One document matched: draft-bellis-enum-send-n-00.txt
ENUM -- Telephone Number Mapping R. Bellis
Working Group Nominet UK
Internet-Draft April 2, 2008
Expires: October 4, 2008
IANA Registrations for the 'Send-N' Enumservice
draft-bellis-enum-send-n-00
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Abstract
This document requests IANA registration of an Enumservice 'Send-N'
and extends the definition of the 'pstndata:' URI scheme. This
service allows more efficient support for overlapped dialling in
E.164 Number Mapping (ENUM) enabled applications.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. ENUM Service Registration for "Send-N" . . . . . . . . . . . . 4
4. IANA Registration Template for URI scheme "pstndata:" . . . . 4
5. Description . . . . . . . . . . . . . . . . . . . . . . . . . 5
6. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7. DNS Considerations . . . . . . . . . . . . . . . . . . . . . . 6
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
10. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 7
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
12.1. Normative References . . . . . . . . . . . . . . . . . . 8
12.2. Informative References . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 10
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1. Introduction
E.164 Number Mapping (ENUM) [I-D.ietf-enum-3761bis] uses the Domain
Name System (DNS) [RFC1035] to refer from E.164 numbers [E.164] to
Uniform Resource Identifiers (URIs) [RFC3986]
Most SIP devices and cellular devices require the user to dial a
complete telephone number and then press a 'send' or 'dial' button to
initiate dialling. This contrasts with the typical operation of PSTN
telephones where dialled digits are sent to the network operator as
soon they are dialled and the call is initiated as soon as the
network recognises that a complete number has been dialled. This
PSTN model for dialling is known as "overlapped dialing".
Currently to support overlapped dialling an ENUM application would
need to perform an ENUM lookup as each and every digit is dialled.
This would impose a significant burden on the ENUM DNS servers and
could also affect call setup time.
By storing additional information within the ENUM database about the
structure of the local numbering plan it is possible to provide hints
to such an application that will allow it to skip unnecessary per-
digit ENUM lookups.
This additional information is encoded within NAPTR records since
this avoids the need for ENUM applications to issue multiple DNS
requests with varying QTYPEs depending on the type of information
being looked up. To differentiate NAPTR records containing 'Send-N'
data from other types of NAPTR record it is necessary to create a new
Enumservice which must be registered with IANA.
[I-D.ietf-enum-cnam] registers the 'cnam' Enumservice for PSTN data
with type 'pstndata' and a specific 'cnam' subtype for Calling Name
Delivery. It also registers the 'pstndata' Uniform Resource
Identifier (URI) scheme. Both the Enumservice and the URI scheme
documented therein are intended to be extensible to represent other
PSTN related data.
This document therefore requests the registration of a new
Enumservice subtype for 'Send-N' and extends the definition of the
'pstndata:' URI scheme.
2. 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 RFC 2119 [RFC2119].
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A "full ENUM record" is an RRset containing NAPTR records about a
complete E.164 telephone number.
3. ENUM Service Registration for "Send-N"
The following template contains information required for the IANA
registrations of the 'Send-N' Enumservice:
Enumservice Name: Send-N
Enum service Class: Ancillary Application Enumservice
Enumservice Type: pstndata
Enumservice Subtype: send-n
URI Schemes: pstndata:
Functional Specification:
This Enumservice indicates that the resource record contains
information that describes the structure of the local E.164
numbering plan below this point.
Security Considerations: see Section 8
Intended Usage: COMMON
Author: Ray Bellis <mailto:ray.bellis@nominet.org.uk>
4. IANA Registration Template for URI scheme "pstndata:"
URI scheme name: pstndata
Status: provisional
URI scheme syntax: (in ABNF [RFC5234])
pstndatauri =/ ( "pstndata:" sendndatatype )
sendndatatype = "send-n/" digitsmin [ "-" digitsmax ]
digitsmin = e164digitcount
digitsmax = e164digitcount
e164digitcount = %x30-%x39 / (%x31 %x30-%x35)
; 0 - 15 digits, per E.164
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where 'pstndatauri' is imported from [I-D.ietf-enum-cnam]
URI scheme semantics: The URI contains information that describes the
structure of the local E.164 numbering plan. This information is
interpreted to be relative to the domain which contained the NAPTR RR
which in turn contained this URI in its 'regexp' field.
Encoding considerations: None, all valid characters are in US ASCII
Applications: ENUM [I-D.ietf-enum-3761bis]
Interoperability considerations: none
Security considerations: see Section 8
Contact: Ray Bellis <mailto:ray.bellis@nominet.org.uk>
References: [I-D.ietf-enum-cnam]
5. Description
The records described here contain meta-information about an ENUM
database - specifically the depth (or range of depths) in the DNS
tree below the current record at which full ENUM records may be
found, as per the local numbering plan.
Note that gaps in the E.164 numbering plan are not represented by
this data. The 'Send-N' data only indicates the _potential_ presence
of numbers, not their absence. The details of how the absence of
ENUM records should be represented (e.g. for invalid or unallocated
numbers) are not addressed in this document.
