Networks The Big Picture

Three Great Leaps of Civilization

Computer Network Single ComputerNetwork of Computers

Why Network? Access information Exchange information Networks help people work faster and smarter by making information available when they need it, where they need it. Makes distances between computers invisible.

Network Services and Benefits Sharing Information You and other network users can have access to the same information. Accessing remote information You can use your personal devices to access information through a public information service. Communicating You can exchange messages with a local group or around the world in a quick and paperless form of communication. Sharing Applications You and several other users can have access to the same application software; for example everyone in a work group can upgrade simultaneously. Sharing Network Resources Networks allow users to share connected devices (i.e. printers)

Overview of Computer Networks A network suggests a collection of related things or people that are somehow interconnected. In a computer network the interconnected parts are computers, peripherals and other devices that communicate with one another. A computer network may connect as few as two computers or as many as thousands even millions.

Computer Networks This is a Network.This is not a Network.

What can a computer network connect? Personal computers, smart phones, etc… Shared resources Network servers Minicomputers and mainframe computers Other networks

What is a computer network made of? Network Components – Hardware: clients and servers; shared devices (peripherals); hubs, routers and switches – Software: applications and underlying control software that allows the components to work together – Network Media: fiber optics, wireless (infrared and radio)

Network Architecture  Client/ Server Network  Peer-to-Peer Networks (P2P)  Firewalls  IP Addresses  Domain Names  Protocols and Ports  Application program  Proxy servers  Caching (cache)

Types of Networks  Local Area Networks (LAN)  Wireless LANs (WLAN)  Personal Area Networks (PAN)  Metropolitan Area Networks (MANs  Wide Area Networks (WAN)  Storage Area Networks (SAN)  Virtual Private Networks (VPN)  Virtual LAN (VLAN)

Network Evolution Host-Based Decentralized Computing Peer-to-Peer Networking

Host-Based computing

Decentralized computing

Peer-to-peer computing

Client/ Server

Peer to Peer (P2P)

Network Connections  Cables and other carriers of a network’s transmission signals are called media.  Wired Connections  Wireless Connections

Wired Connections  Dialup  Ethernet  Cable Internet Access  Fibre optic cables

Wireless Connections  Wi-Fi  WiMax  BlueTooth  3G and 4G

Measuring Network Speed Bandwidth: Network’s speed; the quantity of information that can be transmitted through a communication medium in a given amount of time. Broadband: an Internet connection (DSL or cable modem) that offers higher bandwidth, and therefore faster transmission speed. Units of measurement: bps, Kbps, Mbps, Gbps

Communicating on a Network  MAC Address (MAC)  Protocols  IP- Internet Protocol  TCP- Transmission Control Protocol  Ports

Preventing Unauthorized Access Audit Trails Authorized access Biometrics Data encryption Firewalls Levels of access Login Passwords Proxy server SSL