Queuing Delay

This term is most often used in reference to router. When packets arrive at a router, they have to be processed and transmitted. A router can only process one packet at a time. If packets arrive faster than the router can process them (such as in a burst transmission) the router puts them into the queue (also called the buffer) until it can get around to transmitting them.

The maximum queuing delay is proportional to buffer size. The longer the line of packets waiting to be transmitted, the longer the average waiting time is. However, this is much preferable to a shorter buffer, which would result in ignored ("dropped") packets, which in turn would result in much longer overall transmission times.

This simulation shows a congested network. Packets slowly filling the router's buffer causing more and more delay. Around 0.41 seconds the buffer drop the first packet

The charts show the queuing delay at each node. Select the 'Router' node and watch how the delay is slowly increase until it reaches its limit. Around 0.41 seconds the buffer is full and drop the first packet. From the chart we can see that after the packet was drop the router decrease the queing delay