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L30 - Quality of Service The network wants low congestion...

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Quality of Service The network wants low congestion for better performance. The user needs a good quality of service. Show Fig. 5-30 In delay, “Low” means low sensitivity to delay (or jitter), not low delay (or jitter). “High” means high sensitivity to delay (or jitter). Regarding Reliability and Bandwidth, “High” and “Low” have the normal meaning.
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The biggest type distinction is real time vs. non-real time communication. In real time communication, data must arrive by a certain deadline, or it is useless. In non-real time communication, such as file transfer, there is no precise deadline, though shorter transfer time is desirable. QUALITY FACTORS: # cell loss probability # ability to maintain a specified average rate # ability to accept data burst amounts up to some length # average packet delay # packet delay variation
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Quality of Service Techniques Overprovisioning - more than enough bandwidth, buffer capacity. Buffering - reduces chance of packet loss, but increases delay. Priorities could be given to real-time traffic. Extra delay to playout can smooth jitter. Traffic shaping - regulate average rate coming from sender while allowing for bursts.
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Input rate control - Token bucket There is a “bucket” that holds tokens, up to the bucket capacity. For simplicity, assume a token is one byte, and the bucket can hold up to C bytes.
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