idnits 2.17.1 draft-ietf-mif-mpvd-arch-09.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == The document doesn't use any RFC 2119 keywords, yet seems to have RFC 2119 boilerplate text. -- The document date (January 23, 2015) is 3374 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-05) exists of draft-korhonen-dmm-prefix-properties-03 -- Obsolete informational reference (is this intentional?): RFC 3315 (Obsoleted by RFC 8415) -- Obsolete informational reference (is this intentional?): RFC 5996 (Obsoleted by RFC 7296) -- Obsolete informational reference (is this intentional?): RFC 6555 (Obsoleted by RFC 8305) Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MIF Working Group D. Anipko, Ed. 3 Internet-Draft Unaffiliated 4 Intended status: Informational January 23, 2015 5 Expires: July 25, 2015 7 Multiple Provisioning Domain Architecture 8 draft-ietf-mif-mpvd-arch-09 10 Abstract 12 This document is a product of the work of the MIF Architecture Design 13 team. It outlines a solution framework for some of the issues 14 experienced by nodes that can be attached to multiple networks 15 simultaneously. The framework defines the concept of a Provisioning 16 Domain (PvD) which is a a consistent set of network configuration 17 information. PvD aware nodes learn PvD specific information from the 18 networks they are attached to and / or other sources. PvDs are used 19 to enable separation and configuration consistency in presence of 20 multiple concurrent connections. 22 Status of this Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on July 25, 2015. 39 Copyright Notice 41 Copyright (c) 2015 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents (http://trustee.ietf.org/ 46 license-info) in effect on the date of publication of this document. 47 Please review these documents carefully, as they describe your rights 48 and restrictions with respect to this document. Code Components 49 extracted from this document must include Simplified BSD License text 50 as described in Section 4.e of the Trust Legal Provisions and are 51 provided without warranty as described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 56 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 57 2. Definitions and Types of PvDs . . . . . . . . . . . . . . . . 4 58 2.1. Explicit PvDs . . . . . . . . . . . . . . . . . . . . . . 4 59 2.2. Implicit PvDs and Incremental Adoption of Explicit PvDs . 5 60 2.3. Relationship Between PvDs and Interfaces . . . . . . . . . 6 61 2.4. PvD Identity / Naming . . . . . . . . . . . . . . . . . . 6 62 2.5. The Relationship to Dual-Stack Networks . . . . . . . . . 7 63 3. Conveying PvD information using DHCPv6 and Router Advertisement 8 64 3.1. Separate Messages or One Message? . . . . . . . . . . . . 8 65 3.2. Securing PvD Information . . . . . . . . . . . . . . . . . 8 66 3.3. Backward Compatibility . . . . . . . . . . . . . . . . . . 8 67 3.4. Retracting / Updating PvD Information . . . . . . . . . . 8 68 3.5. Conveying Configuration Information using IKEv2 . . . . . 9 69 4. Example Network Configurations . . . . . . . . . . . . . . . . 9 70 4.1. A Mobile Node . . . . . . . . . . . . . . . . . . . . . . 9 71 4.2. A Node with a VPN Connection . . . . . . . . . . . . . . . 10 72 4.3. A Home Network and a Network Operator with Multiple PvDs . 11 73 5. Reference Model for the PvD-aware Node . . . . . . . . . . . . 11 74 5.1. Constructions and Maintenance of Separate PvDs . . . . . . 12 75 5.2. Consistent use of PvDs for Network Connections . . . . . . 12 76 5.2.1. Name Resolution . . . . . . . . . . . . . . . . . . . 12 77 5.2.2. Next-hop and Source Address Selection . . . . . . . . 13 78 5.2.3. Listening Applications . . . . . . . . . . . . . . . . 14 79 5.2.3.1. Processing of Incoming Traffic . . . . . . . . . . 14 80 5.2.3.1.1. Connection-oriented APIs . . . . . . . . . . . 15 81 5.2.3.1.2. Connectionless APIs . . . . . . . . . . . . . 15 82 5.2.4. Enforcement of Security Policies . . . . . . . . . . . 15 83 5.3. Connectivity Tests . . . . . . . . . . . . . . . . . . . . 15 84 5.4. Relationship to Interface Management and Connection Manage 16 85 6. PvD support in APIs . . . . . . . . . . . . . . . . . . . . . 16 86 6.1. Basic . . . . . . . . . . . . . . . . . . . . . . . . . . 17 87 6.2. Intermediate . . . . . . . . . . . . . . . . . . . . . . . 17 88 6.3. Advanced . . . . . . . . . . . . . . . . . . . . . . . . . 17 89 7. PvD Trust for PvD-Aware Node . . . . . . . . . . . . . . . . . 17 90 7.1. Untrusted PvDs . . . . . . . . . . . . . . . . . . . . . . 17 91 7.2. Trusted PvDs . . . . . . . . . . . . . . . . . . . . . . . 18 92 7.2.1. Authenticated PvDs . . . . . . . . . . . . . . . . . . 18 93 7.2.2. PvDs Trusted by Attachment . . . . . . . . . . . . . . 18 94 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 19 95 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19 96 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 97 11. Security Considerations . . . . . . . . . . . . . . . . . . . 19 98 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 99 12.1. Normative References . . . . . . . . . . . . . . . . . . 20 100 12.2. Informative References . . . . . . . . . . . . . . . . . 20 101 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 22 103 1. Introduction 104 Nodes attached to multiple networks may encounter problems from 105 conflicting configuration between the networks, or attempts to 106 simultaneously use more than one network. While various techniques 107 are currently used to tackle these problems ([RFC6419]), in many 108 cases issues may still appear. The MIF problem statement document 109 [RFC6418] describes the general landscape and discusses many of the 110 specific issues and scenario details. 112 Problems, enumerated in [RFC6418], can be grouped into 3 categories: 114 1. Lack of consistent and distinctive management of configuration 115 elements associated with different networks. 117 2. Inappropriate mixed use of configuration elements associated with 118 different networks during a particular network activity or 119 connection. 121 3. Use of a particular network that is not consistent with the 122 intended use of the network, or the intent of the communicating 123 parties, leading to connectivity failure and / or other undesired 124 consequences. 