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'1') (Obsoleted by RFC 8224) == Outdated reference: A later version (-04) exists of draft-peterson-modern-teri-00 == Outdated reference: A later version (-18) exists of draft-ietf-stir-certificates-02 == Outdated reference: A later version (-02) exists of draft-wendt-modern-drip-00 Summary: 1 error (**), 0 flaws (~~), 14 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Peterson 3 Internet-Draft T. McGarry 4 Intended status: Informational NeuStar, Inc. 5 Expires: September 22, 2016 March 21, 2016 7 Modern Problem Statement, Use Cases, and Framework 8 draft-peterson-modern-problems-04.txt 10 Abstract 12 The functions of the public switched telephone network (PSTN) are 13 rapidly migrating to the Internet. This is generating new 14 requirements for many traditional elements of the PSTN, including 15 telephone numbers (TNs). TNs no longer serve simply as telephone 16 routing addresses, they are now identifiers which may be used by 17 Internet-based services for a variety of purposes including session 18 establishment, identity verification, and service enablement. This 19 problem statement examines how the existing tools for allocating and 20 managing telephone numbers do not align with the use cases of the 21 Internet environment, and proposes a framework for Internet-based 22 services relying on TNs. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on September 22, 2016. 41 Copyright Notice 43 Copyright (c) 2016 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 2.1. Actors . . . . . . . . . . . . . . . . . . . . . . . . . 5 61 2.2. Data Types . . . . . . . . . . . . . . . . . . . . . . . 7 62 2.3. Data Management Architectures . . . . . . . . . . . . . . 8 63 3. Framework . . . . . . . . . . . . . . . . . . . . . . . . . . 9 64 4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 10 65 4.1. Acquisition . . . . . . . . . . . . . . . . . . . . . . . 11 66 4.1.1. CSP Acquires TNs from Registrar . . . . . . . . . . . 11 67 4.1.2. User Acquires TNs from CSP . . . . . . . . . . . . . 12 68 4.1.3. CSP Delegates TNs to Another CSP . . . . . . . . . . 12 69 4.1.4. User Acquires TNs from a Delegate . . . . . . . . . . 13 70 4.1.5. User Acquires Numbers from Registrar . . . . . . . . 13 71 4.2. Management . . . . . . . . . . . . . . . . . . . . . . . 13 72 4.2.1. Management of Administrative Data . . . . . . . . . . 13 73 4.2.1.1. CSP to Registrar . . . . . . . . . . . . . . . . 14 74 4.2.1.2. User to CSP . . . . . . . . . . . . . . . . . . . 14 75 4.2.1.3. User to Registrar . . . . . . . . . . . . . . . . 15 76 4.2.2. Management of Service Data . . . . . . . . . . . . . 15 77 4.2.2.1. CSP to other CSPs . . . . . . . . . . . . . . . . 15 78 4.2.2.2. User to CSP . . . . . . . . . . . . . . . . . . . 16 79 4.2.3. Managing Change . . . . . . . . . . . . . . . . . . . 16 80 4.2.3.1. Changing the CSP for an Existing Communications 81 Service . . . . . . . . . . . . . . . . . . . . . 16 82 4.2.3.2. Terminating a Service . . . . . . . . . . . . . . 16 83 4.3. Retrieval . . . . . . . . . . . . . . . . . . . . . . . . 17 84 4.3.1. Retrieval of Public Data . . . . . . . . . . . . . . 17 85 4.3.2. Retrieval of Semi-restricted Administrative Data . . 18 86 4.3.3. Retrieval of Semi-restricted Service Data . . . . . . 18 87 4.3.4. Retrieval of Restricted Data . . . . . . . . . . . . 18 88 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19 89 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 90 7. Security Considerations . . . . . . . . . . . . . . . . . . . 19 91 8. Informative References . . . . . . . . . . . . . . . . . . . 20 92 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 94 1. Problem Statement 96 The challenges of utilizing telephone numbers (TNs) on the Internet 97 have been known for some time. Internet telephony provided the first 98 use case for routing telephone numbers on the Internet in a manner 99 similar to how calls are routed in the public switched telephone 100 network (PSTN). As the Internet had no service for discovering the 101 endpoints associated with telephone numbers, ENUM [3] created a DNS- 102 based mechanism for resolving TNs in an IP environment, by defining 103 procedures for translating TNs into URIs for use by protocols such as 104 SIP [2]. The resulting database was designed to function in a manner 105 similar to the systems that route calls in the PSTN. Originally, it 106 was envisioned that ENUM would be deployed as a global hierarchical 107 service, though in practice, it has only been deployed piecemeal by 108 various parties. Most notably, ENUM is used as an internal network 109 function, and is hardly used between service provider networks. The 110 original ENUM concept of a single root, e164.arpa, proved to be 111 politically and practically challenging, and less centralized models 112 have thus flourished. Subsequently, the DRINKS [4] framework showed 113 ways that authorities might provision information about TNs at an 114 ENUM service or similar Internet-based directory. These technologies 115 have also generally tried to preserve the features and architecture 116 familiar from the PSTN numbering environment. 118 Over time, Internet telephony has encompassed functions that differ 119 substantially from traditional PSTN routing and management, 120 especially as non-traditional providers have begun to utilize 121 numbering resources. An increasing number of enterprises, over-the- 122 top Voice over IP providers, text messaging services, and related 123 non-carrier services have become heavy users of telephone numbers. 124 An enterprise, for example, could deploy an IP PBX that receives a 125 block of telephone numbers from a carrier and then in turn distribute 126 those numbers to new IP telephones when they associate with the PBX. 127 Internet services offer users portals where they can allocate new 128 telephone numbers on the fly, assign multiple "alias" telephone 129 numbers to a single line service, implement various mobility or find- 130 me-follow-me applications, and so on. Peer-to-peer telephone 131 networks have encouraged experiments with distributed databases for 132 telephone number routing and even allocation. 