SRV-records are used to specify the location of a service.

 

They are used in connection with different directory servers such as LDAP (Lightweight Directory Access Protocol), and Windows directory services, and more recently with SIP servers (see http://www.simpledns.com/kb.aspx?kbid=1218).

 

They can also be used for advanced load balancing and to specify specific ports for services, for example, that a web-server is running on port 8080 instead of the usual port 80 (theoretical example - this is not yet supported by any major browsers).

 

This record type is however NOT supported by most programs in use today, including web-browsers.

 

The name of a SRV-record is defined as "_service._protocol.domain", for example, "_ftp._tcp.xyz.com".

Most internet services are defined in RFC1700 (page 15), and the protocol is generally TCP or UDP.

 

The "service location" is specified through a target, priority, weight, and port:

- Target is the domain name of the server (referencing an A-record or AAAA-record).

- Priority is a preference number used when more servers are providing the same service (lower numbers are tried first).

- Weight is used for advanced load balancing.

- Port is the TCP/UDP port number on the server that provides this service.

 

To create a new SRV-record, right-click a zone in the left list in the DNS Records window, and select "Other new record" from the pop-up menu.

 

This record type is defined in RFC2782.