126 An example of (1) is a single, node-scoped list of DNS server IP 127 addresses learned from different networks leading to failures or 128 delays in resolution of names from particular namespaces; an example 129 of (2) is an attempt to resolve the name of an HTTP proxy server 130 learned from network A using a DNS server learned from network B; an 131 example of (3) is the use of an employer-provided VPN connection for 132 peer-to-peer connectivity unrelated to employment activities. 134 This architecture provides solutions to these categories of problems, 135 respectively, by: 137 1. Introducing the formal notion of PvDs, including identity for 138 PvDs, and describing mechanisms for nodes to learn the intended 139 associations between acquired network configuration information 140 elements. 142 2. Introducing a reference model for PvD-aware nodes that prevents 143 the inadvertent mixed use of configuration information which may 144 belong to different PvDs. 146 3. Providing recommendations on PvD selection based on PvD identity 147 and connectivity tests for common scenarios. 149 1.1. Requirements Language 151 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 152 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 153 document are to be interpreted as described in RFC 2119 [RFC2119]. 155 2. Definitions and Types of PvDs 157 Provisioning Domain: 158 A consistent set of network configuration information. 159 Classically, all of the configuration information available on a 160 single interface is provided by a single source (such as a network 161 administrator) and can therefore be treated as a single 162 provisioning domain. In modern IPv6 networks, multihoming can 163 result in more than one provisioning domain being present on a 164 single link. In some scenarios, it is also possible for elements 165 of the same PvD to be present on multiple links. 167 Typical examples of information in a provisioning domain learned 168 from the network are: 170 * Source address prefixes for use by connections within the 171 provisioning domain 173 * IP address(es) of DNS server(s) 175 * Name of HTTP proxy server (if available) 177 * DNS suffixes associated with the network 179 * Default gateway address 181 PvD-aware node: 182 A node that supports the association of network configuration 183 information into PvDs and the use of these PvDs to serve requests 184 for network connections in ways consistent with the 185 recommendations of this architecture. 187 2.1. Explicit PvDs 189 A node may receive explicit information from the network and / or 190 other sources conveying the presence of PvDs and the association of 191 particular network information with a particular PvD. PvDs that are 192 constructed based on such information are referred to as "explicit" 193 in this document. 195 Protocol changes or extensions will likely be required to support 196 explicit PvDs through IETF-defined mechanisms. As an example, one 197 could think of one or more DHCP options carrying PvD identity and / 198 or its elements. 200 A different approach could be the introduction of a DHCP option which 201 only carries the identity of a PvD. Here, the associations between 202 network information elements with the identity is implemented by the 203 respective protocols, for example with a Router Discovery [RFC4861] 204 option associating an address range with a PvD. 206 Another example of a delivery mechanism for PvDs are key exchange or 207 tunneling protocols, such as IKEv2 [RFC5996] that allow the 208 transport of host configuration information. 210 Specific, existing or new features of networking protocols that 211 enable the delivery of PvD identity and association with various 212 network information elements will be defined in companion design 213 documents. 215 Link-specific and / or vendor-proprietary mechanisms for the 216 discovery of PvD information (differing from IETF-defined mechanisms) 217 can be used by nodes either separate from, or in conjunction with, 218 IETF-defined mechanisms; providing they allow the discovery of the 219 necessary elements of the PvD(s). 221 In all cases, nodes must by default ensure that the lifetime of all 222 dynamically discovered PvD configuration is appropriately limited by 223 relevant events. For example, if an interface media state change is 224 indicated, previously discovered information relevant to that 225 interface may no longer be valid and so need to be confirmed or re- 226 discovered. 228 It is expected that the way a node makes use of PvD information is 229 generally independent of the specific mechanism / protocol that the 230 information was received by. 232 In some network topologies, network infrastructure elements may need 233 to advertise multiple PvDs. Generally, the details of how this is 234 performed will be defined in companion design documents. 236 2.2. Implicit PvDs and Incremental Adoption of Explicit PvDs 238 For the foreseeable future, there will be networks which do not 239 advertise explicit PvD information, because deployment of new 240 features in networking protocols is a relatively slow process. 242 When connected to networks which don't advertise explicit PvD 243 information, a PvD-aware node shall automatically create separate 244 PvDs for received configuration. Such PvDs are referred to in this 245 document as "implicit". 247 Through the use of implicit PvDs, PvD-aware nodes may still provide 248 benefits to their users (when compared to non-PvD aware nodes) by 249 following the best practices described in Section 5. 251 PvD-aware nodes shall treat network information from different 252 interfaces, which is not identified as belonging explicitly to some 253 PvD, as belonging to separate PvDs, one per interface. 255 Implicit PvDs can also occur in a mixed mode, i.e., where of multiple 256 networks that are available on an attached link, only some advertise 257 PvD information. In this case, the PvD-aware node shall create 258 explicit PvDs from information explicitly labeled as beloinging to 259 PvDs. It shall associate configuration information not labeled with 260 an explicit PvD with implicit PvD(s) created for that interface. 262 2.3. Relationship Between PvDs and Interfaces 264 By default, implicit PvDs are limited to the network configuration 265 information received on a single interface and by default one such 266 PvD is formed for each interface. If additional information is 267 available to the host (through mechanisms out of scope of this 268 document), the host may form implicit PvDs with different 269 granularity. For example, PvDs spanning multiple interfaces such a 270 home network with a router that has multiple internal interfaces, or 271 multiple PvDs on a single interface such as a network that has 272 multiple uplink connections. 