A Domain Name System Service Record, SRV is short for service record.
Unlike most DNS records which contain an IP address or name, the SRV record contains the name and port of a specific service location. Commonly, services like Voice-Over-IP (VOIP) or Instant Messaging (IM) will require a port to make sure the call or IM goes to the right person no matter where they are.
It may also be the case that multiple services reside on one server and to ensure the correct service is used a port would be required. There are commonly used ports or companies may choose to specify their own custom ports, depending on the design and implementations from the network and security teams. For a list of commonly used tcp and udp port number check out wikipedia here.
How you create a SRV record will depend on which DNS management system you’re using. If you’re using Micetro, by Men&Mice to create a DNS record you will follow these steps: