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'4' on line 205 looks like a reference -- Missing reference section? '8' on line 630 looks like a reference Summary: 4 errors (**), 0 flaws (~~), 1 warning (==), 6 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Draft R. Stastny 3 Document: draft-stastny-enum-scenarios-00.txt OeFEG 4 Category: Informational 5 Expires: December 2002 June 2002 7 Scenarios for ENUM and ENUM-like Systems 8 10 Status of this Memo 12 This document is an Internet-Draft and is in full conformance with 13 all provisions of Section 10 of RFC2026 [1}. 15 Internet-Drafts are working documents of the Internet Engineering 16 Task Force (IETF), its areas, and its working groups. Note that 17 other groups may also distribute working documents as Internet- 18 Drafts. 20 Internet-Drafts are draft documents valid for a maximum of six months 21 and may be updated, replaced, or obsoleted by other documents at any 22 time. It is inappropriate to use Internet-Drafts as reference 23 material or to cite them other than as "work in progress." 25 The list of current Internet-Drafts can be accessed at 26 http://www.ietf.org/ietf/1id-abstracts.txt 28 The list of Internet-Draft Shadow Directories can be accessed at 29 http://www.ietf.org/shadow.html. 31 Abstract 33 This document analyzes scenarios for ENUM and ENUM-like Systems, both 34 for ENUM used by End Users and also for ENUM-like Systems used by 35 operators for network-specific or infrastructure purposes. It also 36 gives some examples of ENUM Usage and proposes a new URI scheme to be 37 used with ENUM. This may allow a way forward for the definition of 38 ENUM Services and also for the definition of the required URIs and 39 their parameters. 41 This document therefore deals with information stored in the ENUM and 42 the look-up process and the usage of the information retived in this 43 look up process. 45 It does not deal with the administrative process related to the 46 population of the relevant zones. 48 Table of Contents 50 1. Background.....................................................2 51 2. ENUM and ENUM-like Systems.....................................3 52 2.1 User-ENUM and User-ENUM-like Systems..........................3 53 2.2 ENUM-like Systems for Infrastructure Purposes.................3 54 3. Abbreviations..................................................4 55 4. Number ranges to be used in ENUM...............................5 56 4.1 Geographic, mobile and personal numbers.......................5 57 4.2 ENUM Tier 3 and extensions (DDI)..............................5 58 4.3 Service numbers in ENUM.......................................6 59 5. Scenarios for User ENUM and ENUM-like Systems..................7 60 5.1 IP-enabled terminal to IP-enabled terminal....................8 61 5.2 IP-enabled terminal to the GSTN...............................8 62 5.3 From the GSTN to IP-enabled terminals or to the GSTN..........9 63 6. Scenarios for Infrastructure ENUM.............................10 64 6.1 Support of NP services.......................................11 65 6.2 Support for number translation services......................12 66 6.3 Support for routing to IP-based PoIs.........................13 67 6.4 Requirements for Infrastructure ENUM.........................14 68 7. Examples of Usage and Additional Requirements.................14 69 7.1 ENUM Client Applications.....................................15 70 7.2 New URI Scheme enum:.........................................16 71 7.3 Resource Records to be used in ENUM..........................17 72 8. Security Considerations.......................................17 73 9. Acknowlegdements..............................................17 74 10. References...................................................18 75 11. Author's Address.............................................18 77 1. Background 79 The ENUM System as defined in Draft RFC2916bis [2] discusses the use 80 of the DNS for identifying available services connected to an E.164 81 number. Through the transformation of E.164 numbers into DNS names 82 and the use of existing DNS services, especially the NAPTR records as 83 defined in [3], one can look up what services are available for the 84 related E.164 number. 86 The ENUM System as defined in Draft RFC2916bis deals only with the 87 domain "e164.arpa". This also implies that only full E.164 numbers 88 may be used. To clarify, only this system is called "ENUM", all other 89 systems are called ENUM-like Systems within this document. 91 2. ENUM and ENUM-like Systems 93 2.1 User-ENUM and User-ENUM-like Systems 95 In section 1.2 of Draft RFC2916bis it is suggested, that a similar 96 mechanism can be used for private dialing (and/or numbering) plans in 97 a different domain, well-known for all parties using the same plan 98 and the AUS is to be a number without the leading '+'. This is one 99 example of an "ENUM-like" System. 