protocol translation / transition, and reduce certain types of 157 denial-of-service (DoS) attacks. 159 When HIP is used, the actual payload traffic between two HIP hosts is 160 typically, but not necessarily, protected with ESP 161 [I-D.ietf-hip-rfc5202-bis]. The Host Identities are used to create 162 the needed ESP Security Associations (SAs) and to authenticate the 163 hosts. When ESP is used, the actual payload IP packets do not differ 164 in any way from standard ESP protected IP packets. 166 Much has been learned about HIP [RFC6538] since [RFC4423] was 167 published. This document expands Host Identities beyond use to 168 enable IP connectivity and security to general interhost secure 169 signalling at any protocol layer. The signal may establish a 170 security association between the hosts, or simply pass information 171 within the channel. 173 2. Terminology 175 2.1. Terms common to other documents 177 +-------------+-----------------------------------------------------+ 178 | Term | Explanation | 179 +-------------+-----------------------------------------------------+ 180 | Public key | The public key of an asymmetric cryptographic key | 181 | | pair. Used as a publicly known identifier for | 182 | | cryptographic identity authentication. Public is a | 183 | | a relative term here, ranging from "known to peers | 184 | | only" to "known to the world." | 185 | Private key | The private or secret key of an asymmetric | 186 | | cryptographic key pair. Assumed to be known only | 187 | | to the party identified by the corresponding public | 188 | | key. Used by the identified party to authenticate | 189 | | its identity to other parties. | 190 | Public key | An asymmetric cryptographic key pair consisting of | 191 | pair | public and private keys. For example, Rivest- | 192 | | Shamir-Adelman (RSA), Digital Signature Algorithm | 193 | | (DSA) and Elliptic Curve DSA (ECDSA) key pairs are | 194 | | such key pairs. | 195 | End-point | A communicating entity. For historical reasons, | 196 | | the term 'computing platform' is used in this | 197 | | document as a (rough) synonym for end-point. | 198 +-------------+-----------------------------------------------------+ 200 2.2. Terms specific to this and other HIP documents 202 It should be noted that many of the terms defined herein are 203 tautologous, self-referential or defined through circular reference 204 to other terms. This is due to the succinct nature of the 205 definitions. See the text elsewhere in this document and in RFC 5201 206 [I-D.ietf-hip-rfc5201-bis] for more elaborate explanations. 208 +-------------------+-----------------------------------------------+ 209 | Term | Explanation | 210 +-------------------+-----------------------------------------------+ 211 | Computing | An entity capable of communicating and | 212 | platform | computing, for example, a computer. See the | 213 | | definition of 'End-point', above. | 214 | HIP base exchange | A cryptographic protocol; see also Section 6. | 215 | HIP packet | An IP packet that carries a 'Host Identity | 216 | | Protocol' message. | 217 | Host Identity | An abstract concept assigned to a 'computing | 218 | | platform'. See 'Host Identifier', below. | 219 | Host Identity | A name space formed by all possible Host | 220 | namespace | Identifiers. | 221 | Host Identity | A protocol used to carry and authenticate | 222 | Protocol | Host Identifiers and other information. | 223 | Host Identity | The cryptographic hash used in creating the | 224 | Hash | Host Identity Tag from the Host Identity. | 225 | Host Identity Tag | A 128-bit datum created by taking a | 226 | | cryptographic hash over a Host Identifier | 227 | | plus bits to identify which hash used. | 228 | Host Identifier | A public key used as a name for a Host | 229 | | Identity. | 230 | Local Scope | A 32-bit datum denoting a Host Identity. | 231 | Identifier | | 232 | Public Host | A published or publicly known Host Identifier | 233 | Identifier and | used as a public name for a Host Identity, | 234 | Identity | and the corresponding Identity. | 235 | Unpublished Host | A Host Identifier that is not placed in any | 236 | Identifier and | public directory, and the corresponding Host | 237 | Identity | Identity. Unpublished Host Identities are | 238 | | typically short lived in nature, being often | 239 | | replaced and possibly used just once. | 240 | Rendezvous | A mechanism used to locate mobile hosts based | 241 | Mechanism | on their HIT. | 242 +-------------------+-----------------------------------------------+ 244 3. Background 246 The Internet is built from three principal components: computing 247 platforms (end-points), packet transport (i.e., internetworking) 248 infrastructure, and services (applications). The Internet exists to 249 service two principal components: people and robotic services 250 (silicon-based people, if you will). All these components need to be 251 named in order to interact in a scalable manner. Here we concentrate 252 on naming computing platforms and packet transport elements. 254 There are two principal namespaces in use in the Internet for these 255 components: IP addresses, and Domain Names. Domain Names provide 256 hierarchically assigned names for some computing platforms and some 257 services. Each hierarchy is delegated from the level above; there is 258 no anonymity in Domain Names. Email, HTTP, and SIP addresses all 259 reference Domain Names. 261 The IP addressing namespace has been overloaded to name both 262 interfaces (at layer-3) and endpoints (for the endpoint-specific part 263 of layer-3, and for layer-4). In their role as interface names, IP 264 addresses are sometimes called "locators" and serve as an endpoint 265 within a routing topology. 267 IP addresses are numbers that name networking interfaces, and 268 typically only when the interface is connected to the network. 269 Originally, IP addresses had long-term significance. Today, the vast 270 number of interfaces use ephemeral and/or non-unique IP addresses. 271 That is, every time an interface is connected to the network, it is 272 assigned an IP address. 274 In the current Internet, the transport layers are coupled to the IP 275 addresses. Neither can evolve separately from the other. IPng 276 deliberations were strongly shaped by the decision that a 277 corresponding TCPng would not be created. 279 There are three critical deficiencies with the current namespaces. 280 Firstly, dynamic readdressing cannot be directly managed. Secondly, 281 confidentiality is not provided in a consistent, trustable manner. 282 Finally, authentication for systems and datagrams is not provided. 283 All of these deficiencies arise because computing platforms are not 284 well named with the current namespaces. 286 3.1. A desire for a namespace for computing platforms 287 An independent namespace for computing platforms could be used in 288 end-to-end operations independent of the evolution of the 289 internetworking layer and across the many internetworking layers. 290 This could support rapid readdressing of the internetworking layer 291 because of mobility, rehoming, or renumbering. 293 If the namespace for computing platforms is based on public-key 294 cryptography, it can also provide authentication services. If this 295 namespace is locally created without requiring registration, it can 296 provide anonymity. 298 Such a namespace (for computing platforms) and the names in it should 299 have the following characteristics: 301 o The namespace should be applied to the IP 'kernel' or stack. The 302 IP stack is the 'component' between applications and the packet 303 transport infrastructure. 305 o The namespace should fully decouple the internetworking layer from 306 the higher layers. The names should replace all occurrences of IP 307 addresses within applications (like in the Transport Control 308 Block, TCB). This replacement can be handled transparently for 309 legacy applications as the LSIs and HITs are compatible with IPv4 310 and IPv6 addresses [RFC5338]. However, HIP-aware applications 311 require some modifications from the developers, who may employ 312 networking API extensions for HIP [RFC6317]. 314 o The introduction of the namespace should not mandate any 315 administrative infrastructure. Deployment must come from the 316 bottom up, in a pairwise deployment. 318 o The names should have a fixed length representation, for easy 319 inclusion in datagram headers and existing programming interfaces 320 (e.g the TCB). 322 o Using the namespace should be affordable when used in protocols. 323 This is primarily a packet size issue. There is also a 324 computational concern in affordability. 326 o Name collisions should be avoided as much as possible. The 327 mathematics of the birthday paradox can be used to estimate the 328 chance of a collision in a given population and hash space. In 329 general, for a random hash space of size n bits, we would expect 330 to obtain a collision after approximately 1.2*sqrt(2**n) hashes 331 were obtained. For 64 bits, this number is roughly 4 billion. A 332 hash size of 64 bits may be too small to avoid collisions in a 333 large population; for example, there is a 1% chance of collision 334 in a population of 640M. For 100 bits (or more), we would not 335 expect a collision until approximately 2**50 (1 quadrillion) 336 hashes were generated. 338 o The names should have a localized abstraction so that they can be 339 used in existing protocols and APIs. 341 o It must be possible to create names locally. When such names are 342 not published, this can provide anonymity at the cost of making 343 resolvability very difficult. 345 o The namespace should provide authentication services. 347 o The names should be long lived, but replaceable at any time. This 348 impacts access control lists; short lifetimes will tend to result 349 in tedious list maintenance or require a namespace infrastructure 350 for central control of access lists. 352 In this document, a new namespace approaching these ideas is called 353 the Host Identity namespace. Using Host Identities requires its own 354 protocol layer, the Host Identity Protocol, between the 355 internetworking and transport layers. The names are based on public- 356 key cryptography to supply authentication services. Properly 357 designed, it can deliver all of the above stated requirements. 