Printer Working Group. Intended status: Informational April 18, 2010 Expires: April 2011

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1 Printer Wrking Grup P. Zehler Internet Draft Xerx Crpratin Intended status: Infrmatinal April 18, 2010 Expires: April 2011 Dial String syntax fr the tel URI Scheme draft-ietf-teldial-inf-01.txt Status f this Mem This Internet-Draft is submitted in full cnfrmance with the prvisins f BCP 78 and BCP 79. Internet-Drafts are wrking dcuments f the Internet Engineering Task Frce (IETF), its areas, and its wrking grups. Nte that ther grups may als distribute wrking dcuments as Internet- Drafts. Internet-Drafts are draft dcuments valid fr a maximum f six mnths and may be updated, replaced, r bsleted by ther dcuments at any time. It is inapprpriate t use Internet-Drafts as reference material r t cite them ther than as "wrk in prgress." The list f current Internet-Drafts can be accessed at The list f Internet-Draft Shadw Directries can be accessed at This Internet-Draft will expire n April 18, Cpyright Ntice Cpyright (c) 2010 IETF Trust and the persns identified as the dcument authrs. All rights reserved. This dcument is subject t BCP 78 and the IETF Trust s Legal Prvisins Relating t IETF Dcuments ( in effect n the date f publicatin f this dcument. Please review these dcuments carefully, as they describe yur rights and restrictins with respect t this dcument. Zehler Expires April 18, 2011 [Page 1]

2 Internet-Draft Dial String fr tel URI Scheme April 2010 Abstract The "tel" URI (Unifrm Resurce Identifier) fr Telephne Numbers [RFC3966] describes resurces identified by telephne numbers. These resurces specify terminatin pints within a public r private telephne netwrk. The terminatin pints are a glbally r lcally unique endpint. RFC3966 des nt address the means by which the telephne URI can be used t reach terminatin pint frm a specific nde in the telephne netwrk. This dcument specifies the means by which the terminatin pint is reached frm a specific nde in the telephne netwrk. This dcument specifies hw t encde the numbers, symbls and pauses required t traverse the phne netwrk t reach the terminatin pint in an RFC 3966 cmpliant tel URI. Table f Cntents 1. Intrductin Cnventins used in this dcument Terminilgy Dial String Parameters Frmal Syntax Security Cnsideratins IANA Cnsideratins Cnclusins References Nrmative References Infrmative References Acknwledgments Intrductin The "tel" URI fr Telephne Numbers [RFC3966] defines unique endpints in the lcal r glbal telephne netwrk. It is quite useful in its wn right. It permits an unambiguus URI fr an endpint independent f the means required t traverse the telephne netwrk. This is referred t as the Address-Of-Recrd. There are applicatins that require additinal infrmatin t cnnect t the endpint. Examples include an individual s address bk r an address bk embedded in a device such as a FAX machine. There are instances where pre-dial and/r pst-dial infrmatin is required t nt nly cnnect the tw telephne devices but als specify an accunt where the cst fr the phne call will be charged. This is referred t as the Dial String. Zehler Expires Octber 18, 2010 [Page 2]

3 Internet-Draft Dial String fr tel URI Scheme April 2010 The nw bslete URLs fr Telephne Calls [RFC2806] accmmdated sme f this capability. It allwed pst-dial infrmatin t be explicitly specified. The pre-dial infrmatin had t be hidden in the lcal phne number. The tel URI fr Telephne Numbers [RFC3966] clarified the separatin f Dial Strings frm the Address- Of-Recrd. The purpse f this dcument is t specify, in an RFC3966 cmpliant fashin, the parameters that encde the pre-dial and pst-dial Dial Strings. In a phne call carrying the ITU FAX prtcl there are mail bxes that can be addressed. These are referred t as T33 SubAddressing [T.33]. This dcument will als specify the parameter fr T33 SubAddressing. 2. Cnventins used in this dcument The key wrds "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this dcument are t be interpreted as described in RFC-2119 [RFC2119]. In this dcument, these wrds will appear with that interpretatin nly when in ALL CAPS. Lwer case uses f these wrds are nt t be interpreted as carrying RFC-2119 significance. In this dcument, the characters ">>" preceding an indented line(s) indicates a cmpliance requirement statement using the key wrds listed abve. This cnventin aids reviewers in quickly identifying r finding the explicit cmpliance requirements f this RFC Terminilgy As stated in The tel URI fr Telephne Numbers [RFC3966], telephne numbers cmprise tw related but distinct cncepts: Address-Of-Recrd r identifier: The telephne number is understd here as the cannical Address-Of-Recrd r identifier fr a terminatin pint within a specific netwrk. Fr the public netwrk, these numbers fllw the rules in E.164 [E.164], while private numbers fllw the rules f the wner f the private numbering plan. Subscribers publish these identifiers s that they can be reached, regardless f the lcatin f the caller. (Naturally, nt all numbers are reachable frm everywhere, fr a variety f technical and lcal plicy reasns. Als, a single terminatin pint may be reachable frm different netwrks and may have multiple identifiers.) Zehler Expires Octber 18, 2010 [Page 3]

