SRV, which is an abbreviation for Service, is a DNS record, which permits you to employ a domain name for a certain service different from a website. By setting up a few SRV records, you can use the domain address with different companies and forward it to numerous servers at the same time, each and every server handling a separate service. You'll be able to specify the port number for the connection to each machine, so there will never be any interference. You can also set different priorities and weight for two records that are used for the exact same service, but forward to different servers for redundancy or load balancing. Using an SRV record you can use your domain or a subdomain under it for a Voice-Over-IP server, for example, and have the actual software running on a number of machines with different providers. Which one a client of yours will use depends on the priority and weight values that you've set.