359 4. Host Identity namespace 361 A name in the Host Identity namespace, a Host Identifier (HI), 362 represents a statistically globally unique name for naming any system 363 with an IP stack. This identity is normally associated with, but not 364 limited to, an IP stack. A system can have multiple identities, some 365 'well known', some unpublished or 'anonymous'. A system may self- 366 assert its own identity, or may use a third-party authenticator like 367 DNSSEC [RFC2535], PGP, or X.509 to 'notarize' the identity assertion 368 to another namespace. It is expected that the Host Identifiers will 369 initially be authenticated with DNSSEC and that all implementations 370 will support DNSSEC as a minimal baseline. 372 In theory, any name that can claim to be 'statistically globally 373 unique' may serve as a Host Identifier. In the HIP architecture, the 374 public key of a private-public key pair has been chosen as the Host 375 Identifier because it can be self managed and it is computationally 376 difficult to forge. As specified in the Host Identity Protocol 377 [I-D.ietf-hip-rfc5201-bis] specification, a public-key-based HI can 378 authenticate the HIP packets and protect them from man-in-the-middle 379 attacks. Since authenticated datagrams are mandatory to provide much 380 of HIP's denial-of-service protection, the Diffie-Hellman exchange in 381 HIP base exchange has to be authenticated. Thus, only public-key HI 382 and authenticated HIP messages are supported in practice. 384 In this document, the non-cryptographic forms of HI and HIP are 385 presented to complete the theory of HI, but they should not be 386 implemented as they could produce worse denial-of-service attacks 387 than the Internet has without Host Identity. There has been past 388 research in challenge puzzles to use non-cryptographic HI, for Radio 389 Frequency IDentification (RFID), in an HIP exchange tailored to the 390 workings of such challenges (as described further in [urien-rfid] and 391 [urien-rfid-draft]). 393 4.1. Host Identifiers 395 Host Identity adds two main features to Internet protocols. The 396 first is a decoupling of the internetworking and transport layers; 397 see Section 5. This decoupling will allow for independent evolution 398 of the two layers. Additionally, it can provide end-to-end services 399 over multiple internetworking realms. The second feature is host 400 authentication. Because the Host Identifier is a public key, this 401 key can be used for authentication in security protocols like ESP. 403 The only completely defined structure of the Host Identity is that of 404 a public/private key pair. In this case, the Host Identity is 405 referred to by its public component, the public key. Thus, the name 406 representing a Host Identity in the Host Identity namespace, i.e., 407 the Host Identifier, is the public key. In a way, the possession of 408 the private key defines the Identity itself. If the private key is 409 possessed by more than one node, the Identity can be considered to be 410 a distributed one. 412 Architecturally, any other Internet naming convention might form a 413 usable base for Host Identifiers. However, non-cryptographic names 414 should only be used in situations of high trust - low risk. That is 415 any place where host authentication is not needed (no risk of host 416 spoofing) and no use of ESP. However, at least for interconnected 417 networks spanning several operational domains, the set of 418 environments where the risk of host spoofing allowed by non- 419 cryptographic Host Identifiers is acceptable is the null set. Hence, 420 the current HIP documents do not specify how to use any other types 421 of Host Identifiers but public keys. For instance, Back-to-My-Mac 422 [RFC6281] from Apple comes pretty close to the functionality of HIP, 423 but unlike HIP, it is based on non-cryptographic identifiers. 425 The actual Host Identifiers are never directly used at the transport 426 or network layers. The corresponding Host Identifiers (public keys) 427 may be stored in various DNS or other directories as identified 428 elsewhere in this document, and they are passed in the HIP base 429 exchange. A Host Identity Tag (HIT) is used in other protocols to 430 represent the Host Identity. Another representation of the Host 431 Identities, the Local Scope Identifier (LSI), can also be used in 432 protocols and APIs. 434 4.2. Host Identity Hash (HIH) 436 The Host Identity Hash is the cryptographic hash algorithm used in 437 producing the HIT from the HI. It is also the hash used throughout 438 the HIP protocol for consistency and simplicity. It is possible to 439 for the two hosts in the HIP exchange to use different hash 440 algorithms. 442 Multiple HIHs within HIP are needed to address the moving target of 443 creation and eventual compromise of cryptographic hashes. This 444 significantly complicates HIP and offers an attacker an additional 445 downgrade attack that is mitigated in the HIP protocol 446 [I-D.ietf-hip-rfc5201-bis]. 448 4.3. Host Identity Tag (HIT) 450 A Host Identity Tag is a 128-bit representation for a Host Identity. 451 It is created from an HIH and other information, like an IPv6 prefix 452 and a hash identifier. There are two advantages of using the HIT 453 over using the Host Identifier in protocols. Firstly, its fixed 454 length makes for easier protocol coding and also better manages the 455 packet size cost of this technology. Secondly, it presents the 456 identity in a consistent format to the protocol independent of the 457 cryptographic algorithms used. 459 In essence, the HIT is a hash over the public key. As such, two 460 algorithms affect the generation of a HIT: the public-key algorithm 461 of the HI and the used HIH. The two algorithms are encoded in the 462 bit presentation of the HIT. As the two communicating parties may 463 support different algorithms, [I-D.ietf-hip-rfc5201-bis] defines the 464 minimum set for interoperability. For further interoperability, the 465 responder may store its keys in DNS records, and thus the initiator 466 may have to couple destination HITs with appropriate source HITs 467 according to matching HIH. 469 In the HIP packets, the HITs identify the sender and recipient of a 470 packet. Consequently, a HIT should be unique in the whole IP 471 universe as long as it is being used. In the extremely rare case of 472 a single HIT mapping to more than one Host Identity, the Host 473 Identifiers (public keys) will make the final difference. If there 474 is more than one public key for a given node, the HIT acts as a hint 475 for the correct public key to use. 477 4.4. Local Scope Identifier (LSI) 479 An LSI is a 32-bit localized representation for a Host Identity. The 480 purpose of an LSI is to facilitate using Host Identities in existing 481 APIs for IPv4-based applications. Besides facilitating HIP-based 482 connectivity for legacy IPv4 applications, the LSIs are beneficial in 483 two other scenarios [RFC6538]. 485 In the first scenario, two IPv4-only applications are residing on two 486 separate hosts connected by IPv6-only network. With HIP-based 487 connectivity, the two applications are able to communicate despite of 488 the mismatch in the protocol families of the applications and the 489 underlying network. The reason is that the HIP layer translates the 490 LSIs originating from the upper layers into routable IPv6 locators 491 before delivering the packets on the wire. 493 The second scenario is the same as the first one, but with the 494 difference that one of the applications supports only IPv6. Now two 495 obstacles hinder the communication between the application: the 496 addressing families of the two applications differ, and the 497 application residing at the IPv4-only side is again unable to 498 communicate because of the mismatch between addressing families of 499 the application (IPv4) and network (IPv6). With HIP-based 500 connectivity for applications, this scenario works; the HIP layer can 501 choose whether to translate the locator of an incoming packet into an 502 LSI or HIT. 504 Effectively, LSIs improve IPv6 interoperability at the network layer 505 as described in the first scenario and at the application layer as 506 depicted in the second example. The interoperability mechanism 507 should not be used to avoid transition to IPv6; the authors firmly 508 believe in IPv6 adoption and encourage developers to port existing 509 IPv4-only applications to use IPv6. However, some proprietary, 510 closed-source, IPv4-only applications may never see the daylight of 511 IPv6, and the LSI mechanism is suitable for extending the lifetime of 512 such applications even in IPv6-only networks. 514 The main disadvantage of an LSI is its local scope. Applications may 515 violate layering principles and pass LSIs to each other in 516 application-layer protocols. As the LSIs are valid only in the 517 context of the local host, they may represent an entirely different 518 host when passed to another host. However, it should be emphasized 519 here that the LSI concept is effectively a host-based NAT and does 520 not introduce any more issues than the prevalent middlebox based NATs 521 for IPv4. In other words, the applications violating layering 522 principles are already broken by the NAT boxes that are ubiquitously 523 deployed. 525 4.5. Storing Host Identifiers in directories 527 The public Host Identifiers should be stored in DNS; the unpublished 528 Host Identifiers should not be stored anywhere (besides the 529 communicating hosts themselves). The (public) HI along with the 530 supported HIHs are stored in a new RR type. This RR type is defined 531 in HIP DNS Extension [I-D.ietf-hip-rfc5205-bis]. 533 Alternatively, or in addition to storing Host Identifiers in the DNS, 534 they may be stored in various other directories. For instance, a 535 directory based on the Lightweight Directory Access Protocol (LDAP) 536 or a Public Key Infrastructure (PKI) [I-D.ietf-hip-rfc6253-bis] may 537 be used. Alternatively, Distributed Hash Tables (DHTs) [RFC6537] 538 have successfully been utilized [RFC6538]. Such a practice may allow 539 them to be used for purposes other than pure host identification. 541 Some types of applications may cache and use Host Identifiers 542 directly, while others may indirectly discover them through symbolic 543 host name (such as FQDN) look up from a directory. Even though Host 544 Identities can have a substantially longer lifetime associated with 545 them than routable IP addresses, directories may be a better approach 546 to manage the lifespan of Host Identities. For example, an LDAP- 547 based directory or DHT can be used for locally published identities 548 whereas DNS can be more suitable for public advertisement. 