SRV, which is an abbreviation for Service, is a DNS record, which enables you to employ a domain for a certain service different from a website. By setting up a couple of SRV records, you can use the domain address with different companies and direct it to many servers simultaneously, each server managing a separate service. You can specify the port number for the connection to every single machine, so there won't be any interference. You may as well set different priorities and weight for two records that are used for the same service, but point to different servers for redundancy or load balancing. By having an SRV record you can use 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 client of yours is going to use is determined by the priority and weight values which you have set.