134 This dynamic control over telephone numbers has few precedents in the 135 traditional PSTN outside of number portability. Number portability 136 has been implemented in many countries, and the capability of a user 137 to choose and change their service provider while retaining their TN 138 is widely implemented now. However, TN administration processes 139 rooted in PSTN technology and policies dictate that this be an 140 exception process fraught with problems and delays. Originally, 141 processes were built to associate a specific TN to a specific service 142 provider and never change it. With number portability, the industry 143 had to build new infrastructure, new administrative functions and 144 processes to change the association of the TN from one service 145 provider to another. Thanks to the increasing sophistication of 146 consumer mobile devices as Internet endpoints as well as telephones, 147 users now associate TNs with many Internet applications other than 148 telephony. This has generated new interest in models similar to 149 those in place for administering freephone services in the United 150 States, where a user purchases a number through a sort of number 151 registrar and controls its administration (such as routing) on their 152 own, typically using Internet services to directly make changes to 153 the service associated with telephone numbers. 155 Most TNs today are assigned to specific geographies, at both an 156 international level and within national numbering plans. Numbering 157 practices today are tightly coupled with the manenr that service 158 providers interconnect, as well as how TNs are routed and 159 administered: the PSTN was carefully designed to delegate switching 160 intelligence geographically. In interexchange carrier routing in 161 North America, for example, calls to a particular TN are often handed 162 off to the terminating service provider close to the geography where 163 that TN is assigned. But the overwhelming success of mobile 164 telephones has increasing eroded the connection between numbers and 165 regions. Furthermore, the topology of IP networks is not anchored to 166 geography in the same way that the telephone network is. In an 167 Internet environment, establishing a network architecture for routing 168 TNs could depend little on geography. Adapting TNs to the Internet 169 requires more security, richer datasets and more complex query and 170 response capabilities than previous efforts have provided. 172 This document will create a common understanding of the problem 173 statement related to allocating, managing, and resolving TNs in an IP 174 environment. It outlines a framework and lists motivating use cases 175 for creating IP-based mechanisms for TNs. It is important to 176 acknowledge at the outset that there are various evolvling 177 international and national policies and processes related to TNs, and 178 any solutions need to be flexible enough to account for variations in 179 policy and requirements. 181 2. Definitions 183 This section provides definitions for actors, data types and data 184 management architectures as they are discussed in this document. 185 Different numbering spaces may instantiate these roles and concepts 186 differently: practices that apply to non-geographic freephone 187 numbers, for example, may not apply to geographic numbers, and 188 practices that exist under one Numbering Authority may not be 189 permitted under another. The purpose of this framework is to 190 identify the characteristics of protocol tools that will satisfy the 191 diverse requirements for telephone number acquisition, management, 192 and retrieval on the Internet. 194 2.1. Actors 196 The following roles of actors are defined in this document: 198 Numbering Authority: A regulatory body within a country that manages 199 that country's TNs. The Numbering Authority decides national 200 numbering policy for the nation, region, or other domain for which 201 it has authority, including what TNs can be allocated, and which 202 are reserved. 204 Registry: An entity that administers the allocation of TNs based on 205 a Numbering Authority's policies. Numbering authorities can act 206 as the Registries themselves, or they can outsource the function 207 to other entities. There are two subtypes of Registries: an 208 Authoritative Registry and a Distributed Registry. The general 209 term Registry in this document refers to both kinds of Registries. 211 Authoritative Registry: An authoritative Registry is a single entity 212 with sole responsibility for specific numbering resources. 214 Distributed Registry: Distributed Registries are multiple Registries 215 responsible for the same numbering resources. 217 Registrar: An entity that distributes the telephone numbers 218 administered by a Registry; typically, there are many Registrars 219 that can distribute numbers from a single Registry, through 220 Registrars may serve multiple Registries as well. A Registrar has 221 business relationships with its assginees and collects 222 administrative information from them. 224 Communication Service Provider (CSP): A provider of communications 225 services to Users, where those services can be identified by TNs. 226 This includes both traditional telephone carriers or enterprises 227 as well as service providers with no presence on the PSTN who use 228 TNs. This framework does not assume that any single CSP provides 229 all the communications service related to a particular TN. 231 Service Enabler: An entity that works with CSPs to enable 232 communication service to a User; perhaps a vendor, or third-party 233 integrator. 