Download - Computer Networking

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Computer NetworkComputer NetworkSection - IVSection - IV

Stage II -ICMAPStage II -ICMAP

Outline

Fundamentals Types of Network

(LAN, WAN,MAN,VAN,VPN,Intranet,Extranet) Protocols Network Topologies

(Star, Bus, Ring, Mesh, Hybrid) Network Devices Network Media/Cables Internet Security Risk Security Measures

22Stage II -ICMAPStage II -ICMAP

Computer NetworkComputer Network The connection or two or more computer

systems using a communication channel is called computer network.

Group of connected computer connected through a hub/switch/modem to share information through communication medium is called network.


Centralized Data Processing

Places all hardware, software, and processing in one location

Very inconvenient and inefficient Input data had to be physically transported to

computer Processed material had to be delivered to

users

Return


Distributed Data Processing

Uses computers that are at a distance from central computer

Local computers had access to central computers Some processing done on local computers,

some on central computers

Return


Digital and Analog Transmission

Digital transmission Sends data as distinct pulses, either on or off Similar to how data travels through computer

Analog transmission• Continuous electrical signal in the form of a wave

Called carrier wave

• Many communications media already in place for analog (voice) transmission

Phone lines are most common


Components of Communication System

1. Transmitter 2. Medium 3. Receiver


Asynchronous Transmission

Also called start/stop transmission Start bit transmitted at the beginning of each

group of bits Stop bit sent at end of each group Each group typically consists of one character

Receiving device gets start signal and sets up mechanism to accept the group

Used for low-speed communications

Return


Synchronous Transmission

Large block of characters transmitted Internal clocks of devices synchronized Error-check bits make sure all characters

received Much faster, but equipment is more

expensive

Return


Transmission Mode

1. Simplex 2. Half-Duplex 3. Full-Duplex


Simplex, Half-Duplex, and Full-Duplex Transmission

Simplex transmission sends data in one direction only

Example: television broadcasting Half-duplex transmission sends data in both

directions, but only one way at a time Example: bank teller sends data about a deposit; after

data received, a confirmation returns Full-duplex transmission allows transmission in

both directions at same time Example: a conversation Typically used for high-speed data communication


Simplex Communication

Simplex communication is a mode in which data only flows in one direction. Because most modern communications require a two-way interchange of data and information, this mode of transmission is not as popular as it once was.

However, one current usage of simplex communications in business involves certain point-of-sale terminals in which sales data is entered without a corresponding reply.


http://home.olemiss.edu/~misbook/sfsm.htm

Half-Duplex Communication

Half-duplex communication adds an ability for a two-way flow of data between computer terminals. In this directional mode, data travels in two directions, but not simultaneously.

Data can only move in one direction when data is not being received from the other direction. This mode is commonly used for linking computers together over telephone lines.


Full-Duplex Communication The fastest directional mode of communication

is full-duplex communication. Here, data is transmitted in both directions simultaneously on the same channel. Thus, this type of communication can be thought of as similar to automobile traffic on a two-lane road.

Full-duplex communication is made possible by devices called multiplexers. Full-duplex communication is primarily limited to mainframe computers because of the expensive hardware required to support this directional mode.


Network Uses

Electronic mail (e-mail) Facsimile (fax) technology Groupware Teleconferencing Electronic data interchange Electronic fund transfers Computer commuting The Internet


The Internet

A global network of hundreds of thousands of Computers

Widely considered to be the defining technology of the beginning of this century

Return


The Internet Service Provider and the Browser

An Internet service provider (ISP) provides the server computer and software to connect to the Internet

Online service, such as America Online, includes Internet access, Internet service, and a browser

When you connect to the Internet, the browser displays a home page

Return


Uniform Resource Locator (URL)

The complete, unique address of a Web page

Web page URL begins with http• HyperText Transfer Protocol – allows communication

by using links to transfer data between sites Domain name – address of site’s host computer

• Last part of domain name is called a top-level domain• Identifies country or purpose of organization

Return


Local Area Network (LAN)

Contains printers, servers and computers Systems are close to each other Contained in one office or building Organizations often have several LANS LAN is a number of computers connected to

each other by cable in a single location, usually a single floor of building or all the computers in a small company


Wide Area Network (WAN)

Set of connecting links between LAN. These links are made over telephone lines leased from various telephone companies

Wide Area Networks (WAN) Two or more LANs connected Over a large geographic area Typically use public or leased lines

• Phone lines• Satellite

The Internet is a WAN


Difference between LAN & WAN

LAN WAN1. Covers small geographical area

2. Computers are directly connected through physical cable for data transmission

3. LAN card is used for data transmission

4. Data transmission speed is very high

5. Installation and configuration cost is less than WAN

Covers large or wide geographical area

No physical cable or wire is used and data is sent and received through microwave system or satellite.

