VPIM Working Group Jason Collins Internet Draft Nortel Networks Document: November 2000 Category: Standards Track Calling Line Identification for VPIM Messages 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. Collins Expires: 24/05/01 1 Calling Line Identification November 2000 Table of Contents 1. Abstract ........................................................2 2. Conventions used in this document ...............................2 3. Introduction ....................................................2 4. Calling Line Identification Field ...............................3 4.1 Internal Call ...............................................3 4.2 External Call ...............................................3 5. Caller Name Field ...............................................4 6. Formal Syntax ...................................................4 6.1 Calling Line Identification Syntax ..........................4 6.2 Caller Name Syntax ..........................................4 6.3 Example .....................................................4 7. Security Considerations .........................................4 8. References ......................................................5 9. Acknowledgments .................................................5 10. Author's Addresses .............................................5 11. Full Copyright Statement .......................................6 1. Abstract This document describes a method for identifying the originating calling party for a stored VPIM message. 2. Conventions used in this document 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 RFC-2119. 3. Introduction There is currently a need for a mechanism to identify the originating party of a VPIM message, outside of the "FROM" header information. The telephone number and name of the caller are typically available from the telephone network, but there is no obvious header field to store this in an Internet message. This information is intended for use when the VPIM message format is used for storing "Call Answer" voice messages in an Internet Mail message store, i.e. the calling party leaves a voice message for the recipient, who was unable to answer the call. [VPIMV2R2] suggests the originating number be included as an Internet address, using the first method shown below. There are several other ways to store this information, but they all involve some manipulation of the "From" field. For example: 1. From: "416 555 1234" 2. From: "John Doe" <4165551234@host> Collins Expires: 24/05/01 2 Calling Line Identification November 2000 3. From: unknown:; As a result, it is useful to be able to store the calling party's name and number as-is without manipulation. This would allow future generation of the proper Internet address, and also display of this information to the recipient. [RFC2076] currently lists "phone" as an Internet message header which would hold the originating party's telephone number, but it is listed as "non-standard", i.e. usage of this header is not in general recommended. It also has no defined format, making the information unparsable. There is no similar entry for the originator's name. It is proposed that two new message header fields be included to hold this information, namely the Calling Line Identification ("Caller-ID"), and Caller Name ("Caller-Name"). 4. Calling Line Identification Field The Calling Line Identification header ("Caller-ID") is to hold sufficient information for the recipient to call back, or reply to, the sender of the message. This leads to two distinct possibilities: internal and external calling. Note that for both possibilities, this field MUST contain only the digits of the number and MUST be representable using the American Standard Code for Information Interchange (ASCII) character set; it does not include any separating character (e.g. "-"). 4.1 Internal Call For an internal call (e.g. between two extensions within the same company), it is sufficient to relay only the extension of the calling party, based on the company dialing plan. 4.2 External Call For an international call, the CLID must be the full international number as described in [E.164], i.e. Country Code (CC), National Destination Code (NDC) and Subscriber Number (SN). Other information, such as prefixes or symbols (e.g. "+"), MUST NOT be included. This requires provisioning for up to 15 digits. For a call within North America, it is sufficient to only include 10 digits as described in [GR-31-CORE]. Though it is desirable that an international number NOT be truncated to 10 digits if it contains more, it is recognized that this will happen due to limitations of various systems. Also note that [GR-31-Core] also specifies how to include the date and time with the originating telephone number. This MAY be followed, as there is an existing "Date" Internet header intended to hold this information. It is a local implementation decision Collins Expires: 24/05/01 3 Calling Line Identification November 2000 whether this time or the local system time be recorded in the "Date" header. 5. Caller Name Field The name of the person sending the message is also important. If available, it is to be included whether the call is internal or external. The name MUST be representable using the International Reference Alphabet (IRA), formerly know as International Alphabet No.5 or IA5. This is the character set used to transmit the caller name in the PSTN. The IRA character set contains a number of options that help specify national and application oriented versions. If there is no agreement between parties to use these options, then the default character set "International Reference Version (IRV)" will be chosen. The graphical characters of IRV and ASCII are coded exactly the same. As a result, for the caller name header defined in this document, characters are represented with ASCII characters. The length of the name field MUST NOT exceed 15 characters, as defined in [GR-1188-CORE]. It MAY contain punctuation or white spaces as appropriate. 6. Formal Syntax Both Calling Line Identification and Caller Line follow the syntax specification using the augmented Backus-Naur Form (BNF) as described in [RFC2234]. 6.1 Calling Line Identification Syntax "Caller-ID" ":" 1*15DIGIT CRLF 6.2 Caller Name Syntax "Caller-Name" ":" 1*15CHAR CRLF 6.3 Example To: +19725551212@vm1.mycompany.com Caller-ID: 6137684087 7. Security Considerations There are a few scenarios that must be considered. The first is mentioned in section 2.2 - the truncation of an international number to 10 digits. This could result in a misinterpretation of the resulting number. For instance, an international number (e.g. from Ireland) of the form "353 91 73 3307" could be truncated to "53 91 73 3307" if received in North America, and interpreted as "539 112 3456" - a seemingly "North American" style number. Thus leaving the recipient with the incorrect information to reply to the message. Collins Expires: 24/05/01 4 Calling Line Identification November 2000 The second scenario is the possibility of sending an internal extension to an external recipient when a Call Answer message is forwarded. This poses two problems, the recipient is given the wrong phone number, and the company's dialing plan could be exposed. The final concern deals with exercising character options that are available in coding the Calling Name field. An international system may send a message with coding options that are not available on the receiving system. Thus giving the recipient an incorrect Caller Name. 8. References [VPIMV2R2] Vaudreuil, Greg, Parsons, Glenn, "Voice Profile for Internet Mail, version 2", , November 2000. [RFC2076] Palme, "Common Internet Message Headers", RFC 2076, February 1997 [ASCII] American National Standards Institute (ANSI), Coded Character Set - 7-Bit American National Standard Code for Information Interchange, ANSI X3.4, 1986. [RFC2234] Crocker, D. and Overell, P.(Editors), "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, Internet Mail Consortium and Demon Internet Ltd., November 1997 [E.164] ITU-T Recommendation E.164 (1997), "The international public telecommunication numbering plan" [GR-1188-CORE] Telecordia Technologies, "CLASS Feature: Calling Name Delivery Generic Requirements", GR-1188-CORE, Issue 1, June 2000 [GR-31-CORE] Telecordia Technologies, "CLASS Feature: Calling Number Delivery", GR-31-CORE, Issue 1, June 2000 [T.50] ITU-T Recommendation T.50 (1992), "International Reference Alphabet (IRA)" 9. Acknowledgments The previous author of this document was Derrick Dunne. The author would like to thank Derrick for his contributions. 10. Author's Addresses Jason Collins Nortel Networks Ottawa, ON K1Y 4H7 Phone: +1-613-768-4087 Email: jcolli1@nortelnetworks.com Collins Expires: 24/05/01 5 Calling Line Identification November 2000 11. 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