Uncompressed video data is not sensitive to reliability since if one frame is lost it will immediately be replaced by another frame. Some video compression techniques compensate for this sensitivity to data loss by periodically sending complete information about a frame. For example both nv and CU-SeeMe, which were designed to operate over the unreliable Internet, have a refresh mechanism to periodically send blocks of data even if the data in these blocks has not changed. Communication Channels Description Circuit-switched A path of communication is established and kept open for the duration of the session. The information is divided into packets.
All systems require hardware that captures and digitizes the audio and video.
An additional feature found in most systems is a shared drawing area usually called a whiteboard, which is analogous to the whiteboards, found in many conference and classrooms. These whiteboards commonly allow participants to import other graphics such as images and to make annotations. Whiteboards are good for simple sketches, but fine detail is difficult to achieve using a mouse. Many systems allow an easy way to transfer files between participants. Some systems allow application sharing,which enables a participant to take control of an application running on another participant's computer.