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 number of SRV records, you are able to use the domain with different companies and point it to many servers at once, every single server managing a separate service. You can specify the port number for the connection to every machine, so there will never be any interference. You can even set individual priorities and weight for 2 records that are used for the exact same service, but forward to different servers for redundancy or load balancing. With an SRV record you can employ your domain or a subdomain under it for a Voice-Over-IP server, for example, and have the specific software running on several machines with different companies. Which one a customer of yours is going to use will depend on the priority and weight values that you've set.