What is the advantage of using multicast instead of unicast to transport the camera video...

When the video stream is viewed on multiple operator workstations, the network is taxed only with single multicast stream.

Multicast configuration on switching and routing infrastructure is less complex than the configuration for unicast traffic.

You can configure one camera to stream to two media servers at the same time, for data redundancy purposes.

Multicast is not supported in the Cisco Video Surveillance solution.