RFC 2052 (rfc2052) - Page 2 of 10
A DNS RR for specifying the location of services (DNS SRV)
Alternative Format: Original Text Document
RFC 2052 DNS SRV RR October 1996
and retrieves the document from one of the servers in the reply. The
example zone file near the end of the memo contains answering RRs for
this query.
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 or locally.
Some widely used services, notably POP, don't have a single
universal name. If Assigned Numbers names the service
indicated, that name is the only name which is legal for SRV
lookups. Only locally defined services may be named locally.
The Service is case insensitive.
Proto
TCP and UDP are at present the most useful values
for this field, though any name defined by Assigned Numbers or
locally may be used (as for Service). The Proto is case
insensitive.
Name
The domain this RR refers to. The SRV RR is unique in that the
name one searches for is not this name; the example near the end
shows this clearly.
TTL
Standard DNS meaning.
Class
Standard DNS meaning.
Priority
As for MX, the priority of this target host. A client MUST
attempt to contact the target host with the lowest-numbered
priority it can reach; target hosts with the same priority
SHOULD be tried in pseudorandom order. The range is 0-65535.
Gulbrandsen & Vixie Experimental