550 5. New stack architecture 552 One way to characterize Host Identity is to compare the proposed new 553 architecture with the current one. Using the terminology from the 554 IRTF Name Space Research Group Report [nsrg-report] and, e.g., the 555 unpublished Internet-Draft Endpoints and Endpoint Names 556 [chiappa-endpoints], the IP addresses currently embody the dual role 557 of locators and end-point identifiers. That is, each IP address 558 names a topological location in the Internet, thereby acting as a 559 routing direction vector, or locator. At the same time, the IP 560 address names the physical network interface currently located at the 561 point-of-attachment, thereby acting as a end-point name. 563 In the HIP architecture, the end-point names and locators are 564 separated from each other. IP addresses continue to act as locators. 565 The Host Identifiers take the role of end-point identifiers. It is 566 important to understand that the end-point names based on Host 567 Identities are slightly different from interface names; a Host 568 Identity can be simultaneously reachable through several interfaces. 570 The difference between the bindings of the logical entities are 571 illustrated in Figure 1. Left side illustrates the current TCP/IP 572 architecture and right side the HIP-based architecture. 574 Transport ---- Socket Transport ------ Socket 575 association | association | 576 | | 577 | | 578 | | 579 End-point | End-point --- Host Identity 580 \ | | 581 \ | | 582 \ | | 583 \ | | 584 Location --- IP address Location --- IP address 586 Figure 1 588 Architecturally, HIP provides for a different binding of transport- 589 layer protocols. That is, the transport-layer associations, i.e., 590 TCP connections and UDP associations, are no longer bound to IP 591 addresses but rather to Host Identities. In practice, the Host 592 Identities are exposed as LSIs and HITs for legacy applications and 593 the transport layer to facilitate backward compatibility with 594 existing networking APIs and stacks. 596 5.1. On the multiplicity of identities 598 A host may have multiple identities both at the client and server 599 side. This raises some additional concerns that are addressed in 600 this section. 602 For security reasons, it may be a bad idea to duplicate the same Host 603 Identity on multiple hosts because the compromise of a single host 604 taints the identities of the other hosts. Management of machines 605 with identical Host Identities may also present other challenges and, 606 therefore, it is advisable to have a unique identity for each host. 608 Instead of duplicating identities, HIP opportunistic mode can be 609 employed, where the initiator leaves out the identifier of the 610 responder when initiating the key exchange and learns it upon the 611 completion of the exchange. The tradeoffs are related to lowered 612 security guarantees, but a benefit of the approach is to avoid 613 publishing of Host Identifiers in any directories [komu-leap]. The 614 approach could also be used for load balancing purposes at the HIP 615 layer because the identity of the responder can be decided 616 dynamically during the key exchange. Thus, the approach has the 617 potential to be used as a HIP-layer "anycast", either directly 618 between two hosts or indirectly through the rendezvous service 619 [komu-diss]. 621 At the client side, a host may have multiple Host Identities, for 622 instance, for privacy purposes. Another reason can be that the 623 person utilizing the host employs different identities for different 624 administrative domains as an extra security measure. If a HIP-aware 625 middlebox, such as a HIP-based firewall, is on the path between the 626 client and server, the user or the underlying system should carefully 627 choose the correct identity to avoid the firewall to unnecessarily 628 drop HIP-base connectivity [komu-diss]. 630 Similarly, a server may have multiple Host Identities. For instance, 631 a single web server may serve multiple different administrative 632 domains. Typically, the distinction is accomplished based on the DNS 633 name, but also the Host Identity could be used for this purpose. 634 However, a more compelling reason to employ multiple identities are 635 HIP-aware firewalls that are unable see the HTTP traffic inside the 636 encrypted IPsec tunnel. In such a case, each service could be 637 configured with a separate identity, thus allowing the firewall to 638 segregate the different services of the single web server from each 639 other [lindqvist-enterprise]. 641 6. Control plane 643 HIP decouples control and data plane from each other. Two end-hosts 644 initialize the control plane using a key exchange procedure called 645 the base exchange. The procedure can be assisted by new 646 infrastructural intermediaries called rendezvous or relay servers. 647 In the event of IP address changes, the end-hosts sustain control 648 plane connectivity with mobility and multihoming extensions. 649 Eventually, the end-hosts terminate the control plane and remove the 650 associated state. 652 6.1. Base exchange 654 The base exchange is a key exchange procedure that authenticates the 655 initiator and responder to each other using their public keys. 656 Typically, the initiator is the client-side host and the responder is 657 the server-side host. The roles are used by the state machine of a 658 HIP implementation, but discarded upon successful completion. 660 The exchange consists of four messages during which the hosts also 661 create symmetric keys to protect the control plane with Hash-based 662 message authentication codes (HMACs). The keys can be also used to 663 protect the data plane, and IPsec ESP [I-D.ietf-hip-rfc5202-bis] is 664 typically used as the data-plane protocol, albeit HIP can also 665 accommodate others. Both the control and data plane are terminated 666 using a closing procedure consisting of two messages. 668 In addition, the base exchange also includes a computational puzzle 669 [I-D.ietf-hip-rfc5201-bis] that the initiator must solve. The 670 responder chooses the difficulty of the puzzle which permits the 671 responder to delay new incoming initiators according to local 672 policies, for instance, when the responder is under heavy load. The 673 puzzle can offer some resiliency against DoS attacks because the 674 design of the puzzle mechanism allows the responder to remain 675 stateless until the very end of the base exchange [aura-dos]. HIP 676 puzzles have also been studied under steady-state DDoS attacks 677 [beal-dos], on multiple adversary models with varying puzzle 678 difficulties [tritilanunt-dos] and with ephemeral Host Identities 679 [komu-mitigation]. 681 6.2. End-host mobility and multi-homing 683 HIP decouples the transport from the internetworking layer, and binds 684 the transport associations to the Host Identities (actually through 685 either the HIT or LSI). After the initial key exchange, the HIP 686 layer maintains transport-layer connectivity and data flows using its 687 mobility [I-D.ietf-hip-rfc5206-bis] and multihoming 688 [I-D.ietf-hip-multihoming] extensions. Consequently, HIP can provide 689 for a degree of internetworking mobility and multi-homing at a low 690 infrastructure cost. HIP mobility includes IP address changes (via 691 any method) to either party. Thus, a system is considered mobile if 692 its IP address can change dynamically for any reason like PPP, DHCP, 693 IPv6 prefix reassignments, or a NAT device remapping its translation. 694 Likewise, a system is considered multi-homed if it has more than one 695 globally routable IP address at the same time. HIP links IP 696 addresses together, when multiple IP addresses correspond to the same 697 Host Identity. If one address becomes unusable, or a more preferred 698 address becomes available, existing transport associations can easily 699 be moved to another address. 701 When a node moves while communication is already on-going, address 702 changes are rather straightforward. The peer of the mobile node can 703 just accept a HIP or an integrity protected ESP packet from any 704 address and ignore the source address. However, as discussed in 705 Section 12.2 below, a mobile node must send a HIP UPDATE packet to 706 inform the peer of the new address(es), and the peer must verify that 707 the mobile node is reachable through these addresses. This is 708 especially helpful for those situations where the peer node is 709 sending data periodically to the mobile node (that is, re-starting a 710 connection after the initial connection). 712 6.3. Rendezvous mechanism 714 Establishing a contact to a mobile, moving node is slightly more 715 involved. In order to start the HIP exchange, the initiator node has 716 to know how to reach the mobile node. For instance, the mobile node 717 can employ Dynamic DNS [RFC2136] to update its reachability 718 information in the DNS. To avoid the dependency to DNS, HIP provides 719 its own HIP-specific alternative: the HIP rendezvous mechanism as 720 defined in HIP Rendezvous specifications [I-D.ietf-hip-rfc5204-bis]. 722 Using the HIP rendezvous extensions, the mobile node keeps the 723 rendezvous infrastructure continuously updated with its current IP 724 address(es). The mobile nodes trusts the rendezvous mechanism in 725 order to properly maintain their HIT and IP address mappings. 727 The rendezvous mechanism is especially useful in scenarios where both 728 of the nodes are expected to change their address at the same time. 729 In such a case, the HIP UPDATE packets will cross each other in the 730 network and never reach the peer node. 732 6.4. Relay mechanism 734 The HIP relay mechanism [I-D.ietf-hip-native-nat-traversal] is an 735 alternative to the HIP rendezvous mechanism. The HIP relay mechanism 736 is more suitable for IPv4 networks with NATs because a HIP relay can 737 forward all control and data plane communications in order to 738 guarantee successful NAT traversal. 740 6.5. Termination of the control plane 742 The control plane between two hosts is terminated using a secure two 743 message exchange as specified in base exchange specification 744 [I-D.ietf-hip-rfc5201-bis]. The related state (i.e. host 745 associations) should be removed upon successful termination. 