101 In addition, the following scenario may exist for a User-ENUM-like 102 System: 104 The usage of DNS in an alternate root in an Intranet is called in 105 this document "Private-DNS ENUM-like system". Private-DNS ENUM may be 106 used within a company for private dialing plans as mentioned above. 107 In this case the AUS is a number without the leading '+'. 109 In the case of ENUM and the above mentioned scenarios for ENUM-like 110 Systems the ENUM End User has the right to opt-in into the ENUM or 111 ENUM-like system and the ENUM End User is also responsible for 112 provisioning the NAPTR records (although within companies a different 113 policy may apply). 115 It is also the originating user (or a proxy -e.g. a gateway- on 116 behalf of the originating user, if the terminal of the calling user 117 is not capable of accessing the DNS) who is retrieving and evaluating 118 the NAPTR records prior or during establishing the communication. 119 These systems are therefore called "User ENUM" or "User ENUM-like" 120 Systems within this document. 122 2.2 ENUM-like Systems for Infrastructure Purposes 124 All systems for infrastructure purposes are ENUM-like Systems. The 125 following scenarios may exist with for infrastructure purposes 126 (Infrastructure ENUM): 128 a) An operator may use a DNS in an Intranet for his own network- 129 specific purposes e.g. for routing, number portability (NP), 130 freephone (+800) or other IN-like services. These are also variants 131 of "Private DNS ENUM-like Systems". 133 b) A (con)-federation of operators may decide to set up an ENUM-like 134 domain for network-specific purposes (federation infrastructure ENUM- 135 like system) either in an extranet (which is also considered "private 136 DNS") or in a "public" DNS domain different from "e164.arpa", but 137 well-known to the (con)-federation. 139 c) For global services and global usage, a second "golden tree" 140 different from "e164.arpa" (e.g. "e164infra.arpa"" may be set up for 141 network-specific purposes, holding only infrastructure information 142 not related to the user (global infrastructure ENUM-like System). 144 The domain name holder for the domain related to the E.164 Number is 145 in all? (most?) of these cases the operator hosting the E.164 number. 147 The reason for this is the opt-in principle adopted for User-ENUM. 148 Since not all users will opt-into ENUM, not all numbers required by 149 the operator for his service will be available in User-ENUM. The user 150 will also select his ENUM Tier 2 Name Servers, and the operator may 151 have no access-right to this Name Servers, so he has to provision the 152 infrastructure data in other Name Servers of his choice. This 153 requires different domains to be populated. 155 For the entire network-specific infrastructure purposes mentioned 156 above, ENUM-like systems may be used in three ways: 158 a) Independent of the related IN-services on the existing GSTN. In 159 this case the synchronization of the two databases may be 160 problematic. 162 b) ENUM-like systems as a replacement of existing IN-services, 163 providing also an INAP interface (mediation) to the GSTN. 165 c) Access to an existing IN-database, which is providing an ENUM-like 166 DNS interface to IP (mediation), creating the NAPTR records to be 167 returned on the fly. 169 In case b) and in case c) there is no synchronization problem, since 170 the same repository is used from the IP-side and from the GSTN-side. 172 3. Abbreviations 174 ASP Application Service Provider 175 AUS Application Unique String 176 CC Country Code 177 CIC Carrier Identification Code 178 DDI Direct dialing-in 179 DN Dialed Number 180 DNS Domain Name System 181 GSTN Global Switched Telephone Network 182 IN Intelligent Network 183 INAP IN Application Part 184 IPTSP IP Telephony Service Provider 185 NAPTR Naming Authority Pointer 186 NP Number Portability 187 PoI Point of Interconnection 188 PUA Personal User Agent 189 RN Routing Number 190 SCP Service Control Point 191 SIP Session Initiation Protocol 192 TDM Time Division Multiplex 193 UCI Universal Communication Identifier 194 UPT Universal Personal Telecommunication 195 URI Uniform Resource Identifier 196 URL Uniform Resource Locator 197 VASP Value Added Service Provider 198 VoIP Voice over IP 200 4. Number ranges to be used in ENUM 202 ENUM according to Draft RFC2916bis is defined to be used in principle 203 for any E.164 number. 205 ITU-T Recommendation E.164 [4] distinguishes between geographic 206 country codes (CC), CC for global services, CC for networks, shared 207 CC and CC for trials. 