SRV, which is an abbreviation for Service, is a DNS record, which allows you to employ a domain name for a certain service different from a website. By setting up a few SRV records, you are able to use the domain with different providers and point it to numerous servers at the same time, every single server managing a different service. You can specify the port number for the connection to every single machine, so there will not be any interference. You can even set individual priorities and weight for two records that are employed for the exact same service, but direct to different servers for redundancy or load balancing. By having an SRV record you can employ your domain name or a subdomain under it for a Voice-Over-IP server, for instance, and have the actual software running on several machines with different companies. Which one a client of yours is going to use depends on the priority and weight values that you've set.