INTERNET-DRAFT A. Vaha-Sipila Expires 24-Mar-1998 Nokia 19-Sep-1997 URLs for Telephony Status of This Memo This document is an Internet-Draft. 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." 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). Abstract This document specifies URL (Uniform Resource Locator) 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. This specification covers voice calls (normal phone calls, answering machines and voice messaging systems), facsimile (telefax) calls and data calls, both for POTS and digital/mobile subscribers. Version History > Changes to the previous versions are indicated by a bar in the > left margin like in this section. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . 2 1.1 New URL Schemes . . . . . . . . . . . . . . . . . 2 1.2 Formal Definitions . . . . . . . . . . . . . . . . 2 1.3 Requirements . . . . . . . . . . . . . . . . . . . 2 2. URL Schemes for Telephone Calls . . . . . . . . . 2 2.1 Applicability . . . . . . . . . . . . . . . . . . 3 2.2 "tel" URL Scheme . . . . . . . . . . . . . . . . . 3 2.3 "fax" URL Scheme . . . . . . . . . . . . . . . . . 3 2.4 "modem" URL Scheme . . . . . . . . . . . . . . . . 4 2.5 Parsing tel, fax and modem URLs . . . . . . . . . 4 2.6 Examples of Use . . . . . . . . . . . . . . . . . 6 3. References . . . . . . . . . . . . . . . . . . . . 7 A. Vaha-Sipila URLs for Telephony September 1997 INTERNET-DRAFT Expires March, 1998 [Page 2] 4. Security Considerations . . . . . . . . . . . . . 7 5. Authors' Addresses . . . . . . . . . . . . . . . . 8 1. Introduction 1.1 New URL Schemes URLs that designate phone or fax numbers that can be dialed have been brought forward in other (currently expired) Internet-Drafts. However, none of these has reached the RFC status. This document tries to remedy the situation. All interested parties are invited to submit comments on this Internet-Draft. Contact information can be found at the end of this document. > This specification defines three new URL schemes: "tel", "fax" > and "modem". They are intended for describing a terminal that > can be contacted using the telephone network. The description > includes the subscriber (telephone) number of the terminal and > the necessary parameters for successfully connecting to that > terminal. > The "tel" scheme describes a connection to a terminal that > handles normal voice telephone calls, a voice mailbox or another > voice messaging system or a service that can be operated using > DTMF codes or any other telephone call that uses voice. > The "fax" scheme describes a connection to a terminal that can > handle telefaxes (facsimiles). > The "modem" scheme describes a connection to a terminal that can > handle incoming data calls. The term "modem" refers to a device > that does digital-to-analog and analog-to-digital conversions; > in addition to these, a "modem" scheme can describe a fully > digital connection. 1.2 Formal Definitions Rules are separated from definitions by an equal "=", literals are quoted with double quotes "", parentheses "(" and ")" are used to group elements and optional elements are enclosed in "[" and "]" brackets. Elements may be preceded with n* to designate n repetitions of the following element; n defaults to 0. Single quotes '' are used to indicate elements that are not formally specified and are described in free text instead. Indentation indicates that the definition continues from the previous line. 1.3 Requirements Compliant software MUST follow this specification. Requirements are indicated by capitalized words as specified in [RFC2119]. 2. URL Schemes for Telephone Calls A. Vaha-Sipila URLs for Telephony September 1997 INTERNET-DRAFT Expires March, 1998 [Page 3] 2.1 Applicability > In this document, "user agent" means software that can detect > and parse one or more of these URLs and place a call to the > remote terminal using hardware at its disposal. These URL schemes are used to direct the user agent to place a call using the telephone network. The network in question may be a landline or mobile phone network. If the phone network differentiates between (for example) voice and data calls, or if the user agent has several different telecommunications equipment at its disposal, it is possible to specify which kind of call (voice/fax/data) is requested. It is also possible to give information about the capabilities of the remote entity, so that the connection can be established successfully. > None of the URL schemes do have a 'path' in them - they are > always absolute. Everything is case-insensitive. 