TechNet Webcast: Firewall Transversal in Communications Server 2007 (Level 300)
Source: Microsoft Tips
The ability to transverse firewalls is very important to how Microsoft Office Communications Server 2007 allows VoIP calls in a secure manner. The presenter of this webcast talks in depth about the how Interactive Connectivity Establishment (ICE) and TURN are used to allow media to transverse firewalls in a secure manner. The presenter also goes over the ports that are needed on the internal and external firewall as well.