SRV, which is an abbreviation for Service, is a DNS record, which permits you to use a domain for a particular service different from a website. By creating a number of SRV records, you can use the domain address with different providers and point it to a number of servers at a time, each and every server handling a separate service. You can specify the port number for the connection to each and every machine, so there won't be any interference. You can even set individual priorities and weight for 2 records that are used for the very same service, but point to different servers for redundancy or load balancing. With an SRV record you can employ your domain name or a subdomain under it for a Voice-Over-IP server, for example, and have the actual software running on various machines with different providers. Which one a client of yours is going to use depends on the priority and weight values you have set.