274 In the simplest case, explicit PvDs will be scoped for configuration 275 related only to a specific interface. However, there is no 276 requirement in this architecture for such a limitation. Explicit 277 PvDs may include information related to more than one interface if 278 the node learns the presence of the same PvD on those interfaces and 279 the authentication of the PvD ID meets the level required by the node 280 policy (authentication of a PvD ID may be also required in scenarios 281 involving only one connected interface and / or PvD). 283 This architecture supports such scenarios. Hence, no hierarchical 284 relationship exists between interfaces and PvDs: it is possible for 285 multiple PvDs to be simultaneously accessible over one interface, as 286 well as a single PvD to be simultaneously accessible over multiple 287 interfaces. 289 2.4. PvD Identity / Naming 291 For explicit PvDs, the PvD ID is a value that is, or has a high 292 probability of being globally unique, and is received as part of PvD 293 information. It shall be possible to generate a human-readable form 294 of the PvD ID to present to the end-user, either based on the PvD ID 295 itself, or using meta-data associated with the ID. For implicit PvDs, 296 the node assigns a locally generated ID with a high probability of 297 being globally unique to each implicit PvD. 299 A PvD-aware node may use these IDs to select a PvD with a matching ID 300 for special-purpose connection requests in accordance with node 301 policy, as chosen by advanced applications, or to present a human- 302 readable representation of the IDs to the end-user for selection of 303 PvDs. 305 A single network provider may operate multiple networks, including 306 networks at different locations. In such cases, the provider may 307 chose whether to advertise single or multiple PvD identities at all 308 or some of those networks as it suits their business needs. This 309 architecture does not impose any specific requirements in this 310 regard. 312 When multiple nodes are connected to the same link with one or more 313 explicit PvDs available, this architecture assumes that the 314 information about all available PvDs is made available by the 315 networks to all the connected nodes. At the same time, connected 316 nodes may have different heuristics, policies and / or other 317 settings, including their configured sets of trusted PvDs. This may 318 lead to different PvDs actually being used by different nodes for 319 their connections. 321 Possible extensions, whereby networks advertize different sets of 322 PvDs to different connected nodes are out of scope of this document. 324 2.5. The Relationship to Dual-Stack Networks 326 When applied to dual-stack networks, the PvD definition allows for 327 multiple PvDs to be created whereby each PvD contains information 328 relevant to only one address family, or for a single PvD containing 329 information for multiple address families. This architecture 330 requires that accompanying design documents describing PvD-related 331 protocol changes must support PvDs containing information from 332 multiple address families. PvD-aware nodes must be capable of 333 creating and using both single-family and multi-family PvDs. 335 For explicit PvDs, the choice of either of these approaches is a 336 policy decision for the network administrator and / or the node user/ 337 administrator. Since some of the IP configuration information that 338 can be learned from the network can be applicable to multiple address 339 families (for instance DHCP Address Selection Policy Opt [RFC7078]), 340 it is likely that dual-stack networks will deploy single PvDs for 341 both address families. 343 By default for implicit PvDs, PvD-aware nodes shall include multiple 344 IP families into a single implicit PvD created for an interface. At 345 the time of writing, in dual-stack networks it appears to be common 346 practice for the configuration of both address families to be 347 provided by a single source. 349 A PvD-aware node that provides an API to use, enumerate and inspect 350 PvDs and / or their properties shall provide the ability to filter 351 PvDs and / or their properties by address family. 353 3. Conveying PvD information using DHCPv6 and Router Advertisements 355 DHCPv6 and Router Advertisements are the two most common methods of 356 configuring hosts. To support the architecture described in this 357 document, these protocols would need to be extended to convey 358 explicit PvD information. The following sections describe topic 359 which must be considered before finalizing a mechanism to augment 360 DHCPv6 and RAs with PvD information. 362 3.1. Separate Messages or One Message? 364 When information related to several PvDs is available from the same 365 configuration source, there are two possible ways of distributing 366 this information: One way is to send information from each different 367 provisioning domain in separate messages. The second method is 368 combining the information from multiple PvDs into a single message. 369 The latter method has the advantage of being more efficient but could 370 have problems with to authentication and authorization, as well as 371 potential issues with accommodating information not tagged with any 372 PvD information. 374 3.2. Securing PvD Information 376 DHCPv6 and RAs both provide some form of authentication to ensure the 377 identity of the source as well as the integrity of the secured 378 message content. While this is useful, determining authenticity does 379 not tell a node whether the configuration source is actually allowed 380 to provide information from a given PvD. To resolve this, there must 381 be a mechanism for the PvD owner to attach some form of authorization 382 token or signature to the configuration information that is 383 delivered. 385 3.3. Backward Compatibility 387 The extensions to RAs and DHCPv6 should be defined in such a manner 388 than unmodified hosts (i.e. hosts not aware of PvDs) will continue 389 to function as well as they did prior to PvD information being added. 