After permissions have been created, the client has two choices for sending the actual data, (1) it can use the Send mechanism, or (2) it can reserve a channel using the ChannelBind request. The Send mechanism is more straightforward, but contains a larger header, 36 bytes, that can substantially increase the bandwidth in a TURN relayed conversation. By contrast, the ChannelBind method is lighter: the header is only 4 bytes, but it requires a channel to be reserved which needs to be periodically refreshed, among other considerations.