SRV, which is an abbreviation for Service, is a DNS record, which permits you to employ a domain for a particular service different from a website. By setting up a couple of SRV records, you are able to use the domain with different providers and direct it to a number of servers at a time, each and every server managing a separate service. You could specify the port number for the connection to every machine, so there will not 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. By having an SRV record you can use your domain name 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 client of yours is going to use will depend on the priority and weight values that you've set.