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 site. By setting up a few SRV records, you will be able to use the domain name with different companies and forward it to several servers at once, each and every server handling a different service. You could specify the port number for the connection to each machine, so there won't be any interference. You can even set different priorities and weight for 2 records that are employed for the exact same service, but direct to different servers for redundancy or load balancing. Using an SRV record you can employ your domain 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 client of yours is going to use will depend on the priority and weight values that you have set.