2.2 "tel" URL Scheme > The URL syntax is formally described as follows: > tel-url = scheme ":" scheme-specific-part > scheme = "tel" > scheme-specific-part = subscriber-id > subscriber-id = ["+"] phone-number > phone-number = 1*phonedigit > [sub-address-separator 1*phonedigit] > [pause-character *(phonedigit | > dtmf-digit | pause-character)] > phonedigit = digit | "-" | "." > sub-address-separator = "i" > pause-character = "p" | "w" > digit = "0" | "1" | "2" | "3" | "4" | "5" | > "6" | "7" | "8" | "9" > dtmf-digit = "*" | "#" | "A" | "B" | "C" | "D" 2.3 "fax" URL Scheme > The URL syntax is formally described as follows: > fax-url = scheme ":" scheme-specific-part > scheme = "fax" > scheme-specific-part = subscriber-id [fax-params] > subscriber-id = ["+"] phone-number > phone-number = 1*phonedigit > [sub-address-separator 1*phonedigit] > [pause-character *(phonedigit | > dtmf-digit | pause-character)] > phonedigit = digit | "-" | "." > sub-address-separator = "i" | "s" > pause-character = "p" | "w" A. Vaha-Sipila URLs for Telephony September 1997 INTERNET-DRAFT Expires March, 1998 [Page 4] > digit = "0" | "1" | "2" | "3" | "4" | "5" | > "6" | "7" | "8" | "9" > dtmf-digit = "*" | "#" | "A" | "B" | "C" | "D" > fax-params = ";type=" fax-capabilities > fax-capabilities = "T2" | "T3" | "T4" | "T6" 2.4 "modem" URL Scheme > The "modem" URL scheme has two free-text fields, which contain > the user name and password for authentication. Certain > characters in these fields are marked as "reserved", and they > MUST be escaped using URL-encoding if present in the free-text > fields. Characters not present in 7-bit US ASCII, unprintable > characters and whitespace MUST also be escaped. > reserved = " " | ":" | "?" | ";" | "=" | "@" > | "+" > The URL syntax is formally described as follows: > modem-url = scheme ":" scheme-specific-part > scheme = "modem" > scheme-specific-part = [user-name [":" password] "@"] > subscriber-id *[modem-params] > subscriber-id = ["+"] phone-number > phone-number = 1*phonedigit > [sub-address-separator 1*phonedigit] > [pause-character *(phonedigit | > dtmf-digit | pause-character)] > phonedigit = digit | "-" | "." > sub-address-separator = "i" > pause-character = "p" | "w" > digit = "0" | "1" | "2" | "3" | "4" | "5" | > "6" | "7" | "8" | "9" > dtmf-digit = "*" | "#" | "A" | "B" | "C" | "D" > modem-params = ";type=" data-capabilities > data-capabilities = modem-type ["?" data-bits parity > stop-bits] > modem-type = "V21" | "V22" | "V22b" | > "V23" | "V26" | "V32" | > "V32b" | "V34" | "V110" | > "V120" | "B103" | "B212" | > "X75" > data-bits = "7" | "8" > parity = "n" | "e" | "o" | "m" | "s" > stop-bits = "1" | "2" > user-name = 'a user name for authentication; > in URL-encoded notation' > password = 'a password for authentication; > in URL-encoded notation' 2.5 Parsing tel, fax and modem URLs A. The type of call is specified by the scheme specifier. "Tel" A. Vaha-Sipila URLs for Telephony September 1997 INTERNET-DRAFT Expires March, 1998 [Page 5] means that a voice call is opened. "Fax" indicates that the call should be a facsimile (telefax) call. "Modem" means that it should be a data call. > B. "Subscriber-id" is the phone number to be dialed. This phone > number MUST be written in international notation with country > (CC) and national (NSN) numbers, as specified in [E.123] and > [E.164], unless the number only works from inside a certain > geographical area or a network. Note that some numbers may work > from several networks but not from the whole world - these > SHOULD be written in international form. The "subscriber-id" is extracted. If it begins with a "+", it is an international number. This kind of a number is converted to the user agent's local format (for example, if the agent is a browser component that dials out, the "+" is replaced by the international call prefix, or if the country code matches the country code of user agent's home country, the "+" and the country code are replaced by a trunk call prefix). > International numbers MUST begin with "+", which indicates that > the number begins with a country code (CC). Hyphens and dots in > a phone number are only to aid readability; they MUST NOT have > any other meaning. Although [E.123] recommends the use of space > characters as the separators, spaces MUST NOT be used in these > URLs. A phone number may contain "p" or "w" characters which indicate a pause of 1 second while dialing, or a wait for user input, respectively. User agents SHOULD support this method of dialing. If it is not supported, user agents MUST ignore everything after the "p" or "w" characters. All digits after the first "p" or "w" character MUST be sent to line using DTMF (Dual Tone Multifrequency) in-band signaling, even if dialing is done using direct network signaling (a digital subscriber loop or a mobile phone). > A phone number MAY also contain an "i" character which indicates > the start of an ISDN subaddress. ISDN subaddresses are sent to > the remote terminal during call setup by the caller's equipment. > ISDN-connected user agents SHOULD support this method of dialing > and if it is not supported, the "i" character and all subsequent > digits MUST be ignored. > A fax number MAY also contain a "s" character, which indicates > the start of a T.33 subaddress [T.33]. User agents MAY support > this method of dialing. Otherwise the "s" character and all > subsequent digits MUST be ignored. > Any telephone number must contain at least one digit, that is, > numbers consisting only of non-numbers are not allowed. > C. A "type" specifier after "subscriber-id" tells the user-agent > which kind of telefax or modem can be used to contact the remote A. Vaha-Sipila URLs for Telephony September 1997 INTERNET-DRAFT Expires March, 1998 [Page 