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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group P Faltstrom 2 Internet-Draft Tele2 3 Expires: July 25, 2000 January 25, 2000 5 E.164 number and DNS 6 draft-faltstrom-e164-05.txt 8 Status of this Memo 10 This document is an Internet-Draft and is in full conformance with 11 all provisions of Section 10 of RFC2026. 13 Internet-Drafts are working documents of the Internet Engineering 14 Task Force (IETF), its areas, and its working groups. Note that 15 other groups may also distribute working documents as 16 Internet-Drafts. 18 Internet-Drafts are draft documents valid for a maximum of six 19 months and may be updated, replaced, or obsoleted by other documents 20 at any time. It is inappropriate to use Internet-Drafts as reference 21 material or to cite them other than as "work in progress." 23 The list of current Internet-Drafts can be accessed at 24 http://www.ietf.org/ietf/1id-abstracts.txt 26 The list of Internet-Draft Shadow Directories can be accessed at 27 http://www.ietf.org/shadow.html. 29 This Internet-Draft will expire on July 25, 2000. 31 Copyright Notice 33 Copyright (C) The Internet Society (2000). All Rights Reserved. 35 Abstract 37 This document discusses the use of DNS for storage of E.164 numbers. 38 More specifically, how DNS can be used for identifying available 39 services connected to one E.164 number. Routing of the actual 40 connection using the service selected using these methods is not 41 discussed. 43 Discussion on this Internet-Draft is to be held on the mailing list 44 ietf-e164-dns@imc.org, which is hosted by the Internet Mail 45 Consortium. To subscribe, send an email to 46 ietf-e164-dns-request@imc.org, with the text "subscribe" as the only 47 word in the body of the mail. There is an archive of the mailing 48 list at . 50 1. Introduction 52 The NAPTR[1] records in DNS[3] can be used for looking up what 53 services are available for a specific domainname. This technology is 54 used for finding what services exists given an E.164 number. 56 1.1 Terminology 58 "Must" or "Shall" - Software that does not behave in the manner that 59 this document says it must is not conformant to this document. 61 "Should" - Software that does not follow the behavior that this 62 document says it should may still be conformant, but is probably 63 broken in some fundamental way. 65 "May" - Implementations may or may not provide the described 66 behavior, while still remaining conformant to this document. 68 2. E.164 numbers and DNS 70 The domain "e164.int." is being populated in order to provide the 71 infrastructure in DNS for storage of E.164 numbers. In order to 72 facilitate distributed operations, this domain is divided into 73 subdomains. Holders of E.164 numbers which want to be listed in DNS 74 should contact the appropriate zone administrator in order to be 75 listed, by examining the SOA resource record associated with the 76 zone, just like in normal DNS operations. 78 To find the DNS names for a specific E.164 number, the following 79 procedure is to be followed: 81 1. See that the E.164 number is written in its full form, including 82 the countrycode IDDD. Example: +46-8-56264000. 84 2. Remove all characters part from the digits. Example: 46856264000 86 3. Put dots (".") between each digit. Example: 87 4.6.8.5.6.2.6.4.0.0.0 89 4. Change the order of the digits. Example: 0.0.0.4.6.2.6.5.8.6.4 91 5. Append the domain "e164.int" to the end. Example: 92 0.0.0.4.6.2.6.5.8.6.4.e164.int 94 3. Identifying available services 96 For a record in DNS, the NAPTR record is used for identifying 97 available ways of contacting a specific node identified by that 98 name. Specifically it can be used for knowing what services exists 99 for a specific domainname, including phone numbers by the use of the 100 e164.int domain as described above. 102 The identification is using the NAPTR resource record defined for 103 use in the URN resolution process, but it can be generalized in a 104 way that suits the needs specified in this document. 