SRV, which is an abbreviation for Service, is a DNS record, which allows you to employ a domain name for a specific service different from a site. By creating a number of SRV records, you are able to use the domain with different companies and forward it to many servers at a time, every single server handling a separate service. You could specify the port number for the connection to every single machine, so there won't be any interference. You may as well set individual priorities and weight for two records that are employed for the exact same service, but forward to different servers for redundancy or load balancing. By having 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 customer of yours will use depends on the priority and weight values that you have set.