SRV, which is an abbreviation for Service, is a DNS record, which enables you to employ a domain for a certain service different from a website. By setting up a number of SRV records, you’re able to use the domain with different companies and forward it to several servers at once, each server managing a different service. You could specify the port number for the connection to every machine, so there won't be any interference. You may as well set different priorities and weight for two records that are used for the very same service, but forward to different servers for redundancy or load balancing. By having an SRV record you can employ your domain name or a subdomain under it for a Voice-Over-IP server, for example, and have the specific software running on several machines with different providers. Which one a customer of yours is going to use depends on the priority and weight values you have set.