ENUM Working Group R. Shockey - editor
Internet-Draft NeuStar
Expires: November 2007 J. Livingood
Comcast Cable
Communications
K. McCandless
M. Maharishi
Verisign
May, 29 2007
IANA Registration for an Enumservice Calling Name Delivery (CNAM)
Information and IANA Registration for Media type "application/cnam"
draft-ietf-enum-cnam-05.txt
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Copyright (C) The IETF Trust (2007).
Intended Status: Proposed Standard
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Abstract
This document registers the Enumservice "pstn" and subtype "cnam"
using the URI scheme "data:" as per the IANA registration process
defined in the ENUM specification, RFC 3761[1] and registers a new
media type application/cnam [17].
This data is used to facilitate the transfer of Calling Name Delivery
(CNAM) data for calls that originate on the Public Switched Telephone
Network (PSTN) that may be displayed on VoIP or other Real-time
Client User Agents (CUA).
Table of Contents
1. Terminology .......................................... 2
2. Introduction .......................................... 2
3. Protocol Design Consideration.......................... 3
4. Definition of PSTN CNAM Data .......................... 4
5. The CNAM data URI ................................... 4
6. Distribution of CNAM Data ............................. 5
7. Enumservice CNAM Response Examples .................... 5
8. Usage Considerations ................................. 6
9. Privacy Considerations ................................ 6
10. Security Considerations .............................. 7
11. IANA Considerations .................................. 7
11.1 IANA Enumservice Registration for PSTN Data "cnam" 7
11.2 IANA Registration Template for Media Type "application/cnam"
................................................... 8
12. References .......................................... 9
12.1 Normative References ............................. 9
12.2 Informative References ........................... 11
Author’s Addres ....................................... 11
1.
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 BCP 14, RFC 2119 [16].
2.
Introduction
ENUM (E.164 Number Mapping), RFC 3761 is a system that transforms
E.164 numbers (The International Public Telecommunication Number
Plan, ITU-T Recommendation E.164) [2] into domain names and then uses
the Domain Name System (DNS), RFC 1034 [3] and Naming Authority
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Pointer Records (NAPTR) records in the Dynamic Delegation Discovery
System (DDDS) RFC 3403 [4]) to query the services that are available
for a specific domain name.
This document registers an Enumservice "cnam" according to the
guidelines given in RFC 3761, to be used for provisioning a NAPTR [4]
resource record to indicate a type of functionality associated with
an end point and/or telephone number. The registration is defined
within the DDDS (Dynamic Delegation Discovery System [4][5][6][7][8])
hierarchy, for use with the "E2U" DDDS Application defined in RFC
3761.
This document also registers an IANA application specific media type
"application/cnam" per the requirements of BCP 13/RFC 4288.
The purpose of this Enumservice is to enable service providers to
place Calling Name Delivery information (CNAM) into ENUM databases or
to send ENUM queries to a protocol converter that would have access
to the Signaling System 7 (SS7) Network. This, in turn, could enable
such parties to offer Calling Name Delivery services using the
technology provided by RFC 3761.
The service parameters defined in RFC 3761 dictate that a ‘type’ and
one or more "subtype" should be specified. Within this set of
specifications the convention is assumed that the "type" (being the
more generic term) defines the service and at least one of the
"subtype" may indicate the URI scheme.
In this document, one type is specified, "pstn" and one subtype
"cnam" with the URI scheme specified, "data:" as specified in RFC
2397 [15].
3.
Protocol Design Considerations.
The design of this protocol was influenced by several factors:
RFC 3761 has become the defacto query-response protocol of choice for
a variety of data types associated with E.164 numbering and
addressing including data not necessarily associated with a SIP or
other communications session set up. RFC 3761 is already being used
by service providers to query for data that has significant privacy
or security issues associated with it. RFC 4769 [18], for instance,
describes an Enumservice that associates an E.164 number with a PSTN
Local Routing Number. An Enumservice for CNAM data has similar design
requirements of being used in private and closed systems.
