RFC 2219 (rfc2219) - Page 2 of 8
Use of DNS Aliases for Network Services
Alternative Format: Original Text Document
RFC 2219 DNS Aliases October 1997
Perhaps the most visible example of the latter approach at work is in
the case of World-Wide Web HTTP servers. It is common practice to
try prefixing the domain name of an organization with "http://www."
in order to reach its World-Wide Web site, e.g. taking "hivnet.fr"
and arriving at "http://www.hivnet.fr." Some popular World-Wide Web
browsers have gone so far as to provide automatic support for this
domain name expansion.
Ideally, the DNS or some complementary directory service would
provide a means for programs to determine automatically the network
services which are offered at a particular Internet domain, the
protocols which are used to deliver them, and other technical
information. Unfortunately, although much work has been done to
develop said directory service technologies and to define new types
of DNS resource record to provide this type of information, there is
no widely agreed upon or widely deployed solution to the problem -
except in a small number of cases.
The first case is where the DNS already provides a lookup capability
for the type of information being sought after. For example: Mail
Exchanger (MX) records specify how mail to a particular domain should
be routed [RFC-974], the Start of Authority (SOA) records make it
possible to determine who is responsible for a given domain, and Name
Server (NS) records indicate which hosts provide DNS name service for
a given domain.
The second case is where the DNS does not provide an appropriate
lookup capability, but there is some widely accepted convention for
finding this information. Some use has been made of Text (TXT)
[RFC-1035] records in this scenario, but in the vast majority of
cases a Canonical Name (CNAME) or Address (A) record pointer is used
to indicate the host or hosts which provide the service. This
document proposes a slight formalization of this well-known alias
approach.
It should be noted that the DNS provides a Well Known Services (WKS)
[RFC-1035] lookup capability, which makes it possible to determine
the network services offered at a given domain name. In practice
this is not widely used, perhaps because of the absence of a suitable
programming interface. Use of WKS for mail routing was deprecated in
the Host Requirements specification [RFC-1123] in favour of the MX
record, and in the long term it is conceivable that SRV records will
supersede both WKS and MX.
Hamilton & Wright Best Current Practice