SRV, which is an abbreviation for Service, is a DNS record, which allows you to use a domain for a certain service different from a website. By creating a number of SRV records, you can use the domain address with different providers and forward it to several servers at the same time, each and every server managing a different service. You can specify the port number for the connection to every machine, so there will never be any interference. You can also set different priorities and weight for 2 records which are employed for the same service, but forward to different servers for redundancy or load balancing. With an SRV record you can employ your domain address or a subdomain under it for a Voice-Over-IP server, for example, and have the specific software running on a number of machines with different companies. Which one a customer of yours will use will depend on the priority and weight values you have set.