209 The usage of ENUM for geographic CC will be a national matter, the 210 usage for other types of CC is currently under investigation within 211 ITU-T SG2/Q1. 213 Nevertheless, especially the rationale for the usage for service 214 numbers will be similar for global and national numbers. 216 4.1 Geographic, mobile and personal numbers 218 ENUM is defined for personal use; it therefore applies in any case in 219 addition to geographic numbers to mobile numbers and to personal 220 numbers (see also below). In all of these cases the ENUM End User is 221 the e164.arpa domain name holder for the related E.164 number and 222 provisioning directly or indirectly his/her NAPTR records in ENUM 223 Tier 2 Name Servers. 225 4.2 ENUM Tier 3 and extensions (DDI) 227 User ENUM may also be used by companies either having a PBX with 228 direct dialing-in (DDI) and/or a switchboard or Centrex. In all cases 229 the company is the domain name holder of the corresponding pilot 230 number and wants to manage these entries in the ENUM Tier 2 Name 231 Server. On the other hand, the company may want to give the right to 232 provision the extension numbers to the individual user. In this case, 233 an additional Tier 3 is necessary. 235 In this case the following scenario applies and the company may 236 provision the Tier 2 Name Servers with the following information: 238 NAPTR Records to point to the switchboard, to e.g. 239 mailto:office@company.com, to the company webpage and NS records 240 pointing to the ENUM Tier 3 Name Servers holding the extensions 241 visible to the public. 243 The company may in addition operate a private ENUM-like system on its 244 intranet holding all extensions. If the company has access to the 245 Internet, clients may distinguish between the private ENUM-like 246 system by entering the extensions without �+� and escape to ENUM with 247 �+�. 249 It is up to the company to make the whole or part of the private 250 ENUM-like system visible to ENUM (e.g. with Split DNS) by linking the 251 private ENUM System to Tier 2 of e164.arpa. 253 4.3 Service numbers in ENUM 255 UPT Numbers 257 UPT Numbers are personal numbers and may either be implemented 258 nationally or internationally. National UPT numbers may be used like 259 geographic and mobile numbers. 261 International UPT based on +878 is currently not deployed in the GSTN 262 with IN-based systems. The only application of international UPT 263 (+87810) is based on IP. This is one example of a proper GSTN- 264 termination on IP. Providing +87810 in ENUM is therefore not 265 necessarily an alternate-line service, since the same termination 266 (Personal User Agent - PUA) can be reached. If the user is registered 267 on an IP-based terminal or on GSTN-based terminal, an incoming call 268 is forwarded to this terminal. The user may also have the different 269 types of call forwarding active. If +87810 is implemented in ENUM, it 270 will allow incoming calls to the PUA from any IP-based terminal. 272 National IN-based implementations of UPT exist. For these UPT numbers 273 the same requirements on enumservices apply as for geographic and 274 mobile numbers. 276 Freephone Numbers: +800, +1-800, +43-800, ...: 278 Freephone numbers on the GSTN require normally two IN-dips, one NP- 279 dip for the CIC to select the Value Added Service Provider 280 (VASP)providing the service and one IN-dip within the network of the 281 VASP for the translation of the number to the DN (depending on 282 origination, time, day, weather). 284 If the assignee decides to enter his number in ENUM, this is a bypass 285 of the operator providing the 800 service (VASP). 287 Question 1: will this be allowed by national regulators or ITU (in 288 case of +800) policy? 290 Question 2: If yes, what are the requirements on the tel URI to 291 provide similar services (origination context, time and day, ...) 292 (see also section 4. Infrastructure ENUM). 294 Even if freephone numbers are not allowed in User-ENUM, the 295 requirements still apply for infrastructure ENUM, either for private- 296 ENUM (the operator replacing his IN-Service by ENUM, or the operator 297 is providing freephone service on an IP-based network (selected by 298 CIC). 300 For freephone numbers additional requirements may be necessary on 301 enumservices and context information (e.g. phone-context, time-of- 302 day). 304 Premium Rate and Shared Cost Numbers: 306 With freephone numbers the loser is the VASP and the winner is the 307 ENUM End User, because he has to pay no charges to the VASP. With 308 premium-rate and shared cost numbers, the loser is the ENUM End User, 309 because he gets no money. But on the other hand, even if ENUM is not 310 used for voice calls, it may be used for e-mail and web-pages with 311 these types of numbers. For the usage in network-specific-ENUM the 312 same applies as for freephone numbers. 