SRV, which is an abbreviation for Service, is a DNS record, which enables you to employ a domain name for a particular service different from a website. By creating a few SRV records, you can use the domain with different companies and forward it to several servers at once, each and every server handling a separate service. You are able to specify the port number for the connection to each machine, so there won't be any interference. You could also set individual priorities and weight for two records that are used for the exact 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 is going to use depends on the priority and weight values which you have set.