xii Contents Chapter 6 FLOW CONTROL 423 6.1 Introduction,423 6.1.1 Main Objectives of Flow Control,424 Keeping Delay Small within the Subnet,424 Fairness,425 Buffer Overflow,427 6.2 Window Flow Control,429 6.2.1 End-to-End Windows,430 Limitations of End-to-End Windows,432 6.2.2 Node-by-Node Windows for Virtual Circuits,435 6.2.3,The Isarithmic Method,437 6.2.4 Window Flow Control at the User Level,438 6.3 Overview of Flow Control in Practice,439 Flow Control in the ARPANET,439 Flow Control in the TYMNET,440 Flow Control in SNA,440 Flow Control in the Codex Network,441 Flow Control in X.25,442 6.4 Flow Control Schemes Based on Input Rate Adjustment,442 6.4.1 Combined Optimal Routing and Flow Control,443 6.4.2 Max-Min Flow Control,448 6.4.3 Implementation of Input Rates in a Dynamic Environment,453 6.5 Summary,455 6.6 Notes,Sources,and Suggested Reading,455 PROBLEMS,456 REFERENCES 463 INDEX 477xii Contents Chapter 6 FLOW CONTROL 423 6.1 Introduction, 423 6.1.1 Main Objectives of Flow Control, 424 Keeping Delay Small within the Subnet, 424 Fairness, 425 Buffer Overflow, 427 6.2 Window Flow Control, 429 6.2.1 End-to-End Windows, 430 Limitations of End-to-End Windows, 432 6.2.2 Node-by-Node Windows for Virtual Circuits, 435 ý6.2.q , The Isarithmic Method, 437 6.2.4 Window Flow Control at the User Level, 438 6.3 Overview of Flow Control in Practice, 439 Flow Control in the ARPANET, 439 Flow Control in the TYMNET, 440 Flow Control in SNA, 440 Flow Control in the Codex Network, 441 Flow Control in X.25, 442 6.4 Flow Control Schemes Based on Input Rate Adjustment, 442 6.4.1 Combined Optimal Routing and Flow Control, 443 6.4.2 Max-Min Flow Control, 448 6.4.3 Implementation of Input Rates in a Dynamic Environment, 453 6.5 Summary, 455 6.6 Notes, Sources, and Suggested Reading, 455 PROBLEMS, 456 REFERENCES 463 INDEX 477