314 5. Scenarios for User ENUM and ENUM-like Systems 316 User-ENUM and User ENUM-like systems provide an end-to-end service. 317 The database is populated by the recipient of a communication (the 318 called user, ENUM End User) and the database is queried by the 319 originator ("calling" user) before establishing the communication. 320 Only if the origination terminal is not able (or willing) to access 321 the DNS (e.g. from a phone on the GSTN), the user may use the service 322 of an agent or proxy (e.g. a VoIP-gateway) to query the DNS on his 323 behalf. It is depending on the service offered by the agent, if the 324 communication is established without any further interaction by the 325 originator, or if the originator may choose between different 326 options. 328 Related to voice (or phone) services, User-ENUM is always an 329 alternate line service (this may not be true for infrastructure ENUM- 330 like services). This is because it will be required (e.g. by the 331 ENUM-Forum [5]and also by ETSI TS 102 051 "ENUM Administration in 332 Europe" 6 that the ENUM End User is the assignee of an E.164 Number, 333 and that the related E.164 Number has a termination on the GSTN (a 334 working line or at least an announcement). 336 To clarify, since the GSTN is technology-independent, this does not 337 prevent, that the termination is on an IP-network, as we have seen 338 with UPT. In this case the same terminal or User Agent may be used 339 with ENUM (but not necessarily). 341 The only exception of the above mentioned requirement may be, that 342 special national or international numbering resources are made 343 available for ENUM only usage. But also in this case an announcement 344 may be required on the GSTN. 346 Being an alternate line service implies, that the supplementary 347 services connected to the line terminating on the GSTN (e.g. call 348 forwarding) are not synchronized with the voice services provided by 349 the Application Service Provider (ASP) pointed to with ENUM. This may 350 cause user confusion and should especially be considered in using 351 ENUM for call forwarding purposes. 353 5.1 IP-enabled terminal to IP-enabled terminal 355 As already mentioned above, one of the most popular usages of User 356 ENUM may be providing an alternate line service to the ENUM End User. 357 There are benefits for both sides: the ENUM End User, if connected to 358 the Internet, may be reached on his IP-enabled terminal, which is 359 either a PC, a laptop or an IP-Phone, from any calling user on the 360 Internet 362 The ENUM End User needs to subscribe to either a SIP or H323 VoIP 363 Service and is provided with a proper sip: or h323 address. He then 364 chooses a domain related to one of his existing E.164 numbers to be 365 entered into the ENUM System and adds a NAPTR record with the above 366 URI into this domain. The calling user on the Internet only needs a 367 proper client SW to query the ENUM System and a compatible VoIP 368 Client or IP-Phone. If this is not available, the calling user may 369 still establish a call via the GSTN. 371 5.2 IP-enabled terminal to the GSTN 373 This scenario may be valid, if the calling user may not be able to 374 use the information given in ENUM, or the ENUM End User may decide to 375 enter an URI pointing to another E.164 Number (e.g. using a tel: URI 376 pointing to his mobile phone). 378 No additional provisions are necessary for the ENUM End User, but the 379 calling user on the Internet needs to have a subscription to a VoIP 380 Service Provider providing a gateway to the GSTN and the proper IP 381 Phone client. 383 5.3 From the GSTN to IP-enabled terminals or to the GSTN 385 Since calling users on the GSTN (e.g. from a steam phone) may not be 386 able to access ENUM directly, they need a proxy to access ENUM. These 387 proxies may be VoIP gateways provided by IP Telephony Service 388 Providers (IPTSP). 390 The gateway or the device controlling the gateway (e.g. the 391 softswitch) accesses the ENUM System during call setup. It is up to 392 the IPTSP, how this service is provided in detail. 394 Some examples: 396 ENUM Access Numbers: 398 An IPTSP may provide a gateway from the GSTN to the IP network, which 399 can be reached via an access number. 