http://technet.microsoft.com/en-us/library/aa997633.aspx
http://technet.microsoft.com/en-us/library/bb201695.aspx
http://technet.microsoft.com/en-us/library/bb332063(printer).aspx#HowtoConfigureExchangeServices
Office Communication Server 2007 has a number of port requirements that are specific to the feature that you will be deploying. The following diagram breaks out the required ports based on the server role you are deploying.