The SRV resource record allows administrators to use several servers for a single domain, to move services from host to host easily, and to designate some hosts as primary servers for a service and others as backups. The symbolic name of the requested service, as defined in Assigned Numbers or locally. If Assigned Numbers names the service indicated, that name is the only name that is legal for SRV lookups. Only locally defined services can be named locally.
Service is case insensitive.
Proto is case insensitive. The domain this resource record refers to. The SRV resource record is unique in that the name searched for is not this name. Standard DNS meaning. Standard DNS meaning.