SRV, which is an abbreviation for Service, is a DNS record, which enables you to use a domain name for a particular service different from a site. By setting up a number of SRV records, you can use the domain address with different providers and direct it to a number of servers at a time, every single server handling a separate service. You'll be able to specify the port number for the connection to each machine, so there won't be any interference. You can also set individual priorities and weight for two records which are used for the very same service, but direct to different servers for redundancy or load balancing. Using an SRV record you can use your domain name or a subdomain under it for a Voice-Over-IP server, for example, and have the real software running on various machines with different companies. Which one a client of yours will use depends on the priority and weight values you have set.