747 7. Data plane 749 The encapsulation format for the data plane used for carrying the 750 application-layer traffic can be dynamically negotiated during the 751 key exchange. For instance, HICCUPS extensions [RFC6078] define one 752 way to transport application-layer datagrams directly over the HIP 753 control plane, protected by asymmetric key cryptography. Also, S-RTP 754 has been considered as the data encapsulation protocol [hip-srtp]. 755 However, the most widely implemented method is the Encapsulated 756 Security Payload (ESP) [I-D.ietf-hip-rfc5202-bis] that is protected 757 by symmetric keys derived during the key exchange. ESP Security 758 Associations (SAs) offer both confidentiality and integrity 759 protection, of which the former can be disabled during the key 760 exchange. In the future, other ways of transporting application- 761 layer data may be defined. 763 The ESP SAs are established and terminated between the initiator and 764 the responder hosts. Usually, the hosts create at least two SAs, one 765 in each direction (initiator-to-responder SA and responder-to- 766 initiator SA). If the IP addresses of either host changes, the HIP 767 mobility extensions can be used to re-negotiate the corresponding 768 SAs. 770 On the wire, the difference in the use of identifiers between the HIP 771 control and data plane is that the HITs are included in all control 772 packets, but not in the data plane when ESP is employed. Instead, 773 the ESP employs SPI numbers that act as compressed HITs. Any HIP- 774 aware middlebox (for instance, a HIP-aware firewall) interested in 775 the ESP based data plane should keep track between the control and 776 data plane identifiers in order to associate them with each other. 778 Since HIP does not negotiate any SA lifetimes, all lifetimes are 779 subject to local policy. The only lifetimes a HIP implementation 780 must support are sequence number rollover (for replay protection), 781 and SA timeout. An SA times out if no packets are received using 782 that SA. Implementations may support lifetimes for the various ESP 783 transforms and other data-plane protocols. 785 8. HIP and NATs 787 Passing packets between different IP addressing realms requires 788 changing IP addresses in the packet header. This may occur, for 789 example, when a packet is passed between the public Internet and a 790 private address space, or between IPv4 and IPv6 networks. The 791 address translation is usually implemented as Network Address 792 Translation (NAT) [RFC3022] or NAT Protocol translation (NAT-PT) 793 [RFC2766]. 795 In a network environment where identification is based on the IP 796 addresses, identifying the communicating nodes is difficult when NATs 797 are employed because private address spaces are overlapping. In 798 other words, two hosts cannot be distinguished from each other solely 799 based on their IP address. With HIP, the transport-layer end-points 800 (i.e. applications) are bound to unique Host Identities rather than 801 overlapping private addresses. This allows two end-points to 802 distinguish one other even when they are located in different private 803 address realms. Thus, the IP addresses are used only for routing 804 purposes and can be changed freely by NATs when a packet between two 805 HIP capable hosts traverses through multiple private address realms. 807 NAT traversal extensions for HIP [I-D.ietf-hip-native-nat-traversal] 808 can be used to realize the actual end-to-end connectivity through NAT 809 devices. To support basic backward compatibility with legacy NATs, 810 the extensions encapsulate both HIP control and data plane in UDP. 811 The extensions define mechanisms for forwarding the two planes 812 through an intermediary host called HIP relay and procedures to 813 establish direct end-to-end connectivity by penetrating NATs. 814 Besides this "native" NAT traversal mode for HIP, other NAT traversal 815 mechanisms have been successfully utilized, such as Teredo 816 [varjonen-split]. 818 Besides legacy NATs, a HIP-aware NAT has been designed and 819 implemented [ylitalo-spinat]. For a HIP-based flow, a HIP-aware NAT 820 or NAT-PT system tracks the mapping of HITs, and the corresponding 821 ESP SPIs, to an IP address. The NAT system has to learn mappings 822 both from HITs and from SPIs to IP addresses. Many HITs (and SPIs) 823 can map to a single IP address on a NAT, simplifying connections on 824 address poor NAT interfaces. The NAT can gain much of its knowledge 825 from the HIP packets themselves; however, some NAT configuration may 826 be necessary. 828 8.1. HIP and Upper-layer checksums 830 There is no way for a host to know if any of the IP addresses in an 831 IP header are the addresses used to calculate the TCP checksum. That 832 is, it is not feasible to calculate the TCP checksum using the actual 833 IP addresses in the pseudo header; the addresses received in the 834 incoming packet are not necessarily the same as they were on the 835 sending host. Furthermore, it is not possible to recompute the 836 upper-layer checksums in the NAT/NAT-PT system, since the traffic is 837 ESP protected. Consequently, the TCP and UDP checksums are 838 calculated using the HITs in the place of the IP addresses in the 839 pseudo header. Furthermore, only the IPv6 pseudo header format is 840 used. This provides for IPv4 / IPv6 protocol translation. 842 9. Multicast 844 A number of studies investigating HIP-based multicast have been 845 published (including [shields-hip], [xueyong-hip], [xueyong-hip], 846 [amir-hip], [kovacshazi-host] and [xueyong-secure]). In particular, 847 so-called Bloom filters, that allow compressing of multiple labels 848 into small data structures, may be a promising way forward 849 [sarela-bloom]. However, the different schemes have not been adopted 850 by the HIP working group (nor the HIP research group in IRTF), so the 851 details are not further elaborated here. 853 10. HIP policies 854 There are a number of variables that influence the HIP exchange that 855 each host must support. All HIP implementations should support at 856 least 2 HIs, one to publish in DNS or similar directory service and 857 an unpublished one for anonymous usage. Although unpublished HIs 858 will be rarely used as responder HIs, they are likely to be common 859 for initiators. Support for multiple HIs is recommended. This 860 provides new challenges for systems or users to decide which type of 861 HI to expose when they start a new session. 863 Opportunistic mode (where the initiator starts a HIP exchange without 864 prior knowledge of the responder's HI) presents a security tradeoff. 865 At the expense of being subject to MITM attacks, the opportunistic 866 mode allows the initiator to learn the identity of the responder 867 during communication rather than from an external directory. 868 Opportunistic mode can be used for registration to HIP-based services 869 [I-D.ietf-hip-rfc5203-bis] (i.e. utilized by HIP for its own internal 870 purposes) or by the application layer [komu-leap]. For security 871 reasons, especially the latter requires some involvement from the 872 user to accept the identity of the responder similar to how SSH 873 prompts the user when connecting to a server for the first time 874 [pham-leap]. In practice, this can be realized in end-host based 875 firewalls in the case of legacy applications [karvonen-usable] or 876 with native APIs for HIP APIs [RFC6317] in the case of HIP-aware 877 applications. 879 Many initiators would want to use a different HI for different 880 responders. The implementations should provide for a policy mapping 881 of initiator HITs to responder HITs. This policy should also include 882 preferred transforms and local lifetimes. 884 Responders would need a similar policy, describing the hosts allowed 885 to participate in HIP exchanges, and the preferred transforms and 886 local lifetimes. 888 11. Design considerations 890 11.1. Benefits of HIP 892 In the beginning, the network layer protocol (i.e., IP) had the 893 following four "classic" invariants: 895 1. Non-mutable: The address sent is the address received. 897 2. Non-mobile: The address doesn't change during the course of an 898 "association". 900 3. Reversible: A return header can always be formed by reversing the 901 source and destination addresses. 903 4. Omniscient: Each host knows what address a partner host can use 904 to send packets to it. 906 Actually, the fourth can be inferred from 1 and 3, but it is worth 907 mentioning explicitly for reasons that will be obvious soon if not 908 already. 910 In the current "post-classic" world, we are intentionally trying to 911 get rid of the second invariant (both for mobility and for multi- 912 homing), and we have been forced to give up the first and the fourth. 913 Realm Specific IP [RFC3102] is an attempt to reinstate the fourth 914 invariant without the first invariant. IPv6 is an attempt to 915 reinstate the first invariant. 917 Few client-side systems on the Internet have DNS names that are 918 meaningful. That is, if they have a Fully Qualified Domain Name 919 (FQDN), that name typically belongs to a NAT device or a dial-up 920 server, and does not really identify the system itself but its 921 current connectivity. FQDNs (and their extensions as email names) 922 are application-layer names; more frequently naming services than 923 particular systems. This is why many systems on the Internet are not 924 registered in the DNS; they do not have services of interest to other 925 Internet hosts. 927 DNS names are references to IP addresses. This only demonstrates the 928 interrelationship of the networking and application layers. DNS, as 929 the Internet's only deployed and distributed database, is also the 930 repository of other namespaces, due in part to DNSSEC and application 931 specific key records. Although each namespace can be stretched (IP 932 with v6, DNS with KEY records), neither can adequately provide for 933 host authentication or act as a separation between internetworking 934 and transport layers. 936 The Host Identity (HI) namespace fills an important gap between the 937 IP and DNS namespaces. An interesting thing about the HI is that it 938 actually allows a host to give up all but the 3rd network-layer 939 invariant. That is to say, as long as the source and destination 940 addresses in the network-layer protocol are reversible, HIP takes 941 care of host identification, and reversibility allows a local host to 942 receive a packet back from a remote host. The address changes 943 occurring during NAT transit (non-mutable) or host movement (non- 944 omniscient or non-mobile) can be managed by the HIP layer. 