Modem is used for data transmission

slow

Higher than LAN


Metropolitan Area Network (MAN)

Metropolitan Area Network (MAN) Large network that connects different

organizations Shares regional resources An example of a regional resource is a An example of a regional resource is a

supercomputer. For example, Pittsburgh has supercomputer. For example, Pittsburgh has the Pittsburgh Super Computing center the Pittsburgh Super Computing center (www.psc.edu). The various colleges in (www.psc.edu). The various colleges in Pittsburgh connect to the center through a Pittsburgh connect to the center through a MAN in Pittsburgh.MAN in Pittsburgh.


Client/Server Network

Nodes and servers share data roles Nodes are called clients Servers are used to control access

Client requests data from server Server passes only the requested data

Client may perform some processing, but most data processed on server


Peer to Peer Networks (P2PN)

All nodes are equal Nodes access resources on other nodes Each node controls its own resources Most modern OS allow P2PN All computers have equal status Users share each other’s files, printers, etc. as

needed Common in small offices Networks tend to be slow Kazaa


Intranets

A private Internet-like network Internal to a certain company Easy to set up Can be linked to the Internet

Users can retrieve information such as benefits information and job openings Submit vacation requests, applications for open

positions, employee handbooks, corporate policies, and other information in a central location


Extranet

Refer to applications and services that are Intranet based, and use extended, secure access to external users or enterprises. This access is usually accomplished through passwords, user IDs, and other application-level security


Virtual Private Network

Technology that uses the Internet as a channel for private data communication

Uses tunneling technology Offers many benefits over a private

network Much cheaper than dedicated lines Data is secure Turns remote network administration over to

ISP


Tunneling Also called encapsulation Transfers data between two similar networks

over an intermediate network Data packets follow Point-to-Point Tunneling Protocol

(PPTP) Data embedded in TCP/IP packets carried by the

Internet Data packets are encoded before encapsulation

When received, they are separated and returned to their original format

Provides security for data packets

Return


Value-Added Network (VAN) A value-added network (VAN) is a private network provider

(sometimes called a turnkey communications line) that is hired by a company to facilitate electronic data interchange (EDI) or provide other network services.

Before the arrival of the World Wide Web, some companies hired value-added networks to move data from their company to other companies. With the arrival of the World Wide Web, many companies found it more cost-efficient to move their data over the Internet instead of paying the minimum monthly fees and per-character charges found in typical VAN contracts. In response, contemporary value-added network providers now focus on offering EDI translation, encryption, secure e-mail, management reporting, and other extra services for their customers.


http://searchdatacenter.techtarget.com/sDefinition/0,,sid80_gci213925,00.html

http://searchsecurity.techtarget.com/sDefinition/0,,sid14_gci212062,00.html

Virtual Area Network (VAN) A virtual area network (VAN) is a network on which users are

enabled to share a more visual sense of community through high band-width connections.

It is something like a metropolitan area network (MAN) or extended local areanetwork (LAN) in which all users can meet over high-bandwidth connections, enabling "face-to-face" online "coffeehouses," remote medical diagnosis and legal consultation, and online corporate or extracorporate workgroups, focus groups, and conferences.

A VAN requires multi-megabyte data flow and can be implemented through the use of Asymmetric Digital Subscriber Line but more likely through the installation of cable modem. Since the high-bandwidth connections imply a common infrastructure, the first VANs are likely to be local or regional. However, a VAN can also be national or international in geographic scope, assuming all users share similar capabilities.


http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci214083,00.html



http://searchsecurity.techtarget.com/sDefinition/0,,sid14_gci211726,00.html

Baseband & Broadband SignalingBaseband & Broadband Signaling

BasebandBaseband

1)Uses digital signalling1)Uses digital signalling

2)No frequency-division multiplexing2)No frequency-division multiplexing

3)Bi-directional transmission3)Bi-directional transmission

4)Signal travels over short distances4)Signal travels over short distances

BroadbandBroadband

1)Uses analog signalling1)Uses analog signalling

2)Unidirectional transmission2)Unidirectional transmission

3)Frequency-division multiplexing is possible3)Frequency-division multiplexing is possible