Communications service providers are concerned with the impact of
call setup up times on the overall user experience. There is a strong
desire to maintain a single query mechanism for data involving E.164
phone numbers and not complicate call processing applications with
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multiple protocol mechanisms. Were the query for CNAM data to require
a secondary protocol mechanism such as LDAP or IRIS to retrieve the
data, it could significantly impact call setup times.
4.
Definition of PSTN CNAM Data
Calling Name data is a string of up to 15 ASCII [9] characters of
information associated with a specific calling party number [10] [11]
[12] [13] [14]. In the Public Switched Telephone Network (PSTN) this
data is sent by the originating network only at the specific request
of the terminating network via a SS7 Transaction Capabilities
Application Part (TCAP) response message.
5.
The CNAM data URI
RFC 2397 specifies the structure and parameters for the data URI as
follows
dataurl := "data:" [ mediatype ] [ ";base64" ] "," data
mediatype := [ type "/" subtype ] *( ";" parameter )
data := *urlchar
parameter := attribute "=" value
In order to distinguish the Calling Name data media type used within
this URL this document specifically registers with IANA the media
type "application/cnam".
All responses using this specification SHOULD specifically reference
the media type ‘application/cnam’
ANSI standards specify the use of ASCII in the response to TCAP
queries for Calling Name data. This specification does not preclude
the use of internationalized characters within the CNAM data URI, nor
does it preclude the use of more than 15 characters.
5.1 Enumservice Privacy Responses and Parameters
The PSTN defines several values for CNAM data in the event that there
are privacy restrictions on the access to that data or that the data
is unavailable. These are defined as "Reason for Absence of Name" in
GR-1188 [13], consequently the following responses to a query from a
well known database are reserved.
Within the media type "application/cnam" an two optional parameters
are supported.
Calling Name Privacy Indicator: "unavailable=p"
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This parameter defined as the Calling Name data information may be
available but the Calling Party does not wish to have their Calling
Name data displayed by Called Party User Agents.
Usage: data:application/cnam;unavailable=p
Calling Name Status Indicator
Definition: "unavaiable=u"
This parameter is defined as there is no Calling Name data for that
E.164 number available.
Usage: data:application/cnam;unavailable=u
6.
Distribution of CNAM Data
The distribution of CNAM data is often highly restricted. The NAPTR
records described herein should not be part of the e164.arpa DNS
tree. Distribution of this NAPTR data would be either within a
service provider's internal network, or on a private basis between
one or more parties using a variety of security mechanisms to
prohibit general public access.
If such data was distributed in an open DNS system, a national
regulatory body may have jurisdiction, especially since CNAM
information may contain Personally Identifying Information. Such a
body may choose to restrict distribution of the data in such a way
that it may not pass over that country's national borders. How
Personally Identifying Information is collected, distributed and
subsequently regulated is out of the scope of this document.
7.
Enumservice CNAM Response Examples
This section documents an example for illustrative purposes. These
examples shall in no way limit the various forms that this
Enumservice may take.
$ORIGIN 0.0.1.0.5.5.5.3.0.7.1.e164.carrier1.example.net.
NAPTR 10 100 "u" "E2U+pstn:cnam"
"!^.*$!data:application/cnam,Francois%20Marie20%Arouet!".
Should no media type be present in the data URI it is presumed that
the data portion of the URI after the comma is ASCII text as per RFC
2397.
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$ORIGIN 0.0.1.0.5.5.5.3.0.7.1.carrier1.example.net.
NAPTR 10 100 "u" "E2U+pstn:cnam
"!^.*$!data:,Francois%20Marie20%Arouet!".
$ORIGIN 0.0.1.0.5.5.5.3.0.7.1.carrier1.example.net.
NAPTR 10 100 "u" "E2U+pstn:cnam"
"!^.*$!data:application/cnam;unavailable=u,!".
8.
Usage Considerations
Typically, the Calling Name data in the PSTN is delivered to the
called party during the first silent interval after the first ringing
(see GR-1188 requirement R3-341 [13]). If the Called party answers
the call before this, Calling Name data may not be delivered.
This protocol could be invoked, for example, when a user agent within
a service providers network receives an INVITE without a display name
present.
