SRV, which is an abbreviation for Service, is a DNS record, which allows you to use a domain for a certain service different from a site. By setting up a couple of SRV records, you will be able to use the domain name with different companies and forward it to several servers simultaneously, each and every server handling a separate service. You'll be able to specify the port number for the connection to every machine, so there won't be any interference. You can even set individual priorities and weight for two records that are employed for the very same service, but direct to different servers for redundancy or load balancing. Using an SRV record you can use your domain or a subdomain under it for a Voice-Over-IP server, for example, and have the real software running on a number of machines with different providers. Which one a customer of yours is going to use depends on the priority and weight values which you have set.