235 User: An individual reachable through a communications service; 236 usually a customer of a communication service provider. 238 Government Entity: An entity that, due to legal powers deriving from 239 national policy, has privileged access to information about number 240 administration under certain conditions. 242 Note that an individual, company or other entity may act in one or 243 more of the roles above; for example, a company may be a CSP and also 244 a Registrar. Although Numbering Authorities are listed as actors, 245 they are unlikely to actually participate in the protocol flows 246 themselves, though in some situations a Numbering Authority and 247 Registry may be the same administrative entitiy. 249 All actors that are recipients of numbering resources, be they a CSP, 250 Service Enabler, or User, can also be said to have a relationship to 251 a Registry of either an assignee or delegate: 253 Assignee: An actor that is assigned a TN directly by a Registrar; an 254 assignee always has a direct relationship with a Registrar. 256 Delegate: An actor that is delegated a TN from an assignee or 257 another delegate, who does not necessarily have a direct 258 relationship with a Registrar. Delegates may delegate one or more 259 of their TN assignment(s) to one or more further downstream 260 subdelegates. 262 As an example, consider a case where a Numbering Authority also acts 263 as a Registry, and it issues 10,000 blocks of TNs to CSPs, which in 264 this case also act as Registrars. CSP/Registrars would then be 265 responsible for distributing numbering resources to Users and other 266 CSPs. In this case, an enterprise deploying IP PBXs also acts as a 267 CSP, and it acquires number blocks for its enterprise seats in chunks 268 of 100 from a CSP acting as a Registrar with whom the enterprise has 269 a business relationship. The enterprise is in this case the 270 assignee, as it receives numbering resources directly from a 271 Registrar. As it doles out individual numbers to its Users, the 272 enterprise delegates its own numbering resources to those Users and 273 their communications endpoints. The overall ecosystem might look as 274 follows. 276 +---------+ 277 |Numbering| 278 |Authority|Registry 279 +----+----+ 280 | 281 V 10,000 TNs 282 +---------+ 283 | CSP |Registrar 284 +----+----+ 285 | 286 V 100 TNs 287 +---------+ 288 | PBX |Assignee 289 +---------+ 290 | 291 V 1 TN 292 +---------+ 293 | User |Delegate 294 +---------+ 296 Figure 1: Chain of Number Assignment 298 2.2. Data Types 300 The following data types are defined in this document: 302 Administrative Data: assignment data related to the TN and the 303 relevant actors; it includes TN status (assigned, unassigned, 304 etc.), contact data for the assignee or delegate, and typically 305 does not require real-time performance as access to this data is 306 not required for ordinary call or session establishment. 308 Service Data: data necessary to enable service for the TN; it 309 includes addressing data, service features, and so on, and 310 typically does require real-time performance, in so far as this 311 data typically must be queried during call set-up. 313 Administrative and service data can fit into three categories: 315 Public: data that anyone can access, for example a list of which 316 numbering resources (unallocated number ranges) are available for 317 acquisition from the Registry. 319 Semi-restricted: data that a subset of actors can access, for 320 example CSPs may be able to access other CSP's service data. 322 Restricted: data that is only available to a small subset of actors, 323 for example a Government Entity may be able access contact 324 information for a User. 326 While it might appear there are really only two categories, public 327 and restricted based on requestor, the distinction between semi- 328 restricted and restricted is helpful for the use cases below. 330 2.3. Data Management Architectures 332 This framework generally assumes that administrative and service data 333 is maintained by CSPs, Registrars, and Registries. The role of a 334 Registry described here is a "thin" one, where the Registry manages 335 basic allocation information for the numbering space, such as 336 information about whether or not the number is assigned, and if 337 assigned, by which Registrar. It is the Registrar that in turn 338 manages detailed administrative data about those assignments, such as 339 contact or billing information for the assignee. In some models, 340 CSPs and Registrars will be composed (the same administrative 341 entity), and in others the Registry and Registrar may similarly be 342 composed. Typically, service data resides largely at the CSP itself, 343 though in some models a "thicker" Registry may itself contain a 344 pointer to the servicing CSP for a number or number block. In 345 addition to traditional centralized Registries, this framework also 346 supports environments where the same data is being managed by 347 multiple administrative entities, and stored in many locations. A 348 distribute registry system is discussed further in [15]. 350 Data store: a service that stores and enables access to 351 administrative and/or service data. 353 Reference Address: a URL that dereferences to the location of the 354 data store. 356 Distributed data stores: refers to administrative or service data 357 being stored with multiple actors. For example, CSPs could 358 provision their service data to multiple other CSPs. 360 Distributed Registries: refers to multiple Registries managing the 361 same numbering resource. Actors could interact with one or 362 multiple Registries. The Registries would update each other when 363 change occurs. The challenge is to ensure there are no clashes, 364 e.g., two Registries assigning the same TN to two different 365 actors. 