One document matched: draft-ietf-enum-e164-dns-01.txt
Differences from draft-ietf-enum-e164-dns-00.txt
Network Working Group P Faltstrom
Internet-Draft Cisco Systems Inc
Expires: January 8, 2001 July 10, 2000
E.164 number and DNS
draft-ietf-enum-e164-dns-01
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.
This Internet-Draft will expire on January 8, 2001.
Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract
This document discusses the use of DNS for storage of E.164 numbers.
More specifically, how DNS can be used for identifying available
services connected to one E.164 number. Routing of the actual
connection using the service selected using these methods is not
discussed.
Faltstrom Expires January 8, 2001 [Page 1]
Internet-Draft E.164 number and DNS July 2000
1. Introduction
Through transformation of E.164 numbers into DNS names and the use
of existing DNS services like delegation through NS records, and use
of NAPTR[1] records in DNS[2][3], one can look up what services are
available for a specific domainname in a decentralized way with
distributed management of the different levels in the lookup
process.
1.1 Terminology
The key words "MUST", "REQUIRED", "SHOULD", "RECOMMENDED", and "MAY"
in this document are to be interpreted as described in RFC2119[4]
Faltstrom Expires January 8, 2001 [Page 2]
Internet-Draft E.164 number and DNS July 2000
2. E.164 numbers and DNS
The domain "e164.arpa." is being populated in order to provide the
infrastructure in DNS for storage of E.164 numbers. In order to
facilitate distributed operations, this domain is divided into
subdomains. Holders of E.164 numbers which want to be listed in DNS
should contact the appropriate zone administrator in order to be
listed, by examining the SOA resource record associated with the
zone, just like in normal DNS operations.
To find the DNS names for a specific E.164 number, the following
procedure is to be followed:
1. See that the E.164 number is written in its full form, including
the countrycode IDDD. Example: +46-8-9761234
2. Remove all non-digit characters part from the leading '+'.
Example: +4689761234
3. Remove all characters part from the digits. Example: 4689761234
4. Put dots (".") between each digit. Example: 4.6.8.9.7.6.1.2.3.4
5. Change the order of the digits. Example: 4.3.2.1.6.7.9.8.6.4
6. Append the domain "e164.arpa" to the end. Example:
4.3.2.1.6.7.9.8.6.4.e164.arpa
Faltstrom Expires January 8, 2001 [Page 3]
Internet-Draft E.164 number and DNS July 2000
3. Fetching URIs given an E.164 number
For a record in DNS, the NAPTR record is used for identifying
available ways of contacting a specific node identified by that
name. Specifically it can be used for knowing what services exists
for a specific domainname, including phone numbers by the use of the
e164.arpa domain as described above.
The identification is using the NAPTR resource record defined for
use in the URN resolution process, but it can be generalized in a
way that suits the needs specified in this document.
It is the string which is the result of step 2 in section 2 above
which is input to the NAPTR algorithm.
3.1 The NAPTR record
The key fields in the NAPTR RR are order, preference, service,
flags, regexp, and replacement. For a detailed description, see:
o The order field specifies the order in which records MUST be
processed when multiple NAPTR records are returned in response to
a single query.
o The preference field specifies the order in which records SHOULD
be processed when multiple NAPTR records have the same value of
"order".
o The service field specifies the resolution protocol and
resolution service(s) that will be available if the rewrite
specified by the regexp or replacement fields is applied.
o The flags field contains modifiers that affect what happens in
the next DNS lookup, typically for optimizing the process.
o The regexp field is one of two fields used for the rewrite rules,
and is the core concept of the NAPTR record.
o The replacement field is the other field that may be used for the
rewrite rule.
Note that the client applies all the substitutions and performs all
lookups, they are not performed in the DNS servers. Note that URIs
are stored in the regexp field.
3.1.1 Specific handling of non-terminal NAPTR records
An E.164 number, without any characters but leading '+' and digits,
(result of step 2 in section 2 above) is the input to the NAPTR
Faltstrom Expires January 8, 2001 [Page 4]
Internet-Draft E.164 number and DNS July 2000
algorithm, and because of this non-terminal NAPTR records (i.e.
rewrite rules) operate on this string.
