SRV, which is an abbreviation for Service, is a DNS record, which permits you to use a domain for a specific service different from a website. By setting up a couple of SRV records, you can use the domain with different providers and point it to many servers at a time, every single server handling a different service. You could specify the port number for the connection to every single machine, so there won't be any interference. You may as well set individual priorities and weight for two records that are used for the same service, but point to different servers for redundancy or load balancing. By having an SRV record you can use your domain address or a subdomain under it for a Voice-Over-IP server, for example, and have the real software running on various machines with different providers. Which one a customer of yours is going to use is determined by the priority and weight values that you have set.