L20_introd_networks

L20_introd_networks - 1 Networks Hari Balakrishnan...

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Unformatted text preview: 1 Networks Hari Balakrishnan ([email protected]) 6.02 Spring 2008 Lecture #20 April 23, 2008 • Sharing, a fundamental problem • Switches; circuit and packet switching • Queues to mitigate traffic bursts From Links to Networks Your Network Here! So far, we’ve learned about tools to help us communicate over a point-to-point link Digital modulation Channel-coded bits 2 • Idea: Compose many independent point-to- point links over radio or wires How to Build a Network • O(N 2 ) links for N-node network • Too inefficient and expensive • Doesn’t scale well to large regions Solution: Sharing • Fundamental to all interesting network designs • Occurs at multiple levels • Radio channel sharing to allow many nodes to share common spectrum well • Link sharing to alleviate O(N 2 ) scaling problem 2 • Idea: Compose many independent point-to- point links over radio or wires How to Build a Network • O(N 2 ) links for N-node network • Too inefficient and expensive • Doesn’t scale well to large regions Solution: Sharing • Fundamental to all interesting network designs • Occurs at multiple levels • Radio channel sharing to allow many nodes to share common spectrum well • Link sharing to alleviate O(N 2 ) scaling problem 3 Switches Orchestrate Link Sharing • A switch is a computing device that allows many concurrent communications to share the network Switch This structure is called a network topology 4 • Chappe (1763-1805), a “defense contractor”; 1st message successfully sent in 1794 • 1799: Napoleon seizes power; sends “ Paris is quiet, and the good citizens are content .” • 1814: Extends from Paris to Belgium & Italy • 1840: 4000 miles, 556 stations, 8 main lines, 11 sublines, each hop ~10 km • Many modern techniques: framing, codes, redundant relays, message acks, priority...
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This note was uploaded on 08/23/2009 for the course EECS 6.02 taught by Professor Terman during the Spring '08 term at MIT.

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L20_introd_networks - 1 Networks Hari Balakrishnan...

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