Networks0 - Introduction Networks - What are They What is a...

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Introduction Networks - What are They What is a network - a bit difficult to define We use the word all the time and seem to understand its meaning Can talk of networks of People Roads Companies Telephones Here we’re going to talk about networks of computers In the early days of computing Had one big computer Painted blue Kept in an air conditioned room and fed punch cards All the data and information kept in one place Cheaper computers Allowed more computers Moved them out of the air conditioned room onto the desktop Stuff suddenly got distributed People still needed to share the stuff Sharing stuff At the start sharing stuff meant Writing the stuff to be shared to a tape or big floppy disk Walking over to the person who needed the stuff Copying the files to the new computer Synchronizing stuff became an immediate problem Major breakthrough RS232 Someone got the bright idea Let’s connect the computers together using a couple of wires Pins 2, 3, and 7 that’s all you need - trust me That was the start and the end The rest is history Stuff What is stuff Can mean a lot of things Let’s start at the bottom We start with a collection of symbols or marks These are our alphabet In isolation they have no meaning - 1 of 36 -
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We next associate a meaning with the symbols This gives us numbers letters or other such primitives Still these have no real meaning We next begin grouping the symbols or associating a context We now have data This is the first step towards something useful The symbol 1 may mean a single buffalo or a biological need The symbols leaf may indicate a tree appendage or a new set of clothes Applying additional groupings and context to data Gives information Note The word information will be used throughout Convey the general notion of Mark Symbol Relation Data Relation Information Relation Knowledge Relation Stuff Moving stuff Different from meaning here Intent should be evident from the context Continuing gives knowledge This gives a hierarchy of the form Each level provides A richer expressive power Greater flexibility History - Early Networks Primitive with Word of mouth Drums Smoke Polished Glass Messengers Pony express Passing message from person to person Primitive routers Alexander Objective of Networks Move information from one place to another As amount and importance of information increased Complexity and sophistication of the network Increased correspondingly - 2 of 36 -
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Elements of a Network Piece of information - Message May be encoded Represented some way Means by which to send it - Transport mechanism Hardware / software / whatever Place or places to send from and to The Hardware Can offer a number of different views Observe the views are not orthogonal Can have combinations Types by Transmission Technologies Broadcast Multicast Point to Point Types by Information Flow Serial Bit Character Word Parallel Bit Character Word Types by Topology Star Ring Tree Full or complete connectivity Ad hoc Network can be Interconnected collection of nodes and arc
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Networks0 - Introduction Networks - What are They What is a...

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