There are times where two networks are joined together and address translation (NAT) is being used. In order for computers on one side to find the IP addresses to be used on the other side, some mechanism is required to translate the names into the translated IP addresses.
Typically, this problem is solved by using a HOSTS file. While convenient for quick translation, it is difficult to manage (since it is local to each computer) and only facilitates the equivalent of the DNS A and CNAME record types. Usually those records are sufficient, but the SRV record type is also important for applications (such as Microsoft Active Directory, Microsoft Office Communications Server, and others).