In telecommunication and computer engineering, the queuing delay (or queueing delay) is the time a job waits in a queue until it can be executed. It is a key component of network delay.
This term is most often used in reference to routers. 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.
During network congestion, queuing delays can be considered infinite when the packet is dropped. The retransmission of such packets causes significant overall delay because all forms of delay will be incurred more than once. If the network congestion continues, the packet may be dropped many times. Many protocols, such as TCP, will "throttle back" their sending and wait for the network to clear up.
In Kendall's notation, the M/M/1/K queuing model, where K is the size of the buffer, may be used to analyze the queuing delay in a specific system. Check.[1]
Wireless communications;Theodore S. pappaport