Download - Network Technology 2 Computer Networks
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Network Technology
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Computer Networks
A network exists whenever two or more computers are linked together through some type of medium. Computer networks have many uses:• Sharing information and resources• Handling the present by enabling transactions and
capturing/storing transaction data• Remembering the past by providing access to
shared data storage• Prepare for the future by providing communications
to aid decision making
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Computer Networks: Network Type
Networks may be classified by size:
• Local Area Networks (LANs)• Wide Area Networks (WANs)• The Internet
Connections to the Internet are through:• LANS• Internet Service Providers (ISP)
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Computer Networks: Network Backbone
Internet
Customer service LAN
Distribution LAN
HumanResources LAN
Com
pany B
ackbone
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ISP
Customer’sPC
Regional Network Regional Network
Internet Backbone
Company Lan
Employee PC
ISP Connection to Internet
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Wide Area Networks (WAN)
ApplicationSoftware
NetworkingSoftware
Physical
ApplicationSoftware
NetworkingSoftware
Physical
Sender Receiver
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WAN: Application Software Layer
The software that the user sees and uses to send and receive messages. (E-mail, Web browser, etc)
• Formats the messages to fit a protocol– Simple mail transfer protocol (SMTP)– Hypertext transfer protocol (HTTP)– Electronic Data Interchange (EDI)
• May also process message in other ways (encryption for example)
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WAN: Networking Software Layer
Works behind the scenes to format the message so that it may be sent over network.
• Popular transmission protocols include:– Transmission control protocol/internet protocol
(TCP/IP)– Ansi X 12 or Edifact– Wi-Fi
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WAN: TCP/IP
The transmission protocol for the Internet:• Converts address of destination computer to
IP address– [email protected] 198.137.241.30
• Divides message into packets
11001101011100110011… 11001101010 128.192.93.53
11100110011 128.192.93.53
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WAN: Physical Layer
Once the message is ready, it is sent out over the physical layer.
The physical layer includes connection devices and various transmission media.
• Twisted pair (standard telephone)• Coaxial Cable (cable television)• Fiber optic cable• Microwaves
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Media Cost Error Rates Speed
Twisted Pair Low Low Low-high
Coaxial cable
Moderate Low Low-high
Fiber optics High Very low High –very high
Radio Low Moderate Low
Infrared Low Moderate Low
Microwave Moderate Low-moderate
Moderate
Satellite Moderate Low-moderate
Moderate
WAN: Physical Layer
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WAN: Transmission Speeds
Media Speeds Comments
Standard telephone
56 Kbps Available everywhere
ISDN 128 Kbps Available in most urban areas but requires special adapters
DSL 1.544 M in;
128 K out
Becoming more available; doesn’t require special equipment. Doesn’t slow down as more people sign up.
TV Cable As high as 30M but 2.5M to 500K on average
Cable must support 2-way communication; available in many locations but slows down as more people use it.
T-1 to T-4 1.544M-275M Used for commercial purposes. A single T-1 line costs over $1000 per month.
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WAN: Physical Layer Routing
• Packet switching – technology used to route the individual packets through the network to their final destination
• Router – specialized computers on the network with the sole purpose of determining the best way to send packets to destination
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ServerComputer
ISP
Router
Router
RouterPackets
Packets
Packets
Packets
Packets
User’s PC
Router
Router
Router
Sending Data over the Internet
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WAN: Electronic Data Interchange (EDI)
EDI is a set of protocols for submitting common business documents between business partners.
• Uses traditional communication channels (mostly phone)
• Reduces human involvement and paperwork
• Often sent over Value Added Networks (VANs)
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Local Area Networks (LAN)
Two main types in use today:• Dedicated server networks
• Servers – computers dedicated to managing all or part of the network
• Clients – computers that individuals may use to connect to the network
• Peer-to-peer networks• Designed for smaller networks where emphasis is on
sharing files between computers• Each computer functions as both a client and a
server
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LAN Components
• Network cabling – physically connects each component to the network
• Hub – a device that allows cables to be connected together
• Network interface card – allows network cabling to be connected to a computer
• Network Operating System – software that controls the network
• Bus – a main cable to which all clients and servers are connected
• Ethernet - protocol for transmitting packets over a bus
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Wireless Networks
The fastest growing trend in networks – no wires are necessary to make connections
• Wireless Application Protocol (WAP) – a special protocol that allows mobile telephones to connect to the Internet
• Short Message Service (SMS) – a service for sending text messages up to 160 characters long to mobile phones
• Global System for Mobile (GSM) communication protocol – the most widely used mobile telephone protocol worldwide
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Wireless Networks: Wireless LANs
LAN cabling is replaced with wireless transmissions between computers
• Uses radio frequencies to transmit information between individual computers
• Hubs and routers are used as connection devices between the computers and as bridges to traditional wired networks
• Wi-Fi (wireless fidelity) which uses the IEEE 802.11b standard is currently the most popular approach to wireless LANs
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Can be thought of as a “Network of Networks”
• Server address – part of Internet address that identifies the computer what you want to connect to
• Domain name – a server address that identifies the computer using several parts ranging from specific to general (top-level)
• E-mail address – combination of username and server address
sales @ fareastfoods.com
Username
Server address
The Internet
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Internet: Internet Operations
E-Mail Asynchronously exchange electronic messages with other Internet users
FTP Download files (software, documents, or data) from or upload to a server located on the Internet
Newsgroups Participate in a wide variety of online discussion groups
Telnet Work on a computer elsewhere on the Internet
IRC Synchronously exchange electronic messages with other Internet users
World Wide Web Transfer text, images, video, and sound to your computer; search for information on the Internet
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The World Wide Web
The Web – software, protocols and conventions based on hypertext and multimedia that make the Internet easy to use and browse
• Hypertext – a method of linking related information in which there is no hierarchy or menu system
• Multimedia – an interactive combination of text, graphics, animation, images, audio, and video displayed by and under the control of a personal computer
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The World Wide Web: BrowserBrowser - application software that allows your computer to act as a client when contacting servers of the Internet (client-server network)
• Hypertext Markup Language (HTML) – computer language used to create Web pages that consist of text, links, and multimedia elements
• Web Page – a special type of document (file) that contains HTML and hypertext links to other documents or elements
• Web Site – an Internet server that stores a collection of related Web Pages
• Uniform Resource Locator (URL) – a standard means of locating Web pages or other resources over the web
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The World Wide Web
Characteristics Web Page Physical Page
Form Electronic Ink on paper
Amount of information Can extend beyond a single screen
Restricted to single piece of paper
Types of information Can include text, images, audio, and video information
Restricted to text and images
Links to other pages Can be linked to other pages through hypertext
Can be linked only through a separate index
Creation Can be created with HTML and saved to a server
Can be created using word processor and printer