367 3. Framework 369 The framework outlined in this document requires three Internet-based 370 mechanisms for managing and resolving telephone numbers (TNs) in an 371 IP environment. These mechanisms will likely reuse existing 372 protocols for sharing structured data; it is unlikely that new 373 protocol development work will be required, though new information 374 models specific to the data itself will be a major focus of framework 375 development. Likely candidates for reuse here include work done in 376 DRINKS and WEIRDS, as well as the TeRI [12] framework. 378 These protocol mechanisms are scoped in a way that makes them likely 379 to apply to a broad range of future policies for number 380 administration. It is not the purpose of this framework to dictate 381 number policy, but instead to provide tools that will work with 382 policies as they evolve going forward. These mechanisms therefore do 383 not assume that number administration is centralized, nor that number 384 allocations are restricted to any category of service providers, 385 though these tools must and will work in environments with those 386 properties. 388 The three mechanisms are: 390 Acquisition: a protocol mechanism for acquiring TNs, including an 391 enrollment process. 393 Management: a protocol mechanism for associating data with TNs. 395 Retrieval: a protocol mechanism for retrieving data about TNs. 397 The acquisition mechanism will enable actors to acquire TNs for use 398 with a communications service. The acquisition mechanism will 399 provide a means to request numbering resources from a service 400 operated by a Registrar, CSP or similar actor. TNs may be requested 401 either on a number-by-number basis, or as inventory blocks. Any 402 actor who grants numbering resources will retain metadata about the 403 assignment, including the responsible organization or individual to 404 whom numbers have been assigned. 406 The management mechanism will let actors provision data associated 407 with TNs. For example, if a User has been assigned a TN, they may 408 select a CSP to provide a particular service associated with the TN, 409 or a CSP may assign a TN to a User upon service activation. In 410 either case, a mechanism is needed to provision data associated with 411 the TN at that CSP. 413 The retrieval mechanism will enable actors to learn information about 414 TNs, typically by sending a request to a CSP. For some information, 415 an actor may need to send a request to a Registry rather than a CSP. 416 Different parties may be authorized to receive different information 417 about TNs. 419 As an example, a CSP might use the acquisition interface to acquire a 420 chunk of numbers from a Registrar. Users might then provision 421 administrative data associated with those numbers at the CSP through 422 the management interface, and query for service data relating to 423 those numbers through the retrieval interface of the CSP. 425 +--------+ 426 |Registry| 427 +---+----+ 428 | 429 V 430 +---------+ 431 |Registrar| 432 +---------+ 433 \ 434 \\ 435 Acquisition \\ 436 \\+-------+ 437 \ CSP | 438 +---+---+ 439 A A 440 | | 441 Management | | Retrieval 442 | | 443 | | 444 +-------++ ++-------+ 445 | User | | User | 446 +--------+ +--------+ 448 Figure 2: Example of the Three Interfaces 450 4. Use Cases 452 The high-level use cases in this section will provide an overview of 453 the expected operation of the three interfaces in the MODERN problem 454 space. 456 4.1. Acquisition 458 There are various scenarios for how TNs can be acquired by the 459 relevant actors: a CSP, Service Enabler, or User. There are three 460 actors from which numbers can be acquired: a Registrar, a CSP and a 461 User (presumably one who is delegating to another party). It is 462 assumed that Registrars are either composed with Registries, or that 463 Registrars have established business relationships with Registries 464 that enable them to distribute the numbers that the Registries here 465 administer. In these use cases, a User may acquire TNs either from a 466 CSP or a Registry, or from an intermediate delegate. 468 4.1.1. CSP Acquires TNs from Registrar 470 The most fundamental and traditional numbering use case is one where 471 a CSP, such as a carrier, requests a block of numbers from a 472 Registrar to hold as inventory or assign to customers. 474 Through some out-of-band business process, a CSP develops a 475 relationship with a Registrar. The Registrar maintains a profile of 476 the CSP and what qualifications they possess for requesting TNs. The 477 CSP may then request TNs from within a specific pool of numbers in 478 the authority of the Registry; such as region, mobile, wireline, 479 tollfree, etc. The Registrar must authenticate and authorize the 480 CSP, and then either grant or deny a request. When an assignment 481 occurs, the Registry creates and stores administrative information 482 related to the assignment such as TN status and contact information, 483 and removes the specific TN(s) from the pool of those that are 484 available for assignment. As a part of the acqusition and assignment 485 process, the Registry provides any necessary credentials (for 486 example, STIR certificates [13]) to the CSP to be used to prove the 487 assignment for future transactions. 489 Before it is eligible to receive TN assignments, per the policy of a 490 national authority, the CSP may need to have submitted (again, 491 through some out-of-band process) additional qualifying information 492 such as current utilization rate or a demand forecast. 494 There are two scenarios under which a CSP requests resources; they 495 are requesting inventory, or they are requesting for a specific User 496 or delegate. TNs assigned to a User are always considered assigned 497 by the Registrar, not inventory. In this use case, after receiving a 498 number assignment from the Registrar, a User will then obtain 499 communications service from a CSP, and provide to the CSP the TN to 500 be used for that service along with the credential. The CSP will 501 associate service information for that TN, e.g., service address, and 502 make it available to other CSPs to enable interoperability. The CSP 503 may need to update the Registrar regarding this service activation 504 (this is part of the "TN status" maintained by the Registrar). 