The exact mechanism or determination of when to issue an ENUM-CNAM
request, and the formatting of SIP (RFC 3261 [19]) messages is beyond
the scope of this document.
9.
Privacy Considerations
It is assumed that carriers, service providers, or other
organizations that originate Calling Name data will not publish such
information in a globally visible DNS tree, such as e164.arpa for
reasons of personal privacy protection unless such publication is
consistent with national regulatory policy.
Service providers and other organizations will probably privately
exchange and publish this data in their internally cached ENUM
databases, which is only able to be queried by trusted elements of
their network, such as soft switches and SIP proxy servers.
Service providers using this query response technique are advised
that many national jurisdictions have strict regulations on the use
of Calling Name data and that National Regulatory Authorities may
have special regulations that permit subscribers to block the use of
such data before call setup. Other jurisdictions have services known
as anonymous caller rejection, meaning that calls made from a system
where Calling Line Identification and Calling Name data are blocked
are prevented from establishing a session.
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10.
Security Considerations
DNS, as used by ENUM, is a global, distributed database. Thus, an
implementation of this Enumservice that uses e164.arpa or any other
publicly accessible domain means that the information stored there is
visible to anyone anonymously. While this is not qualitatively
different from publication in a Telephone Directory, it does open or
ease access to such data without any indication that such data has
been accessed or who has accessed it.
The CNAM Enumservice defined in this document is assumed to be used
in an environment where elements are trusted and where attackers are
not supposed to have access to the protocol messages between those
elements. Traffic protection between network elements is sometimes
achieved by using IPSec and sometimes by physically protecting the
underlying network. In any case, it is presumed the environment
where the CNAM request-response mechanism will be used can ensure the
integrity and the confidentiality of the contents of the CNAM data.
An analysis of threats specific to the dependence of ENUM on the DNS
and the applicability of DNSSEC [A] to this is provided in RFC 3761.
A thorough analysis of threats to the DNS itself is covered in RFC
3833 [B].
11.
IANA Considerations
This document registers the "cnam" Enumservice using the type "pstn"
and the subtype "cnam" in the Enumservice registry described in the
IANA considerations in RFC 3761. Details of this registration are
provided in sections 13 and 14 of this document.
This document also registers with the IANA the media type
‘application/cnam’ per BCP 13/RFC 4288 [19]
11.1 IANA Enumservice Registration for PSTN Data "cnam"
Enumservice Name: "cnam"
Enumservice Type: "pstn"
Enumservice Subtypes: "cnam"
URI Schemes: "data:"
Functional Specification:
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This Enumservice indicates that a resource record contains Calling
Name Delivery Information that can be addressed by the associated
"data:" URI scheme [RFC 2397] and a specific media type will be
defined as application/cnam in order to facilitate the display of
Calling Party information from a PSTN endpoint to a VoIP Client User
Agent or other application.
Security Considerations: See Section 9.
Intended Usage: COMMON
Authors:
Richard Shockey and Jason Livingood, et. al. (for author contact
detail see Authors' Addresses section)
Any other information the author deems interesting:
None
11.2 IANA Registration Template for Media Type "application/cnam"
To: ietf-types@iana.org
Subject: Registration of media type application/cnam
Type name: application
Subtype name: cnam
Required parameters: none
Optional parameters:
Two optional parameters are defined.
a) Calling Name Privacy Indicator: "unavailable=p"
This parameter defined as the Calling Name information may be
available but the Calling Party does not wish to have their Calling
Name data displayed by Called Party User Agents.
Intended usage: "unavailable=p"
b) Calling Name Status Indicator: "unavailable=u"
This parameter is defined as there is no Calling Name data for that
E.164 number available.
Intended usage: "unavailable=u"
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Encoding considerations: ASCII
Security considerations:
Interoperability considerations: Published specification: Usage of
this media type is defined in RFC 3761
Applications that use this media type: This media type may be used
in various forms of SIP applications that interact with PSTN
databases for the purpose of displaying Calling Name Information on
SIP Client/User agents or other compatible devices.