4) Any data connection faster than 56 Kbps

4)Signal can travel over long distances before being attenuated4)Signal can travel over long distances before being attenuated3131Stage II -ICMAPStage II -ICMAP

Integrated Systems Digital Network (ISDN)

Special type of telephone circuit Can move data at 128,000 bps Includes two phone lines, so you can talk on

the phone while online• Two data channels each support 64 Kbps

Drawbacks Expensive, especially at installation Not available in all areas

Return


Digital Subscriber Line (DSL)

Offers speeds up to 30 Mbps Simultaneous use of phone and data Asynchronous DSL

• Different up and download speeds

Drawbacks You must be within three miles of telephone company’s

switching office Costly Not available in all areas


Network Protocols Protocol - a set of rules for the exchange of data

between a terminal and a computer or two computers Agreement on how data is to be sent and receipt acknowledged Needed to allow computers from different vendors to

communicate Language of the network

Rules of communication Error resolution Defines collision and collision recovery Size of packet Naming rules for computers


Network Packet and Payload

Packets Pieces of data transmitted over a network Packet header

• Contains control information• Sending and receiving address

Packet payload• Contains actual data


Protocol Data Units (PDUs)Protocol Data Units (PDUs)


Network Protocols Transmission Control Protocol/Internet Protocol (TCP/IP)

Most popular protocol Required for Internet access TCP creates and reassembles packets IP handles addressing

• Ensures that packets are routed to their ultimate destination• Machines assigned a name of 4 numbers

IP address

Dynamic Host Configuration Protocol• Simplifies assignment of IP addresses

NetBEUI Network BIOS Extended User Interface Used by Windows to name computers It provides services related to the It provides services related to the session layer of the of the OSI model allowing allowing

applications on separate computers to communicate over a applications on separate computers to communicate over a local area network..


http://en.wikipedia.org/wiki/Session_layer

http://en.wikipedia.org/wiki/OSI_model

http://en.wikipedia.org/wiki/Local_area_network

Network Protocols IPX/SPX

Internet Packet Exchange/Sequenced Packet Exchange Associated with Novell Netware Replaced by TCP/IP

IPX is a IPX is a network layer protocol while SPX is a protocol while SPX is a transport layer protocol . The protocol . The SPX provides connection-oriented services between two nodes on the SPX provides connection-oriented services between two nodes on the network.network.

IPX and SPX both provide connection services similar to IPX and SPX both provide connection services similar to TCP/IP, with the , with the IPX protocol having similarities to IPX protocol having similarities to IP, and SPX having similarities to , and SPX having similarities to TCP..

IPX/SPX was primarily designed for IPX/SPX was primarily designed for local area networks (LANs), and is a (LANs), and is a very efficient protocol for this purpose (typically its performance exceeds very efficient protocol for this purpose (typically its performance exceeds that of TCP/IP on a LAN). TCP/IP has, however, become the that of TCP/IP on a LAN). TCP/IP has, however, become the de factode facto standard protocol. This is in part due to its superior performance over standard protocol. This is in part due to its superior performance over wide area networks and the Internet (which uses TCP/IP exclusively), and and the Internet (which uses TCP/IP exclusively), and also because TCP/IP is a more mature protocol, designed specifically with also because TCP/IP is a more mature protocol, designed specifically with this purpose in mind.this purpose in mind.


http://en.wikipedia.org/wiki/Network_layer

http://en.wikipedia.org/wiki/Transport_layer

http://en.wikipedia.org/wiki/TCP/IP

http://en.wikipedia.org/wiki/Internet_Protocol

http://en.wikipedia.org/wiki/Transmission_Control_Protocol

http://en.wikipedia.org/wiki/Local_area_network

http://en.wikipedia.org/wiki/Wide_area_networks

Ethernet - LAN Protocols

Dominant network protocol Uses either bus or star topology Node “listens” to see when the network is

available If two computers transmit at same time,

collision occurs Network detects the collision Each computer waits random amount of time

and retransmitsReturn


Token Ring - LAN Protocols

Uses ring topology Token (electrical signal) controls which

node can send messages Token circulates among nodes A computer waits for an empty token,

attaches message, and transmits Only one token, so only one device can

access network at a timeReturn


File Transfer Protocol (FTP)

