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Material Type: Notes; Professor: Boughton; Class: INTRODUCTION TO COMPUTER INFORMATION SYSTEMS; Subject: Computer Info Systems; University: Harper College; Term: Unknown 1989;
Typology: Study notes
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Connected system of objects or people Telephone network "Old boy" network Computer network: computers and other hardware devices connected together for sharing hardware, software, and data, as well as communicating Computers and other devices Internet: largest (world-wide) computer network
Topology (physical arrangement) Architecture (the way they are designed to communicate) Extent (how large of an area the network services)
Can be used in combination
Local area network (LAN): covers a relatively small geographical area, such as a home, office building, or school Metropolitan area network (MAN): covers a metropolitan area, typically a city or county Would consist of LANs connected together Wide area network (WAN): covers a large geographical area Would consist of LANs and MANs connected together Internet is the world-wide WAN
Personal area network (PAN): connects personal devices for one individual, such as portable PC, cell phone, and portable printer Intranet: private network, such as a company LAN, set up by an organization for its employees Extranet: intranet that is at least partially accessible to authorized outsiders Virtual private network (VPN): paths over the Internet that provide authorized users secure access to a private network Extents not exclusive, e.g., VPN could be a WAN
Must have: Sending device Receiving device Connecting media Sending and receiving devices might be two computers but do not have to be Data transmitted has specific characteristics Media can be: Wired connection: physical cables Wireless connection: typically radio signals
An analog signal is a continuous wave A digital signal consists of a series of ons and offs representing binary 0 s and 1 s
Serial transmission Only 1 bit transmitted at a time At a time means each clock tick Used for network connections Parallel transmission Several bits transmitted at a time, e.g., 1 byte Used inside system unit
Synchronous Transmission occurs at regular, timed intervals Sender and receiver walk in step timewise A conference telephone call is a form of synchronous communication Asynchronous Transmission occurs whenever necessary Sender receives the data when it is able to E-mail is a form of asynchronous communication
Simplex One-way only Example is TV station Half duplex Two ways but not at the same time Example is walkie-talkie and cell phone Full duplex Two ways at the same time Example is regular telephone call
Wired network connection: the PC is physically cabled to the network Common in schools, business, and government facilities Wireless networks: typically use radio waves to communicate Becoming more popular in homes and businesses Wireless hotspots are commonly available in public locations
Broadcast radio transmissions Short-range: connect a wireless keyboard or mouse to a PC Bluetooth Medium-range: used for wireless LANs and to connect portable PC users to the Internet at public hotspots Wireless Fidelity (Wi-Fi) Microwave and satellite transmissions Microwave stations (earth based) Communications satellites (placed in orbit)
Use cellular towers within cells Calls are transferred from cell tower to cell tower as the individual moves Different transmission frequencies are used to avoid interference and allow multiple conversations to take place via a single tower at one time Widely used, but cell service not available everywhere
The most widely used communications protocol for LANs Typically used with bus or star topology and twisted-pair or coaxial cables 10 Mbps bandwidth originally. This is the "old standard" bandwidth for LANs Now 100 Mbps and 1 Gbps versions available Utilizes a set of procedures (CSMA/CD) to send data and make sure it arrives Procedures are the way the devices share the cable Devices don't "take turns", they "fight over" the cable
Communications protocol used with a ring network topology Utilizes a token to send and retrieve data Devices take turns sending, by using the token, so collisions never occur Token circulates in one direction Token is either free or carries a message to be delivered to a device Devices can grab a free token and add a message
The protocols used for transferring data over the Internet Web pages, e-mail, file transfers, etc. Two separate protocols, TCP and IP IP uses IP addresses Built into every modern computer Transmits data as packets Web pages, etc., divided into individual packets for sending, then reassebled when received Each packet is individually routed across the Internet (packet switching)
Phoneline or Home PNA standard Allows computers to be networked through ordinary phone wiring and phone jacks, without interfering with voice telephone calls Designed for quick and easy home networks 10 Mbps bandwidth Powerline standard Allows PCs to be networked over existing power lines using conventional electrical outlets 10 Mbps bandwidth
Always used when the communcation signals are analog, e.g., telephone line Converts between analog and digital signals Sometimes used when signals are digital Converts between different digital signals Type of modem needed depends on the type of network connection Dial-up (analog to digital) DSL (analog to digital) Cable (digital to digital) Satellite (analog to digital)
Dialup Phone line
Dialup modem
56 Kbps bandwidth Built into every computer DSL Phone line
DSL modem Must be within 3 miles of phone switch Bandwidth depends on locations Cable TV cable
Cable modem and Ethernet NIC
Usually the most bandwidth Less secure than DSL Satellite Satellite Satellite modem
Less bandwidth than cable and probably DSL Must be able to see satellite
