SRV - DNS Record

(Service Locator). A SRV is a generalized service location record, used for newer protocols instead of creating protocol-specific records such as MX.

As with PTR records, SRV records must point to the canonical name of the host. Aliases or CNAMEs cannot be used as valid targets.

An SRV record or Service record is a category of data in the Internet Domain Name System specifying information on available services. Newer internet protocols such as SIP and XMPP often require SRV support from clients.

The SRV RR allows administrators to use several servers for a single domain, to move services from host to host with little fuss, and to    designate some hosts as primary servers for a service and others as backups.