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Quality of Service Introduction

Explore the importance of Quality of Service (QoS) in communication networks, addressing user expectations, limited resources, and the impact of service variety. Discover the critical dimensions and characteristics of various services.

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Quality of Service Introduction

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  1. Quality of Service Introduction Special Topics in Communications Networks: QOS Hanoch Levy Computer Science Tel-Aviv University 2000 .Levy, Advanced Comm, CS, TAU, DOS

  2. What is QoS? • User wants its data (service) to arrive: • “Completely” • “On time” • What is “completely”? • What is “on time”? ==> a) Function of service b) Function of money .Levy, Advanced Comm, CS, TAU, DOS

  3. Example: Web transfer chain • User computer ISP (proxy) network server User computer servers .Levy, Advanced Comm, CS, TAU, DOS

  4. test: Why QoS?1.Limited Resource • QoS is an issue due to limited resource problem. • If resources are unlimited ==> no “quality” problem. • Got to consider in light of some predictions of bandwidth becomes ”unlimited”. .Levy, Advanced Comm, CS, TAU, DOS

  5. Why QoS2. Variety of Services • Problem of QoS simplifies under single objectives == single service. • e.g. -- telephone system -- quality problem was not an issue. • e.g. -- butttt. Cellular phone -- quality is an issue. .Levy, Advanced Comm, CS, TAU, DOS

  6. Why QoS(cont) • Problem of QoS magnifies in light of multiple objectives == multiple services. • Two quality dimensions: • Time constraints (timely service) • Precision • Two traffic characteristics • Quantity (rate) • Burstiness .Levy, Advanced Comm, CS, TAU, DOS

  7. Services • Voice: Timely - high Precision - low Volume - medium Burstiness - medium • Email: Timely - low precision - high volume - variable (low - huge)burstiness - might be high .Levy, Advanced Comm, CS, TAU, DOS

  8. Services (cont) • Web: Timely - medium precision - high volume - medium burstiness - high • IRC: Timely - medium-high precision - high volume - small burstiness - small .Levy, Advanced Comm, CS, TAU, DOS

  9. Services (cont) • Live Video: Timely - high precision - low volume - highburstiness - highFTP: Timely - low precision - high volume - highburstiness - depends .Levy, Advanced Comm, CS, TAU, DOS

  10. Effects of Variety • Makes mechanisms complex • Can benefit from sophistication ==> can get good utilization! .Levy, Advanced Comm, CS, TAU, DOS

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