106 3.1 The NAPTR record 108 The key fields in the NAPTR RR are order, preference, service, 109 flags, regexp, and replacement. For a detailed description, see: 111 o The order field specifies the order in which records MUST be 112 processed when multiple NAPTR records are returned in response to 113 a single query. 115 o The preference field specifies the order in which records SHOULD 116 be processed when multiple NAPTR records have the same value of 117 "order". 119 o The service field specifies the resolution protocol and 120 resolution service(s) that will be available if the rewrite 121 specified by the regexp or replacement fields is applied. 123 o The flags field contains modifiers that affect what happens in 124 the next DNS lookup, typically for optimizing the process. 126 o The regexp field is one of two fields used for the rewrite rules, 127 and is the core concept of the NAPTR record. 129 o The replacement field is the other field that may be used for the 130 rewrite rule. 132 Note that the client applies all the substitutions and performs all 133 lookups, they are not performed in the DNS servers. Note also that 134 it is the belief that regexps should rarely be used. The replacement 135 field seems adequate for the vast majority of situations. 137 3.1.1 Specific use of some fields in the NAPTR record 139 The flags can be "s" or "a" for the next step in the resolution 140 process described in this document. "s" flag means that the next 141 lookup should be for SRV records, and "a" that the result of the 142 rewrite is a URI. Other flags are the "a" and the "p" flags. 144 The service supported for a call must be N2R. 146 3.1.2 Example of use 148 tele2.se. 149 ;; ord pr fl service re replacement 150 IN NAPTR 100 10 "a" "sip+N2R" "" "sip:information@tele2.se" 151 IN NAPTR 102 10 "a" "smtp+N2R" "" "mailto:information@tele2.se" 153 This describes that the domain tele2.se is preferrable contacted via 154 the SIP protocol, secondly via SMTP (for VPIM voicemail over SMTP 155 for example). 157 In both cases, the next step in the resolution process is to use the 158 resolution mechanism for each of the protocols, (SIP and SMTP) to 159 know what node to contact for each. 161 3.1.3 When the virtual address is a phone number 163 When the target address is a phone number, it is first translated 164 into a RR name in the e164.int domain according to the method 165 described above. 167 Example: 169 2.8.0.4.6.2.6.5.8.6.4.e164.int. 170 IN NAPTR 10 10 "a" "sip+N2R" "" "sip:paf@swip.net". 171 IN NAPTR 102 10 "s" "potscall+N2R" "" _potscall._tcp.paf.swip.net. 172 IN NAPTR 102 10 "a" "smtp+N2R" "" "mailto:paf@swip.net". 174 Note that the prefered method is to use the SIP protocol, but the 175 result of the rewrite of the NAPTR record is a URI (the "a" flag in 176 the NAPTR record). In the case of the protocol SIP, the URI might be 177 a SIP URI, which is resolved as described in RFC 2543[4]. 179 The rest of the resolution of the routing is done as described 180 above. 182 3.1.4 The potscall protocol name 184 The potscall protocol name is just a placeholder so one knows that 185 the protocol to use is plain old telephony. Because the protocol is 186 not run on top of IP, the address to use when addressing the endnode 187 has to be a phone number. This address is given back when looking up 188 the SRV record for the _potscall._tcp service in the given domain. 190 Example: 192 _potscall._tcp.paf.swip.net. 194 IN SRV 10 10 2.8.0.4.6.2.6.5.8.6.4.e164.int. 195 IN SRV 20 10 0.0.0.4.6.2.6.5.8.6.4.e164.int. 197 4. IANA Considerations 199 IANA is to allocate the protocol name "potscall" as a placeholder 200 for a protocol name in the SRV record type. No portnumber have to be 201 allocated for this protocol name. 203 5. Security Considerations 205 As this system is built on top of DNS, one can not be sure that the 206 information one get back from DNS is more secure than any DNS query. 207 To solve that, the use of DNSSEC for securing and verifying zones is 208 to be recommended. 