Internet Draft James Yu Document: NeuStar, Inc. Category: Informational July 2000 Extensions to the "tel" and "fax" URLs to Support Number Portability Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [RFC]. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Informational-Expiration on January 2001 1 Extension to the "tel" and "fax" URLs to Support NP July 2000 1. Abstract Number portability (NP) allows the telephone subscribers to keep their telephone numbers when they change service provider, move to a new location, or change the subscribed services. The NP implementations in many countries presently support service provider portability for geographic numbers and non-geographical numbers. It has been identified that NP has impacts on several works-in-progress at the IETF. One of the impacts is to carry the NP related information in the SIP INVITE message. This document proposed the extensions to the "tel" and "fax" Uniform Resource Locators (URLs) to support NP so that they can be used to carry the NP related information in the Session Initiation Protocol (SIP) Request-URI. 2. Introduction This document proposes the extensions to the "tel" and "fax" Uniform Resource Locators (URLs) for supporting number portability (NP). [NP] provides an overview of the NP in the GSTN and points out the impacts of NP in several works-in-progress at the IETF Working Groups. One of the impacts is to be able to carry the NP related information in the Session Initiation Protocol (SIP) INVITE message. The NP related information includes the dialed directory number, a routing number and an indicator that indicates whether a query to the Number Portability Database (NPDB) has been performed. The routing number allows the network, either the Global Switched Telephone Network (GSTN) or the IP-based network, to route the call to the network or switch that currently serves the dialed called party number that has ported out of the donor network. The NPDB dip indicator informs the network entities downstream towards the terminating network (e.g., the network that currently serves the called party number) that NPDB dip has been performed; therefore, there is no need to dip the NPDB again. The dialed called party number is needed at the terminating switch so that the call can be terminated to a correct line card. If the routing number only points to the terminating network, the called party number would be used for another NPDB query to retrieve another routing number that is typically a network-specific routing number for routing the call to the terminating switch. 3. SIP Request-URI The SIP INVITE message contains a "Request-URI" element that is used by the SIP servers for making routing decisions. As indicated in [SIP], SIP servers may support Request-URIs with schemes other than "SIP," for example, the "tel" URI scheme. [TEL] specifies the URL schemes "tel," "fax" and "modem" for specifying the location of a terminal in the phone network and the connection types (modes of operation) that can be used to connect to that entity. By examining the SIP URL and "tel" URL, it seems that the "tel" URL is a better Informational - Expiration in January 2001 2 Extension to the "tel" and "fax" URLs to Support NP July 2000 place to carry the NP related information. Since the "fax" URL may be used for fax calls, both the "tel" and "fax" URLs need to be enhanced to support NP. 4. Proposed extensions to the "tel" RUL Scheme The following shows the extensions to the "tel" URL. Only the impacted items/lines are shown below. global-phone-number = (no change) (no change) (no change) *1(number-portability) local-phone-number = (no change) (no change) (no change) (no change) future-extension) *1(number-portability) number-portability = ";" routing-number *1(";" npdb-dip-indicator) routing-number = rn-tag "=" *1("+") rn-ident rn-tag = "rn" rn-ident = *15(hex excluding "F") npdi-dip-indicator = npdi-tag "=" npdi-ident npdi-tag = "npdi" npdi-ident = "yes" / "no" It is assumed that national routing number may appear with other global-phone-number information and international routing number may appear with other local-phone-number information. The routing number digit can be any hexadecimal digit except the digit "F." The routing number and the NPDB dip indicator can appear at most once if present. The routing number can contain hexadecimal digits from 0 to E. When the routing number is present, the NPDB dip indicator may or may not be present. This is because that the routing number may be present independent of NP. When the "npdi" parameter is not present, it indicates that either NPDB dip has not been performed (equivalent to npdi=no) or NP is not relevant. If a SIP server is set to perform the NPDB queries and if a received INVITE message does not contain "yes" in the "npdi" parameter, it will perform the NPDB query. The NPDB query is outside the scope of this document. The routing number received in the response (plus the "+" and the country code when necessary) will replace the routing number in the "rn" parameter if present or will be used by the new "rn" parameter if "rn" parameter is not present. The "npdi" parameter will be set to "yes" in this case. The routing number can be a global routing number (e.g., with "+" and the country code) or a local (e.g., network-specific) routing number. When the "rn" parameter is present, it must be used for making routing decisions (e.g., against the TRIP routing tables)[TRIP]. If the "rn" parameter is not present, the telephone number right after "tel:" is used as the routing number. Informational - Expiration in January 2001 3 Extension to the "tel" and "fax" URLs to Support NP July 2000 It is possible that interworking between SIP and Signaling System No. 7 (SS7) Integrated