Performance Metrics - Computer Networks - Lecture Slides, Slides of Computer Networks

Download Performance Metrics - Computer Networks - Lecture Slides and more Slides Computer Networks in PDF only on Docsity! Performance Metrics • bandwidth (throughput) • latency (delay) • Bandwidth – – single physical link – logical process to channel • Definition of bandwidth: Number of bits transmitted/second Docsity.com Width of Bit and Bandwidth 1 sec Each bit – 1 s wideμ 1 sec Each bit – 0.5 s wideμ ⇒ Large Bandwidth Docsity.com Performance Characteristics • channel could be 1 Mbps / 100 Mbps • Application behave different – across the continent – across the room • Round trip time: – 1 Mbps - 100ms – 100 Mbps - 1ms Docsity.com Performance Characteristics • Example: – Channel Capacity: 1x10 Mbps – Datalength: 10 bits – Transmit time = 10 microseconds – Channel = 100 Mbps bits / sec – Transmit time = 0.010 microseconds Docsity.com Performance Characteristics • RTT = 100 ms, 1 ms • Latency = 100+10 × 10-3 • = 100.010 ms • Latency = 1+10× 10-3 • = 1.001 ms – Latency dominated by RTT. Docsity.com Performance Metrics • 4000 instr / mile is lost – Is it worth going across network? – Bandwidth wasted – Solution • Treat the channel as pipe Docsity.com Network as Pipe • The pipe holds data delay BW Docsity.com Network as a Pipe • Example – Latency - 50 ms – BW - 50 Mbps • Pipe can hold – 50×10-3×50×106 bits of data – Bandwidth wasted if sender does not fill the pipe Docsity.com Throughput • Throughput for 1 Mbps channel – 80/80.1 Mbps = 99.87 Mbps very efficient reaches channel capacity • Throughput for 1 Gbps channel – 80/0.180 Mbps =444.4 Mbps very inefficient very low compared to channel capacity Docsity.com Throughput • Stream of packets – 1 Mbps channel src dest 1 Mb 1 Mb 1 Mbps 1 Mb 1 Mb Docsity.com Throughput • Single packet - 1 Gbps channel src dest 1 Gbps 80 MB Docsity.com