946 With the exception of High-Performance Computing applications, the 947 Sockets API is the most common way to develop network applications. 948 Applications use the Sockets API either directly or indirectly 949 through some libraries or frameworks. However, the Sockets API is 950 based on the assumption of static IP addresses, and DNS with its 951 lifetime values was invented at later stages during the evolution of 952 the Internet. Hence, the Sockets API does not deal with the lifetime 953 of addresses [RFC6250]. As the majority of the end-user equipment is 954 mobile today, their addresses are effectively ephemeral, but the 955 Sockets API still gives a fallacious illusion of persistent IP 956 addresses to the unwary developer. HIP can be used to solidify this 957 illusion because HIP provides persistent surrogate addresses to the 958 application layer in the form of LSIs and HITs. 960 The persistent identifiers as provided by HIP are useful in multiple 961 scenarios (see, e.g., [ylitalo-diss] or [komu-diss], for a more 962 elaborate discussion): 964 o When a mobile host moves physically between two different WLAN 965 networks and obtains a new address, an application using the 966 identifiers remains isolated regardless of the topology changes 967 while the underlying HIP layer re-establishes connectivity (i.e. a 968 horizontal handoff). 970 o Similarly, the application utilizing the identifiers remains again 971 unaware of the topological changes when the underlying host 972 equipped with WLAN and cellular network interfaces switches 973 between the two different access technologies (i.e. a vertical 974 handoff). 976 o Even when hosts are located in private address realms, 977 applications can uniquely distinguish different hosts from each 978 other based on their identifiers. In other words, it can be 979 stated that HIP improves Internet transparency for the application 980 layer [komu-diss]. 982 o Site renumbering events for services can occur due to corporate 983 mergers or acquisitions, or by changes in Internet Service 984 Provider. They can involve changing the entire network prefix of 985 an organization, which is problematic due to hard-coded addresses 986 in service configuration files or cached IP addresses at the 987 client side [RFC5887]. Considering such human errors, a site 988 employing location-independent identifiers as promoted by HIP may 989 experience less problems while renumbering their network. 991 o More agile IPv6 interoperability can be achieved, as discussed in 992 Section 4.4. IPv6-based applications can communicate using HITs 993 with IPv4-based applications that are using LSIs. Additionally, 994 the underlying network type (IPv4 or IPv6) becomes independent of 995 the addressing family of the application. 997 o HITs (or LSIs) can be used in IP-based access control lists as a 998 more secure replacement for IPv6 addresses. Besides security, HIT 999 based access control has two other benefits. First, the use of 1000 HITs can potentially halve the size of access control lists 1001 because separate rules for IPv4 are not needed [komu-diss]. 1002 Second, HIT-based configuration rules in HIP-aware middleboxes 1003 remain static and independent of topology changes, thus 1004 simplifying administrative efforts particularly for mobile 1005 environments. For instance, the benefits of HIT based access 1006 control have been harnessed in the case of HIP-aware firewalls, 1007 but can be utilized directly at the end-hosts as well [RFC6538]. 1009 While some of these benefits could be and have been redundantly 1010 implemented by individual applications, providing such generic 1011 functionality at the lower layers is useful because it reduces 1012 software development effort and networking software bugs (as the 1013 layer is tested with multiple applications). It also allows the 1014 developer to focus on building the application itself rather than 1015 delving into the intricacies of mobile networking, thus facilitating 1016 separation of concerns. 1018 HIP could also be realized by combining a number of different 1019 protocols, but the complexity of the resulting software may become 1020 substantially larger, and the interaction between multiple possibly 1021 layered protocols may have adverse effects on latency and throughput. 1022 It is also worth noting that virtually nothing prevents realizing the 1023 HIP architecture, for instance, as an application-layer library, 1024 which has been actually implemented in the past [xin-hip-lib]. 1025 However, the tradeoff in moving the HIP layer to the application 1026 layer is that legacy applications may not be supported. 1028 11.2. Drawbacks of HIP 1030 In computer science, many problems can be solved with an extra layer 1031 of indirection. However, the indirection always involves some costs 1032 as there is no such a thing as "free lunch". In the case of HIP, the 1033 main costs could be stated as follows: 1035 o In general, a new layer and a new namespace always involve some 1036 initial effort in terms of implementation, deployment and 1037 maintenance. Some education of developers and administrators may 1038 also be needed. However, the HIP community at the IETF has spent 1039 years in experimenting, exploring, testing, documenting and 1040 implementing HIP to ease the adoption costs. 1042 o HIP decouples identifier and locator roles of IP addresses. 1043 Consequently, a mapping mechanism is needed to associate them 1044 together. A failure to map a HIT to its corresponding locator may 1045 result in failed connectivity because a HIT is "flat" by its 1046 nature and cannot be looked up from the hierarchically organized 1047 DNS. HITs are flat by design due to a security tradeoff. The 1048 more bits are allocated for the hash in the HIT, the less likely 1049 there will be (malicious) collisions. 1051 o From performance viewpoint, HIP control and data plane processing 1052 introduces some overhead in terms of throughput and latency as 1053 elaborated below. 1055 The key exchange introduces some extra latency (two round trips) in 1056 the initial transport layer connection establishment between two 1057 hosts. With TCP, additional delay occurs if the underlying network 1058 stack implementation drops the triggering SYN packet during the key 1059 exchange. The same cost may also occur during HIP handoff 1060 procedures. However, subsequent TCP sessions using the same HIP 1061 association will not bear this cost (within the key lifetime). Both 1062 the key exchange and handoff penalties can be minimized by caching 1063 TCP packets. The latter case can further be optimized with TCP user 1064 timeout extensions [RFC5482] as described in further detail by 1065 Schuetz et al [schuetz-intermittent]. 1067 The most CPU-intensive operations involve the use of the asymmetric 1068 keys and Diffie-Hellman key derivation at the control plane, but this 1069 occurs only during the key exchange, its maintenance (handoffs, 1070 refreshing of key material) and tear down procedures of HIP 1071 associations. The data plane is typically implemented with ESP 1072 because it has a smaller overhead due to symmetric key encryption. 1073 Naturally, even ESP involves some overhead in terms of latency 1074 (processing costs) and throughput (tunneling) (see e.g. 1075 [ylitalo-diss] for a performance evaluation). 1077 11.3. Deployment and adoption considerations 1079 This section describes some deployment and adoption considerations 1080 related to HIP from a technical perspective. 1082 11.3.1. Deployment analysis 1084 HIP has commercially been utilized at Boeing airplane factory for 1085 their internal purposes [paine-hip]. It has been included in a 1086 security product called Tofino to support layer-two Virtual Private 1087 Networks [henderson-vpls] to facilitate, e.g, supervisory control and 1088 data acquisition (SCADA) security. However, HIP has not been a "wild 1089 success" [RFC5218] in the Internet as argued by Levae et al 1090 [leva-barriers]. Here, we briefly highlight some of their findings 1091 based on interviews with 19 experts from the industry and academia. 1093 From a marketing perspective, the demand for HIP has been low and 1094 substitute technologies have been favored. Another identified reason 1095 has been that some technical misconceptions related to the early 1096 stages of HIP specifications still persist. Two identified 1097 misconceptions are that HIP does not support NAT traversal, and that 1098 HIP must be implemented in the OS kernel. Both of these claims are 1099 untrue; HIP does have NAT traversal extensions 1100 [I-D.ietf-hip-native-nat-traversal], and kernel modifications can be 1101 avoided with modern operating systems by diverting packets for 1102 userspace processing. 1104 The analysis by Levae et al clarifies infrastructural requirements 1105 for HIP. In a minimal set up, a client and server machine have to 1106 run HIP software. However, to avoid manual configurations, usually 1107 DNS records for HIP are set up. For instance, the popular DNS server 1108 software Bind9 does not require any changes to accommodate DNS 1109 records for HIP because they can be supported in binary format in its 1110 configuration files [RFC6538]. HIP rendezvous servers and firewalls 1111 are optional. No changes are required to network address points, 1112 NATs, edge routers or core networks. HIP may require holes in legacy 1113 firewalls. 1115 The analysis also clarifies the requirements for the host components 1116 that consist of three parts. First, a HIP control plane component is 1117 required, typically implemented as a userspace daemon. Second, a 1118 data plane component is needed. Most HIP implementations utilize the 1119 so called BEET mode of ESP that has been available since Linux kernel 1120 2.6.27, but is included also as a userspace component in a few of the 1121 implementations. Third, HIP systems usually provide a DNS proxy for 1122 the local host that translates HIP DNS records to LSIs and HITs, and 1123 communicates the corresponding locators to HIP userspace daemon. 1124 While the third component is not mandatory, it is very useful for 1125 avoiding manual configurations. The three components are further 1126 described in the HIP experiment report [RFC6538]. 