Input Port Queuing Fabric slower than input ports combined -queueing may occur at input queues OHead-of-the-Line (HOL)blocking:queued datagram at front of queue prevents others in queue from moving forward queueing delay and loss due to input buffer overflow! .cc switch. switch fabric output port contention green packet at time t-only one red experiences HOL blocking packet can be transferred Network Layer 4-29 Network Layer 4-29 Input Port Queuing  Fabric slower than input ports combined -> queueing may occur at input queues  Head-of-the-Line (HOL) blocking: queued datagram at front of queue prevents others in queue from moving forward  queueing delay and loss due to input buffer overflow!