DELAY MODELING IN DATA CENTER NETWORKS: A TAXONOMY AND PERFORMANCE ANALYSIS A thesis submitted to Kent State University in partial fulfillment of the requirements for the degree of Master of Science by Reem Abdullah Alshahrani August 2013 Thesis written by Reem Abdullah Alshahrani B.S., Dammam University, 2008 M.S., Kent State University, 2013 Approved by Dr. Hassan Peyravi , Advisor Dr. Javed I. Khan , Chair, Department of Computer Science Dr. James L. Blank , Dean, College of Arts and Sciences TABLE OF CONTENTS LIST OF FIGURES ...................................................................................................... VII LIST OF TABLES .......................................................................................................... IX DEDICATION.................................................................................................................. X ACKNOWLEDGEMENTS ........................................................................................... XI CHAPTER 1 INTRODUCTION ..................................................................................... 1 1.1 Design Principles of DCNs ....................................................................................... 3 1.2 Thesis contribution .................................................................................................... 5 1.3 Thesis Organization ................................................................................................... 5 CHAPTER 2 PREVIOUS AND CURRENT WORK .................................................... 6 2.1 Data Centers Networking .......................................................................................... 6 2.2 DCNs Classification .................................................................................................. 7 2.3 Hierarchical Structures .............................................................................................. 8 2.3.1 Fat-tree ............................................................................................................ 9 2.3.2 VL2................................................................................................................ 10 2.3.3 Portland ......................................................................................................... 11 2.4 Random Structures .................................................................................................. 12 2.4.1 Jellyfish ......................................................................................................... 13 2.4.2 Small World Data Centers (SWDC) ............................................................. 14 2.4.3 Scafida ........................................................................................................... 15 2.4.4 SPAIN ........................................................................................................... 16 iii 2.5 Hypercube (Hierarchical Cell) Structures ............................................................... 16 2.5.1 DCell ............................................................................................................. 17 2.5.2 BCube ............................................................................................................ 19 2.5.3 3D Torus ........................................................................................................ 20 2.5.4 CamCube ....................................................................................................... 21 2.6 Wireless Structure ................................................................................................... 22 2.6.1 Cayley............................................................................................................ 22 2.7 Hybrid ...................................................................................................................... 23 2.7.1 C-Through (HyPaC) ...................................................................................... 24 2.7.2 Flyways ......................................................................................................... 25 2.8 Comparison ............................................................................................................. 25 CHAPTER 3 TRANSMISSION CONTROL PROTOCOL (TCP) ISSUES IN DATA CENTER NETWORKS ..................................................................................... 29 3.1 Introduction ............................................................................................................. 29 3.2 TCP Incast ............................................................................................................... 30 3.3 Congestion Trees ..................................................................................................... 32 3.4 TCP Outcast ............................................................................................................ 33 3.5 Traffic Patterns within Data Center Networks ........................................................ 33 3.6 Proposed Solutions .................................................................................................. 36 3.6.1 DCTCP .......................................................................................................... 36 3.6.2 ICTCP............................................................................................................ 37 iv 3.6.3 MPTCP .......................................................................................................... 37 CHAPTER 4 ROUTING SCHEMES ........................................................................... 39 4.1 Routing in DCNs ..................................................................................................... 39 4.2 Routing Optimization .............................................................................................. 40 4.3 Centralized routing .................................................................................................. 41 4.3.1 Hedera ........................................................................................................... 41 4.4 Distributed Routing ................................................................................................. 42 4.4.1 Equal-Cost-Multi-Path (ECMP) .................................................................... 42 4.4.2 Valiant Load Balancing (VLB) ..................................................................... 42 4.4.3 DARD............................................................................................................ 43 4.5 Load-Balancing Techniques .................................................................................... 43 CHAPTER 6 CASE STUDY: FAT-TREE TOPOLOGY ........................................... 45 6.1 Theoretical Background on Fat-tree ........................................................................ 45 6.2 Approximated Fat-tree ............................................................................................ 46 6.3 Original Fat-tree and Approximated Fat-tree in Communication Network Environment ...................................................................................................................... 47 6.4 Bottlenecks in Fat-tree ............................................................................................ 49 6.5 Utilization in Fat-tree .............................................................................................. 50 6.6 Theoretical Analysis of End-to-End Delay in Fat-tree Topology ........................... 51 6.6.1 End-to-End Delay Analysis for Downlink Traffic (Client-Server) ............... 54 6.6.2 End-to-End Delay Analysis for Uplink Traffic (Server-Client).................... 58 v CHAPTER 7 SIMULATION ......................................................................................... 63 7.1 Models ..................................................................................................................... 63 7.2 OPNET the Simulator ............................................................................................. 63 7.3 Data Center Networks Models ................................................................................ 65 7.3.1 Fat-tree DCN Model...................................................................................... 65 7.3.2 Cisco DCN Model ......................................................................................... 66 7.4 Traffic Modeling ..................................................................................................... 67 7.5 Applications Simulation .......................................................................................... 69 7.6 M/M/1 Traffic Simulation Results .......................................................................... 71 7.7 Applications Simulation Results ............................................................................. 72 7.8 Findings ................................................................................................................... 73 CHAPTER 8 CONCLUSION ........................................................................................ 75 8.1 Conclusion ............................................................................................................... 75 8.2 Future Work ............................................................................................................ 76 REFERENCES ...............................................................................................................