SRV, which is an abbreviation for Service, is a DNS record, which allows you to employ a domain for a particular service different from a site. By creating a few SRV records, you will be able to use the domain name with different companies and forward it to numerous servers at the same time, each server managing a separate service. You could specify the port number for the connection to every machine, so there will never be any interference. You may as well set different priorities and weight for two records which are used for the exact same service, but direct to different servers for redundancy or load balancing. By having 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 a number of machines with different companies. Which one a client of yours will use depends on the priority and weight values you have set.