506 4.1.2. User Acquires TNs from CSP 508 Today, a User typically acquires a TN from CSP when signing up for 509 communications service or turning on a new device. In this use case, 510 the User becomes the delegate of the CSP. 512 A User creates or has a relationship with the CSP, and subscribes to 513 a communications service which includes the use of a TN. The CSP 514 collects and stores administrative data about the User. The CSP then 515 activates the User on their network and creates any necessary service 516 data to enable interoperability with other CSPs. The CSP could also 517 update public or privileged databases accessible by other Actors. 518 The CSP provides any necessary credentials to the User (for example, 519 a STIR certificate [13]) to prove the assignment for future 520 transactions. Such credential could be delegated from the one 521 provided by the Registrar to the CSP to continue the chain of 522 assignment. 524 The CSP could assign a TN from its existing inventory or it could 525 acquire a new TN from the Registrar as part of the assignment 526 process. If it assigns it from its existing inventory it would 527 remove the specific TN from the pool of those available for 528 assignment. It may also update the Registrar about the assignment so 529 the Registrar has current assignment data. 531 4.1.3. CSP Delegates TNs to Another CSP 533 A reseller or a service bureau might acquire a block of numbers from 534 a CSP to be issued to Users. 536 In this case, the delegate CSP has a business relationship with the 537 assignee CSP. The assignee CSP collects and stores administrative 538 data about the delegate. The assignee then activates the delegate on 539 their network and creates any necessary service data to enable 540 interoperability with other CSPs. The CSP could also update public 541 or privileged databases accessible by other Actors. The CSP provides 542 any necessary credentials to the delegate CSP (for example, a STIR 543 certificate [13]) to prove the assignment for future transactions. 544 Such credentials could be delegated from the one provided by the 545 Registry to the CSP to continue the chain of assignment. 547 The CSP could assign a block from its existing inventory or it could 548 acquire new TNs from the Registrar as part of the assignment process. 549 If it assigns it from its existing inventory it would remove the 550 specific TN from the pool of those available for assignment. It may 551 also update the Registrar about the assignment so the Registrar has 552 current assignment data. The Delegate may need to provide 553 utilization and assignment data to the Registry, either directly or 554 through the CSP. 556 4.1.4. User Acquires TNs from a Delegate 558 Aquiring a TN from a delegate follows the process in Section 4.1.2, 559 as it should be similar to how a User acquires TNs from a CSP. In 560 this case, the delegate re-delegating the TNs would be performing 561 functions done by the CSP, e.g., providing any credentials, 562 collecting administrative data, creative service data, and so on. 564 4.1.5. User Acquires Numbers from Registrar 566 Today, a user wishing to acquire a freephone number may browse the 567 existing inventory through one or more Registrars, comparing their 568 prices and services. Each such Registrar either is a CSP, or has a 569 business relationship wtih a CSP to provide services for that 570 freephone number. 572 Acquiring a TN from a Registrar follows the process in Section 4.1.1, 573 as it should be similar to how a CSP acquires TNs from a Registrar. 574 In this case, the User must establish some business relationship 575 directly to a Registrar, similarly to how such functions are 576 conducted today when Users purchase domain names. For the purpose of 577 status information kept by the Registry, TNs assigned to a User are 578 always considered assigned, not inventory. 580 In this use case, after receiving a number assignment from the 581 Registrar, a User will then obtain communications service from a CSP, 582 and provide to the CSP the TN to be used for that service. The CSP 583 will associate service information for that TN, e.g., service 584 address, and make it available to other CSPs to enable 585 interoperability. 587 4.2. Management 589 The management protocol mechanism is needed to associate 590 administrative and service data with TNs, and may be used to refresh 591 or rollover associated credentials. 593 4.2.1. Management of Administrative Data 595 Administrative data is primarily related to the status of the TN, its 596 administrative contacts, and the actors involved in providing service 597 to the TN. Protocol interactions for administrative data will 598 therefore predominantly occur between CSPs and Users to the 599 Registrar, or between Users and delegate CSPs to the CSP. 601 Most administrative data is not a good candidate for a distributed 602 data store model. Access to it does not require real-time 603 performance therefore local caches are not necessary. And it will 604 include sensitive information such as user and contact data. 606 Some of the data could lend itself to being publicly available, such 607 as CSP and TN assignment status. In that case it would be deemed 608 public information for the purposes of the retrieval interface. 