SRV, which is an abbreviation for Service, is a DNS record, which permits you to use a domain name for a specific service different from a website. By creating a few SRV records, you can use the domain name with different companies and point it to several servers at a time, every single server handling a different service. You'll be able to specify the port number for the connection to every machine, so there won't be any interference. You could also set individual priorities and weight for two records that are employed for the same service, but direct to different servers for redundancy or load balancing. By having an SRV record you can employ your domain address or a subdomain under it for a Voice-Over-IP server, for example, and have the specific software running on several machines with different providers. Which one a client of yours will use will depend on the priority and weight values which you have set.