SRV, which is an abbreviation for Service, is a DNS record, which permits you to use a domain name for a specific service different from a site. By setting up a number of SRV records, you are able to use the domain with different providers and point it to several servers at a time, every single server handling a different service. You could specify the port number for the connection to every 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. With an SRV record you can employ your domain or a subdomain under it for a Voice-Over-IP server, for example, and have the specific software running on various machines with different providers. Which one a customer of yours is going to use depends on the priority and weight values that you've set.