QuickTime streaming chooses the best protocol (a method of communicating via the Internet) for your needs. Typically, QuickTime streaming uses Real-Time Streaming Protocol (RTSP) to ensure the best performance. If your network connection is protected by a firewall, you may want to use the HTTP protocol instead.
To use HTTP streaming:
Choose HTTP from the Transport Protocol pop-up menu.
If QuickTime can configure itself for your firewall, you can now watch streaming QuickTime movies. If you still experience problems, contact your network administrator or see the information on the Apple QuickTime website (www.apple.com/quicktime/).
Located in QuickTime Help with the Help Topic: Viewing Streamed Files Behind a Firewall