6] > entity. The user agent MUST call out using compatible hardware, > or request that the network provides such a service. For the > "modem" URL, this also means that the number of data and stop > bits and parity MUST be set according to the information given > in the URL or to default values, if the information is not > present. The capability tokens are listed below. If parsed capabilities suggest that it is impossible to create a connection, the connection MUST NOT be created. > D. After a data connection has been established, "user-name" and > "password" parts instruct the user agent of how to identify > itself to the remote entity. How this identifying information is > used is outside the scope of this document. For example, they > might be given as parameters to an autologin script. > If new modem or fax types are standardized by ITU-T, this list > can be extended with those capability tokens. Tokens are formed > by taking the name of the standard and joining together the > first letter, number and the first letter of the postfix. New > capabilities SHOULD then be documented in an RFC. New non-ITU-T > capabilities MUST be specified in an RFC. Capability Explanation V21 ITU-T V.21 V22 ITU-T V.22 V22b ITU-T V.22bis V23 ITU-T V.23 V26t ITU-T V.26ter V32 ITU-T V.32 V32b ITU-T V.32bis V34 ITU-T V.34 V110 ITU-T V.110 V120 ITU-T V.120 X75 ITU-T X.75 B103 Bell 103 B212 Bell 212 > T2 ITU-T T.2 (G1) facsimile > T3 ITU-T T.3 (G2) facsimile > T4 ITU-T T.4 (G3) facsimile > T6 ITU-T T.6 (G4) facsimile Data bits: "8" or "7" The number of data bits. If not specified, defaults to "8". Parity: "n", "e", "o", Parity. None, even, odd, mark or "m", "s" space parity, respectively. If not specified, defaults to "n". Stop bits: "1" or "2" The number of stop bits. If not specified, defaults to "1". 2.4 Examples of Use tel:+358-55-1234567 A. Vaha-Sipila URLs for Telephony September 1997 INTERNET-DRAFT Expires March, 1998 [Page 7] This URL instructs the user agent to place a voice call to the specified number in Finland. The hyphens are included to make the number more human-readable: country and area codes have been separated from the subscriber number. fax:+358.55.1234567 The above URL instructs the user agent to place a fax call to the specified number. It uses dots instead of hyphens as separators. modem:+358551234567;type=v34?7e1;type=v110 This URL instructs the user agent to place a data call to the specified number. The user agent may opt to use either a ITU-T V.34 modem (or a slower one, which is compatible with V.34), using settings of 7 data bits, even parity and one stop bit, or an ISDN connection using ITU-T V.110 protocol. tel:+358-55-1234567pp22 The above URL instructs the user agent to place a voice call to +358-55-1234567, then wait two seconds and emit two DMTF dialing tones "2" on the line (for example, to choose a particular extension number). As a side note, ost Hayes AT compatible modems accept commas "," as the pause characters. 3. References [RFC1738] Uniform Resource Locators (URL). December 1994. T. Berners-Lee et al. [RFC2119] Key Words for Use in RFCs to Indicate Requirement Levels. March 1997. S. Bradner. > [E.123] ITU-T Recommendation E.123: Telephone Network and ISDN > Operation, Numbering, Routing and Mobile Service: Notation for > National and International Telephone Numbers. 1993. > [E.164] ITU-T Recommendation E.164: Telephone Network and ISDN > Operation, Numbering, Routing and Mobile Service: Numbering Plan > for the ISDN Era. 1991. > [T.33] ITU-T Recommendation T.33: Facsimile Routing Utilizing > the Subaddress. 1996. 4. Security Considerations It should be noted that the user agent SHOULD NOT call out without the knowledge of the user because of associated risks, which include - call costs (including long calls, long distance calls, A. Vaha-Sipila URLs for Telephony September 1997 INTERNET-DRAFT Expires March, 1998 [Page 8] international calls and prime rate calls) - wrong numbers inserted on web pages by malicious users - making the user's phone line unavailable (off-hook) for a malicious purpose - opening a data call to a remote host, thus possibly opening a back door to the user's computer The user agent SHOULD have some mechanism that the user can use to filter out unwanted numbers. The user agent SHOULD NOT use rapid redialing of the number if it is busy to avoid the congestion of the (signaling) network. Also, the user agent SHOULD detect if the number is unavailable or if the call is terminated before the dialing string has been completely processed (for example, the call is terminated while waiting for user input) and not try to call again, unless instructed by the user. 5. Authors' Addresses Contact person for this specification: Nokia Mobile Phones Antti Vaha-Sipila P. O. Box 68 FIN-33721 Tampere Finland Electronic mail: antti.vaha-sipila@nmp.nokia.com Please include your name and electronic mail address in all communications. If you want to receive the newest version of this specification electronically, send mail to the address above. This document expires on the 24th of March, 1998, or when a new version is released. A. Vaha-Sipila URLs for Telephony September 1997