390 This could imply that some information may need to be duplicated in 391 order to be conveyed to legacy hosts. Similarly, PvD aware hosts 392 need to be able to correctly utiilize legacy configuration sources 393 which do not provide PvD information. There are also several 394 initiatives that are aimed at adding some form of additional 395 information to prefixes [I-D.bhandari-dhc-class-based-prefix] and 396 [I-D.korhonen-dmm-prefix-properties] and any new mechanism should try 397 to consider co-existence with such deployed mechanisms. 399 3.4. Retracting / Updating PvD Information 400 After PvD information is provisioned to a host, it may become 401 outdated or superseded by updated information before the hosts would 402 normally request updates. To resolve this requires that the 403 mechanism be able to update and / or withdraw all (or some subset) of 404 the information related to a given PvD. For efficiency reasons, there 405 should be a way to specify that all information from the PvD needs to 406 be reconfigured instead of individually updating each item associated 407 with the PvD. 409 3.5. Conveying Configuration Information using IKEv2 411 Internet Key Exchange protocol version 2 (IKEv2) [RFC5996] [RFC5739] 412 is another widely used method of configuring host IP information. 413 For IKEv2, the provisioning domain could be implicitly learned from 414 the Identification - Responder (IDr) payloads that the IKEv2 415 initiator and responder inject during their IKEv2 exchange. The IP 416 configuration may depend on the named IDr. Another possibility could 417 be adding a specific provisioning domain identifying payload 418 extensions to IKEv2. All of the considerations for DHCPv6 and RAs 419 listed above potentially apply to IKEv2 as well. 421 4. Example Network Configurations 423 4.1. A Mobile Node 425 Consider a mobile node with two network interfaces: one to the mobile 426 network, the other to the Wi-Fi network. When the mobile node is 427 only connected to the mobile network, it will typically have one PvD, 428 implicit or explicit. When the mobile node discovers and connects to 429 a Wi-Fi network, it will have zero or more (typically one) additional 430 PvD(s). 432 Some existing OS implementations only allow one active network 433 connection. In this case, only the PvD(s) associated with the active 434 interface can be used at any given time. 436 As an example, the mobile network can explicitly deliver PvD 437 information through the PDP context activation process. Then, the 438 PvD aware mobile node will treat the mobile network as an explicit 439 PvD. Conversely, the legacy Wi-Fi network may not explicitly 440 communicate PvD information to the mobile node. The PvD aware mobile 441 node will associate network configuration for the Wi-Fi network with 442 an implicit PvD in this case. 444 The following diagram illustrates the use of different PvDs in this 445 scenario: 447 <----------- Wi-Fi 'Internet' PvD -------> 448 +--------+ 449 | +----+ | +----+ _ __ _ _ 450 | |WiFi| | | | ( ` ) ( ` )_ 451 | |-IF +-|----+ |--------------------------( `) 452 | | | | |WiFi| ( ) (_ Internet _) 453 | +----+ | | AP | ( ) `- __ _) - 454 | | | | ( Service ) 455 | | +----+ ( Provider's ) 456 | | ( Networks - 457 | +----+ | `_ ) _ _ 458 | |CELL| | ( ) ( ` )_ 459 | |-IF +-|-------------------------------------( `) 460 | | | | (_ __) (_ Internet _) 461 | +----+ | `- -- `- __ _) - 462 +--------+ 463 <------- Mobile 'Internet' PvD -----------> 465 An example of PvD use with Wi-Fi and mobile interfaces. 467 4.2. A Node with a VPN Connection 469 If the node has established a VPN connection, zero or more (typically 470 one) additional PvD(s) will be created. These may be implicit or 471 explicit. The routing to IP addresses reachable within this PvD will 472 be set up via the VPN connection, and the routing of packets to 473 addresses outside the scope of this PvD will remain unaffected. If a 474 node already has N connected PvDs, after the VPN session has been 475 established typically there will be N+1 connected PvDs. 477 The following diagram illustrates the use of different PvDs in this 478 scenario: 480 <----------- 'Internet' PvD ------> 481 +--------+ 482 | +----+ | +----+ _ __ _ _ 483 | |Phy | | | | ( ` ) ( ` )_ 484 | |-IF +-|----+ |--------------------( `) 485 | | | | | | ( ) (_ Internet _) 486 | +----+ | | | ( ) `- __ _) - 487 | | |Home| ( Service ) || 488 | | |gate| ( Provider's ) || 489 | | |-way| ( Network - || 490 | +----+ | | | `_ ) +---------+ +------------+ 491 | |VPN | | | | ( ) | VPN | | | 492 | |-IF +-|----+ |---------------------+ Gateway |--+ Private | 493 | | | | | | (_ __) | | | Services | 494 | +----+ | +----+ `- -- +---------+ +------------+ 495 +--------+ 496 <-------------- Explicit 'VPN' PvD -----> 498 An example of PvD use with VPN. 500 4.3. A Home Network and a Network Operator with Multiple PvDs 502 An operator may use separate PvDs for individual services which they 503 offer to their customers. These may be used so that services can be 504 designed and provisioned to be completely independent of each other, 505 allowing for complete flexibility in combinations of services which 506 are offered to customers. 508 From the perspective of the home network and the node, this model is 509 functionally very similar to being multihomed to multiple upstream 510 operators: Each of the different services offered by the service 511 provider is its own PvD with associated PvD information. In this 512 case, the operator may provide a generic / default PvD (explicit or 513 implicit), which provides Internet access to the customer. 514 Additional services would then be provisioned as explicit PvDs for 515 subscribing customers. 517 The following diagram illustrates this, using video-on-demand as a 518 service-specific PvD: 520 <------ Implicit 'Internet' PvD ------> 521 +----+ +----+ _ __ _ _ 522 | | | | ( ` ) ( ` )_ 523 | PC +-----+ |--------------------------( `) 524 | | | | ( ) (_ Internet _) 525 +----+ | | ( ) `- __ _) - 526 |Home| ( Service ) 527 |gate| ( Provider's ) 528 |-way| ( Network - 529 +-----+ | | `_ ) +---------+ 530 | Set | | | ( ) |ISP Video| 531 | Top +----+ |---------------------------+on Demand| 532 | Box | | | (_ __) | Service | 533 +-----+ +----+ `- -- +---------+ 534 <-- Explicit 'Video-on-Demand' PvD --> 536 An example of PvD use within a home network. 