SRV, which is an abbreviation for Service, is a DNS record, which allows you to employ a domain name for a specific service different from a website. By setting up a couple of SRV records, you are able to use the domain with different companies and point it to many servers at once, each server handling a different service. You could specify the port number for the connection to every single machine, so there will not be any interference. You can also set different priorities and weight for two records which are employed for the very same service, but direct to different servers for redundancy or load balancing. With an SRV record you can employ your domain name or a subdomain under it for a Voice-Over-IP server, for example, and have the actual software running on various machines with different providers. Which one a customer of yours will use will depend on the priority and weight values which you have set.