A protocol for transferring files among computers

Requires FTP Client and FTP Server FTP servers maintain collections of

downloadable files Downloading can often be done anonymously,

without logging in Many FTP servers can be accessed

through Web browserReturn


Telnet

A protocol that allows remote users to log onto a host computer Users use their own PCs Users log in over the Internet Users’ experience is the same as if they were

sitting at the host computer’s local terminal Remote user typically has to have a user

ID and password

Return


OSI Model

Open System Interconnection (OSI)

Created by International Organization for Standardization (ISO)

primary model for network communications


Comparison of OSI and Comparison of OSI and TCP/IPTCP/IP


Physical LayerPhysical Layer


Data Link LayerData Link Layer


Network LayerNetwork Layer


Transport LayerTransport Layer


Session LayerSession Layer


Application LayerApplication Layer


Network Topology The physical layout of a network i.e.

wires and equipment Choice affects

• Network performance• Network size• Network collision detection

Star Ring Bus Mesh Hybrid


Bus Topology Also called linear bus

One wire connects all nodes Terminator ends the wires If messages collide with other messages, sending node resends

message Nodes can be added/removed from network without affecting

network Advantages

• Easy to setup• Small amount of wire

Disadvantages• Slow• Easy to crash


Bus Topology


Star Topology

All nodes connect to a hub• Packets sent to hub

• Hub sends packet to destination

• Helps prevent collisions among messages Advantages

• Easy to setup One cable can not crash network If a node fails, network does not fail

• Disadvantages One hub crashing downs entire network Uses lots of cable

Most common topology5454Stage II -ICMAPStage II -ICMAP

Star Topology


Ring Topology Nodes connected in a circle

Tokens used to transmit data• Nodes must wait for token to send

Data messages travel around ring in a single direction Each node checks message to see whether that node is

addressee, If not, message passed to next node Advantages

• Time to send data is known• No data collisions

Disadvantages• Complex software required for token management

• Slow• Lots of cable


Ring Topology


Mesh Topology

All computers connected together Internet is a mesh network Advantage

• Data will always be delivered

• Reliable

• Fault Tolerant

• Dedicated Path –Fast transmission

• No Collision Disadvantages

• Lots of cable- Expensive

• Hard to setup


Mesh Topology


Hybrid Topology


Network Hardware

Modem Network Interface Card (NIC) Hub Bridge Switch Router Gateway Amplifier Repeater


Modem

Converts digital signal to analog and vice versa

Conversion from digital to analog called modulation

Conversion from analog to digital called demodulation

Measured in bits per second (bps) Fastest current modems transmit

at 56,000 bpsReturn


Network Interface Cards (NIC)

Ethernet Card /Network Adapters Network adapter

Connects each computer to wiring in the network Handles sending, receiving, and error checking of transmitted

data

Connects node to the media


Hubs

Center of a star network

All nodes receive transmitted packets

Slow and insecure Active Hub –

Amplification Passive Hub – no

amplification


Bridge

Connects two or more LANs together Packets sent to remote LAN cross

• Other packets do not cross Segments the network on MAC addresses

Bridge allows connection of similar networks (those using the same protocol)


Switches

Replacement for hubs Only intended node

receives transmission Fast Secure Keep track of MAC

Addresses Intelligent Device


Routers

Router Connects two or more

LANs, WANs together Packets sent to remote

LAN cross Connect internal

networks to the Internet Selection of best

available path and path forwarding

Need configured before installation


Gateway

Connects two dissimilar networks Primary function is converting protocol among

networks i.e. protocol translation


Amplifier

An Amplifier is an electronic device that increases the voltage , current , or power of a signal . Amplifiers are used in wireless communications and broadcasting, and in audio equipment of all kinds.


