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 Active Directory, and more recently with SIP servers (see https://simpledns.plus/kb/112).
The SRV record identification (record name) is made of of 3 parts:
Service: Most internet services are defined in RFC1700 (page 15).
Protocol: Generally TCP or UDP, but other values are also valid.
Domain name.
The "service location" is specified through a priority, weight, port and target:
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.
Target is the domain name of the server (referencing an A-record or AAAA-record).
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.
Note: While this record type could potentially have been used by web-browser software (to locate web-servers), this was never implemented by any major browsers. Instead browsers have recently (2021) started supporting the HTTPS record-type which provdides similar functionality specifically for web-sites.