SRV, which is an abbreviation for Service, is a DNS record, which allows you to use a domain for a particular service different from a site. By creating a couple of SRV records, you will be able to use the domain name with different companies and forward it to many servers simultaneously, each and every server handling a different service. You are able to specify the port number for the connection to each machine, so there won't be any interference. You can also set different priorities and weight for two records that are used for the very same service, but forward to different servers for redundancy or load balancing. Using an SRV record you can use 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 providers. Which one a customer of yours will use depends on the priority and weight values that you have set.