SRV, which is an abbreviation for Service, is a DNS record, which enables you to use a domain for a certain service different from a site. By setting up a few SRV records, you’re able to use the domain name with different companies and forward it to a number of servers at once, every single server managing a different service. You'll be able to specify the port number for the connection to every machine, so there will not be any interference. You can also set different priorities and weight for two records that are employed for the very same service, but forward to different servers for redundancy or load balancing. By having an SRV record you can employ your domain or a subdomain under it for a Voice-Over-IP server, for instance, and have the actual software running on a number of machines with different providers. Which one a client of yours will use will depend on the priority and weight values which you have set.