4 Internet-Draft Dial String fr tel URI Scheme April 2010 Dial string: "Dial strings" are the actual numbers, symbls, and pauses entered by a user t place a phne call. A dial string is cnsumed by ne r mre netwrk entities and understd in the cntext f the cnfiguratin f these entities. It is used t generate an Address-Of-Recrd r identifier (in the sense described abve) s that a call can be ruted. Dial strings may require prepended digits t exit the private branch exchange (PBX) the end system is cnnected t, and they may include pstdial dual-tne multi-frequency (DTMF) signaling that culd cntrl an interactive vice respnse (IVR) system r reach an extensin. 3. Dial String Parameters This dcument specifies Dial string parameters fr the tel URI scheme. The dial string parameters encde the numbers, symbls and pauses required t traverse the phne netwrk t reach an Address- Of-Recrd. All f these parameters are ptinal. Lcal entities SHOULD supprt these. Otherwise they MUST be ignred and the initiater f the call SHOULD be infrmed. The Dial String parameters defined here are nt intended t be glbally applicable. They are applicable fr a specific telephne nde enabling it t reach the desired terminatin pint. Fr example a telephne in cmpanies A and B may bth be used t reach a Cmpany C as specified by an Address-Of-Recrd. Cmpany A may require an 8 t be dialed befre entering the Address-Of-Recrd. Cmpany B may nt require any such pre-dialing and can reach Cmapany C simply by dialing the Address-Of-Recrd. Three Dial String parameters are defined here: Predial: The Dial string entered befre the Address-Of-Recrd is applied. Pstdial: The Dial string entered after the Address-Of-Recrd is applied. T33 SubAddress: A FAX specific Dial string passed thrugh t the FAX Prtcl cmpnent that uses the T33 SubAddress in the FAX prtcl carried ver the telephne cnnectin. Zehler Expires Octber 18, 2010 [Page 4]

5 Internet-Draft Dial String fr tel URI Scheme April Frmal Syntax The fllwing syntax specificatin uses the augmented Backus-Naur Frm (BNF) as described in RFC-2234 [RFC2234]. The fllwing syntax is defined in RFC3966 and is required t define the ABNF fr the Dial String parameters. parameter = ";" pname ["=" pvalue ] pname = 1*( alphanum / "-" ) pvalue = 1*paramchar paramchar = param-unreserved / unreserved / pct-encded unreserved = alphanum / mark mark = "-" / "_" / "." / "!" / "~" / "*" / alphanum = ALPHA / DIGIT phnedigit = DIGIT / [ visual-separatr ] visual-separatr = "-" / "." / "(" / ")" "'" / "(" / ")" pct-encded = "%" HEXDIG HEXDIG param-unreserved = "[" / "]" / "/" / ":" / "&" / "+" / "$" The Dial String parameter syntax is described belw. The syntax is based n syntax frm RFC2806. Changes have been made t be cmpliant with RFC3966 and t define Dial Strings befre the telephne number as well as afterwards. Dial-string-params = pre-dial / pst-dial / t33-subaddress pre-dial = ";pred=" 1*(phnedigit / dtmf-digit / pause-character) pst-dial = ";pstd=" 1*(phnedigit / dtmf-digit / pause-character) t33-subaddress = ";tsub=" 1*phnedigit pause-character = ne-secnd-pause / wait-fr-dial-tne ne-secnd-pause = "p" wait-fr-dial-tne = "w" dtmf-digit = "*" / "A" / "B" / "C" / "D" / sharp-digit sharp-digit = %23" 5. Security Cnsideratins The security cnsideratins include thse f the tel URI scheme [RFC3966]. Thse cnsideratin include that applicatins MUST NOT Zehler Expires Octber 18, 2010 [Page 5]

6 Internet-Draft Dial String fr tel URI Scheme April 2010 use the URI t place calls withut the explicit cnsent f the user f that applicatin. Placing calls withut user cnsent expses a number f risks including: The call may incur a cst. The call will take the user s phne line ff hk preventing its use by thers. The cal can reveal a user s phne number t an attacker. The URI may be used t place annying r malicius calls. URIs embedded in HTML links culd hide the true nature f the URI The use f the Dial Strings intrduces sme additinal security cncerns. Dial Strings parameters are lcally significant. Using the Dial String parameters in anther dmain may have unintended side effects. Dial String parameters may include accunt infrmatin and SHOULD NOT be publically (i.e. unencrypted) visible t ther users. 6. IANA Cnsideratins The Dial String parameters d nt require IANA registratin. 7. Cnclusins <Add any cnclusins> 8. References 8.1. Nrmative References [RFC2119] Bradner, S., "Key wrds fr use in RFCs t Indicate Requirement Levels", BCP 14, RFC 2119, March [RFC2234] Crcker, D. and Overell, P.(Editrs), "Augmented BNF fr Syntax Specificatins: ABNF", RFC 2234, Internet Mail Cnsrtium and Demn Internet Ltd., Nvember Zehler Expires Octber 18, 2010 [Page 6]

7 Internet-Draft Dial String fr tel URI Scheme April 2010 [RFC3966] H. Schulzrinne, "The tel URI fr Telephne Numbers", RFC 3966, Clumbia University, December [E.164] [T.33] Internatinal Telecmmunicatins Unin, "The internatinal public telecmmunicatin numbering plan", Recmmendatin E.164, May ITU-T Recmmendatin T.33: Facsimile Ruting Utilizing the Subaddress Infrmative References [Fab1999] Faber, T., Tuch, J. and W. Yue, "The TIME-WAIT state in TCP and Its Effect n Busy Servers", Prc. Infcm 1999 pp [RFC2806] A. Vaha-Sipila, "URLs fr Telephne Calls", RFC 2806, Nkia, April Acknwledgments <Add any acknwledgements> This dcument was prepared using 2-Wrd-v2.0.template.dt. Authrs Addresses Peter Zehler Xexx Crpratin 800 Phillips Rd M/S E Webster, NY Phne: (585) Peter.Zehler@Xerx.cm Zehler Expires Octber 18, 2010 [Page 7]