The service supported for a call is N2R.
3.1.2 Example 1
$ORIGIN 4.3.2.1.6.7.9.8.6.4.e164.arpa.
IN NAPTR 100 10 "u" "sip+N2R" "!^.*$!sip:information@tele2.se!" .
IN NAPTR 102 10 "u" "smtp+N2R" "!^.*$!mailto:information@tele2.se!" .
This describes that the domain tele2.se is preferrable contacted via
the SIP protocol, secondly via SMTP.
In both cases, the next step in the resolution process is to use the
resolution mechanism for each of the protocols, (SIP and SMTP) to
know what node to contact for each.
3.1.3 Example 2
$ORIGIN 4.3.2.1.6.7.9.8.6.4.e164.arpa.
IN NAPTR 10 10 "u" "sip+N2R" "!^.*$!sip:paf@swip.net!" .
IN NAPTR 102 10 "u" "smtp+N2R" "!^.*$!mailto:paf@swip.net!" .
IN NAPTR 102 10 "u" "tel+N2R" "!^.*$!tel:+4689761234!" .
Note that the prefered method is to use the SIP protocol, but the
result of the rewrite of the NAPTR record is a URI (the "u" flag in
the NAPTR record). In the case of the protocol SIP, the URI might be
a SIP URI, which is resolved as described in RFC 2543[5]. In the
case of the "tel" URI scheme[6], the procedure is restarted with
this new E.164 number. The client is responsible for loop detection.
The rest of the resolution of the routing is done as described
above.
3.1.4 Example 3
$ORIGIN 6.4.e164.arpa.
* IN NAPTR 100 10 "u" "sip+N2R"
"!^+46(.*)$!ldap://ldap.example.se/cn=0$1!" .
We see in this example that information about all E.164 numbers in
the 46 countrycode (for sweden) exists in an LDAP server, and the
search to do is specified by the LDAP URI[7].
Faltstrom Expires January 8, 2001 [Page 5]
Internet-Draft E.164 number and DNS July 2000
4. IANA considerations
IANA is to create the E164.ARPA domain in the ARPA zone, and
delegate names in the zone to parties according to the ITU
recommendation E.164. The names allocated should be hierarichally
allocated according to the description in this document, and the
codes assigned in the E.164 recommendation by ITU.
Delegations should be done after Expert Review, and the IESG will
appoint a designated expert.
Faltstrom Expires January 8, 2001 [Page 6]
Internet-Draft E.164 number and DNS July 2000
5. Security Considerations
As this system is built on top of DNS, one can not be sure that the
information one get back from DNS is more secure than any DNS query.
To solve that, the use of DNSSEC[8] for securing and verifying zones
is to be recommended.
The caching in DNS can make the propagation time for a change take
the same amount of time as the time to live for the NAPTR and SRV[9]
records in the zone that is changed. The TTL should because of that
be kept to a minimum. The use of this in an environment where
IP-addresses are for hire (for example when using DHCP[10]) must
therefore be done very carefully.
Faltstrom Expires January 8, 2001 [Page 7]
Internet-Draft E.164 number and DNS July 2000
6. Acknowledgement
Support and ideas has come from people at Ericsson, especially Bjorn
Larsson, especially the group which implemented this scheme in their
lab to see that it worked. Input has also come from ITU-T SG2,
Working Party 1/2 (Numbering, Routing, Global Mobility and Service
Definition), the ENUM working group in the IETF, and Leif Sunnegardh
at Tele2 for information about how SS7 really works.
Faltstrom Expires January 8, 2001 [Page 8]
Internet-Draft E.164 number and DNS July 2000
References
[1] Mealling, M and R Daniel, "The Naming Authority Pointer (NAPTR)
DNS Resource Record", draft-ietf-urn-naptr-rr-03.txt (work in
progress), June 1998.
[2] Mockapetris, P.V., "Domain names - concepts and facilities",
RFC 1034, STD 13, Nov 1987.
[3] Mockapetris, P.V., "Domain names - implementation and
specification", RFC 1035, STD 13, Nov 1987.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, BCP 14, March 1997.
[5] Handley, M., Schulzrinne, H., Schooler, E. and J. Rosenberg,
"SIP: Session Initiation Protocol", RFC 2543, March 1999.
