ENUM Working Group R. Shockey - editor
Internet-Draft NeuStar
Expires: Sept 2006 J. Livingood
Comcast Cable Communications
Kevin McCandless
Verisign
Manjul Maharishi
Verisign
April 2006
IANA Registration for an Enumservice
Calling Name Delivery (CNAM) Information
draft-ietf-enum-cnam-00
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Abstract
This document registers the Enumservice "pstn" and the compound
subtypes subtype "cnam" and "data" using the URI scheme 'data:', as
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per the IANA registration process defined in the ENUM specification,
RFC 3761.
This data is used to facilitate the transfer of Calling Name Delivery
(CNAM) data for calls that originate on the 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. IANA Enumservice Registration:.................................3
4. Definition of CNAM Data........................................3
5. IANA Enumservice Registration for PSTN Data "cnam".............3
6. Structure of CNAM data.........................................4
7. Distribution of CNAM Data......................................5
8. Enumservice CNAM Response Example..............................5
9. Example of E2U+pstn:cnam:data in Call Processing...............6
Dialed Number..................................................6
10. SIP considerations............................................6
11. Security Considerations.......................................7
12. Privacy Considerations........................................7
13. Internationalized Character Set Considerations................8
14. IANA Considerations...........................................8
15. References....................................................8
Normative References...........................................8
Informative References.........................................9
Authors' Addresses...............................................10
Intellectual Property and Copyright Statements...................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 [1].
2. Introduction
ENUM (E.164 Number Mapping, RFC 3761 [1]) 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
DNS (Domain Name System, RFC 1034 [3]) delegation through NS records
and NAPTR records (Dynamic Delegation Discovery System (DDDS) Part
Three: The Domain Name System (DNS) Database, RFC 3403 [4]) to query
the services that are available for a specific domain name.
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This document registers an Enumservice according to the guidelines
given in RFC 3761 [1], 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.
3. IANA Enumservice Registration:
This Enumservice could enable service providers to place Calling Name
Delivery information into ENUM databases or to send ENUM queries to a
protocol converter that would have access to the 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" defines the URI scheme.
In this document, one type is specified, "pstn" and one compound
subtype cnam:data with the URI scheme specified, 'data:', as
specified in RFC 2397 [9].
4. Definition of CNAM Data
Caller Display Name is a data string of up to 15 ASCII characters of
information associated with a specific calling party number [13] [14]
[15] [16] [17]. 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. IANA Enumservice Registration for PSTN Data "cnam"
Enumservice Name: "cnam"
Enumservice Type: "pstn"
Enumservice Subtypes: "cnam"
Enumservice Subtypes: "data"
URI Schemes: 'data:'
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Functional Specification:
This Enumservice indicates that a resource record contains Calling
Name Delivery Information that can be addressed by the associated
'data' URI scheme [RFC 2397] 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
6. Structure of CNAM data
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
Enumservice Privacy Responses and Parameters
The PSTN defines several values for CNAM data in the event that there
are restrictions or that the data is unavailable. These are defined
as "Reason for Absence of Name" [R3-50] in GR-1188, consequently the
following responses to a query from a well known database are
reserved.
The data element "unavailable" is reserved for responses from the
well known database and two indicators are defined.
Calling Name Privacy Indicator
Definition: Parameter defined as the Calling Party does not wish to
have their Display Name displayed
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Usage: data:unavailable;cnp=p
Calling Name Status Indicator
Definition: for "not available/unavailable" defined as the well known
database has no data available for that particular E.164 number
Usage: data:unavailable;cns=u
7. Distribution of CNAM Data
The distribution of CNAM data is often highly restricted. The NAPTR
records described herein probably would not be part of the e164.arpa
DNS tree. Distribution of this NAPTR data would be either (a) on a
private basis (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) or (b) openly available
on a national basis according to national regulatory policy.
The authors believe it is most likely that these records will be
distributed on a purely private basis. If such data was distributed
nationally, a national regulatory body may have jurisdiction,
especially since CNAM information may contain Personally Identifying
Information [PII]. 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 PII data is collected, distributed and
subsequently regulated is out of the scope of this document.
8. Enumservice CNAM Response Example
This section documents an example for illustrative purposes. This
example shall in no way limit the various forms that this Enumservice
may take.
$ORIGIN 3.1.8.7.1.8.9.5.1.2.1.carrier1.example.
NAPTR 10 100 "u" "E2U+pstn:cnam:data"
"!^.*$!data:Francois%20Marie20%Arouet!".
Escape codes are placed between names per URI formatting in RFC 2396
$ORIGIN 3.1.8.7.1.8.9.5.1.2.1.carrier1.example.
NAPTR 10 100 "u" "E2U+pstn:cnam:data"
"!^.*$!data::unavaiable;cns=u !".
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9. Example of E2U+pstn:cnam:data in Call Processing
Typically, the Caller Display Name in the PSTN is delivered to the
called party during the first long silence interval after the first
ringing [16] (see requirement R3-341). If the Called party answers
the call before this, Calling Name may not be delivered. .
This is an example of how a switch, proxy, or other calling
application may make use of this Enumservice type during the call
initiation process.
