Understanding how software distributes video across networks can be confusing. When you think about video transfers across a network, you need to forget everything you know about network file transfers. Video streams differ fundamentally from other network data transmissions. Because video crosses the network as a stream and its data flow needs to remain continuous, video software programs don't include error checking or correcting functions, and they don't resend packets that the network drops. Those packet losses are usually OK because video transmissions can lose a surprising percentage of video frames without hampering a presentation.
Another interesting fact about the transfer of multimedia presentations across networks is that presentations' audio and video arrive at the end user's viewing station as two separate streams. Video software uses the timestamp features of streaming protocols to synchronize audio and video for flowing multimedia presentations.
Finally, many video users are confused about the difference between Video on Demand (VoD), broadcast video, and multicast video. VoD provides video content that users can access whenever they want. VoD requires dedicated network bandwidth from the video server to each user who can access the video. Unlike other techniques for distributing video across networks, VoD lets end users pause, rewind, fast-forward, and restart video streams. VoD broadcasts are also known as unicast traffic: They travel from one source to one destination (usually an IP address). If two users request the same VoD file at the same time, the video server sends a separate stream to each user.
Broadcast video is a misnomer in the world of networked computers broadcast traffic generally performs network functions, not video distribution. Broadcasting sends one data stream from one IP address to all participants across a network. Every machine on the network receives the broadcast, regardless of whether it requests the information. Therefore, broadcasts generally handle network services such as address resolution. This inefficiency reduces network performance. Broadcasts sometimes transport video streams, but they aren't as efficient for transmitting video as other methods. Broadcast traffic usually resides on IP addresses that end in .255.
Administrators most commonly use multicast video for distributing scheduled video streams across a network. Multicast video is similar to broadcasting because the video server sends the stream to every system on the network however, multicast video streams let end users refuse to receive the data. Multicast transmissions don't restrict broadcasting to certain IP addresses, as unicast transmissions do. IP addresses associated with multicast transmissions range from 224.0.0.0 to 239.255.255.255