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Introduction

Introduction - 1 Computer Networks CSci232 Introduction 1...

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Unformatted text preview: 1 Computer Networks CSci232: Introduction 1 Introduction to Networking • What is a (computer/data) network? • Statistical multiplexing – Packet switching • OSI Model and Internet Architecture • Introduction to the Internet • Readings – Chapter 1 Computer Networks CSci232: Introduction 2 What is a Network? There are many types of networks! ¡ Transportation Networks ¡ Transport goods using trucks, ships, airplanes, … ¡ Postal Services ¡ Delivering letters, parcels, etc. ¡ Broadcast and cable TV networks ¡ Telephone networks ¡ Internet ¡ “Social/Human networks” ¡ … Computer Networks CSci232: Introduction 3 Key Features of Networks ¡ Providing certain services ¡ transport goods, mail, information or data ¡ Shared resources ¡ used by many users, often concurrently ¡ Basic building blocks ¡ nodes (active entities): process and transfer goods/data ¡ links (passive medium): passive “carrier” of goods/data ¡ Typically “multi-hop” ¡ two “end points” cannot directly reach each other ¡ need other nodes/entities to relay Computer Networks CSci232: Introduction 4 Data/Computer Networks ¡ Delivery of information (“data”) among computers of all kinds ¡ servers, desktops, laptop, PDAs, cell phones, ...... ¡ General-Purpose ¡ Not for specific types of data or groups of nodes, or using specific technologies ¡ Utilizing a variety of technologies ¡ “physical/link layer” technologies for connecting nodes ¡ copper wires, optical links, wireless radio, satellite ¡ or even “non-electronic” means: e.g., cars, postal services, humans -- e.g., recent “delay-tolerant networks” efforts for 3 rd world countries Computer Networks CSci232: Introduction 5 How to Build Data/Computer Networks Two possibilities ¡ infrastructure-less ( ad hoc, peer-to-peer ) ¡ (end) nodes also help other (end) nodes, i.e., peers, to relay data ¡ infrastructure-based ¡ use special nodes (switches, routers, gateways) to help relay data Computer Networks CSci232: Introduction 6 Connectivity and Inter-networking • Point-to-point vs. • broadcast links/ wireless media • switched networks • connecting “clouds” (existing physical networks) – inter-networking using gateways, virtual tunnels, overlays (a) (b) base station 2 Computer Networks CSci232: Introduction 7 Resource Sharing in Switched Networks Multiplexing Strategies • Circuit Switching – set up a dedicated route (“circuit”) first – carry all bits of a “conversation” on one circuit • original telephone network • Analogy: railroads and trains • Packet Switching – divide information into small chunks (“packets”) – each packet delivered independently – “store-and-forward” packets • Internet (also Postal Service, but they don’t tear your mail into pieces first!) • Analogy: highways and cars Computer Networks CSci232: Introduction 8 Common Circuit Switching Methods Sharing of network resources among multiple users • Common multiplexing strategies for circuit switching...
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Introduction - 1 Computer Networks CSci232 Introduction 1...

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