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Network Delays, Statistical Multiplexing. EE 122 Discussion 9/12/11. Transmission and Propagation Delay. Host 1. Switch 1. Propagation delay between Host 1 and Switch1. Speed of light Physical distance. Transmission delay. Size of transfer Bandwidth of link.
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Network Delays, Statistical Multiplexing EE 122 Discussion 9/12/11
Transmission and Propagation Delay Host 1 Switch 1 Propagation delay between Host 1 and Switch1 Speed of light Physical distance Transmission delay Size of transfer Bandwidth of link
Queuing Delay (Problem #3) A C B Transmission delay doubles Brown packet waits for half the trans. delay of blue packet
Statistical Multiplexing • Over-subscribe “peak” requirements of flows and hope that “average” requirements are under capacity • “Hope is a good thing, maybe the best of things…”
Animation from class Data Rate 1 Time Data Rate 2 Capacity Time Data Rate 3 Time
Animation from class Data Rate 1 Time Data Rate 2 Capacity / 3 Capacity / 3 Time Capacity / 3 Data Rate 3 Time
Animation from class Time Below capacity of link all the time! Time Time
Why and when will this work? Zone #2 Zone #1 Zone #3 • Probability of a flow transmitting in each time zone is 1/3 • What is the expected value of the overall flow? Time Time Time