SRV, which is an abbreviation for Service, is a DNS record, which enables you to employ a domain name for a certain service different from a website. By creating a few SRV records, you are able to use the domain with different companies and point it to numerous servers at a time, each server managing a separate service. You could specify the port number for the connection to every machine, so there won't be any interference. You can even 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 instance, and have the specific software running on several machines with different companies. Which one a client of yours will use will depend on the priority and weight values that you have set.