Dialed Number
a) A PSTN user, say from +1-703-729-1234, which is connected to a
calling application, dials an E.164 telephone number: +1-215-
981-7813.
b) The calling application uses the dialed number to form a FQDN
NAPTR query: 3.1.8.7.1.8.9.5.1.2.1.e164.arpa.
c) The DNS finds an E2U+sip record and returns a sip URI for
processing by the calling application: sip:+1-215-981-
7813@carrier2.example;user=phone.SBC1.cox.net
SBC2.cox.net etc
d) A SIP invite is sent to the Called Party proxy at
carrier2.example.
e) The Called Party's SIP proxy/User Agent sees the SIP message
and before alerting the Called User, performs another ENUM
request using the E164 number in the SIP INVITE's From field
(i.e. +1-703-729-1234), and sends this query to a well known
database source for CNAM queries:
4.3.2.1.9.2.7.3.0.7.1.cnamedb.networks.example
f) Once the tel URI containing the CNAM data is returned from the
well-known database source, the Called party's proxy/User
Agent alerts the Called User about the incoming call and
includes the Calling Name in the SIP INVITE sent to the Called
User. It then sends a "180 Ringing" message to the Calling
party's proxy, signaling the desire to establish the session.
At that point the Called Party's Client User Agent could
display the CNAM data.
g) Once the Called User decides to accept the call, the RTP
stream commences and the session begins.
NOTE: The above example describes in general the approach that
would be required by a terminating SIP UA/Proxy to acquire and
send CNAM information to the Called Party. The exact mechanism,
determination of when to issue ENUM-CNAM request, and formatting
of SIP messages is beyond the scope of this document.
10. SIP considerations
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In those cases where SIP proxy's must carry CNAM data as P-asserted
identity fields as defined in RFC 3325
11. Security Considerations
DNS, as used by ENUM, is a global, distributed database. Thus, an
implementation of this Enumservice that uses e164.apra 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
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.
Carriers, service providers, and other users may simply choose not to
publish such information in a DNS tree, but may instead simply
privately exchange and publish this in their internal ENUM database,
which is only able to be queried by trusted elements of their
network, such as soft switches and SIP proxy servers.
An analysis of threats specific to the dependence of ENUM on the DNS
and the applicability of DNSSEC [13] to this is provided in RFC 3761
[1]. A thorough analysis of threats to the DNS itself is covered in
RFC 3833 [14].
12. Privacy Considerations
This document does not take into consideration issues of privacy as
it relates to Personally Identifying Information transmitted over IP
networks. Service providers using this query response technique are
advised that many national jurisdictions have strict regulations on
the use of Caller Display 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 Caller
Display Name are blocked are prevented from establishing a session.
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13. Internationalized Character Set Considerations
ANSI standards specify the use of ASCII for in the response to TCAP
queries for Caller Display Name. This specification does not
preclude the use of internationalized characters for the 'cnam='
parameter, nor does it preclude the use of more than 15 characters.
As a practical matter, however, it is recommended that the 'cnam='
parameter be no longer than 64 characters.
14. IANA Considerations
This document registers the 'cnam' Enumservice using the type "pstn"
and the compound subtypes "cnam" and "data" in the Enumservice
registry described in the IANA considerations in RFC 3761. Details
of this registration are provided in sections 3,4 and 5 of this
document.
15. References
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.
[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.
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[9] Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966,
December 2004.10] Rosenberg, J., et al., "SIP: Session Initiation
Protocol", RFC 3261, June 2002.
[11] V. Gurbani, C. Jennings., "The Internet Assigned Number
Authority (IANA) tel Uniform Resource Identifier (URI)Parameter
Registry, draft-jennings-iptel-tel-reg-01.txt (work-in-progress)
[12] American National Standards Institute (ANSI), Coded
Character Set - 7-Bit American National Standard Code for Information
Interchange, ANSI X3.4, 1986.
[13] 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
[14] American National Standards Institute (ANSI), Telecommunications
- Integrated Services Digital Network (ISDN) _ Calling Line
identification Presentation and Restriction Supplementary Services,
ANSI T1.625-1993
[15] American National Standards Institute (ANSI),Telecommunications
- Calling Name Identification Presentation, ANSI T1.641-1995
[16] Telcordia Technologies, "CLASS Feature: Calling Name Delivery
Generic Requirements", GR-1188-CORE, Issue 2,December 2000
[17] Telcordia Technologies, "CLASS Feature: Calling Number
Delivery", GR-31-CORE, Issue 1, June 2000
[18] Jennings, C., et.al "Private Extensions to the Session
Initiation Protocol (SIP) for Asserted Identity within Trusted
Networks", RFC 3325, November 2002
[19] Masinter, L., "The "data" URL scheme", RFC 2397, August 1998
Informative References
[1] Bradner, et al., "IANA Registration for Enumservices email, fax,
mms, ems and sms", draft-ietf-enum-msg-05.txt, May 2005.
[2] Arends, R. and et al., "Protocol Modifications for the DNS
Security Extensions", RFC 4035, March 2005.
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[3] Atkins, D. and Austein, R., "Threat Analysis of the Domain Name
System (DNS)", RFC 3833, August 2004.
[4] Peterson, J., "enumservice Registration for Session Initiation
Protocol (SIP) Addresses-of-Record", RFC 3764, April 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
Manjul Maharishi
Verisign
21345 Ridgetop Circle
Dulles VA 20166
Phone :+1 703-948-3255
Email : mmaharishi@verisign.com
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