Input queuing has become dominant and popular building blocks for high speed crossbar switches with many ports and fast line rates because they require minimum speed-up of memory bandwidth. Input queued switches with finite virtual output queues guarantees QoS performance in terms of throughput and average delay. A switch performs two functions queuing and scheduling. Queue management algorithm manages the size of the queues and drops packets when necessary or appropriate. Scheduling algorithms determine next packet to transfer and solves conflicts with the switching fabric.