1128 Based on the interviews, Levae et al suggest further directions to 1129 facilitate HIP deployment. Transitioning the HIP specifications to 1130 the standards track may help, but other measures could be taken. As 1131 a more radical measure, the authors suggest to implement HIP as a 1132 purely application-layer library [xin-hip-lib] or other kind of 1133 middleware. On the other hand, more conservative measures include 1134 focusing on private deployments controlled by a single stakeholder. 1135 As a more concrete example of such a scenario, HIP could be used by a 1136 single service provider to facilitate secure connectivity between its 1137 servers [komu-cloud]. 1139 11.3.2. HIP in 802.15.4 networks 1141 The IEEE 802 standards have been defining MAC layered security. Many 1142 of these standards use EAP [RFC3748] as a Key Management System (KMS) 1143 transport, but some like IEEE 802.15.4 [IEEE.802-15-4.2011] leave the 1144 KMS and its transport as "Out of Scope". 1146 HIP is well suited as a KMS in these environments: 1148 o HIP is independent of IP addressing and can be directly 1149 transported over any network protocol. 1151 o Master Keys in 802 protocols are commonly pair-based with group 1152 keys transported from the group controller using pair-wise keys. 1154 o AdHoc 802 networks can be better served by a peer-to-peer KMS than 1155 the EAP client/server model. 1157 o Some devices are very memory constrained and a common KMS for both 1158 MAC and IP security represents a considerable code savings. 1160 11.4. Answers to NSRG questions 1162 The IRTF Name Space Research Group has posed a number of evaluating 1163 questions in their report [nsrg-report]. In this section, we provide 1164 answers to these questions. 1166 1. How would a stack name improve the overall functionality of the 1167 Internet? 1169 HIP decouples the internetworking layer from the transport 1170 layer, allowing each to evolve separately. The decoupling 1171 makes end-host mobility and multi-homing easier, also across 1172 IPv4 and IPv6 networks. HIs make network renumbering easier, 1173 and they also make process migration and clustered servers 1174 easier to implement. Furthermore, being cryptographic in 1175 nature, they provide the basis for solving the security 1176 problems related to end-host mobility and multi-homing. 1178 2. What does a stack name look like? 1180 A HI is a cryptographic public key. However, instead of using 1181 the keys directly, most protocols use a fixed size hash of the 1182 public key. 1184 3. What is its lifetime? 1186 HIP provides both stable and temporary Host Identifiers. 1187 Stable HIs are typically long lived, with a lifetime of years 1188 or more. The lifetime of temporary HIs depends on how long 1189 the upper-layer connections and applications need them, and 1190 can range from a few seconds to years. 1192 4. Where does it live in the stack? 1194 The HIs live between the transport and internetworking layers. 1196 5. How is it used on the end points? 1198 The Host Identifiers may be used directly or indirectly (in 1199 the form of HITs or LSIs) by applications when they access 1200 network services. Additionally, the Host Identifiers, as 1201 public keys, are used in the built in key agreement protocol, 1202 called the HIP base exchange, to authenticate the hosts to 1203 each other. 1205 6. What administrative infrastructure is needed to support it? 1207 In some environments, it is possible to use HIP 1208 opportunistically, without any infrastructure. However, to 1209 gain full benefit from HIP, the HIs must be stored in the DNS 1210 or a PKI, and a new rendezvous mechanism is needed 1211 [I-D.ietf-hip-rfc5205-bis]. 1213 7. If we add an additional layer would it make the address list in 1214 SCTP unnecessary? 1216 Yes 1218 8. What additional security benefits would a new naming scheme 1219 offer? 1221 HIP reduces dependency on IP addresses, making the so called 1222 address ownership [Nik2001] problems easier to solve. In 1223 practice, HIP provides security for end-host mobility and 1224 multi-homing. Furthermore, since HIP Host Identifiers are 1225 public keys, standard public key certificate infrastructures 1226 can be applied on the top of HIP. 1228 9. What would the resolution mechanisms be, or what characteristics 1229 of a resolution mechanisms would be required? 1231 For most purposes, an approach where DNS names are resolved 1232 simultaneously to HIs and IP addresses is sufficient. 1233 However, if it becomes necessary to resolve HIs into IP 1234 addresses or back to DNS names, a flat resolution 1235 infrastructure is needed. Such an infrastructure could be 1236 based on the ideas of Distributed Hash Tables, but would 1237 require significant new development and deployment. 1239 12. Security considerations 1241 This section includes discussion on some issues and solutions related 1242 to security in the HIP architecture. 1244 12.1. MiTM Attacks 1246 HIP takes advantage of the new Host Identity paradigm to provide 1247 secure authentication of hosts and to provide a fast key exchange for 1248 ESP. HIP also attempts to limit the exposure of the host to various 1249 denial-of-service (DoS) and man-in-the-middle (MitM) attacks. In so 1250 doing, HIP itself is subject to its own DoS and MitM attacks that 1251 potentially could be more damaging to a host's ability to conduct 1252 business as usual. 1254 Resource exhausting denial-of-service attacks take advantage of the 1255 cost of setting up a state for a protocol on the responder compared 1256 to the 'cheapness' on the initiator. HIP allows a responder to 1257 increase the cost of the start of state on the initiator and makes an 1258 effort to reduce the cost to the responder. This is done by having 1259 the responder start the authenticated Diffie-Hellman exchange instead 1260 of the initiator, making the HIP base exchange 4 packets long. The 1261 first packet sent by the responder can be prebuilt to further 1262 mitigate the costs. This packet also includes a computational puzzle 1263 that can optionally be used to further delay the initiator, for 1264 instance, when the responder is overloaded. The details are 1265 explained in the base exchange specification 1266 [I-D.ietf-hip-rfc5201-bis]. 1268 Man-in-the-middle (MitM) attacks are difficult to defend against, 1269 without third-party authentication. A skillful MitM could easily 1270 handle all parts of the HIP base exchange, but HIP indirectly 1271 provides the following protection from a MitM attack. If the 1272 responder's HI is retrieved from a signed DNS zone or securely 1273 obtained by some other means, the initiator can use this to 1274 authenticate the signed HIP packets. Likewise, if the initiator's HI 1275 is in a secure DNS zone, the responder can retrieve it and validate 1276 the signed HIP packets. However, since an initiator may choose to 1277 use an unpublished HI, it knowingly risks a MitM attack. The 1278 responder may choose not to accept a HIP exchange with an initiator 1279 using an unknown HI. 1281 Other types of MitM attacks against HIP can be mounted using ICMP 1282 messages that can be used to signal about problems. As a overall 1283 guideline, the ICMP messages should be considered as unreliable 1284 "hints" and should be acted upon only after timeouts. The exact 1285 attack scenarios and countermeasures are described in full detail the 1286 base exchange specification [I-D.ietf-hip-rfc5201-bis]. 1288 The need to support multiple hashes for generating the HIT from the 1289 HI affords the MitM to mount a potentially powerful downgrade attack 1290 due to the a-priori need of the HIT in the HIP base exchange. The 1291 base exchange has been augmented to deal with such an attack by 1292 restarting on detecting the attack. At worst this would only lead to 1293 a situation in which the base exchange would never finish (or would 1294 be aborted after some retries). As a drawback, this leads to an 1295 6-way base exchange which may seem bad at first. However, since this 1296 only occurs in an attack scenario and since the attack can be handled 1297 (so it is not interesting to mount anymore), we assume the subsequent 1298 messages do not represent a security threat. Since the MitM cannot 1299 be successful with a downgrade attack, these sorts of attacks will 1300 only occur as 'nuisance' attacks. So, the base exchange would still 1301 be usually just four packets even though implementations must be 1302 prepared to protect themselves against the downgrade attack. 1304 In HIP, the Security Association for ESP is indexed by the SPI; the 1305 source address is always ignored, and the destination address may be 1306 ignored as well. Therefore, HIP-enabled Encapsulated Security 1307 Payload (ESP) is IP address independent. This might seem to make 1308 attacking easier, but ESP with replay protection is already as well 1309 protected as possible, and the removal of the IP address as a check 1310 should not increase the exposure of ESP to DoS attacks. 1312 12.2. Protection against flooding attacks 1314 Although the idea of informing about address changes by simply 1315 sending packets with a new source address appears appealing, it is 1316 not secure enough. That is, even if HIP does not rely on the source 1317 address for anything (once the base exchange has been completed), it 1318 appears to be necessary to check a mobile node's reachability at the 1319 new address before actually sending any larger amounts of traffic to 1320 the new address. 1322 Blindly accepting new addresses would potentially lead to flooding 1323 Denial-of-Service attacks against third parties [RFC4225]. In a 1324 distributed flooding attack an attacker opens high volume HIP 1325 connections with a large number of hosts (using unpublished HIs), and 1326 then claims to all of these hosts that it has moved to a target 1327 node's IP address. If the peer hosts were to simply accept the move, 1328 the result would be a packet flood to the target node's address. To 1329 prevent this type of attack, HIP mobility extensions include a return 1330 routability check procedure where the reachability of a node is 1331 separately checked at each address before using the address for 1332 larger amounts of traffic. 1334 A credit-based authorization approach for host mobility with the Host 1335 Identity Protocol [I-D.ietf-hip-rfc5206-bis] can be used between 1336 hosts for sending data prior to completing the address tests. 