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 website. By creating a number of SRV records, you can use the domain with different companies and point it to numerous servers at once, each server managing a different service. You can specify the port number for the connection to each machine, so there will not be any interference. You can even set individual priorities and weight for 2 records which are used for the very same service, but forward 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 specific software running on a number of machines with different providers. Which one a customer of yours is going to use will depend on the priority and weight values that you've set.