MIT16_36s09_lec19

MIT16_36s09_lec19 - MIT OpenCourseWare http://ocw.mit.edu...

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Unformatted text preview: MIT OpenCourseWare http://ocw.mit.edu 16.36 Communication Systems Engineering Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms . 16.36: Communication Systems Engineering Lecture 19: Delay Models for Data Networks Part 1: Introduction Eytan Modiano Eytan Modiano Slide 1 Packet Switched Networks Packet Network PS PS PS PS PS PS PS Buffer Packet Switch Messages broken into Packets that are routed To their destination Eytan Modiano Slide 2 Queueing Systems Used for analyzing network performance In packet networks, events are random Random packet arrivals Random packet lengths While at the physical layer we were concerned with bit-error-rate, at the network layer we care about delays How long does a packet spend waiting in buffers ? How large are the buffers ? Applications far beyond just communication networks Air transportation systems, air traffic control Manufacturing systems Service centers, phone banks, etc. Eytan Modiano Slide 3 Random events Arrival process Packets arrive according to a random process Typically the arrival process is modeled as Poisson The Poisson process Arrival rate of packets per second Over a small interval , P(exactly one arrival) = P(0 arrivals) = 1 - P(more than one arrival) = 0 It can be shown that: P(narrivalsinintervalT) = ( !...
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This note was uploaded on 11/07/2011 for the course AERO 16.38 taught by Professor Alexandremegretski during the Spring '09 term at MIT.

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MIT16_36s09_lec19 - MIT OpenCourseWare http://ocw.mit.edu...

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