1337 Otherwise, if HIP is used between two hosts that fully trust each 1338 other, the hosts may optionally decide to skip the address tests. 1339 However, such performance optimization must be restricted to peers 1340 that are known to be trustworthy and capable of protecting themselves 1341 from malicious software. 1343 12.3. HITs used in ACLs 1345 At end-hosts, HITs can be used in IP-based access control lists at 1346 the application and network layers. At middleboxes, HIP-aware 1347 firewalls [lindqvist-enterprise] can use HITs or public keys to 1348 control both ingress and egress access to networks or individual 1349 hosts, even in the presence of mobile devices because the HITs and 1350 public keys are topologically independent. As discussed earlier in 1351 Section 7, once a HIP session has been established, the SPI value in 1352 an ESP packet may be used as an index, indicating the HITs. In 1353 practice, firewalls can inspect HIP packets to learn of the bindings 1354 between HITs, SPI values, and IP addresses. They can even explicitly 1355 control ESP usage, dynamically opening ESP only for specific SPI 1356 values and IP addresses. The signatures in HIP packets allow a 1357 capable firewall to ensure that the HIP exchange is indeed occurring 1358 between two known hosts. This may increase firewall security. 1360 A potential drawback of HITs in ACLs is their 'flatness' means they 1361 cannot be aggregated, and this could potentially result in larger 1362 table searches in HIP-aware firewalls. A way to optimize this could 1363 be to utilize Bloom filters for grouping of HITs [sarela-bloom]. 1364 However, it should be noted that it is also easier to exclude 1365 individual, misbehaving hosts out when the firewall rules concern 1366 individual HITs rather than groups. 1368 There has been considerable bad experience with distributed ACLs that 1369 contain public key related material, for example, with SSH. If the 1370 owner of a key needs to revoke it for any reason, the task of finding 1371 all locations where the key is held in an ACL may be impossible. If 1372 the reason for the revocation is due to private key theft, this could 1373 be a serious issue. 1375 A host can keep track of all of its partners that might use its HIT 1376 in an ACL by logging all remote HITs. It should only be necessary to 1377 log responder hosts. With this information, the host can notify the 1378 various hosts about the change to the HIT. There have been attempts 1379 to develop a secure method to issue the HIT revocation notice 1380 [zhang-revocation]. 1382 Some of the HIP-aware middleboxes, such as firewalls 1383 [lindqvist-enterprise] or NATs [ylitalo-spinat], may observe the on- 1384 path traffic passively. Such middleboxes are transparent by their 1385 nature and may not get a notification when a host moves to a 1386 different network. Thus, such middleboxes should maintain soft state 1387 and timeout when the control and data plane between two HIP end-hosts 1388 has been idle too long. Correspondingly, the two end-hosts may send 1389 periodically keepalives, such as UPDATE packets or ICMP messages 1390 inside the ESP tunnel, to sustain state at the on-path middleboxes. 1392 One general limitation related to end-to-end encryption is that 1393 middleboxes may not be able to participate to the protection of data 1394 flows. While the issue may affect also other protocols, Heer at al 1395 [heer-end-host] have analyzed the problem in the context of HIP. 1396 More specifically, when ESP is used as the data-plane protocol for 1397 HIP, the association between the control and data plane is weak and 1398 can be exploited under certain assumptions. In the scenario, the 1399 attacker has already gained access to the target network protected by 1400 a HIP-aware firewall, but wants to circumvent the HIP-based firewall. 1401 To achieve this, the attacker passively observes a base exchange 1402 between two HIP hosts and later replays it. This way, the attacker 1403 manages to penetrate the firewall and can use a fake ESP tunnel to 1404 transport its own data. This is possible because the firewall cannot 1405 distinguish when the ESP tunnel is valid. As a solution, HIP-aware 1406 middleboxes may participate to the control plane interaction by 1407 adding random nonce parameters to the control traffic, which the end- 1408 hosts have to sign to guarantee the freshness of the control traffic 1409 [heer-midauth]. As an alternative, extensions for transporting data 1410 plane directly over the control plane can be used [RFC6078]. 1412 12.4. Alternative HI considerations 1414 The definition of the Host Identifier states that the HI need not be 1415 a public key. It implies that the HI could be any value; for example 1416 a FQDN. This document does not describe how to support such a non- 1417 cryptographic HI, but examples of such protocol variants do exist 1418 ([urien-rfid], [urien-rfid-draft]). A non-cryptographic HI would 1419 still offer the services of the HIT or LSI for NAT traversal. It 1420 would be possible to carry HITs in HIP packets that had neither 1421 privacy nor authentication. Such schemes may be employed for 1422 resource constrained devices, such as small sensors operating on 1423 battery power, but are not further analyzed here. 1425 If it is desirable to use HIP in a low security situation where 1426 public key computations are considered expensive, HIP can be used 1427 with very short Diffie-Hellman and Host Identity keys. Such use 1428 makes the participating hosts vulnerable to MitM and connection 1429 hijacking attacks. However, it does not cause flooding dangers, 1430 since the address check mechanism relies on the routing system and 1431 not on cryptographic strength. 1433 13. IANA considerations 1435 This document has no actions for IANA. 1437 14. Acknowledgments 1439 For the people historically involved in the early stages of HIP, see 1440 the Acknowledgments section in the Host Identity Protocol 1441 specification. 1443 During the later stages of this document, when the editing baton was 1444 transferred to Pekka Nikander, the comments from the early 1445 implementers and others, including Jari Arkko, Tom Henderson, Petri 1446 Jokela, Miika Komu, Mika Kousa, Andrew McGregor, Jan Melen, Tim 1447 Shepard, Jukka Ylitalo, Sasu Tarkoma, and Jorma Wall, were 1448 invaluable. Also, the comments from Lars Eggert, Spencer Dawkins and 1449 Dave Crocker were also useful. 1451 The authors want to express their special thanks to Tom Henderson, 1452 who took the burden of editing the document in response to IESG 1453 comments at the time when both of the authors were busy doing other 1454 things. Without his perseverance original document might have never 1455 made it as RFC4423. 1457 This main effort to update and move HIP forward within the IETF 1458 process owes its impetuous to a number of HIP development teams. The 1459 authors are grateful for Boeing, Helsinki Institute for Information 1460 Technology (HIIT), NomadicLab of Ericsson, and the three 1461 universities: RWTH Aachen, Aalto and University of Helsinki, for 1462 their efforts. Without their collective efforts HIP would have 1463 withered as on the IETF vine as a nice concept. 1465 Thanks also for Suvi Koskinen for her help with proofreading and with 1466 the reference jungle. 1468 15. Changes from RFC 4423 1470 In a nutshell, the changes from RFC 4423 [RFC4423] are mostly 1471 editorial, including clarifications on topics described in a 1472 difficult way and omitting some of the non-architectural 1473 (implementation) details that are already described in other 1474 documents. A number of missing references to the literature were 1475 also added. New topics include the drawbacks of HIP, discussion on 1476 802.15.4 and MAC security, deployment considerations and description 1477 of the base exchange. 1479 16. References 1480 16.1. Normative References 1482 [I-D.ietf-hip-multihoming] 1483 Henderson, T., Vogt, C., and J. Arkko, "Host Multihoming 1484 with the Host Identity Protocol", draft-ietf-hip- 1485 multihoming-03 (work in progress), July 2013. 1487 [I-D.ietf-hip-native-nat-traversal] 1488 Keranen, A. and J. Melen, "Native NAT Traversal Mode for 1489 the Host Identity Protocol", draft-ietf-hip-native-nat- 1490 traversal-06 (work in progress), December 2013. 1492 [I-D.ietf-hip-rfc5201-bis] 1493 Moskowitz, R., Heer, T., Jokela, P., and T. Henderson, 1494 "Host Identity Protocol Version 2 (HIPv2)", draft-ietf- 1495 hip-rfc5201-bis-14 (work in progress), October 2013. 1497 [I-D.ietf-hip-rfc5202-bis] 1498 Jokela, P., Moskowitz, R., and J. Melen, "Using the 1499 Encapsulating Security Payload (ESP) Transport Format with 1500 the Host Identity Protocol (HIP)", draft-ietf-hip- 1501 rfc5202-bis-05 (work in progress), November 2013. 1503 [I-D.ietf-hip-rfc5203-bis] 1504 Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) 1505 Registration Extension", draft-ietf-hip-rfc5203-bis-05 1506 (work in progress), March 2014. 1508 [I-D.ietf-hip-rfc5204-bis] 1509 Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) 1510 Rendezvous Extension", draft-ietf-hip-rfc5204-bis-03 (work 1511 in progress), December 2013. 1513 [I-D.ietf-hip-rfc5205-bis] 1514 Laganier, J., "Host Identity Protocol (HIP) Domain Name 1515 System (DNS) Extension", draft-ietf-hip-rfc5205-bis-04 1516 (work in progress), January 2014. 1518 [I-D.ietf-hip-rfc5206-bis] 1519 Henderson, T., Vogt, C., and J. Arkko, "Host Mobility with 1520 the Host Identity Protocol", draft-ietf-hip-rfc5206-bis-06 1521 (work in progress), July 2013. 1523 [I-D.ietf-hip-rfc6253-bis] 1524 Heer, T. and S. Varjonen, "Host Identity Protocol 1525 Certificates", draft-ietf-hip-rfc6253-bis-01 (work in 1526 progress), October 2013. 1528 [RFC5482] Eggert, L. and F. Gont, "TCP User Timeout Option", RFC 1529 5482, March 2009. 1531 16.2. Informative references 1533 [IEEE.802-15-4.2011] 1534 , "Information technology - Telecommunications and 1535 information exchange between systems - Local and 1536 metropolitan area networks - Specific requirements - Part 1537 15.4: Wireless Medium Access Control (MAC) and Physical 1538 Layer (PHY) Specifications for Low-Rate Wireless Personal 1539 Area Networks (WPANs)", IEEE Standard 802.15.4, September 1540 2011, . 1543 [Nik2001] Nikander, P., "Denial-of-Service, Address Ownership, and 1544 Early Authentication in the IPv6 World", in Proceesings of 1545 Security Protocols, 9th International Workshop, Cambridge, 1546 UK, April 25-27 2001, LNCS 2467, pp. 12-26, Springer, 1547 2002. 