Routing Procedures in Communications Networks-Part II: Directory Procedures

This part of the report on routing procedures is devoted to procedures involving no random choices. Estimates of the average traverse time of each message and average traffic flow through each node are derived by statistical methods and compared with the corresponding results obtained in Part I for routing procedures based on random choices. These estimates are verified by means of a large-scale simulation experiment. The overwhelming advantages of directory procedures in efficiency and capacity of operation are expressed quantitatively by these results. The disadvantages of directory procedures are also investigated. Principal among these are the necessity of determining optimal routes from directory information and maintaining the directories in the presence of a hostile or fluid environment. Estimates of the degradation characteristics of such procedures are obtained under various assumptions on the effects of the environment. The final section presents a summary and conclusions.