We have some legacy windows application web service clients that will not be updating their software version soon, and we cannot update their web references to https://service2.domain.com.
The old server is running IIS 6.0. The new server is running IIS 7.0. We could probably upgrade it to 7.5 if needed, but I'm not certain.
We could also probably make a seamless transition of the old web service to a new server using public DNS, but we cannot change the DNS name of "service1.domain.com."