Abstract: Multicast adaptive stream switching for delivery of video content over an IP-based packet network is provided. A network device obtains multiple synchronized multicast streams of the same video content, where each of the multiple synchronized multicast streams includes a different bit-rate encoding. The network device receives, from a user device, a request to join a multicast group for one of the multiple synchronized multicast streams and provides, to the user device, the one of the multiple synchronized multicast streams corresponding to the requested multicast group. The user device detects a congestion level associated with the current multicast stream. The network device receives, from the user device, a request to join a different multicast group for a different one of the multiple synchronized multicast streams and provides, to the user device, the different one of the multiple synchronized multicast streams corresponding to the requested different multicast group.