Unicast Versus Multicast

The Unicast delivery option sets up a one-to-one video stream between the Windows Media server and each client system, whereas the Multicast delivery option sends a single video stream that can be accessed by multiple users simultaneously.

The unicast delivery method is simpler to configure and more likely to work without much network infrastructure (router, firewall, system configuration) changes. However, unicast is a significantly more bandwidth-intensive environment. Because each client-toserver session is a separate video stream, a broadcast with 10 users would have 10 video streams from the server to the clients, and a broadcast with 100 users would feature 100 video streams from the server to the clients. For a relatively small or lowdemand Windows Media server environment, unicast delivery is easier to implement, but be careful when using unicast delivery in large or broadly distributed environments.

The multicast delivery method sends a single video stream out on the network, which can be accessed by multiple client systems simultaneously. With a multicast delivery stream, whether 10 users or 100 users need to access the system, there is only a single broadcast either way. However, for a multicast delivery to work, the routers must be configured to support multicast routing. The client systems receiving the multicast broadcasts need to be running Windows 2000 Professional, Windows XP Professional, Windows Vista, Windows 7, Windows 2000 Server, Windows Server 2003, Windows Server 2008, or Windows Server 2008 R2.

An additional consideration for choosing between the unicast and multicast delivery methods is the number of clients that expect to connect to the broadcast stream and the variation of client configurations. If the compatibility to accept broadcasts from various systems is important and the number of connections to a broadcast stream is limited, the unicast method will provide better compatibility. If the organization controls the desktop configurations and knows the client systems can accept multicast broadcasts and the organization is broadcasting a video to be received by many users, the multicast delivery method will lessen the demand on network bandwidth.

Source of Information : Sams - Windows Server 2008 R2 Unleashed