610 4.2.1.1. CSP to Registrar 612 After a CSP acquires a TN or block of TNs from the Registrar (per 613 Section 4.1.1 above), it then provides administrative data to the 614 Registrar as a step in the acquisition process. The Registrar will 615 authenticate the CSP and determine if the CSP is authorized to 616 provision the administrative data for the TNs in question. The 617 Registry will update the status of the TN, i.e., that it is 618 unavailable for assignment. The Registrar will also maintain 619 administrative data provided by the CSP. 621 Changes to this administrative data will not be frequent. Examples 622 of changes would be terminating service (see Section 4.2.3.2) and 623 changing a CSP or delegate. Changes should be authenticated by a 624 credential to prove administrative responsibility for the TN. 626 In a distributed Registry model, TN status, e.g., allocated, 627 assigned, available, unavailable, would need to be provided to other 628 Registries in real-time. Other administrative data could be sent to 629 all Registries or other Registries could get a reference address to 630 the host Registry's data store. 632 4.2.1.2. User to CSP 634 After a User acquires a TN or block of TNs from a CSP, the User will 635 provide administrative data to the CSP. The CSP commonly acts as a 636 Regisrar in this case, maintaining the administrative data and only 637 notify the Registry of the change in TN status. In this case, the 638 Registry maintains a reference address to the CSP/Registrar's 639 administrative data store so relevant actors have the ability to 640 access the data. Alternatively a CSP could send the administrative 641 data to an external Registrar to store. If there is a delegate 642 between the CSP and user, they will have to ensure there is a 643 mechanism for the delegate to update the CSP as change occurs. 645 4.2.1.3. User to Registrar 647 If the User has a direct relationship with the Registrar, then 648 naturally the user could could provision administrative data 649 associated with their TN directly to the Registrar. This is the 650 case, for example, with the freephone example, where a User has a 651 business relationship with its freephone provider, and the freephone 652 provider maintains account and billing data. While delegates 653 necessarily are not assignees, some environments as an optimization 654 might want to support a model where the delegate updates the 655 Registrar directly on changes, as opposed to sending that data to the 656 CSP or through the CSP to the Registrar. As stated already, the 657 protocol should enable Users to acquire TNs directly from a 658 Registrar, which Registrar may or may not also act as a CSP. In 659 these cases the updates would be similar to that described in 660 Section 4.2.1.1. 662 4.2.2. Management of Service Data 664 Service data is data required by an originating or intermediate CSP 665 to enable communications service to a User: a SIP URI is an example 666 of one service data element commonly used to route communications. 667 CSPs typically create and manage service data, however it is possible 668 that delegates and Users could as well. For most use cases involving 669 individual Users, it is anticipated that lower-level service 670 information changes would be communicated to CSPs via existing 671 protocols (like the baseline SIP REGISTER [2] method) rather than 672 through any new interfaces defined by MODERN. 674 4.2.2.1. CSP to other CSPs 676 After a User enrolls for service with a CSP, in the case where the 677 CSP was assigned the TN by a Registrar, the CSP will then create a 678 service address (such as a SIP URI) and associate it with the TN. 679 The CSP needs to update this data to enable service interoperability. 680 There are multiple ways that this update can occur, though most 681 commonly service data is exposed through the retrieval interface (see 682 Section 4.3. For certain deployment architectures, like a 683 distributed data store model, CSPs may need to provide data directly 684 to other CSPs. 686 If the CSP is assigning a TN from its own inventory it may not need 687 to perform service data updates as change occurs because the existing 688 service data associated with inventory may be sufficient once the TN 689 is put in service. They would however likely update the Registry on 690 the change in status. 692 4.2.2.2. User to CSP 694 Users could also associate service data to their TNs at the CSP. An 695 example is a User acquires a TN from the Registrar (as described in 696 Section 4.1.5) and wants to provide that TN to the CSP so the CSP can 697 enable service. In this case, once the user provides the number to 698 the CSP, the CSP would update the Registry or other actors as 699 outlined in Section 4.2.2.1. 701 4.2.3. Managing Change 703 This section will address some special use cases that were not 704 covered in other sections of 4.2. 706 4.2.3.1. Changing the CSP for an Existing Communications Service 708 A User who subscribes to a communications service, and received their 709 TN from that CSP, wishes to retain the same TN but move their service 710 to a different CSP. The User provides their credential to the new 711 CSP and the CSP initiates the change in service. 713 In the simplest scenario, where there's an authoritative composed 714 Registry/Registrar that maintains service data, the new CSP provides 715 the new service data with the User's credential to the Registry/ 716 Registrar, which then makes the change. The old credential is 717 revoked and a new one is provided. The new CSP or the Registrar 718 would send a notification to the old CSP, so they can disable 719 service. The old CSP will undo any delegations to the User, 720 including invalidating any cryptographic credentials (e.g. STIR 721 certificates [13]) previously granted to the User. Any service data 722 maintained by the CSP must be removed, and similarly, the CSP must 723 delete any such information it provisioned in the Registry. 725 In a similar model to common practice in some environments today, the 726 User could provide their credential to the old CSP, and the old CSP 727 initiates the change in service. 729 If there was a distributed Registry that maintained service data, the 730 Registry would also have to update the other Registries of the 731 change. 