401 The customer dials an access number to reach an IP Telephony Gateway 402 and dials the E.164 number of the B-Subscriber. The gateway queries 403 the ENUM database, if an entry for the E.164 number exists. If yes, 404 the call is completed according the ENUM entry. If not, the call is 405 placed on the IP network as usual, terminating finally on the GSTN. 407 The service could either be open to the public, or requiring a 408 subscription and identification (similar to a phone or credit card 409 service). In the first case the billing would be the same for any 410 type of call, regardless of destination, in the second case the 411 access number would be a freephone number and the billing to the 412 customer account may be dependant on destination. 414 ENUM Portals: 416 The above mentioned access to the gateway could be enhanced by 417 providing a voice portal, allowing the calling customer to select 418 between different choices, if provided by ENUM. So could the customer 419 leave a voice message in a voice-box or send a voice-mail, if none of 420 the voice services can be reached. 422 IN trigger for ENUM (similar to "call-by-call" or "preselection"): 424 A customer with a GSTN phone could subscribe to a supplementary 425 service, that all outgoing calls are checked first with ENUM. If 426 there is no entry in ENUM, the call will be completed normally on the 427 GSTN. If the call may be completed via ENUM on IP, the tariff may be 428 lower than a call completion on the GSTN. The subscriber may pay a 429 fixed amount per month for this supplementary service. 431 A simple way to implement this supplementary service is to trigger an 432 IN-query for this subscriber and query ENUM via the SCP. If an entry 433 is found, the call is routed to the next IP telephony gateway. If 434 not, the call is treated by the SCP like a normal call and completed 435 on the GSTN. 437 6. Scenarios for Infrastructure ENUM 439 All infrastructure ENUM-like scenarios do not provide an end-to-end 440 service. The ENUM-like DNS database is not provisioned by the End 441 User, even if the number used is an E.164 Number, it is provisioned 442 by the operator hosting the number or another entity. Therefore the 443 opt-in principle does not apply and all required numbers may be 444 entered. This implies that no information violating any End User 445 privacy shall be contained in the database, if it is available on the 446 Internet. 448 The infrastructure ENUM-like DNS database is also not queried by the 449 originating user establishing the communication, even if the database 450 is available on the internet. One reason is that the information is 451 of no direct use for the End User. The database is queried by network 452 operators and service providers only during call setup or within the 453 service provided. In some cases an existing IN database may be used 454 as a repository. 456 The ENUM-like database may be internal to an operator, used by a 457 (con)-federation of operators either in an extranet or in a public 458 domain on the Internet or in a second global tree within .arpa. 460 The ENUM-like database may be used for only one specific service or 461 for more than one service. In the latter case it is necessary to 462 define enumservices to distinguish between the services (ala Service 463 ID in IN?) 465 During one call setup, a number of ENUM queries (dips) may be 466 necessary. 468 The following scenarios are not exhaustive, but may serve as basis 469 for the necessary requirements for enumservice, tel:URI and 470 parameters. 472 6.1 Support of NP services 474 Number portability allows the telephone subscribers to keep their 475 telephone numbers when they change service providers, move to a new 476 location or change the the subscribed service (see draft-ietf-enum- 477 e164-gstn-np-03) 7. If services providers use an IP-based 478 infrastructure to provide telephone services, they need to support 479 number portability as well. This can be achieved by either accessing 480 the existing IN-infrastructure via the existing IN protocols, or by 481 providing equivalent services via an ENUM-like DNS database. 483 As already mentioned in 1.2.2, the ENUM-like DNS database may either 484 be separate from the IN-based database, or may use the same 485 repository. 487 The support of ENUM may therefore apply for the following scenarios: 489 Geographic number portability � an E.164 number is ported between to 490 switching systems of the same operator within an geographic area, if 491 the subscriber is changing location. The porting area is dependant on 492 the national numbering plan used. 494 Provider portability for geographic numbers � an E.164 number is 495 ported from one operator to another operator, but staying on the same 496 location. 498 Provider portability for mobile numbers � an E.164 number is ported 499 from one mobile operators to another within the same country. 501 National service portability (freephone, personal numbers, ...) � an 502 E.164 number is ported from one VASP to another within the same 503 country. 