538 In this case, the number of PvDs that a single operator could 539 provision is based on the number of independently provisioned 540 services which they offer. Some examples may include: 542 o Real-time packet voice 544 o Streaming video 546 o Interactive video (n-way video conferencing) 548 o Interactive gaming 550 o Best effort / Internet access 552 5. Reference Model for the PvD-aware Node 553 5.1. Constructions and Maintenance of Separate PvDs 555 It is assumed that normally, the configuration information contained 556 in a single PvD shall be sufficient for a node to fulfill a network 557 connection request by an application, and hence there should be no 558 need to attempt to merge information across different PvDs. 560 Nevertheless, even when a PvD lacks some necessary configuration 561 information, merging of information associated with different PvD(s) 562 shall not be done automatically as this will typically lead to the 563 issues described in [RFC6418]. 565 A node may use other sources, for example: node local policy, user 566 input or other mechanisms not defined by the IETF for any of the 567 following: 569 o Construction of a PvD in its entirety (analogous to statically 570 configuring IP on an interface) 572 o Supplementing some, or all learned PvDs with particular 573 configuration elements 575 o Merging of information from different PvDs (if this is explicitly 576 allowed by policy) 578 As an example, a node administrator could inject a DNS server which 579 is not ISP-specific into PvDs for use on any of the networks that the 580 node could attach to. Such creation / augmentation of PvD(s) could 581 be static or dynamic. The specific mechanism(s) for implementing 582 this are outside of scope of this document. 584 5.2. Consistent use of PvDs for Network Connections 586 PvDs enable PvD-aware nodes to consistently use the correct set of 587 configuration elements to serve specific network requests from 588 beginning to end. This section provides examples of such use. 590 5.2.1. Name Resolution 592 When a PvD-aware node needs to resolve the name of the destination 593 for use by a connection request, the node could use one, or multiple 594 PvDs for a given name lookup. 596 The node shall chose a single PvD if, for example, the node policy 597 required the use of a particular PvD for a specific purpose (e.g. to 598 download an MMS message using a specific APN over a cellular 599 connection). To make this selection, the node could use a match 600 between the PvD DNS suffix and an FQDN which is being resolved or 601 match of PvD ID, as determined by the node policy. 603 The node may pick multiple PvDs, if for example, the PvDs are for 604 general purpose Internet connectivity, and the node is attempting to 605 maximize the probability of connectivity similar to the Happy 606 Eyeballs [RFC6555] approach. In this case, the node could perform 607 DNS lookups in parallel, or in sequence. Alternatively, the node may 608 use only one PvD for the lookup, based on the PvD connectivity 609 properties, user configuration of preferred Internet PvD, etc. 611 If an application implements an API that provides a way of explicitly 612 specifying the desired interface or PvD, that interface or PvD should 613 be used for name resolution (and the subsequent connection attempt), 614 provided that the host's configuration permits this. 616 In either case, by default a node uses information obtained via a 617 name service lookup to establish connections only within the same PvD 618 as the lookup results were obtained. 620 For clarification, when it is written that the name service lookup 621 results were obtained "from a PvD", it should be understood to mean 622 that the name service query was issued against a name service which 623 is configured for use in a particular PvD. In that sense, the 624 results are "from" that particular PvD. 626 Some nodes may support transports and / or APIs which provide an 627 abstraction of a single connection, aggregating multiple underlying 628 connections. MPTCP [RFC6182] is an example of such a transport 629 protocol. For connections provided by such transports/APIs, a PvD- 630 aware node may use different PvDs for servicing that logical 631 connection, provided that all operations on the underlying 632 connections are performed consistently within their corresponding 633 PvD(s). 635 5.2.2. Next-hop and Source Address Selection 637 For the purpose of this example, let us assume that the preceding 638 name lookup succeeded in a particular PvD. For each obtained 639 destination address, the node shall perform a next-hop lookup among 640 routers associated with that PvD. As an example, the node could 641 determine such associations via matching the source address prefixes/ 642 specific routes advertized by the router against known PvDs, or 643 receiving an explicit PvD affiliation advertized through a new Router 644 Discovery [RFC4861] option. 646 For each destination, once the best next-hop is found, the node 647 selects the best source address according to rules defined in 648 [RFC6724], but with the constraint that the source address must 649 belong to a range associated with the used PvD. If needed, the node 650 would use prefix policy from the same PvD for selecting the best 651 source address from multiple candidates. 653 When destination / source pairs are identified, they are sorted using 654 the [RFC6724] destination sorting rules and prefix policy table from 655 the used PvD. 657 5.2.3. Listening Applications 659 Consider a host connected to several PvDs, running an application 660 that opens a listening socket / transport API object. The 661 application is authorized by the host policy to use a subset of 662 connected PvDs that may or may not be equal to the complete set of 663 the connected PvDs. As an example, in the case where there are 664 different PvDs on the Wi-Fi and cellular interfaces, for general 665 Internet traffic the host could use only one, preferred PvD at a time 666 (and accordingly, advertise to remote peers the host name and 667 addresses associated with that PvD), or it could use one PvD as the 668 default for outgoing connections, while still allowing use of the 669 other PvDs simultaneously. 671 Another example is a host with an established VPN connection. Here, 672 security policy could be used to permit or deny application's access 673 to the VPN (and other) PvD(s). 