SRV, which is an abbreviation for Service, is a DNS record, which permits you to employ a domain for a certain service different from a website. By creating a number of SRV records, you will be able to use the domain address with different companies and direct it to several servers at a time, every single server managing a separate service. You'll be able to specify the port number for the connection to each machine, so there won't be any interference. You may as well set different priorities and weight for 2 records that are used for the very same service, but forward 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 example, and have the specific software running on several machines with different companies. Which one a client of yours will use depends on the priority and weight values that you have set.