Internet DRAFT - draft-fenner-iana-dns-srv
draft-fenner-iana-dns-srv
Network Working Group B. Fenner
Internet-Draft AT&T Labs - Research
Updates: 2782 (if approved) June 21, 2005
Expires: December 23, 2005
An IANA Registry for DNS SRV service names
draft-fenner-iana-dns-srv-00
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document proposes a registry for service names used in DNS SRV
records.
1. Introduction
The traditional interpretation of the service name used in SRV
records [RFC2782] is that the name from the port number registry
<http://www.iana.org/assignments/port-numbers>[[anchor2: is this the
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best way to refer to this? urn:iana:port-numbers? "The IANA Port
Number registry"? --wcf]] is used as the name of the service.
However, one of the possible uses for SRV records is to avoid the
need for a unique port number, by having the port number specified in
the DNS record. The use of the port-numbers repository requires
assignment of a port number along with the name.
One community resource that has sprung up to address this problem is
<http://www.dns-sd.org/ServiceTypes.html>. There may, of course, be
others, and of course registration in this registry doesn't prevent
the same name being used for a port number, or being registered in a
different community registry, etc.
This document proposes the use of a registry that consists only of
service names, with no associated port numbers, and describes
procedures for maintaining this registry.
2. Registry for Service Names
The service name registry
<http://www.iana.org/assignments/service-names> was originally
established for the names of services as used in WKS records. Since
[RFC2782] only refers to "as defined in Assigned Numbers", which
contains both of these registries, it's not clear which registry is
meant. Since this registry contains only service names and
descriptions, it's a better match to the requirements of SRV records.
This document proposes moving to this registry, with a plan for
transition and rules for maintenance of the new registry.
3. Transition
All service names in the port-numbers registry will be copied to the
service-names registry, along with their descriptions and any
available references. Ad-hoc registries such as
<http://www.dns-sd.org/ServiceTypes.html> should be copied too;
readers are requested to notify the author if they know of any other
ad-hoc registries; IANA will be asked to copy from the list of ad-hoc
registries that exist in this document at the time of publication.
4. Future Registrations
In order to point to the correct registry, RFC 2782 is modified to
read:
Service The symbolic name of the desired service, as defined in
<http://www.iana.org/assignments/service-names>[[anchor5:
urn:iana:service-names ? "The IANA Service Names
registry"? --wcf]] or locally. An underscore (_) is
prepended to the service identifier to avoid collisions
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with DNS labels that occur in nature.
Any future registries in the port-numbers registry will be mirrored
in the service-names registry. The protocol name space is shared
between the port-numbers and service-names registry; new
registrations in the port-numbers registry must not be allowed to
overlap with a name in the service-names registry (unless they are
the same protocol).
5. IANA Considerations
New registrations in the service-names registry should be assigned on
a First Come First Served basis as defined in [RFC2434]. The
information required is a service name, description, and reference to
the protocol specification or any additional information. The
protocol specification may be referred to by RFC number or URL, and
is optional.
As in the port number registry, the service name is limited to 14
characters, composed of letters, digits and hyphens. The service
name is not case-sensitive and is normally registered in all
lowercase.[[anchor6: Are these the right restrictions on the
character set and/or length of service names? --wcf]][[anchor7: 14
chars, letters-digits-hyphens just like port names --marc]][[anchor8:
63 octets dns label limit --olaf]]
New registrations in the port-numbers registry will automatically be
added to the service-names registry as well. A registration in the
service-names registry that requires a port number in the future may
be registered using the normal port-numbers procedure.
As described in Section 3, IANA is asked to copy into the service-
names registry existing registrations from the port number registry
and the following ad-hoc community registries:
o <http://www.dns-sd.org/ServiceTypes.html>
o (...any others that are identified before RFC publication)
6. Security Considerations
Having a single registry for SRV service names eliminates the
confusion caused by duplicate service names, where a client could
look up one service and get a different service that uses the same
name.
7. Acknowledgements
This proposal first floated on the namedroppers list in May, 2004.
Paul Vixie, Marc Krochmal, Stuart Cheshire and Olaf Kolkman provided
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valuable feedback on earlier versions of this draft.
8. Normative References
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
Author's Address
Bill Fenner
AT&T Labs - Research
75 Willow Rd
Menlo Park, CA 94025
USA
Phone: +1 650 330-7893
Email: fenner@research.att.com
Appendix A. Contents of new service-names registry
This is the proposed contents of the service-names registry. (note:
the contents of ad-hoc registries have not yet been incorporated)
[[anchor11: This hasn't been checked against the current contents of
the service-names for duplicates. I originally included this in the
file, but since it made the I-D 98 pages long, I moved it:
--wcf]]<http://rtg.ietf.org/~fenner/ietf/service-names.txt>
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