Routing and Congestion Control in Datagram Networks Zheng Wang Submitted for the degree of PhD at University College London January 1992 ProQuest Number: 10608852 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 10608852 Published by ProQuest LLC(2017). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 ABSTRACT Routing and congestion control can be viewed as two closely related processes in a resource control system which manages the network resources. One of the basic prob­ lems is to adapt to changing conditions. Our analysis shows that inadequate information and delayed feedback can cause oscillation and instability. In this dissertation we exam­ ine the problems in routing and congestion control in a datagram environment and pro­ pose a number of solutions. The essence of the ideas is to deal with momentary fluctua­ tions and average steady trends separately. The behavior of shorest-path routing algorithms is investigated. A new approach for dynamic routing based on the concept of decentralized decision making is introduced. A dynamic routing algorithm based on this new approach, Shortest Path First with Emer­ gency Exits (SPF-EE)y is developed, which eliminates many of the problems that the Shortest Path First (SPF) algorithm exhibits under heavy and dynamic traffic. The SPF- EE algorithm allows local and temporary alteration of routes without global route updat­ ing. Simulation shows that the SPF-EE algorithm achieves substantial improvement over the SPF algorithm. A new traffic adjustment algorithm called synchronized traffic adjustment (STA) and three information feedback schemes are proposed. The STA algorithm attempts to estab­ lish the sharing of the resources only when there are significant traffic changes and to maintain fairness by synchronized adjustment. Three congestion control schemes, based the STA approach and the proposed binary and quantitative feedback schemes, are presented. Extensive simulation shows that the STA algorithm eliminates the oscillation problems in the additive increase and multiplicative decrease (AIMD) algorithm and con­ verges more quickly. ACKNOWLEDGMENTS I would like to thank my supervisor, Jon Crowcroft, for his guidance, help and encouragement during the course of my research. I would also like to thank the various members of the Computer Science Department for their assistance and advice during my stay at UCL: thanks are due to Peter Kirstein, Yuko Murayama, Dervish Deniz, Jiang Fan and Ping Hu. I have benefited a great deal from the stimulating discussions in the TCP/IP com­ munity. Various people across the Internet have provided me valuable comments on a number of my papers where the ideas and preliminary results in this dissertation were first presented, my thanks and appreciation to Lixia Zhang (Xerox PARC), Keshav Srinivasan (AT&T Bell Labs), Paul Tsuchiya (Bellcore), Craig Partridge (BBN), Andrew Heybey (MIT), Paul McKenney (SRI), Bob Walsh (DEC), Van Jacobson (LBL), Allison Mankin (Mitre) and Gregory Finn (ISI). I am also indebted to Jon Crowcroft, Ian Wakeman, Peter Kirstein and Soren Soren­ sen who have carefully read and commented on the draft version of this dissertation. During my research I have been supported by the British Council and the State Edu­ cation Committee of People’s Republic of China for which I am grateful. Finally, I would like to thank my parents and my wife Wei for their love and sup­ port during my study, and for making life more pleasurable on the good days and bear­ able on the not-so-good ones. TABLE OF CONTENTS Abstract.................................................................................................................................. i Acknowledgements ............................................................................................................... ii Table of Contents................................................................................................................. iii List of Figures ....................................................................................................................... vi List of Tables ........................................................................................................................ ix Chapter One: Introduction................................................................................................. 1 1.1 Evolution of Packet Switching ......................................................................................... 3 1.1.1 Early History ............................................................................................................ 3 1.1.2 The Pioneers ............................................................................................................. 3 1.1.3 Recent Trends in Packet Switching .......................................................................... 6 1.2 Research on Routing and Congestion Control .................................................................. 7 1.2.1 Routing ..................................................................................................................... 7 1.2.2 Congestion Control ........................................................... 9 1.3 Organization of Dissertation ............................................................................................ 11 Chapter Two: Computer Network Architecture................................................................ 13 2.1 Computer Network Architecture ....................................................................................... 13 2.1.1 Network Layering ............................................................................................... 13 2.1.2 OSI Reference Model ............................................................................................... 16 2.1.2.1 OSI Terminology .......................................................................................... 16 2.1.2.2 The Seven-Layer Model ................................................................................. 17 2.2 DARPA Internet Architecture ........................................................................................... 24 2.2.1 Architecture Overview.............................................................................................. 25 2.2.2 Internet Protocol (IP) ............................................................................................... 27 2.2.3 Transmission Control Protocol (TCP) ...................................................................... 28 2.3 Summary ........................................................................................................................... 30 iii Chapter Three: Routing and Congestion Control ............................................................. 31 3.1 Routing ............................................................................................................................. 31 3.1.1 Design Goals............................................................................................................ 32 3.1.1.1 Efficiency ....................................................................................................... 32 3.1.1.2 Reliability ....................................................................................................... 32 3.1.1.3 Stability .......................................................................................................... 32 3.1.1.4 Adaptability .................................................................................................... 32 3.1.1.5 Optimality ...................................................................................................... 33 3.1.2 Decomposition of Routing Algorithms ..................................................................... 33 3.1.2.1 Distance Estimation ....................................................................................... 33 3.1.2.2 Information propagation ................................................................................ 34 3.1.2.3 Route Computation ................................................................ ...................... 34 3.1.2.4 Packet forwarding .......................................................................................... 35 3.1.3 Classification of Routing Algorithms ....................................................................... 35 3.1.3.1 Centralized and Distributed ........................................................................... 35 3.1.3.2 Static, Quasi-Static and Dynamic .................................................................. 36 3.1.4 Distributed Shortest-Path Routing Algorithms ......................................................... 38 3.1.4.1 Distance-Vector Algorithms.......................................................................... 38 3.1.4.2 Link-State Algorithms ................................................................................... 42 3.1.5 Source Routing ........................................................................................................