733 4.2.3.2. Terminating a Service 735 A User who subscribes to a communications service, and received their 736 TN from the CSP, wishes to terminate their service. At this time, 737 the CSP will undo any delegations to the User, including invalidating 738 any cryptographic credentials (e.g. STIR certificates [13]) 739 previously granted to the User. Any service data maintained by the 740 CSP must be removed, and similarly, the CSP must delete any such 741 information it provisioned in the Registrar. 743 The TN will change state from assigned to unassigned, the CSP will 744 update the Registry. Depending on policies the TN could go back into 745 the Registry, CSP, or delegate's pool of available TNs and would 746 likely enter an aging process. 748 In an alternative use case, a User who received their own TN 749 assignment directly from a Registrar terminates their service with a 750 CSP. At this time, the User might terminate their assignment from 751 the Registrar, and return the TN to the Registry for re-assignment. 752 Alternatively, they could retain the TN and elect to assign it to 753 some other service at a later time. 755 4.3. Retrieval 757 Retrieval of administrative or service data will be subject to access 758 restrictions based on the category of the specific data; public, 759 semi-restricted or restricted. Both administrative and service data 760 can have data elements that fall into each of these categories. It 761 is expected that the majority of administrative and service data will 762 fall into the semi-restricted category: access to this information 763 may require some form of authorization, though service data crucial 764 to reachability will need to be accessible. In some environments, 765 it's possible that none of the service data will be considered 766 public. 768 The retrieval protocol mechanism for semi-restricted and restricted 769 data needs a way for the receiver of the request to identify the 770 originator of the request and what is being requested. The receiver 771 of the request will process that request based on this information. 773 4.3.1. Retrieval of Public Data 775 Under most circumstances, a CSP wants its communications service to 776 be publicly reachable through TNs, so the retrieval interface 777 supports public interfaces that permit clients to query for service 778 data about a TN. Some service data may however require that the 779 client by authorized to receive it, per the use case in Section 4.3.3 780 below. 782 Public data can simply be posted on websites or made available 783 through a publicly available API. Public data hosted by a CSP may 784 have a reference address at the Registry. 786 4.3.2. Retrieval of Semi-restricted Administrative Data 788 A CSP is having service problems completing calls to a specific TN, 789 so it wants to contact the CSP serving that TN. The Registry 790 authorizes the originating CSP to access to this information. It 791 initiates a query to the Registry, the Registry verifies the 792 requestor and the requested data and Registry responds with the 793 serving CSP and contact data. 795 Alternatively that information could be part of a distributed data 796 store and not stored at the Registry. In that case, the CSP has the 797 data in a local distributed data store and it initiates the query to 798 the local data store. The local data store responds with the CSP and 799 contact data. No verification is necessary because it was done when 800 the CSP was authorized to receive the data store. 802 4.3.3. Retrieval of Semi-restricted Service Data 804 A User on a CSP's network calls a TN. The CSP initiates a query for 805 service data associated with the TN to complete the call, and will 806 receive special service data because the CSP operates in a closed 807 environment where different CSPs receive different responses, and 808 only authorized CSPs may access service data. The query and response 809 must have real-time performance. There are multiple scenarios for 810 the query and response. 812 In a distributed data store model each CSP distributes its updated 813 service data to all other CSPs. The originating CSP has the service 814 data in its local data store and queries it. The local data store 815 responds with the service data. The service data can be a reference 816 address to a data store maintained by the serving CSP or it can be 817 the service address itself. In the case where it's a reference 818 address the query would go to the serving CSP and they would verify 819 the requestor and the requested data and respond. In the case where 820 it's the service address it would process the call using that. 822 In some environments, aspects of the service data may reside at the 823 Registry itself (for example, the assigned CSP for a TN), and thus a 824 the query may be sent to the Registry. The Registry verifies the 825 requestor and the requested data and responds with the service data, 826 such as a SIP URI containing the domain of the assigned CSP. 828 4.3.4. Retrieval of Restricted Data 830 In this case, a Government Entity wishes to access information about 831 a particular User, who subscribes to a communications service. The 832 entity that operates the Registry on behalf of the National Authority 833 in this case has some pre-defined relationship with the Government 834 Entity. When the CSP acquired TNs from the National Authority, it 835 was a condition of that assignment that the CSP provide access for 836 Government Entities to telephone numbering data when certain 837 conditions apply. The required data may reside either in the CSP or 838 in the Registrar. 