675 For non-PvD aware applications, the operating system has policies 676 that determine the authorized set of PvDs and the preferred outgoing 677 PvD. For PvD-aware applications, both the authorized set of PvDs and 678 the default outgoing PvD can be determined as the common subset 679 produced between the OS policies and the set of PvD IDs or 680 characteristics provided by the application. 682 Application input could be provided on per-application, per- 683 transport-API-object or per-transport-API-call basis. The API for 684 application input may have an option for specifying whether the input 685 should be treated as a preference instead of a requirement. 687 5.2.3.1. Processing of Incoming Traffic 689 Unicast IP packets are received on a specific IP address associated 690 with a PvD. For multicast packets, the host can derive the PvD 691 association from other configuration information, such as an explicit 692 PvD property or local policy. 694 The node OS or middleware may apply more advanced techniques for 695 determining the resultant PvD and / or authorization of the incoming 696 traffic. Those techniques are outside of scope of this document. 698 If the determined receiving PvD of a packet is not in the allowed 699 subset of PvDs for the particular application / transport API object, 700 the packet should be handled in the same way as if there were no 701 listener. 703 5.2.3.1.1. Connection-oriented APIs 705 For connection-oriented APIs, when the initial incoming packet is 706 received, the packet PvD is remembered for the established connection 707 and used for handling of outgoing traffic for that connection. While 708 typically, connection-oriented APIs use a connection-oriented 709 transport protocol, such as TCP, it is possible to have a connection- 710 oriented API that uses a generally connectionless transport protocol, 711 such as UDP. 713 For APIs/protocols that support multiple IP traffic flows associated 714 with a single transport API connection object (for example, multi 715 path TCP), the processing rules may be adjusted accordingly. 717 5.2.3.1.2. Connectionless APIs 719 For connectionless APIs, the host should provide an API that PvD- 720 aware applications can use to query the PvD associated with the 721 packet. For outgoing traffic on this transport API object, the OS 722 should use the selected outgoing PvDs, determined as described above. 724 5.2.4. Enforcement of Security Policies 726 By themselves, PvDs do not define, and cannot be used for 727 communication of, security policies. When implemented in a network, 728 this architecture provides the host with information about connected 729 networks. The actual behavior of the host then depends on the host's 730 policies (provisioned through mechanisms out of scope of this 731 document), applied taking received PvD information into account. In 732 some scenarios, e.g. a VPN, such policies could require the host to 733 use only a particular VPN PvD for some / all of the application's 734 traffic (VPN 'disable split tunneling' also known as 'force 735 tunneling' behavior), or apply such restrictions only to selected 736 applications and allow the simultaneous use of the VPN PvD together 737 with the other connected PvDs by the other or all applications (VPN 738 'split tunneling' behavior). 740 5.3. Connectivity Tests 742 Although some PvDs may appear as valid candidates for PvD selection 743 (e.g. good link quality, consistent connection parameters, etc.), 744 they may provide limited or no connectivity to the desired network or 745 the Internet. For example, some PvDs provide limited IP connectivity 746 (e.g., scoped to the link or to the access network), but require the 747 node to authenticate through a web portal to get full access to the 748 Internet. This may be more likely to happen for PvDs which are not 749 trusted by a given PvD-aware node. 751 An attempt to use such a PvD may lead to limited network connectivity 752 or application connection failures. To prevent the latter, a PvD- 753 aware node may perform a connectivity test for the PvD before using 754 it to serve application network connection requests. In current 755 implementations, some nodes already implement this e.g., by trying to 756 reach a dedicated web server (see [RFC6419]). 758 Section 5.2 describes how a PvD-aware node shall maintain and use 759 multiple PvDs separately. The PvD-aware node shall perform a 760 connectivity test and, only after validation of the PvD, consider 761 using it to serve application connections requests. Ongoing 762 connectivity tests are also required, since during the IP session, 763 the end-to-end connectivity could be disrupted for various reasons 764 (e.g. L2 problems, IP QoS issues); hence, a connectivity monitoring 765 function is needed to check the connectivity status and remove the 766 PvD from the set of usable PvDs if necessary. 768 There may be cases where a connectivity test for PvD selection may 769 not be appropriate and should be complemented, or replaced, by PvD 770 selection based on other factors. For example, this could be 771 realized by leveraging some 3GPP and IEEE mechanisms, which would 772 allow the exposure of some PvD characteristics to the node (e.g. 773 3GPP Access Network Discovery and Selection Function (ANDSF) 774 [TS23402], IEEE 802.11u [IEEE802.11u]/ANQP). 776 5.4. Relationship to Interface Management and Connection Managers 778 Current devices, such as mobile handsets make use of proprietary 779 mechanisms and custom applications to manage connectivity in 780 environments with multiple interfaces and multiple sets of network 781 configuration. These mechanisms or applications are commonly known 782 as connection managers [RFC6419]. 784 Connection managers sometimes rely on policy servers to allow a node 785 that is connected to multiple networks to perform network selection. 786 They can also make use of routing guidance from the network (e.g. 787 3GPP ANDSF [TS23402]). Although connection managers solve some 788 connectivity problems, they rarely address network selection problems 789 in a comprehensive manner. With proprietary solutions, it is 790 challenging to present coherent behavior to the end user of the 791 device, as different platforms present different behaviors even when 792 connected to the same network, with the same type of interface, and 793 for the same purpose. The architecture described in this document 794 should improve the hosts behavior by providing the hosts with tools 795 and guidance to make informed network selection decisions. 