Repeater

In digital communication systems, a repeater is a device that receives a digital signal on an electromagnetic or optical transmission medium and regenerates the signal along the next leg of the medium. 7070Stage II -ICMAPStage II -ICMAP

Types of Communications Media

Unshielded /Shielded Twisted pairs

Coaxial cables Fiber optics


Twisted-Pair

Two wires twisted around each other to reduce electrical interference

Inexpensive Already in place (for telephone systems) Susceptible to electrical interference and noise -

anything causes signal distortion Most common LAN cable + telephone systems May be shielded from interference Speeds range from 1 Mbps to 1,000 Mbps

Return


Unshielded and Shielded TPUnshielded and Shielded TP

Unshielded Twisted Pair (UTP)Unshielded Twisted Pair (UTP) Ordinary telephone wireOrdinary telephone wire

CheapestCheapest

Easiest to installEasiest to install

Suffers from external EM interferenceSuffers from external EM interference

Shielded Twisted Pair (STP)Shielded Twisted Pair (STP) Metal braid or sheathing that reduces interferenceMetal braid or sheathing that reduces interference

More expensiveMore expensive

Harder to handle (thick, heavy)Harder to handle (thick, heavy)


Coaxial Cable A center conductor wire surrounded by layer of insulation and

metallic sheath Commonly used to connect to cable TV Higher bandwidth and less susceptibility to noise than twisted pair Shielded from interference Speeds up to 10 Mbps

Television distributionTelevision distribution

Antenna to TVAntenna to TV

Cable TVCable TV

Long distance telephone transmissionLong distance telephone transmission

Can carry 10,000 voice calls simultaneouslCan carry 10,000 voice calls simultaneouslyyReturn


Fiber Optic Use light instead of electricity to

send data Much higher bandwidth than

coaxial cable Immune to electrical

interference Materials cheaper than coaxial,

but installation costs high

Very secure Hard to work with Speeds up to

100 Gbps(billion bits per billion bits per secondsecond)


Computer Crime

Hacker – someone who attempts to gain access to computer systems illegally Originally referred to as someone with a high

degree of computer expertise Social engineering – a tongue-in-cheek term

for con artist actions• Persuade people to give away password information


Methods Computer Criminals Use

Bomb Data diddling Denial of service attac

ks Piggybacking Salami technique

Scavenging Trapdoor Trojan horse Zapping Worm Virus Spamming Cookies


Bomb

Causes a program to trigger damage under certain conditions Usually set to go off at a later date

Sometimes planted in commercial software Shareware is more prone to having a bomb

planted in it

Return


Data Diddling

Refers to changing data before or as it enters the system

Auditors must verify accuracy of the source data as well as the processing that occurs

Return


Denial of Service(DOS) Attack

Hackers bombard a site with more requests than it can possibly handle Prevents legitimate users from accessing the

site Hackers can cause attacks to come from

many different sites simultaneously

Return


Piggybacking

An illicit user “rides” into the system on the back of an authorized user If the user does not exit the system properly,

the intruder can continue where the original user has left off

Always log out of any system you log into

Return


Scavenging

Searching company trash cans and dumpsters for lists of information Thieves will search garbage and recycling

bins of individuals looking for bank account numbers, credit card numbers, etc.

Return


Trapdoor

An illicit program left within a completed legitimate program Allows subsequent unauthorized and

unknown entry by the perpetrator to make changes to the program

Salami Technique An embezzlement technique where small

“slices” of money are funneled into accountsReturn


Trojan Horse

Involves illegal instructions placed in the middle of a legitimate program Program does something useful, but the

Trojan horse instructions do something destructive in the background

Return


Worm

A program that transfers itself from computer to computer

self-replicating computer program.self-replicating computer program. Plants itself as a separate file on the target

computer’s disks

Return


Virus A set of illicit instructions that passes itself on to

other files Transmitting a virus Can cause tremendous damage to computer and data

Antivirus software Detects virus signature Scans hard disk every time you boot the computer

Viruses tend to show up on free software or software downloaded from the Internet

Often distributed as e-mail attachments Do not open e-mail attachments without scanning them or if you

do not know the person sending the e-mail

Return


Spamming

Mass advertising via e-mail Can overflow your e-mail inbox Bogs down your e-mail server, increasing the

cost of e-mail service Zapping

Refers to a variety of software designed to bypass all security systems

Return


Cookies A small text file stored on your hard drive File is sent back to the server each time you visit that

site Web sites can easily collect information when a user just

visits the site Web sites use cookies to store your preferences

Stores preferences, allowing Web site to be customized Stores passwords, allowing you to visit multiple pages within the

site without logging in to each one Tracks surfing habits, targeting you for specific types of

advertisements

Return


Computer Forensics

Uncovering computer-stored information suitable for use as evidence in courts of law

