A high-capacity, scalable video-on-demand system architecture, based on a 3-stage Clos network

We present a high performance, scalable architecture for a video on demand (VoD) system, using a three stage Clos switch. Three stage Clos switching networks have been used in the past in multiprocessor interconnection networks as well as for ATM switching fabrics due to their attractive low latency and fault tolerance properties. The proposed VoD system mainly consists of such a three stage Clos switch, which scales to 1024 OC-3 inputs and 1024 OC-3 outputs, offering more than 132 Gbps of pure switching capacity. Video data is transported through the switching network using the ATM cell format and switching protocol, connection oriented network services and fast virtual circuit switching. Routing is centrally performed by means of intelligent nearly nonblocking control algorithms, developed for Clos networks, which increase the switch utilization and significantly reduce the blocking probability at call setup. The proposed architecture can manipulate up to several Terabytes of video data and simultaneously serve 22000 to 66000 out of a total of 262144 end users. Depending on the number of middle stage switches and the control algorithm used, the blocking probability at call setup can range between zero and 5e-4.