1549 [RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound, 1550 "Dynamic Updates in the Domain Name System (DNS UPDATE)", 1551 RFC 2136, April 1997. 1553 [RFC2535] Eastlake, D., "Domain Name System Security Extensions", 1554 RFC 2535, March 1999. 1556 [RFC2766] Tsirtsis, G. and P. Srisuresh, "Network Address 1557 Translation - Protocol Translation (NAT-PT)", RFC 2766, 1558 February 2000. 1560 [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network 1561 Address Translator (Traditional NAT)", RFC 3022, January 1562 2001. 1564 [RFC3102] Borella, M., Lo, J., Grabelsky, D., and G. Montenegro, 1565 "Realm Specific IP: Framework", RFC 3102, October 2001. 1567 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 1568 Levkowetz, "Extensible Authentication Protocol (EAP)", RFC 1569 3748, June 2004. 1571 [RFC4225] Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E. 1572 Nordmark, "Mobile IP Version 6 Route Optimization Security 1573 Design Background", RFC 4225, December 2005. 1575 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 1576 4306, December 2005. 1578 [RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol 1579 (HIP) Architecture", RFC 4423, May 2006. 1581 [RFC5218] Thaler, D. and B. Aboba, "What Makes For a Successful 1582 Protocol?", RFC 5218, July 2008. 1584 [RFC5338] Henderson, T., Nikander, P., and M. Komu, "Using the Host 1585 Identity Protocol with Legacy Applications", RFC 5338, 1586 September 2008. 1588 [RFC5887] Carpenter, B., Atkinson, R., and H. Flinck, "Renumbering 1589 Still Needs Work", RFC 5887, May 2010. 1591 [RFC6078] Camarillo, G. and J. Melen, "Host Identity Protocol (HIP) 1592 Immediate Carriage and Conveyance of Upper-Layer Protocol 1593 Signaling (HICCUPS)", RFC 6078, January 2011. 1595 [RFC6250] Thaler, D., "Evolution of the IP Model", RFC 6250, May 1596 2011. 1598 [RFC6281] Cheshire, S., Zhu, Z., Wakikawa, R., and L. Zhang, 1599 "Understanding Apple's Back to My Mac (BTMM) Service", RFC 1600 6281, June 2011. 1602 [RFC6317] Komu, M. and T. Henderson, "Basic Socket Interface 1603 Extensions for the Host Identity Protocol (HIP)", RFC 1604 6317, July 2011. 1606 [RFC6537] Ahrenholz, J., "Host Identity Protocol Distributed Hash 1607 Table Interface", RFC 6537, February 2012. 1609 [RFC6538] Henderson, T. and A. Gurtov, "The Host Identity Protocol 1610 (HIP) Experiment Report", RFC 6538, March 2012. 1612 [amir-hip] 1613 Amir, K., Forsgren, H., Grahn, K., Karvi, T., and G. 1614 Pulkkis, "Security and Trust of Public Key Cryptography 1615 for HIP and HIP Multicast", International Journal of 1616 Dependable and Trustworthy Information Systems (IJDTIS), 1617 2(3), 17-35, DOI: 10.4018/jdtis.2011070102, 2013. 1619 [aura-dos] 1620 Aura, T., Nikander, P., and J. Leiwo, "DOS-resistant 1621 Authentication with Client Puzzles", 8th International 1622 Workshop on Security Protocols, pages 170-177. Springer, , 1623 April 2001. 1625 [beal-dos] 1626 Beal, J. and T. Shephard, "Deamplification of DoS Attacks 1627 via Puzzles", , October 2004. 1629 [chiappa-endpoints] 1630 Chiappa, J., "Endpoints and Endpoint Names: A Proposed 1631 Enhancement to the Internet Architecture", URL 1632 http://www.chiappa.net/~jnc/tech/endpoints.txt, 1999. 1634 [heer-end-host] 1635 Heer, T., Hummen, R., Komu, M., Goetz, S., and K. Wehre, 1636 "End-host Authentication and Authorization for Middleboxes 1637 based on a Cryptographic Namespace", ICC2009 Communication 1638 and Information Systems Security Symposium, , 2009. 1640 [heer-midauth] 1641 Heer, T. and M. Komu, "End-Host Authentication for HIP 1642 Middleboxes", Working draft draft-heer-hip-middle-auth-02, 1643 September 2009. 1645 [henderson-vpls] 1646 Henderson, T. and D. Mattes, "HIP-based Virtual Private 1647 LAN Service (HIPLS)", Working draft draft-henderson-hip- 1648 vpls-07, Dec 2013. 1650 [hip-srtp] 1651 Tschofenig, H., Muenz, F., and M. Shanmugam, "Using SRTP 1652 transport format with HIP", Working draft draft- 1653 tschofenig-hiprg-hip-srtp-01, October 2005. 1655 [karvonen-usable] 1656 Karvonen, K., Komu, M., and A. Gurtov, "Usable Security 1657 Management with Host Identity Protocol", 7th ACS/IEEE 1658 International Conference on Computer Systems and 1659 Applications, (AICCSA-2009), 2009. 1661 [komu-cloud] 1662 Komu, M., Sethi, M., Mallavarapu, R., Oirola, H., Khan, 1663 R., and S. Tarkoma, "Secure Networking for Virtual 1664 Machines in the Cloud", International Workshop on Power 1665 and QoS Aware Computing (PQoSCom2012), IEEE, ISBN: 1666 978-1-4244-8567-3, September 2012. 1668 [komu-diss] 1669 Komu, M., "A Consolidated Namespace for Network 1670 Applications, Developers, Administrators and Users", 1671 Dissertation, Aalto University, Espoo, Finland ISBN: 1672 978-952-60-4904-5 (printed), ISBN: 978-952-60-4905-2 1673 (electronic). , December 2012. 1675 [komu-leap] 1676 Komu, M. and J. Lindqvist, "Leap-of-Faith Security is 1677 Enough for IP Mobility", 6th Annual IEEE Consumer 1678 Communications and Networking Conference IEEE CCNC 2009, 1679 Las Vegas, Nevada, , January 2009. 1681 [komu-mitigation] 1682 Komu, M., Tarkoma, S., and A. Lukyanenko, "Mitigation of 1683 Unsolicited Traffic Across Domains with Host Identities 1684 and Puzzles", 15th Nordic Conference on Secure IT Systems 1685 (NordSec 2010), Springer Lecture Notes in Computer 1686 Science, Volume 7127, pp. 33-48, ISBN: 978-3-642-27936-2, 1687 October 2010. 1689 [kovacshazi-host] 1690 Kovacshazi, Z. and R. Vida, "Host Identity Specific 1691 Multicast", International conference on Networking and 1692 Services (ICNS'06), IEEE Computer Society, Los Alamitos, 1693 CA, USA, 1694 http://doi.ieeecomputersociety.org/10.1109/ICNS.2007.66, 1695 2007. 1697 [leva-barriers] 1698 Levae, A., Komu, M., and S. Luukkainen, "Adoption Barriers 1699 of Network-layer Protocols: the Case of Host Identity 1700 Protocol", The International Journal of Computer and 1701 Telecommunications Networking, ISSN: 1389-1286, March 1702 2013. 1704 [lindqvist-enterprise] 1705 Lindqvist, J., Vehmersalo, E., Manner, J., and M. Komu, 1706 "Enterprise Network Packet Filtering for Mobile 1707 Cryptographic Identities", International Journal of 1708 Handheld Computing Research, 1 (1), 79-94, , January-March 1709 2010. 1711 [nsrg-report] 1712 Lear, E. and R. Droms, "What's In A Name:Thoughts from the 1713 NSRG", draft-irtf-nsrg-report-10 (work in progress), 1714 September 2003. 1716 [paine-hip] 1717 Paine, R., "Beyond HIP: The End to Hacking As We Know It", 1718 BookSurge Publishing, ISBN: 1439256047, 9781439256046, 1719 2009. 1721 [pham-leap] 1722 Pham, V. and T. Aura, "Security Analysis of Leap-of-Faith 1723 Protocols", Seventh ICST International Conference on 1724 Security and Privacy for Communication Networks, , 1725 September 2011. 1727 [sarela-bloom] 1728 Saerelae, M., Esteve Rothenberg, C., Zahemszky, A., 1729 Nikander, P., and J. Ott, "BloomCasting: Security in Bloom 1730 filter based multicast", , Lecture Notes in Computer 1731 Science 2012, , pages 1-16, Springer Berlin Heidelberg, 1732 2012. 1734 [schuetz-intermittent] 1735 Schuetz, S., Eggert, L., Schmid, S., and M. Brunner, 1736 "Protocol enhancements for intermittently connected 1737 hosts", SIGCOMM Comput. Commun. Rev., 35(3):5-18, , July 1738 2005. 1740 [shields-hip] 1741 Shields, C. and J. Garcia-Luna-Aceves, "The HIP protocol 1742 for hierarchical multicast routing", Proceedings of the 1743 seventeenth annual ACM symposium on Principles of 1744 distributed computing, pages 257-266. ACM, New York, NY, 1745 USA, ISBN: 0-89791-977-7, DOI: 10.1145/277697.277744, 1746 1998. 1748 [tritilanunt-dos] 1749 Tritilanunt, S., Boyd, C., Foo, E., and J. Nieto, 1750 "Examining the DoS Resistance of HIP", OTM Workshops (1), 1751 volume 4277 of Lecture Notes in Computer Science, pages 1752 616-625,Springer , 2006. 1754 [urien-rfid-draft] 1755 Urien, P., Lee, G., and G. Pujolle, "HIP support for 1756 RFIDs", IRTF Working draft draft-irtf-hiprg-rfid-07, April 1757 2013. 1759 [urien-rfid] 1760 Urien, P., Chabanne, H., Bouet, M., de Cunha, D., Guyot, 1761 V., Pujolle, G., Paradinas, P., Gressier, E., and J. 1762 Susini, "HIP-based RFID Networking Architecture", IFIP 1763 International Conference on Wireless and Optical 1764 Communications Networks, DOI: 10.1109/WOCN.2007.4284140, 1765 July 2007. 1767 [varjonen-split] 1768 Varjonen, S., Komu, M., and A. Gurtov, "Secure and 1769 Efficient IPv4/IPv6 Handovers Using Host-Based Identifier- 1770 Location Split", Journal of Communications Software and 1771 Systems, 6(1), 2010, ISSN: 18456421, 2010. 1773 [xin-hip-lib] 1774 Xin, G., "Host Identity Protocol Version 2.5", Master's 1775 Thesis, Aalto University, Espoo, Finland, , June 2012. 1777 [xueyong-hip] 1778 Xueyong, Z., Zhiguo, D., and W. Xinling, "A Multicast 1779 Routing Algorithm Applied to HIP-Multicast Model", 1780 Proceedings of the 2011 International Conference on 1781 Network Computing and Information Security - Volume 01 1782 (NCIS '11), Vol. 1. IEEE Computer Society, Washington, DC, 1783 USA, pages 169-174, DOI: 10.1109/NCIS.2011.42, 2011. 1785 [xueyong-secure] 1786 Xueyong, Z. and J. Atwood, "A Secure Multicast Model for 1787 Peer-to-Peer and Access Networks Using the Host Identity 1788 Protocol", Consumer Communications and Networking 1789 Conference. CCNC 2007. 4th IEEE, pages 1098,1102, DOI: 1790 10.1109/CCNC.2007.221, January 2007. 1792 [ylitalo-diss] 1793 Ylitalo, J., "Secure Mobility at Multiple Granularity 1794 Levels over Heterogeneous Datacom Networks", Dissertation, 1795 Helsinki University of Technology, Espoo, Finland ISBN 1796 978-951-22-9531-9, 2008. 1798 [ylitalo-spinat] 1799 Ylitalo, J., Salmela, P., and H. Tschofenig, "SPINAT: 1800 Integrating IPsec into overlay routing", Proceedings of 1801 the First International Conference on Security and Privacy 1802 for Emerging Areas in Communication Networks (SecureComm 1803 2005). Athens, Greece. IEEE Computer Society, pages 1804 315-326, ISBN: 0-7695-2369-2, September 2005. 1806 [zhang-revocation] 1807 Zhang, D., Kuptsov, D., and S. Shen, "Host Identifier 1808 Revocation in HIP", IRTF Working draft draft-irtf-hiprg- 1809 revocation-05, Mar 2012. 1811 Authors' Addresses 1813 Robert Moskowitz (editor) 1814 Verizon 1815 1000 Bent Creek Blvd, Suite 200 1816 Mechanicsburg, PA 1817 USA 1819 Email: robert.moskowitz@verizon.com 1821 Miika Komu 1822 Aalto University 1823 Konemiehentie 2 1824 Espoo 1825 Finland 1827 Email: miika.komu@aalto.fi