SRV, which is an abbreviation for Service, is a DNS record, which enables you to use a domain name for a certain service different from a website. By creating a number of SRV records, you can use the domain address with different companies and direct it to several servers simultaneously, each server managing a different service. You could specify the port number for the connection to each and every machine, so there will never be any interference. You may as well set different priorities and weight for 2 records which are used for the same service, but direct to different servers for redundancy or load balancing. With an SRV record you can use 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 providers. Which one a client of yours will use will depend on the priority and weight values which you have set.