SRV, which is an abbreviation for Service, is a DNS record, which enables you to use a domain for a particular service different from a website. By creating a few SRV records, you are able to use the domain name with different providers and point it to numerous servers at once, every single server handling a different service. You'll be able to specify the port number for the connection to every machine, so there won't be any interference. You could also set different priorities and weight for two records that are used for the same service, but forward to different servers for redundancy or load balancing. With an SRV record you can use your domain or a subdomain under it for a Voice-Over-IP server, for instance, and have the real software running on several machines with different providers. Which one a client of yours is going to use is determined by the priority and weight values you have set.