Recently we had the challenge of imaging 40 + PCs simultaneously while limiting network bandwidth/utilization. MDT 2010 must be installed on a Windows Server 2008 box running Windows Deployment Services.
Great description on Multicasting from Windows-Noob.com
The key advantage of multicast is of course allowing multiple computers to receive a communication simultaneously. The sender (the WDS server) sends the information to be communicated only once. Each client must then listen to the entire communication from begin to end to receive it. Since all clients are specifically listening to one network address simultaneously, the benefit is twofold: enhanced deployment speed since the network is less congested with multiple clients performing the same task; and decreased network saturation since every client is listening to the single stream
To enable the multicast deployments with MDT 2010 installed on the same computer as WDS follow these steps:
1. Install Windows Server 2008 or later operating system
2. Install WDS Server Role
3. Install WAIK 2.0
4. Install MDT 2010
5. Start the Workbench
6. Right-click on the deployment share and choose Properties. On the General Tab select the box “Enable Multicast for this deployment share (requires Windows Server 2008 Windows Deployment Services).
7. Update your deployment share.
When completed, the Deployment Workbench creates an Auto-Cast WDS Multicast transmission from the deployment share. *Note* to validate the mutlicast transfer is working you can review the LTIApply_WDSMcast.log in C:\MiniNT\SMSOSD\OSDLogs or C:\Windows\Temp\DeploymentLogs
There are other deployment scenarios, you might want to consider.
Configuring Multicast Deployments when imaging from Windows Deployment Services. http://www.windows-noob.com/forums/index.php?/topic/452-how-can-i-multicast-an-image-in-windows-deployment-services-windows-server-2008/
Enabling Multicast Deployments for Operating System Deployment. http://technet.microsoft.com/en-us/library/cc161854.aspx