Services Digital Network User Part (ISUP) is required at the border between the Global Switched Telephone Network (GSTN) and the IP-based network. For SIP to GSTN interworking and depending on the ISUP support of NP, the information in the "tel" URL will be mapped/carried in the proper ISUP parameters. For example, for the GSTN in the U.S., the routing number in the "rn" parameter is carried in the ISUP Called Party Number Parameter. The phone number after "tel:" is carried in the ISUP Generic Address Parameter. Only national numbers are carried (e.g., without the "+" and the country code) in the ISUP parameter. The "npdi" parameter that contains "yes" cause the Forward Call Indicator parameter to be properly set to indicate that NPDB has been dipped. If the terminating GSTN supports concatenated routing number and directory number (e.g., in Europe), then the routing number and the phone number are concatenated and put in the ISUP Called Party Number parameter. The NOA value will be set according the terminating GSTN's NP standards. For GSTN to IP interworking, when the ISUP signaling contains the NP related information, the NP related information is mapped to the "tel" URL. This happens for domestic calls where the originating GSTN has performed the NPDB query, or for international calls that have arrived at the terminating country's GSTN where that GSTN has performed the NPDB query. It is assumed that the GSTN routes the call via the IP-based network to the terminating switch or network in the same country, and SIP and ISUP interworking is involved. For the GSTN in the U.S., the interworking is straightforward. The indication in the ISUP Forward Call Indicator parameter that NPDB dip has been performed will set "npdi" to "yes," the number in the Called Party Number parameter plus the "+" and the country code, if a global routing number, is carried in the "rn" parameter, and called party number in the Generic Address Parameter plus the "+" and the country code, if a global phone number, appears after "tel:". For GSTN that supports concatenated routing number and directory number (e.g., in Europe), the IP entity that performs the interworking needs to know the routing number used by the GSTN so that the routing number and the directory number in the concatenated format in the ISUP Called Party Number parameter can be separate out and transported in the "rn" parameter and after "tel:" by adding the "+" and the country code to them if they are global routing number and phone numbers. 5. Proposed extension to the "fax" URL Scheme The following shows the extensions to the "fax" URL. Only the impacted items/lines are shown below. fax-global-phone = (no change) (no change) (no change) Informational - Expiration in January 2001 4 Extension to the "tel" and "fax" URLs to Support NP July 2000 future extension) *1(number-portability) fax-local-phone = (no change) (no change) (no change) (no change) future-extension) *1(number-portability) number-portability = ";" routing-number *1(";" npdb-dip-indicator) routing-number = rn-tag "=" *1("+") rn-ident rn-tag = "rn" rn-ident = *15(hex excluding "F") npdi-dip-indicator = npdi-tag "=" npdi-ident npdi-tag = "npdi" npdi-ident = "yes" / "no" The same discussions in Section 5 also apply to this section. 6. Examples To simply the example and to focus on the "tel" URL in the Request- URI, only the Request-Line of a complete SIP INVITE message is shown. A SIP server receives an INVITE message as shown below where +1-202-533-1234 is the dialed called party number and has been ported out of the donor network. INVITE tel:+1-202-533-1234 SIP/2.0 Assume that this SIP server is set to perform the NPDB query. Since this INVITE message does not contain the "npdi" parameter, this SIP server will perform a NPDB query. After receiving a response back from a NPDB, it formulates the following SIP INVITE message: INVITE tel:+1-202-533-1234;rn=+1-202-544-0000;npdi=yes SIP/2.0 This SIP server then uses the "rn" parameter to make the routing decisions (e.g., using the routing number in the "rn" parameter to check against the TRIP tables to determine the terminating GSTN gateway). If the dialed called party number +1-202-533-1234 is not ported and the dialed called party number can be used as the routing number, the outbound SIP INVITE message may look like INVITE tel:+1-202-533-1234;rn=+1-202-533-1234;npdi=yes SIP/2.0 or INVITE tel:+1-202-533-1234;npdi=yes SIP/2.0 The concept is that "rn," if present, is used for making routing decisions, and the phone number after "tel:" is used if "rn" is not present. Informational - Expiration in January 2001 5 Extension to the "tel" and "fax" URLs to Support NP July 2000 7. Conclusion This Internet Draft proposes extensions to the "tel" and "fax" URLs described in [TEL] to allow the SIP to carry the NP related information in the "tel" and "fax" URLs. If agreed, it is proposed to incorporate the proposed extensions in the next revision of RFC2806. REFERENCES [NP] M. Foster, T. McGarry and J. Yu, "Number Portability in the GSTN: An Overview," draft-foster-e164-gstn-np-01.txt, July 2000. [TEL] A. Vaha-Sipila, "URLs for Telephone Calls," RFC 2806, April 2000. [SIP] M. Handley, H. Schulzrinne, E. Schooler and J. Rosenberg, "SIP: Session Initiation Protocol," draft--ietf-sip- rfc2543bis-00.ps, May 2000. [TRIP] J. Rosenberg, H. Salama and M. Squire, draft-ietf-iptel-trip- 02.txt, "Telephony Routing Information Protocol (TRIP)," May 2000. Acknowledgement The author would like to thank Jonathan Rosenberg and Henning Schulzrinne for the discussion of SIP support of NP. Full Copyright Statement "Copyright (C) The Internet Society (date). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. 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