Additional information:
Magic number(s): None
File extension(s): None
Macintosh file type code(s):None
Person & email address to contact for further information: Richard
Shockey or Jason Livingood
[richard.shockey@neustar.biz or jason_livingood@cable.comcast.com]
Intended usage: Common
Restrictions on usage: This content type is designed to carry
potentially personal information and as such, may be subject to
restrictions within various national jurisdictions.
Author/Change Controller: This specification is a work item of
the IETF ENUM working group, with the mailing list address
enum@ietf.org
Other Information: none
Security Considerations: none
12.
References
12.1 Normative References
[1] Faltstrom, P. and M. Mealling, "The E.164 to Uniform Resource
Identifiers (URI) Dynamic Delegation Discovery System (DDDS)
Application (ENUM)", RFC 3761, April 2004.
[2] ITU-T, "The International Public Telecommunication Number Plan",
Recommendation E.164, May 1997.
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[3] Mockapetris, P., "Domain Names - Concepts and Facilities", RFC
1034, November 1987.
[4] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
Three: The Domain Name System (DNS) Database", RFC 3403, October
2002.
[5] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
One: The Comprehensive DDDS", RFC 3401, October 2002.
[6] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
Two: The Algorithm", RFC 3402, October 2002.
[7] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
Four: The Uniform Resource Identifiers (URI)", RFC 3404, October
2002.
[8] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
Five: URI.ARPA Assignment Procedures", RFC 3405, October 2002.
[9] American National Standards Institute (ANSI), Coded
Character Set - 7-Bit American National Standard Code for Information
Interchange, ANSI X3.4, 1986.
[10] American National Standards Institute (ANSI),Telecommunications
_ Network-to-Customer Installation Interfaces _ Analog Voicegrade
Switched Access Lines with Calling Number Delivery, Calling Name
Delivery, or Visual Message-Waiting Indicator Features, ANSI
T1.6401.03-1998
[11] American National Standards Institute (ANSI), Telecommunications
- Integrated Services Digital Network (ISDN) _ Calling Line
identification Presentation and Restriction Supplementary Services,
ANSI T1.625-1993
[12] American National Standards Institute (ANSI),Telecommunications
- Calling Name Identification Presentation, ANSI T1.641-1995
[13] Telcordia Technologies, "CLASS Feature: Calling Name Delivery
Generic Requirements", GR-1188-CORE, Issue 2,December 2000
[14] Telcordia Technologies, "CLASS Feature: Calling Number
Delivery", GR-31-CORE, Issue 1, June 2000
[15] Masinter, L., "The "data" URL scheme", RFC 2397, August 1998
[16] Bradner, S., "Key words for use in RFC’s to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
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[17] Freed, N, et.al. "Media Type Specifications and Registration
Procedures", BCP 13 RFC 4288, December 2005
[18] Livinggood, J and Shockey, R "IANA Registration for an
Enumservice Containing Public Switched Telephone Network (PSTN)
Signaling Information", RFC 4769, November 2006
[19] Rosenberg, J., et al., "SIP: Session Initiation Protocol", RFC
3261, June 2002.
12.2 Informative References
[A] Arends, R. and et al., "Protocol Modifications for the DNS
Security Extensions", RFC 4035, March 2005.
[B] Atkins, D. and Austein, R., "Threat Analysis of the Domain Name
System (DNS)", RFC 3833, August 2004.
Authors' Addresses
Richard Shockey
NeuStar
46000 Center Oak Plaza
Sterling, VA 20166
USA
Phone: +1-571-434-5651
Email: richard.shockey@neustar.biz
Jason Livingood
Comcast Cable Communications
1500 Market Street
Philadelphia, PA 19102
USA
Phone: +1-215-981-7813
Email: jason.livingood@cable.comcast.com
Kevin McCandless
Verisign
7400 West 129th Street
Overland Park, KS 66213
USA
Phone : +1 913-814-6397
Email : KMcCandless@verisign.com
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Manjul Maharishi
Verisign
21345 Ridgetop Circle
Dulles VA 20166
Phone :+1 703-948-3255
Email : mmaharishi@verisign.com
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