In recent years, there has been a growing demand for data streaming via unicast. Although multi-cast streaming has been around for many years, the cost and complexity of installing the necessary hardware has made it less popular. Multicast streaming has traditionally been dependent on the Real-time Transport Protocol (RTP)/Real-time Streaming Protocol (RTSP), the use of which has been declining with the spread of more versatile protocols such as Hypertext Transfer Protocol (HTTP) streaming. Hence, the shift has been towards unicast streaming using more modern protocols.
The main disadvantage of unicast streaming is that it creates a potential bottleneck at the data content streaming source with a linear increase in bandwidth demand as the number of renderers of data content increases. A possible solution to that problem is to do web caching, where local copies of the stream are stored in a given network segment for consumption by all the renderers within that segment.
On the open Internet, such caching and redistribution is achieved by via Content Distribution Networks (CDNs). Larger private networks by contrast interconnect multiple network segments representing geographically distributed offices with fixed virtual private network (VPN) links. Inside an office, the network is constructed with high capacity links and switches. Traffic from and to the public Internet is routed through a gateway link of fixed capacity or through one or more segments until a gateway link is reached.
The main bottlenecks in private networks are the VPN and gateway links which are typically not dimensioned to sustain the load of delivering one or more data content streams to a large amount of renderers of the data content at the same time. Overcoming those bottlenecks can be attained by having web caching appliances distributed throughout the network as needed. However, that entails the procurement, administration, and maintenance of those appliances.