210 The caching in DNS can make the propagation time for a change take 211 the same amount of time as the time to live for the NAPTR and SRV 212 records in the zone that is changed. The TTL should because of that 213 be kept to a minimum. The use of this in an environment where 214 IP-addresses are for hire (i.e. DHCP) must therefore be done very 215 carefully. 217 6. Acknowledgement 219 I thank the people at Ericsson, especially Bjorn Larsson, for 220 support and ideas, and especially the group which implemented this 221 scheme in their lab to see that it worked. I also thank the people 222 of ITU-T SG2, Working Party 1/2 (Numbering, Routing, Global Mobility 223 and Service Definition) for comments, and Leif Sunnegardh at Tele2 224 for information about how SS7 really works. 226 References 228 [1] Mealling, M and R Daniel, "The Naming Authority Pointer (NAPTR) 229 DNS Resource Record", Internet-Draft 230 draft-ietf-urn-naptr-rr-03.txt, June 1998. 232 [2] Gulbrandsen, A and R Daniel, "A DNS RR for specifying the 233 location of services (DNS SRV)", Internet-Draft 234 draft-ietf-urn-naptr-rr-03.txt, June 1998. 236 [3] Mockapetris, P, "Domain names - Implementation and 237 Specification", RFC 1035, November 1987. 239 [4] Handley, M, Schulzrinne, H, Schooler, E and J Rosenberg, "SIP: 240 Session Initiation Protocol", RFC 2543, March 1999. 242 Author's Address 244 Patrik Faltstrom 245 Tele2 246 Borgarfjordsgatan 16 247 127 61 Kista 248 Sweden 250 EMail: paf@swip.net 251 URI: http://www.tele2.se 253 Appendix A. Example SIP 255 Caller (A) uses a phone, connected to the PSTN network, on number 256 +46-8-7525252. 258 Callee (B) is buying a service by provider X, which is telephony 259 over the Internet via the use of SIP. 261 Callee want to get reached on the message number +46-76-11223344, 262 which is in this example supposed to be directed to the correct SIP 263 URI. 265 On the buissness card, the callee have printed the number 266 +46-76-11223344 (and probably the SIP URI 267 "sip:foobar@x.example.net". 269 Caller reads the buissness card, lifts the handle, and punches the 270 number +46-76-11223344. 272 The SCP looks up the NAPTR record in DNS for 273 4.4.3.3.2.2.1.1.6.7.6.4.e164.int. The DNS server for Number Inc. has 274 the following information in its DNS: 276 4.4.3.3.2.2.1.1.6.7.6.4.e164.int. IN SOA .... 277 IN NS .... 278 IN NAPTR 100 10 "a" "sip+N2R" ""sip:foobar@x.example.net". 280 This shows to the switch that the only way B can be contacted is via 281 the SIP protocol, using the URI "sip:foobar@x.example.net". 283 The resolution of the SIP URI, using SRV records etc, is described 284 in appendix D of RFC 2543. 286 Full Copyright Statement 288 Copyright (C) The Internet Society (2000). All Rights Reserved. 290 This document and translations of it may be copied and furnished to 291 others, and derivative works that comment on or otherwise explain it 292 or assist in its implmentation may be prepared, copied, published 293 and distributed, in whole or in part, without restriction of any 294 kind, provided that the above copyright notice and this paragraph 295 are included on all such copies and derivative works. However, this 296 document itself may not be modified in any way, such as by removing 297 the copyright notice or references to the Internet Society or other 298 Internet organizations, except as needed for the purpose of 299 developing Internet standards in which case the procedures for 300 copyrights defined in the Internet Standards process must be 301 followed, or as required to translate it into languages other than 302 English. 304 The limited permissions granted above are perpetual and will not be 305 revoked by the Internet Society or its successors or assigns. 307 This document and the information contained herein is provided on an 308 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 309 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 310 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 311 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 312 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 314 Acknowledgement 316 Funding for the RFC editor function is currently provided by the 317 Internet Society.