kind of queue, usually a line, until a server is available. The mathematical notion of a queue, at least at the basic level, is a system where there is an incoming flow of work and a collection of servers. The incoming flow is usu- ally a collection of discrete arrivals where each arrival has some workload associated with it. We denote the various mathematical queuing models with a three- to five- letter notation, A/B/c/K/N. A. The first letter is the interarrival time distribution. The letter D denotes constant interarrival times, an arrival every 2 minutes without exception. The letter M denotes exponential interarrival times, a memoryless process where the time distribution until the next arrival does not depend on how much time has passed since the last arrival. The letter G denotes a general interarrival distribution. For queuing theory specialists, there are Er, r-stage Erlangian, and HR, R-stage hyperexponential, distributions as well. B. The second letter the service time distribution. The letter D denotes constant ser- vice time; every customer requires exactly 5 minutes of work. The letter M denotes ex- ponential service time. And the letter G denotes a general service time. There are Er, r-stage Erlangian, and HR, R-stage hyperexponential, distributions for service time as well. C. The third symbol is the number of servers. This can be a constant such as 1, 2, or 3 or a variable C that appears in the solution equations. K. The fourth symbol is the storage capacity of the queue, the maximum number of arrivals that can wait in line. Any arrivals beyond K are dropped from the system. If Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Traffic Engineering for Voice and Data Traffic Engineering for Voice and Data the last two symbols are left out (e.g., M/M/1), then there is no limit; the storage ca- pacity is infinite, and K = 80. N. T