Some experts are available for hire, but most are on the staffs of police departments and law firms


Security: Playing It Safe

Security – a system of safeguards Protects system and data from deliberate or

accidental damage Protects system and data from unauthorized

access• Controlling Access

Biometric Devices

• Encryption• Firewall• Digital Signature


Controlling Access

Four means of controlling who has access to the computer What you have What you know What you do What you are


What You Have

Requires you to have some device to gain access to the computer Badge, key, or card to give you physical

access to the computer room or a locked terminal

Debit card with a magnetic strip gives you access to your bank account at an ATM

Active badge broadcasts your location by sending out radio signals

Return


What You Know & Do

What You Know Requires you to know something to gain

access Password and login name give you access to

computer system What You Do

Software can verify scanned and online signatures

Return


What You Are

Uses biometrics – the science of measuring body characteristics

Uses fingerprinting, voice pattern, retinal scan, etc. to identify a person

Can combine fingerprinting and reading a smart card to authenticate

Return


Biometric Devices

BiometricsBiometrics refers to methods for uniquely refers to methods for uniquely recognizing humans based upon one or more recognizing humans based upon one or more intrinsic physical or behavioral traits. In intrinsic physical or behavioral traits. In information technology, in particular, biometrics information technology, in particular, biometrics is used as a form of identity access is used as a form of identity access management and access control. It is also used management and access control. It is also used to identify individuals in groups that are under to identify individuals in groups that are under surveillance.surveillance.

Biometric Devices read personal characteristics and Biometric Devices read personal characteristics and attributes (voice ,face, retina etc) to authenticate aattributes (voice ,face, retina etc) to authenticate a

before allowing him to use the computerbefore allowing him to use the computer9595Stage II -ICMAPStage II -ICMAP

Encryption

Scrambling data so that it can only be read by a computer with the appropriate key

Encryption key converts the message into an unreadable form

Message can be decrypted only by someone with the proper key

Private key encryption – senders and receivers share the same key

Public key encryption – encryption software generates the key

Return


Firewall

A combination of hardware and software that sits between an organization’s network and the Internet

All traffic between the two goes through the firewall

Protects the organization from unauthorized access

Can prevent internal users from accessing inappropriate Internet sites

Return


Digital Signature

An electronic signature that can be used to authenticate An electronic signature that can be used to authenticate the identity of the sender of a message or the signer of a the identity of the sender of a message or the signer of a document, and possibly to ensure that the original document, and possibly to ensure that the original content of the message or document that has been sent content of the message or document that has been sent is unchanged. is unchanged.

The ability to ensure that the original signed message The ability to ensure that the original signed message arrived means that the sender cannot easily repudiate it arrived means that the sender cannot easily repudiate it later.later.

A A Digital CertificatDigital Certificate contains the digital signature of the e contains the digital signature of the certificate-issuing authority so that anyone can verify that certificate-issuing authority so that anyone can verify that the certificate is real.the certificate is real.


Bluetooth

Uses radio waves to connect mobile devices. A wireless protocol for exchanging data over A wireless protocol for exchanging data over

short distances from fixed and mobile devices, short distances from fixed and mobile devices, creating personal area networks (PANs). It can creating personal area networks (PANs). It can connect several devices, overcoming problems connect several devices, overcoming problems of synchronization.of synchronization.

A short-range radio technology aimed at A short-range radio technology aimed at simplifying communications among Internet simplifying communications among Internet devices and between devices and the Internet.devices and between devices and the Internet.


WAP(Wireless ireless AApplication pplication PProtocolrotocol)

A secure specification that allows users to access A secure specification that allows users to access information instantly via handheld wireless devices such information instantly via handheld wireless devices such as mobile phones, pagers, two-way radios, smart as mobile phones, pagers, two-way radios, smart phones.phones.

Supports most wireless networks i.e.CDMA, GSM,. Supports most wireless networks i.e.CDMA, GSM,. WAP is supported by all operating systems. WAP is supported by all operating systems. WAPs that use displays and access the Internet run what WAPs that use displays and access the Internet run what

are called micro browsers--browsers with small file sizes are called micro browsers--browsers with small file sizes that can accommodate the low memory constraints of that can accommodate the low memory constraints of handheld devices and the low-bandwidth constraints of a handheld devices and the low-bandwidth constraints of a wireless-handheld network. wireless-handheld network.


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