iptel B. Rosen Internet-Draft NeuStar Expires: September 4, 2006 March 03, 2006 Dialstring parameter for the Session Initiation Protocol URI draft-rosen-iptel-dialstring-03.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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 September 4, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract RFC3966 explicitly states 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 or SIPS URI. Rosen Expires September 4, 2006 [Page 1] Internet-Draft Dialstring Parameter March 2006 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7 Intellectual Property and Copyright Statements . . . . . . . . . . 8 Rosen Expires September 4, 2006 [Page 2] Internet-Draft Dialstring Parameter March 2006 1. Introduction 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 in a SIP or SIPS URI [RFC3261]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. The "user=phone" parameter in a SIP or SIPS URI could denote a telephone number, but would need another value to denote a dialstring. 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. 2. Terminology 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]. 3. Requirements A mechanism to express a dialstring in a SIP or SIPS uri is required. A dialstring consists of a sequence of Rosen Expires September 4, 2006 [Page 3] Internet-Draft Dialstring Parameter March 2006 * The digits 0-9 * The special characters # and * * The MF digits A-D Note: DTMF = Dual Tone MultiFrequency. Each "tone:" is actually two frequencies superimposed. DTMF is a 4 x 4 matrix with four row frequencies (697, 770, 852, 941 Hz) and four column frequencies (1209, 1336, 1477, 1633). Most telephones only implement 3 of the 4 columns, which are used just like the telephone dial pad implies they are. Thus, the digit 2 is the first row, second column, and consists of 770Hz and 1209Hz frequencies mixed together. The fourth column is not used in the PSTN. The "digits" for the fourth column are usually expressed using the letters A through D. Thus, "C" is 852/1633Hz. Some equipment does use these digits, so we include them in the definition of the dialstring. 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 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 of the SIP/SIPS URI schemes 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 [RFC3966] MUST be specified. A proxy server or B2BUA which is authoritative 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. Rosen Expires September 4, 2006 [Page 4] Internet-Draft Dialstring Parameter March 2006 (Examples of dialstring use include) ; what a SIP Phone might emit when a user dials extension 123 sip:123@sippbx.example.com;user=dialstring; phone-context='AtlantaDialPlan' ;existing voicemail systems have a local access extension, ;then expect to see the extension number as DTMF for the mailbox sips:4500P4123@sip.example.com;user=dialstring; phone-context='BiloxiDialPlan' () 5. IANA Considerations [RFC3969] defines a SIP/SIPS URI Parameter sub registry. The "user" parameter is specified as having predefined values. This RFC defines a new value for the "user" parameter, "dialstring". This RFC would be added to the references listed for the "user" parameter. This RFC defines a new parameter in the sub-registry, "phone- context", whose meaning and syntax are derived from the same parameter in [RFC3969] 6. 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. 7. References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [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. [RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966, December 2004. [RFC3969] Schulzrinne, H., "The tel URI for Telephone Numbers", Rosen Expires September 4, 2006 [Page 5] Internet-Draft Dialstring Parameter March 2006 RFC 3966, December 2004. Rosen Expires September 4, 2006 [Page 6] Internet-Draft Dialstring Parameter March 2006 Author's Address Brian Rosen NeuStar 470 Conrad Dr Mars, PA 16046 US Phone: +1 724 382 1051 Email: br@brianrosen.net Rosen Expires September 4, 2006 [Page 7] Internet-Draft Dialstring Parameter March 2006 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights 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; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Rosen Expires September 4, 2006 [Page 8]