840 For a case where the CSP delegates a number to the User, the CSP 841 might provision the Registrar (or itself, if the CSP is composed with 842 a Registrar) with information relevant to the User. At such a time 843 as the Government Entity needs information about that User, the 844 Government Entity may contact the Registrar or CSP to acquire the 845 necessary data. The interfaces necessary for this will be the same 846 as those described in Section 4.3; the Government Entity will be 847 authenticated, and an authorization decision will be made by the 848 Registrar or CSP under the policy dictates established by the 849 National Authority. 851 5. Acknowledgments 853 We would like to thank Henning Schulzrinne for his contributions to 854 this problem statement and framework, and to thank Pierce Gorman for 855 detailed comments. 857 6. IANA Considerations 859 This memo includes no instructions for the IANA. 861 7. Security Considerations 863 The acquisition, management, and retrieval of administrative and 864 service data associated with telephone numbers raises a number of 865 security issues. 867 Any mechanism that allows an individual or organization to acquire 868 telephone numbers will require a means of mutual authentication, of 869 integrity protection, and of confidentiality. A Registry as defined 870 in this document will surely want to authenticate the source of an 871 acquisition request as a first step in the authorization process to 872 determine whether or not the resource will be granted. Integrity of 873 both the request and response is essential to ensuring that tampering 874 does not allow attackers to block acquisitions, or worse, to 875 commandeer resources. Confidentiality is essential to preventing 876 eavesdroppers from learning about allocations, including the 877 personally identifying information associated with the administrative 878 or technical contracts for allocations. 880 A management interface for telephone numbers has similar 881 requirements. Without proper authentication and authorization 882 mechanisms in place, an attack could use the management interface to 883 disrupt service data or administrative data, which could deny service 884 to users, enable new impersonation attacks, prevent billing systems 885 from operating properly, and cause similar system failures. 887 Finally, a retrieval interfaces has its own needs for mutual 888 authentication, integrity protection, and for confidentiality. Any 889 CSP sending a request to retrieve service data associated with a 890 number will want to know that it is reaching the proper authority, 891 that the response from that authority has not been tampered with in 892 transit, and in most cases the CSP will not want to reveal to 893 eavesdroppers the number it is requesting or the response that it has 894 received. Similarly, any service answering such a query will want to 895 have a means of authenticating the source of the query, and of 896 protecting the integrity and confidentiality of its responses. 898 8. Informative References 900 [1] Peterson, J. and C. Jennings, "Enhancements for 901 Authenticated Identity Management in the Session 902 Initiation Protocol (SIP)", RFC 4474, 903 DOI 10.17487/RFC4474, August 2006, 904 . 906 [2] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 907 A., Peterson, J., Sparks, R., Handley, M., and E. 908 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 909 DOI 10.17487/RFC3261, June 2002, 910 . 912 [3] Bradner, S., Conroy, L., and K. Fujiwara, "The E.164 to 913 Uniform Resource Identifiers (URI) Dynamic Delegation 914 Discovery System (DDDS) Application (ENUM)", RFC 6116, 915 DOI 10.17487/RFC6116, March 2011, 916 . 918 [4] Channabasappa, S., Ed., "Data for Reachability of Inter- 919 /Intra-NetworK SIP (DRINKS) Use Cases and Protocol 920 Requirements", RFC 6461, DOI 10.17487/RFC6461, January 921 2012, . 923 [5] Watson, M., "Short Term Requirements for Network Asserted 924 Identity", RFC 3324, DOI 10.17487/RFC3324, November 2002, 925 . 927 [6] Jennings, C., Peterson, J., and M. Watson, "Private 928 Extensions to the Session Initiation Protocol (SIP) for 929 Asserted Identity within Trusted Networks", RFC 3325, 930 DOI 10.17487/RFC3325, November 2002, 931 . 933 [7] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication 934 of Named Entities (DANE) Transport Layer Security (TLS) 935 Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August 936 2012, . 938 [8] Elwell, J., "Connected Identity in the Session Initiation 939 Protocol (SIP)", RFC 4916, DOI 10.17487/RFC4916, June 940 2007, . 942 [9] Schulzrinne, H., "The tel URI for Telephone Numbers", 943 RFC 3966, DOI 10.17487/RFC3966, December 2004, 944 . 946 [10] Rosenberg, J. and C. Jennings, "The Session Initiation 947 Protocol (SIP) and Spam", RFC 5039, DOI 10.17487/RFC5039, 948 January 2008, . 950 [11] Peterson, J., Jennings, C., and R. Sparks, "Change Process 951 for the Session Initiation Protocol (SIP) and the Real- 952 time Applications and Infrastructure Area", BCP 67, 953 RFC 5727, DOI 10.17487/RFC5727, March 2010, 954 . 956 [12] Peterson, J., "A Framework and Information Model for 957 Telephone-Related Information (TeRI)", draft-peterson- 958 modern-teri-00 (work in progress), October 2015. 960 [13] Peterson, J., "Secure Telephone Identity Credentials: 961 Certificates", draft-ietf-stir-certificates-02 (work in 962 progress), July 2015. 964 [14] Barnes, M., Jennings, C., Rosenberg, J., and M. Petit- 965 Huguenin, "Verification Involving PSTN Reachability: 966 Requirements and Architecture Overview", draft-jennings- 967 vipr-overview-06 (work in progress), December 2013. 969 [15] Bellur, H. and C. Wendt, "Distributed Registry Protocol", 970 draft-wendt-modern-drip-00 (work in progress), October 971 2015. 973 [16] Rosenberg, J. and H. Schulzrinne, "Session Initiation 974 Protocol (SIP): Locating SIP Servers", RFC 3263, 975 DOI 10.17487/RFC3263, June 2002, 976 . 978 Authors' Addresses 980 Jon Peterson 981 Neustar, Inc. 982 1800 Sutter St Suite 570 983 Concord, CA 94520 984 US 986 Email: jon.peterson@neustar.biz 988 Tom McGarry 989 Neustar, Inc. 990 1800 Sutter St Suite 570 991 Concord, CA 94520 992 US 994 Email: tom.mcgarry@neustar.biz