RFC 2782 (rfc2782) - Page 2 of 12
A DNS RR for specifying the location of services (DNS SRV)
Alternative Format: Original Text Document
RFC 2782 DNS SRV RR February 2000
Definitions
The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT" and "MAY"
used in this document are to be interpreted as specified in [BCP 14].
Other terms used in this document are defined in the DNS
specification, RFC 1034.
Applicability Statement
In general, it is expected that SRV records will be used by clients
for applications where the relevant protocol specification indicates
that clients should use the SRV record. Such specification MUST
define the symbolic name to be used in the Service field of the SRV
record as described below. It also MUST include security
considerations. Service SRV records SHOULD NOT be used in the absence
of such specification.
Introductory example
If a SRV-cognizant LDAP client wants to discover a LDAP server that
supports TCP protocol and provides LDAP service for the domain
example.com., it does a lookup of
_ldap._tcp.example.com
as described in [ARM]. The example zone file near the end of this
memo contains answering RRs for an SRV query.
Note: LDAP is chosen as an example for illustrative purposes only,
and the LDAP examples used in this document should not be considered
a definitive statement on the recommended way for LDAP to use SRV
records. As described in the earlier applicability section, consult
the appropriate LDAP documents for the recommended procedures.
The format of the SRV RR
Here is the format of the SRV RR, whose DNS type code is 33:
_Service._Proto.Name TTL Class SRV Priority Weight Port Target
(There is an example near the end of this document.)
Service
The symbolic name of the desired service, as defined in Assigned
Numbers [STD 2] or locally. An underscore (_) is prepended to
the service identifier to avoid collisions with DNS labels that
occur in nature.
Gulbrandsen, et al. Standards Track