505 Global service portability (freephone, UPT, ...) � an E.164 number is 506 ported from one global service provider to another. A quite 507 challenging example for an infrastructure ENUM implementation may be 508 the number portability in UPT. The current UPT implementation 509 provides service provider portability, but only within the 510 confederation using +87810 (VISIONng). If other confederation 511 implement different numbering ranges either on IP or on the GSTN, 512 infrastructure ENUM may be used for portability between 513 confederations. 515 Although many different implementations of NP exist in different 516 networks and countries, most require the identification of a PoI of 517 the terminating (hosting) network, either by a CIC or a routing 518 number. For IP-based, the identification of the PoI and the protocol 519 used may be sufficient. 521 For service provider portability it is necessary, to find the service 522 provider (carrier, operator) currently hosting the E.164 number and 523 the Point of Interconnect. This is necessary e.g. for number 524 portability of geographic, mobile and service numbers. For geographic 525 number portability the RN may be necessary. 527 For a given number, the following information needs to be retrieved: 529 Service Provider: (CIC, RN, PoI) 530 Protocol used at PoI: (also IP or TDM) 531 Additional Parameters (e.g. context) 532 What else? 534 What are the requirements for enumservices, URIs and parameters? 536 Note that the information retrieved (e.g. PoI) may be dependent on 537 origination information (context). 539 Remark: In this case the dialed number (DN) does not change. 541 6.2 Support for number translation services 543 In case of service portability, if the network hosting the service 544 has been reached, it is necessary to translate the dialed service 545 number into another number - the final destination number. This 546 translation may be dependant of origination information (context), 547 date and time of day and other parameters. Also some billing 548 information may be required. 550 The support of ENUM may therefore apply for the following scenarios: 552 Freephone service � the dialed freephone number (e.g. +800) is 553 translated to the final destination number, depending on additional 554 parameters. 556 The same applies for premium rate, shared cost and other service 557 numbers, like emergency numbers, etc. 559 For a given number, the following information needs to be retrieved: 561 Translated Number: New dialed number (DN) 562 Additional Parameters: (e.g. context, date and time of day, etc.) 563 What else? 565 What are the requirements for enumservices, URIs and parameters? 567 6.3 Support for routing to IP-based PoIs 569 Most phone calls currently are traversing at least three networks, 570 the originating network, the transit network and the destination 571 network, even in national calls. With international calls, even more 572 transit networks may be involved. The PoIs between these networks are 573 in all cases TDM-based, since no IP-based PoIs are defined yet. 575 Currently a number of network operators are migrating from TDM-based 576 networks to NGN IP-based networks by replacing parts of their 577 networks with IP-based infrastructure (e.g. IP trunking). If all 578 three of the above mentioned networks are using IP-based 579 infrastructure within their networks, and the PoIs between the 580 networks are TDM-based, a call may cross TDM-IP gateways six times, 581 causing unacceptable delay and QoS. 583 It is therefore necessary to introduce IP-based PoIs as soon as 584 possible, to allow for the reduction of the number of TDM-IP gateways 585 within a call to one or two. 587 If a certain ingress network offers two types of PoI, it is necessary 588 for the egress network to have some means to select between the two 589 types of PoI offered and also to select the appropriate one. 591 It is proposed to use infrastructure ENUM-like services for this 592 purpose. 594 Since the information about the network infrastructure and the 595 optimal PoI to be used for a certain destination number is only known 596 by the ingress (terminating) network, the appropriate information has 597 to be provisioned in the infrastructure ENUM-like system by the 598 terminating network. The information may be similar to the 599 information used for number portability. 