SRV, which is an abbreviation for Service, is a DNS record, which permits you to employ a domain name for a certain service different from a website. By setting up a few SRV records, you can use the domain name with different companies and point it to many servers at the same time, every single server handling a separate service. You'll be able to specify the port number for the connection to each machine, so there will never be any interference. You can even set individual priorities and weight for two records that are used for the very same service, but point 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 instance, and have the actual software running on various machines with different companies. Which one a customer of yours will use is determined by the priority and weight values that you've set.