SRV, which is an abbreviation for Service, is a DNS record, which allows you to employ a domain for a certain service different from a site. By creating a couple of SRV records, you are able to use the domain with different providers and forward it to a number of servers at the same time, each and every server managing a different service. You can specify the port number for the connection to each and every machine, so there will not be any interference. You can even set different priorities and weight for 2 records that are employed for the very same service, but point to different servers for redundancy or load balancing. By having an SRV record you can use your domain address or a subdomain under it for a Voice-Over-IP server, for instance, and have the specific software running on a number of machines with different providers. Which one a customer of yours is going to use will depend on the priority and weight values that you have set.