SRV, which is an abbreviation for Service, is a DNS record, which allows you to employ a domain name for a particular service different from an Internet site. By setting up a few SRV records, you can use the domain address with different providers and direct it to several servers at once, each server handling a different service. You can specify the port number for the connection to each and every machine, so there won't be any interference. You can even set different priorities and weight for 2 records which are employed for the very same service, but direct to different servers for redundancy or load balancing. With an SRV record you can use your domain or a subdomain under it for a Voice-Over-IP server, for example, and have the specific software running on various machines with different companies. Which one a client of yours is going to use depends on the priority and weight values which you have set.