The 'digitsmin' field of the data MUST correspond to the minimum
number of additional digits to be dialled, relative to the current
record, which might result in reaching a full ENUM record in the ENUM
database.
It is RECOMMENDED that the 'digitsmax' field also be supplied and
where supplied it MUST correspond to the maximum number of additional
digits that might be valid in the relevant numbering plan. If the
'digitsmax' field is omitted this represents that the information is
unknown and MUST NOT be assumed to be the same as 'digitsmin'.
6. Example
An example ENUM entry containing 'Send-N' data looks like:
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$ORIGIN 5.6.8.1.4.4.e164.arpa.
@ IN NAPTR ( 100 10 "u"
"E2U+pstndata:send-n"
"!^.*$!pstndata:send-n/5-6!" .
)
This record indicates that between 5 and 6 additional digits are
required to reach any valid E.164 number beginning +441865 according
to the local numbering plan.
Having received the NAPTR record from the previous example, the
application might subsequently receive the five additional digits
"33221". Based on the previously received record the application
knows that it need not perform any ENUM lookups for each of the next
four digits, but on receiving the fifth it then performs another ENUM
lookup, returning the record below:
$ORIGIN 1.2.2.3.3.5.6.8.1.4.4.e164.arpa.
@ IN NAPTR ( 100 10 "u"
"E2U+pstndata:send-n"
"!^.*$!pstndata:send-n/1-1!" .
)
This data indicates that exactly one further digit needs to be
dialled before a full ENUM record might be returned.
7. DNS Considerations
These records MUST NOT be used with DNS wildcards since DNS wildcards
can represent an arbitrary number of labels (or digits, in the ENUM
case) and the data in a 'Send-N' record is specific to an exact
position in the ENUM tree
These records are mostly likely to be used in intermediate records in
the ENUM database, although in countries (such as Austria) that use
open numbering plans it might be possible to find both full NAPTR
records and 'Send-N' NAPTR records in the same RRset.
An example of this is where a company switchboard might be reached by
dialling the main number and extensions are reached by dialling
additional digits. In that case the country-level administrator
would maintain 'Send-N' records that describe the national dialling
plan, but end user ENUM registrations could supply additional
'Send-N' records that describe their internal numbering plan.
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8. Security Considerations
This Enumservice and URI scheme were originally designed for use on a
large private ENUM database, where no security issues are believed to
exist.
Security issues resulting from use of this data in public ENUM
database where delegations are made to third parties have not been
assessed in detail, however it is believed that no new security or
privacy issues would arise from the use of this data.
9. IANA Considerations
This document requests the IANA registration of the Enumservice
'Send-N' with Type 'pstndata' and Subtype 'send-n' according to the
definitions in this document, RFCxxxx
[I-D.ietf-enum-enumservices-guide] and RFC3761bis
[I-D.ietf-enum-3761bis]. The required template is contained in
Section 3.
This document requests an update to the IANA registration of the URI
scheme 'pstndata:' according to the definitions in this document and
following the process described in [RFC4395]. The required template
is contain in Section 4.
10. Change Log
[Note to editors: This section is to be removed before publication -
XML source available on request]
draft-bellis-enum-send-n-00
initial draft
11. Acknowledgements
The author would like to thank those members of the Network
Interoperability Consultative Committee (<http://www.nicc.org.uk/>)
and in particular to Clive Feather, who contributed to the NICC
specification for a Central Number Portability Database from which
this work is derived.
The author would also like to thank Alexander Mayrhofer for his
assistance.
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12. References
12.1. Normative References
[I-D.ietf-enum-3761bis]
Bradner, S., Conroy, L., and K. Fujiwara, "The E.164 to
Uniform Resource Identifiers (URI) Dynamic Delegation
Discovery System (DDDS) Application (ENUM)",
draft-ietf-enum-3761bis-03 (work in progress), March 2008.
[I-D.ietf-enum-cnam]
Shockey, R., "IANA Registration for an Enumservice Calling
Name Delivery (CNAM) Information and IANA Registration
for URI type 'pstndata' URI type 'pstn'",
draft-ietf-enum-cnam-07 (work in progress), October 2007.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
12.2. Informative References
[E.164] ITU-T, "The international public telecommunication
numbering plan", Recommendation E.164 (02/05), Feb 2005.
[I-D.ietf-enum-enumservices-guide]
Hoeneisen, B., Mayrhofer, A., and J. Livingood, "IANA
Registration of Enumservices: Guide, Template and IANA
Considerations", draft-ietf-enum-enumservices-guide-08
(work in progress), March 2008.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
Registration Procedures for New URI Schemes", BCP 115,
RFC 4395, February 2006.
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Author's Address
Ray Bellis
Nominet UK
Edmund Halley Road
Oxford OX4 4DQ
United Kingdom
Phone: +44 1865 332211
Email: ray.bellis@nominet.org.uk
URI: http://www.nominet.org.uk/
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