797 6. PvD support in APIs 799 For all levels of PvD support in APIs described in this chapter, it 800 is expected that the notifications about changes in the set of 801 available PvDs are exposed as part of the API surface. 803 6.1. Basic 805 Applications are not PvD-aware in any manner and only submit 806 connection requests. The node performs PvD selection implicitly, 807 without any application participation, based purely on node-specific 808 administrative policies and / or choices made by the user from a user 809 interface provided by the operating environment, not by the 810 application. 812 As an example, PvD selection can be done at the name service lookup 813 step by using the relevant configuration elements, such as those 814 described in [RFC6731]. As another example, PvD selection could be 815 made based on application identity or type (i.e., a node could always 816 use a particular PvD for a VOIP application). 818 6.2. Intermediate 820 Applications indirectly participate in PvD selection by specifying 821 hard requirements and soft preferences. As an example, a real time 822 communication application intending to use the connection for the 823 exchange of real time audio / video data may indicate a preference or 824 a requirement for connection quality, which could affect PvD 825 selection (different PvDs could correspond to Internet connections 826 with different loss rates and latencies). 828 Another example is the connection of an infrequently executed 829 background activity, which checks for application updates and 830 performs large downloads when updates are available. For such 831 connections, a cheaper or zero cost PvD may be preferable, even if 832 such a connection has a higher relative loss rate or lower bandwidth. 833 The node performs PvD selection based on applications' inputs and 834 policies and / or user preferences. Some / all properties of the 835 resultant PvD may be exposed to applications. 837 6.3. Advanced 839 PvDs are directly exposed to applications for enumeration and 840 selection. Node polices and / or user choices may still override the 841 applications' preferences and limit which PvD(s) can be enumerated 842 and / or used by the application, irrespective of any preferences 843 which the application may have specified. Depending on the 844 implementation, such restrictions (imposed by node policy and / or 845 user choice) may or may not be visible to the application. 847 7. PvD Trust for PvD-Aware Node 849 7.1. Untrusted PvDs 851 Implicit and explicit PvDs for which no trust relationship exists are 852 considered untrusted. Only PvDs which meet the requirements in 853 Section 7.2 are trusted; any other PvD is untrusted. 855 In order to avoid the various forms of misinformation that could 856 occur when PvDs are untrusted, nodes that implement PvD separation 857 cannot assume that two explicit PvDs with the same identifier are 858 actually the same PvD. A node that makes this assumption will be 859 vulnerable to attacks where, for example, an open Wifi hotspot might 860 assert that it was part of another PvD and thereby attempt to draw 861 traffic intended for that PvD onto its own network. 863 Since implicit PvD identifiers are synthesized by the node, this 864 issue cannot arise with implicit PvDs. 866 Mechanisms exist (for example, [RFC6731]) whereby a PvD can provide 867 configuration information that asserts special knowledge about the 868 reachability of resources through that PvD. Such assertions cannot be 869 validated unless the node has a trust relationship with the PvD; 870 therefore, assertions of this type must be ignored by nodes that 871 receive them from untrusted PvDs. Failure to ignore such assertions 872 could result in traffic being diverted from legitimate destinations 873 to spoofed destinations. 875 7.2. Trusted PvDs 877 Trusted PvDs are PvDs for which two conditions apply: First, a trust 878 relationship must exist between the node that is using the PvD 879 configuration and the source that provided that configuration; this 880 is the authorization portion of the trust relationship. Second, 881 there must be some way to validate the trust relationship. This is 882 the authentication portion of the trust relationship. Two mechanisms 883 for validating the trust relationship are defined. 885 It shall be possible to validate the trust relationship for all 886 advertised elements of a trusted PvD, irrespective of whether the PvD 887 elements are communicated as a whole, e.g., in a single DHCP option, 888 or separately, e.g., in supplementary RA options. The feasibility of 889 mechanisms to implement a trust relationship for all PvD elements 890 will be determined in the respective companion design documents. 892 7.2.1. Authenticated PvDs 894 One way to validate the trust relationship between a node and the 895 source of a PvD is through the combination of cryptographic 896 authentication and an identifier configured on the node. 898 If authentication is done using a public key mechanism such as a TLS 899 certificate or DANE, authentication by itself is not enough since 900 theoretically any PvD could be authenticated in this way. In 901 addition to authentication, the node would need configuration to 902 trust the identifier being authenticated. Validating the 903 authenticated PvD name against a list of PvD names configured as 904 trusted on the node would constitute the authorization step in this 905 case. 907 7.2.2. PvDs Trusted by Attachment 908 In some cases, a trust relationship may be validated by some means 909 other than those described in Section 7.2.1 simply by virtue of the 910 connection through which the PvD was obtained. For instance, a 911 handset connected to a mobile network may know through the mobile 912 network infrastructure that it is connected to a trusted PvD. 913 Whatever mechanism was used to validate that connection constitutes 914 the authentication portion of the PvD trust relationship. 915 Presumably, such a handset would be configured from the factory (or 916 else through mobile operator or user preference settings) to trust 917 the PvD, and this would constitute the authorization portion of this 918 type of trust relationship. 