SRV, which is an abbreviation for Service, is a DNS record, which enables you to employ a domain for a certain service different from a site. By setting up a few SRV records, you are able to use the domain address with different companies and direct it to many servers at once, each server handling a different service. You can specify the port number for the connection to every single machine, so there will not be any interference. You could also set individual priorities and weight for 2 records which are employed for the same service, but point to different servers for redundancy or load balancing. Using an SRV record you can employ your domain or a subdomain under it for a Voice-Over-IP server, for instance, and have the specific software running on several machines with different companies. Which one a customer of yours will use is determined by the priority and weight values that you've set.