sipping B. Rosen Internet-Draft Marconi Expires: November 16, 2004 May 18, 2004 Dialstring parameter for the sip URI draft-rosen-iptel-dialstring-00.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. This Internet-Draft will expire on November 16, 2004. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract RFC2806bis explicitly disclaims that tel uris may not represent a dial string. That leaves no way specify a dialstring in a standardized way. Great confusion exists with the SIP URI parameter "user=phone", and specifically, if it can represent a dial string. This memo creates a new value for the user parameter "dialstring", so that one may specify "user=dialstring" to encode a dialstring as a SIP URI. Rosen Expires November 16, 2004 [Page 1] Internet-Draft Dialstring parameter May 2004 Table of Contents 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 2. Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 5 Intellectual Property and Copyright Statements . . . . . . . . 6 Rosen Expires November 16, 2004 [Page 2] Internet-Draft Dialstring parameter May 2004 1. Requirements notation The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 2. Problem A user at a phone often has a limited User Interface, and in some cases, is limited to a 10 key pad (and sometimes a "flash" function with the switchhook). One enters a series of digits that invoke some kind of function. The entered sequence, called a "dialstring" might be translated to a telephone number, or it may invoke a special service. In many newer designs, the mapping between a dialstring and a phone number or service URI is contained within the phone (digitmap). However, there are many phones and terminal adapters that do not have internal translation mechanisms. Without a translation mechanism in the phone, the phone must send the dialstring to an intermediary that can transform the dialstring to a phone number or a service invocation. At some point, a dialstring is translated to a phone number. After that point, it is no longer a dialstring. However, there is no current way for any entity to determine if translation has already been accomplished. Use of DTMF detectors post dial is not uncommon. A common functions some systems have is to express a string that incorporates fixed time delays, or in some cases, actual "wait for call completion" after which additional DTMF signals are emitted. For example, many voicemail systems use a common phone number, after which the system expects the desired mailbox number as DTMF to deposit a message for. Many gateways have the ability to interpret such strings, but there is no standardized way to express them, leading to interoperability problems between endpoints. 3. Requirements A mechanism to express a dialstring is required. A dialstring consists of a sequence of * The digits 0-9 * The special characters # and * * The MF digits A-D A dialstring always exists within a context. The context MUST be specified when expressing a dialstring. It MUST be possible to distinguish between a dialstring and a phone Rosen Expires November 16, 2004 [Page 3] Internet-Draft Dialstring parameter May 2004 number. It MUST be possible to express a short pause, and a "Wait for call completion" in a dialstring. 4. Solution A new value for the user parameter is defined, "dialstring". This value may be used in a sip or sips URI when the userpart is a dialstring. The userpart is a sequence of the characters 0-9, A-F, P and X. E is represent *, F represents #, P is a pause (short wait, like a comma in a modem string) and X represents call completion. When the "user=dialstring" is used, a context parameter as defined in RFC2806bis MUST be specified. A proxy server or B2BUA which is authoratative for the context may translate the dialstring to a telephone number or service invocation URI. If such a translation is performed, the proxy server MUST change the URI to specify user=phone. 5. Security Considerations Dialstrings exposed to the Internet may reveal information about internal network details or service invocations that could allow attackers to use the PSTN or the Internet to attack such internal systems. Dialstrings normally should not be sent over the open Internet without some kind of protection against eavesdropping. 6 References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2806] Vaha-Sipila, A., "URLs for Telephone Calls", RFC 2806, April 2000. [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. Rosen Expires November 16, 2004 [Page 4] Internet-Draft Dialstring parameter May 2004 Author's Address Brian Rosen Marconi 2000 Marconi Drive Warrendale, PA 15086 US Phone: +1 724 742 6826 EMail: brian.rosen@marconi.com Rosen Expires November 16, 2004 [Page 5] Internet-Draft Dialstring parameter May 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. 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This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION Rosen Expires November 16, 2004 [Page 6] Internet-Draft Dialstring parameter May 2004 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Rosen Expires November 16, 2004 [Page 7]