Communication Networks I (16:332:543)

Delays in communication networks: Lets consider a bit pipe which offers a capacity of C bits/sec. Assuming we have packets of a fixed length L traversing the bit pipe with the time between packet arrivals being T. If L/C < T then the packets are moving out faster than they come in and we can use the bit pipe to its maximum capacity. However, the preceding statement is true only if L and T are deterministic. Typically, L (the packet length) and T (packet inter-arrival times) are random variables and there is large delay and congestion even as E[L]/E[T] approaches the full capacity of the bit pipe.