[6] Vaha-Sipila, A., "URLs for Telephone Calls", RFC 2806, April
2000.
[7] Howes, T. and M. Smith, "An LDAP URL Format", RFC 1959, June
1996.
[8] Eastlake, D., "Domain Name System Security Extensions", RFC
2535, March 1999.
[9] Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[10] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
Author's Address
Patrik Faltstrom
Cisco Systems Inc
170 W Tasman Drive SJ-13/2
San Jose CA 95134
USA
EMail: paf@cisco.com
URI: http://www.cisco.com
Faltstrom Expires January 8, 2001 [Page 9]
Internet-Draft E.164 number and DNS July 2000
Appendix A. Scenario
Say that the content of the e164.arpa zone is the following:
$ORIGIN e164.arpa.
6.4 IN NS ns.regulator-e164.example.se.
The regulator has in turn given a series of 10000 numbers to the
telco with the name Telco-A. The regulator because of that has in
his DNS.
$ORIGIN 6.4.e164.arpa.
6.7.9.8 IN NS ns.telco-a.example.se.
A user named Sven Svensson has from Telco A got the phone number
+46-8-9761234. The user gets the service of running DNS from the
company Redirection Service. Sven Svensson has asked Telco A to
point out Redirection Service as the authoritative source for
information about the number +46-8-9761234. Telco A because of this
puts in his DNS the following.
$ORIGIN 6.7.9.8.6.4.e164.arpa.
4.3.2.1 IN NS ns.redirection-service.example.se.
Sven Svensson has already plain telephony from Telco A, but also a
SIP service from the company Sip Service which provides Sven with
the SIP URI "sip:sven@sipservice.example.se". The ISP with the name
ISP A runs email and webpages for Sven, under the emailaddress
sven@ispa.example.se, and URL http://svensson.ispa.example.se.
The DNS for the redirection service because of this contains the
following.
$ORIGIN 4.3.2.1.6.7.9.8.6.4.e164.arpa.
IN NAPTR 10 10 "a" "sip+N2R" "!^.*$!sip:sven@sipservice.example.se!" .
IN NAPTR 10 10 "a" "smtp+N2R" "!^.*$!mailto:sven@ispa.example.se!" .
IN NAPTR 10 10 "a" "http+N2R" "!^.*$!http://svensson.ispa.example.se!" .
IN NAPTR 10 10 "a" "tel+N2R" "!^.*$!tel:+46-8-9761234!" .
A user, John Smith, want to contact Sven Svensson, he to start with
only has the E.164 number of Sven, i.e. +46-8-9761234. He takes the
number, and enters the number in his communication client, which
happen to know how to handle the SIP protocol. The client removes
the dashes, and ends up with the E.164 number +4689761234. That is
what is used in the algorithm for NAPTR records, which is as
Faltstrom Expires January 8, 2001 [Page 10]
Internet-Draft E.164 number and DNS July 2000
follows.
The client converts the E.164 number into the domainname
4.3.2.1.6.7.9.8.6.4.e164.arpa., and queries for NAPTR records for
this domainname. Using DNS mechanisms which includes following the
NS record referals, the following records are returned:
$ORIGIN 4.3.2.1.6.7.9.8.6.4.e164.arpa.
IN NAPTR 10 10 "a" "sip+N2R" "!^.*$!sip:sven@sipservice.example.se" .
IN NAPTR 10 10 "a" "smtp+N2R" "!^.*$!mailto:sven@ispa.example.se" .
IN NAPTR 10 10 "a" "http+N2R" "!^.*$!http://svensson.ispa.example.se" .
IN NAPTR 10 10 "a" "tel+N2R" "!^.*$!tel:+46-8-9761234" .
Because this client know sip, the first record above is selected,
and the SIP URI is extracted, and used according to SIP resolution.
Faltstrom Expires January 8, 2001 [Page 11]
Internet-Draft E.164 number and DNS July 2000
Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC editor function is currently provided by the
Internet Society.
Faltstrom Expires January 8, 2001 [Page 12]
| PAFTECH AB 2003-2026 | 2026-04-24 02:39:55 |