SRV, which is an abbreviation for Service, is a DNS record, which enables you to employ a domain for a particular service different from a site. By creating a few SRV records, you will be able to use the domain name with different companies and direct it to several servers at the same time, each server handling a different service. You are able to specify the port number for the connection to every single machine, so there won't be any interference. You could also set individual priorities and weight for 2 records that are used for the exact 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 instance, and have the real software running on various machines with different providers. Which one a customer of yours will use depends on the priority and weight values you have set.