lecture1-Overview.pptVIP

COMP/ELEC 429Introduction to Computer Networks Lecture 1: Overview Slides used with permissions from Edward W. Knightly, T. S. Eugene Ng, Ion Stoica, Hui Zhang Things that Make Computer Networks Fascinating and Challenging Most people use it, but few understand it (black box) Scale Billions of users, many attackers Thousands of applications Hundreds of thousands of routers, millions of switches Hundreds of millions of end hosts (computer, phone, …) Complexity Network has many functions Network is made of many technologies Network has complex structure and dynamics Distributed Network is shared Network has no one central coordination point Network has many dynamic agents (applications, OS, humans) Routers cannot do too much or will be too slow History of Computer Networks Communication Telecommunication Telecommunication network Computer network Convergence network Early Communication over Long Distance Between human beings Letter and messenger Information carried by physical objects Speed limited by transportation means: horse, bird, train, car Hard disks over FedEx? Bandwidth? distance? security? Fire Early optical communication Speed of light Bandwidth? distance? security? Telegraph: Communication Using Electrons Between human beings Major milestones: 1827: Ohm’s Law 1837: “workable” telegraph invented by Samuel Morse 1838: demonstration over 10 miles at 10 w.p.m. 1844: Capitol Hill to Baltimore 1851: Western Union founded 1868: transatlantic cable laid 1985: last telegraph circuit closed down Other important dates 1869: transcontinental railway 1876: Alexander Bell invented telephone Telegraph Engineering Technical issues How to encode information? How to feed/input information to the system? How to output information? How to improve the distance? How to improve the speed? Common issues faced by all telecommunication systems Telephony Interactive telecommunication between people Analog voice Transmitter/receiver continuously in contact with electroni