601 The information related to the destination number in the 602 infrastructure ENUM-like service is queried by the originating or 603 transit network. If an IP-based PoI is found, the call is routed on 604 the IP-network directly to the given PoI, if an TDM-based PoI or no 605 information is found, the call is routed via the GSTN. 607 The support of ENUM may therefore apply for the following scenarios: 609 Usage of infrastructure ENUM within a network � if an operator has 610 IP- and TDM-based technology within his network, and certain numbers 611 may only be reached via IP-based technology (e.g. an GSTN access node 612 connected to an IP-gateway), infrastructure ENUM may support a proper 613 routing to his gateway. 615 Usage of infrastructure ENUM on a global scale between networks - if 616 an operator has IP- and TDM-based technology within his network, and 617 certain numbers may only be reached via IP-based technology, he may 618 provide IP- and TDM-based ingress PoIs to his network. It is now up 619 to this operator to provide information related to the E.164 numbers 620 he his hosting within his network in a global infrastructure ENUM 621 database (e.g. e164infra.arpa). The information will be similar to 622 the information provided for NP. 624 It should be mentioned, that this global infrastructure ENUM database 625 may also serve as basis for a global number protability database. 627 6.4 Requirements for Infrastructure ENUM 629 It can be assumed, that within infrastructure ENUM mainly NAPTRs with 630 tel: URIs will be used [8] 632 It is therefore necessary to update the definition of the tel: URI 633 accordingly and also define an enumservice to be used in the NAPTR 634 records. 636 For the ongoing discussion see 9 and "The ENUM 'tel' enumservice" 10 639 7. Examples of Usage and Additional Requirements 641 ENUM was created to allow the mapping E.164 numbers to Internet names 642 (e.g. sip:user@foo) to enable the reachability of VoIP clients (e.g. 643 h323, sip) by E.164 numbers, either from the Internet or from the 644 conventional phone network. 646 In parallel the idea came up to use ENUM as an always up-to-date, 647 public available business card, allowing to point to any URI, but 648 especially to e-mail addresses (at least all ENUM tutorials use a 649 VoIP URI and an e-mail address as an example). 651 If one looks at any business card, one sees normally a name, a street 652 address and/or a postal address, a phone number, a fax number (which 653 is also a phone number), and an e-mail address, and some people now 654 also point to their home-page and eventually to an IM address. Many 655 people also list their mobile phone numbers, indicating intrinsically 656 at least in Europe an sms-enabled number. 658 If one wants to send a text document and both a fax and an e-mail 659 address is provided at the business card, it is the choice of the 660 originator (e.g. depending on the currently available device), 661 whether the document is sent by fax or e-mail. 663 Considering ENUM as an electronic business card service, this 664 information is exactly what an ENUM End User wants to provide and 665 what the originator expects to get, if he queries ENUM. 667 Another way to use ENUM may be to provide URLs in documents or on web 668 pages triggering an ENUM query, e.g. mailto:+12345 or fax:+12345 . In 669 this case it is obvious, that either an e-mail or a Fax should be 670 sent. 672 Note: This requires an update to the relevant URI definitions. 674 7.1 ENUM Client Applications 676 Stand-alone ENUM Client Application 678 The simplest way to trigger an ENUM query from an IP-enabled terminal 679 is to use a stand-alone application. In this case either an E.164 680 Number +12345 or a non-E.164 Number 12345 is entered. In case of the 681 E.164 Numbers, the client is querying e164.arpa, in the other case a 682 previously defined alternate domain may be used (e.g. a private 683 dialing plan). 685 The application queries ENUM or the ENUM-like System and displays the 686 results (all the NAPTR records) in a human readable format similar to 687 the information displayed on a business card or an e-mail signature, 688 i.e containing the URI and additional information of the type of 689 service. 691 The user may now select a suitable URI and cut and paste or drag and 692 drop the URI in the appropriate application (e.g. MS Outlook or a SIP 693 Phone). The application may also be launched via mouse click, if the 694 results are displayed as URLs. 696 It is therefore necessary to define the enumservices in such a way, 697 that a proper grouping if the information displayed may be possible. 699 From a specific application 701 If the user has already launched a specific application (e.g. an e- 702 mail client or a SIP or H323 phone), the application may have an add- 703 on, that in case of the input of an E.164 Number in the format +12345 704 an ENUM query is launched. 