As the client renders the stream, the interruption of flow while the client temporarily stores streaming content before playing it, in order to protect against playback interruption. The streaming content is downloaded into a buffer, and then played after an amount sufficient to prevent playback interruption has been stored. Buffering will always occur if the encoded bit rate of the stream exceeds the available network bandwidth. Because a Smooth Streaming presentation contains multiple copies of the video, each encoded at different bit rates, the client can use Smooth Streaming heuristics to switch to a bit rate that avoids buffering.