UDP

UDP is a what they call a send and pray protocol. You throw data onto the network and you have no guarantee if the data reaches its destination or when. Because of this, it is extremely fast, efficient, but also unreliable.

Next to TCP, it is one of the primary basic Internet Protocols that every major OS supports.

Raw UDP cannot normally be used as is for streaming. RTP is used on top of UDP to provide proper data timestamps and ordering. RTP/UDP is extensively used for streaming live audio/video. In this case it is not important that you receive all data, as long as you receive some data continuously and fast.

VLC supports this protocol for streaming, but not all audio/video codecs can be used. See the matrices here: http://www.videolan.org/streaming-features.html