706 In this case only ONE NAPTR record shall be selected, to replace the 707 entered E.164 Number with the appropriate URI. 709 It is therefore necessary to define the enumservices, which allow the 710 application SW to identify in combination with the URI the proper 711 NAPTR record to be used. 713 From an URL containing an E.164 number 715 It will also be useful to extend the definitions of existing URIs or 716 define new URIs, which may be imbedded in documents or web pages to 717 launch an ENUM query and the appropriate application: 719 This will be easy for mailto. If mailto is used in the format 720 mailto:+12345, this should imply, that an ENUM query is launched and 721 the proper client application is provided with the result, namely an 722 mailto:user@host (or the proper client is launched and then the ENUM 723 query is done, if the application is ENUM enabled). 725 7.2 New URI Scheme enum: 727 An enumservice (e.g. "enum") may be required to indicate that all 728 services for a given E.164 number can be found within the ENUM entry 729 of another E.164 number (instead of using CNAME, which may case 730 problems in general and also within the DDDS algorithm). 732 For example, a user owns three numbers, but wants to administrate his 733 NAPTR records only in one place by pointing all his numbers to one 734 set of services. 736 Since the single NAPTR record requires an URI, which is not linked to 737 a specific service, a new URI scheme "enum:" is required, which 738 points to this E.164 number. 740 It should be noted, that this new URI may also be convenient for 741 usage to trigger an ENUM query from a link in a web-page or document 742 (e.g. in an e-mail signature). 744 The new URI has the format enum:+number and shall trigger the launch 745 e.g. the lauch of the above mentioned ENUM stand-alone application, 746 showing all information stored under this number. 748 7.3 Resource Records to be used in ENUM 750 Within the domain e164.arpa NS, NAPTR, CNAME and TXT records may be 751 used. 753 NS Records are used for delegation, the combined usage of NS records 754 and NAPTR records shall be possible (e.g. for announcements, tones or 755 a pointer to a switchboard). 757 CNAME may be used e.g. for avoiding duplication of data, if parallel 758 NDCs are used to reach the same destination during numbering plan 759 modifications (e.g. pointing from 2.2.2.3.4.e164.arpa to 760 1.3.4.e164.arpa). The usage of CNAME for ENUM End Users is ffs). 762 TXT records may be used within the delegation tree to add information 763 and ALSO to the ENUM End User. Therefore at least the stand-alone 764 clients shall be able to display the information contained in the TXT 765 records. 767 Note: It is one target of the trials to investigate the best way to 768 inform users of invalid or incomplete numbers. This may either be 769 done with NAPTR records pointing to tones or announcements, TXT 770 records or the file (info) enumservice. Also the usage of the 771 possibility to add additional information by the user with TXT 772 records should be investigated. TXT records may also be useful during 773 the trial for maintenance information. 775 8. Security Considerations 777 This document does not not introduce new security implications other 778 than those associated with the ENUm Service as defined in Draft 779 RFC2916bis. 781 9. Acknowlegdements 783 The author would like to thank Lawrence Conroy and Rudi Brandner for 784 their comments and invaluable help. 786 10. References 788 1 Scott Bradner, RFC2026, "The Internet Standards Process � Revision 789 3, "October 1996. 791 2 P. Faltstrom, "The E.164 to URI DDDS Application", 792 draft-ietf-enum-rfc2916bis-01.txt, 793 Work in Progress, March 2002 795 3 M.Mealling, "Dynamic Delegation Discovery System (DDDS) Part 796 Three: The DNS Database" 797 draft-ietf-urn-dns-ddds-database-08.txt, 798 Work in Progress, February 2002 800 4 ITU-T Rec E.164 "The International Public Telecommunication Number 801 Plan", Recommendation E.164, May 1997. 803 5 US ENUM Forum, www.enum-forum.org 805 6 ETSI Technical Specification TS 102 051 "ENUM Administration in 806 Europe" Work in Progress, April 2002 808 7 M. Foster, T. McGarry and J. Yu "Number Portability in the GSTN: 809 An Overview", draft-ietf-enum-e164-np-03.txt, 810 Work in Progress, March 2002. 812 8 Vaha-Sipila, A., "URLs for Telephone Calls", 813 RFC2806, April 2000. 815 9 J. Yu, "Extensions to the 'tel' and 'fax' URLs to Support Number 816 Portability and Freephone Service", draft-yu-tel-url�04.txt, Work 817 in Progress, March 2002. 819 10 R. Brandner and L. Conroy, "The ENUM 'tel' enumservice", draft- 820 brandner-enum-tel-00.txt, Work in Progress, February 2002. 822 11. Author's Address 824 Richard Stastny 825 OeFEG 826 Postbox 147 Phone: +43-664-420-4100 827 1103 Vienna, Austria Email: richard.stastny@oefeg.at