DNS - SRV Records
These allow domains to identify the services offered and the hosts responsible for providing the services:
Service - name of the service (http, telnet, etc)
Proto - Usually the Layer 4 protocol
Domain - Domain this applies to
TTL/Class - Same as other DNS records
Priority - Lower number = higher priority. Higher priortity hosts get contacted first
Weight - Used to load balance hosts with identical Priorities
Port - Port of service
Target - FQDN for service host