920 8. Contributors 922 The following individuals contributed to this document (listed in no 923 specific order): Alper Yegin (alper.yegin@yegin.org), Aaron Yi Ding 924 (yding@cs.helsinki.fi), Zhen Cao (caozhenpku@gmail.com), Dapeng Liu 925 (liudapeng@chinamobile.com), Dave Thaler (dthaler@microsoft.com), 926 Dmitry Anipko (dmitry.anipko@microsoft.com), Hui Deng 927 (denghui@chinamobile.com), Jouni Korhonen (jouni.nospam@gmail.com), 928 Juan Carlos Zuniga (JuanCarlos.Zuniga@InterDigital.com), Konstantinos 929 Pentikousis (k.pentikousis@huawei.com), Marc Blanchet 930 (marc.blanchet@viagenie.ca), Margaret Wasserman 931 (margaretw42@gmail.com), Pierrick Seite (pierrick.seite@orange.com), 932 Suresh Krishnan (suresh.krishnan@ericsson.com), Teemu Savolainen 933 (teemu.savolainen@nokia.com), Ted Lemon (ted.lemon@nominum.com) and 934 Tim Chown (tjc@ecs.soton.ac.uk). 936 9. Acknowledgments 938 The authors would like to thank (in no specific order) Ian Farrer, 939 Marcus Stenberg and Mikael Abrahamsson for their review and comments. 941 10. IANA Considerations 943 This memo does not include any IANA requests. 945 11. Security Considerations 947 There are at least three different forms of attacks that can be 948 performed using configuration sources that support multiple 949 provisioning domains. 951 Tampering with provided configuration information: An attacker may 952 attempt to modify information provided inside the PvD container 953 option. These attacks can easily be prevented by using message 954 integrity features provided by the underlying protocol used to 955 carry the configuration information. E.g. SEND [RFC3971] would 956 detect any form of tampering with the RA contents and the DHCPv6 957 [RFC3315] AUTH option that would detect any form of tampering with 958 the DHCPv6 message contents. This attack can also be performed by 959 a compromised configuration source by modifying information inside 960 a specific PvD, in which case the mitigations proposed in the next 961 subsection may be helpful. 963 Rogue configuration source: A compromised configuration source, such 964 as a router or a DHCPv6 server, may advertise information about 965 PvDs that it is not authorized to advertise. E.g., a coffee shop 966 WLAN may advertise configuration information purporting to be from 967 an enterprise and may try to attract enterprise related traffic. 968 This may also occur accidentally if two sites choose the same 969 identifier (e.g., "linsky"). 971 In order to detect and prevent this, the client must be able to 972 authenticate the identifier provided by the network. This means 973 that the client must have configuration information that maps the 974 PvD identifier to an authenticatable identity, and must be able to 975 authenticate that identity. 977 In addition, the network must provide information the client can 978 use to authenticate the identity. This could take the form of a 979 PKI-based or DNSSEC-based trust anchor, or a key remembered from a 980 previous leap-of-faith authentication of the identifier. 982 Because the PvD-specific information may come to the network 983 infrastructure with which the client is actually communicating 984 from some upstream provider, it is necessary in this case that the 985 PvD container and its contents be relayed to the client unchanged, 986 leaving the upstream provider's signature intact. 988 Replay attacks: A compromised configuration source or an on-link 989 attacker may try to capture advertised configuration information 990 and replay it on a different link, or at a future point in time. 991 This can be avoided by including a replay protection mechanism 992 such as a timestamp or a nonce inside the PvD container to ensure 993 the validity of the provided information. 995 12. References 997 12.1. Normative References 999 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1000 Requirement Levels", BCP 14, RFC 2119, March 1997. 1002 12.2. Informative References 1004 [I-D.bhandari-dhc-class-based-prefix] 1005 Systems, C., Halwasia, G., Gundavelli, S., Deng, H., 1006 Thiebaut, L., Korhonen, J. and I. Farrer, "DHCPv6 class 1007 based prefix", Internet-Draft draft-bhandari-dhc-class- 1008 based-prefix-05, July 2013. 1010 [I-D.korhonen-dmm-prefix-properties] 1011 Korhonen, J., Patil, B., Gundavelli, S., Seite, P. and D. 1012 Liu, "IPv6 Prefix Mobility Management Properties", 1013 Internet-Draft draft-korhonen-dmm-prefix-properties-03, 1014 October 2012. 1016 [IEEE802.11u] 1017 IEEE, "IEEE Standard 802.11u-2011 (Amendment 9: 1018 Interworking with External Networks)", 2011. 1020 [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and 1021 M. Carney, "Dynamic Host Configuration Protocol for IPv6 1022 (DHCPv6)", RFC 3315, July 2003. 1024 [RFC3971] Arkko, J., Kempf, J., Zill, B. and P. Nikander, "SEcure 1025 Neighbor Discovery (SEND)", RFC 3971, March 2005. 1027 [RFC4861] Narten, T., Nordmark, E., Simpson, W. and H. Soliman, 1028 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1029 September 2007. 1031 [RFC5739] Eronen, P., Laganier, J. and C. Madson, "IPv6 1032 Configuration in Internet Key Exchange Protocol Version 2 1033 (IKEv2)", RFC 5739, February 2010. 1035 [RFC5996] Kaufman, C., Hoffman, P., Nir, Y. and P. Eronen, "Internet 1036 Key Exchange Protocol Version 2 (IKEv2)", RFC 5996, 1037 September 2010. 1039 [RFC6182] Ford, A., Raiciu, C., Handley, M., Barre, S. and J. 1040 Iyengar, "Architectural Guidelines for Multipath TCP 1041 Development", RFC 6182, March 2011. 1043 [RFC6418] Blanchet, M. and P. Seite, "Multiple Interfaces and 1044 Provisioning Domains Problem Statement", RFC 6418, 1045 November 2011. 1047 [RFC6419] Wasserman, M. and P. Seite, "Current Practices for 1048 Multiple-Interface Hosts", RFC 6419, November 2011. 1050 [RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with 1051 Dual-Stack Hosts", RFC 6555, April 2012. 1053 [RFC6724] Thaler, D., Draves, R., Matsumoto, A. and T. Chown, 1054 "Default Address Selection for Internet Protocol Version 6 1055 (IPv6)", RFC 6724, September 2012. 1057 [RFC6731] Savolainen, T., Kato, J. and T. Lemon, "Improved Recursive 1058 DNS Server Selection for Multi-Interfaced Nodes", RFC 1059 6731, December 2012. 1061 [RFC7078] Matsumoto, A., Fujisaki, T. and T. Chown, "Distributing 1062 Address Selection Policy Using DHCPv6", RFC 7078, January 1063 2014. 1065 [TS23402] 3GPP, "3GPP TS 23.402; Architecture enhancements for non- 1066 3GPP accesses; release 12", 2014. 1068 Author's Address 1070 Dmitry Anipko, editor 1071 Unaffiliated 1073 Phone: +1 425 442 6356 1074 Email: dmitry.anipko@gmail.com