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Networks 2b

In: Computers and Technology

Submitted By gc116
Words 2608
Pages 11
QUESTION1
Power Problems
Alternating current (AC), which is “food” to PCs and other network devices, is normally 110 volts and changes polarity 60 times a second (or 60 Hertz). These values are referred to as line voltage. Any deviation from these values can create problems for a PC or other network device. Power problems fall into three categories:
* Overage
* Underage
* Quality

Power Overage Problems
During a power overage, too much power is coming into the computer. Power overage can take two forms:

* A power spike occurs when the power level rises above normal levels and then drops back to normal in less than one second.

* A power surge occurs when the power level rises above normal levels and stays there for more than one or two seconds.

Typically, power surges last longer than a second or two, and they may last for several minutes.
Two types of devices are used to protect computers and other network devices from power overage problems:
* Surge protectors
* Line conditioners

A surge protector contains a special electronic circuit that monitors the incoming voltage level and trips a circuit breaker when the overvoltage reaches a certain level (called the over- voltage threshold). The problem with surge protectors is that the threshold is set too high to be safe.Nor does a surge protector protect against power surges and spikes that are lower than the threshold. For the most part, a surge protector is better than nothing, but not by much. It is really only a multiple-outlet strip and should not be considered anything more.

Line conditioners are a much better choice for protecting against surges and spikes. Line conditioners use several electronic methods to “clean” all power coming into them. An Uninterruptible Power Supply uses a battery and power inverter to run the computer equipment that plugs into it. A battery charger continuously charges the battery. The battery charger is the only thing that runs off line voltage. The computer itself runs off steady voltage supplied by the UPS.

Power Underage Problems

Power underage occurs when power levels drop below the standard, and they are almost as common as power overages. There are three types of power underages:
* Sag is an inverted spike. Sags occur when power levels drop below normal and rise back to normal within a brief period of time (usually less than one second).

* A brownout, on the other hand, occurs when power drops below normal levels for several seconds or longer. In other words, a brownout is an inverted surge.

* A blackout is a total loss of power for several seconds, several minutes, or several hours.

To ward off power underage problems, you need only one device: a UPS, which allows net- work devices to continue to function even in the complete absence of power. Some are intelligent and can shut down your computer in the case of a blackout.

Power Quality Problems
Power quality problems generally indicate that stray frequencies have entered the power supply through the power cord.

Electrostatic Discharge Problems
ESD occurs when two items with dissimilar static electrical charges are brought together. Nature doesn’t like things to be unequal, so static electrical charges will “jump” from the item with more electrons.

Electromagnetic Interference Problems
EMI occurs when magnetic fields intersect network or computer cables, causing interference in the cables. Motors and transformers, which are everywhere in an office (in air conditioners, heaters, and so on), are a typical source of EMI.. Radio Frequency Interference Problems
RFI occurs when radio signals interfere with the normal operation of electronic circuits (computers in particular).
Network devices (including computers and servers) are very sensitive to temperature extremes and can fail prematurely if subjected to them.

QUESTION2
You can use a wireless network (WLAN) to share Internet access, files, printers, game consoles, and other devices among all the computers in your home. After you’ve completed the initial wireless router setup and added your computers and devices to the network, you can use your home network to surf the web or to play online games—whether you're sitting in your living room or relaxing in your backyard.

2.2

Client
The client is software that allows your machine to talk to servers on the network. Each server vendor uses a different way of designing its network access. There- fore, if a computer needs to get to both a Novell and a Microsoft network, the computer must have two pieces of client software installed one for each type of server.

Adapter
The adapter is, technically, the peripheral hardware that installs into your computer, but in this case, it refers to the software that defines how the computer talks to that hardware. If you do not have the proper adapter software installed, your PC will not be able to talk properly to the NIC, and you will not be able to access the network until you change the adapter to one that is compatible with the hardware.

Protocol
Once the client service and the adapter are installed, you have cleared a path for communication from your machine to network servers. The protocol is the computer language that you use to facilitate communication between the machines

Service
A service is a component that gives a bit back to the network that gives it so much. Services add functionality to the network by providing resources or doing tasks for other computers.

2.3

1. Connect to the Internet
Make sure that your Internet connection and your DSL or cable modem are working. Your wireless network depends on this connection.

2. Connect your wireless router
These are the steps for connecting a stand-alone wireless router to your DSL modem or cable modem. If you have a modem router, follow your ISP’s instructions for connecting your network.
Since you'll be temporarily disconnected from the Internet, print these instructions before you go any further.
First, locate your cable modem or DSL modem and unplug it to turn it off.

Next, connect your router to your modem: * If you currently have your computer connected directly to your modem: Unplug the network cable from the back of your computer, and plug it into the port labeled Internet, WAN, or WLAN on the back of your router. * If you do not currently have a computer connected to the Internet: Plug one end of a network cable (included with your router) into your modem, and plug the other end of the network cable into the Internet, WAN, or WLAN port on your wireless router. * If you currently have your computer connected to a router: Unplug the network cable connected to the Internet, WAN, or WLAN port from your current router, and plug this end of the cable into the Internet, WAN, or WLAN port on your wireless router. Then, unplug any other network cables, and plug them into the available ports on your wireless router. You no longer need your original router, because 3. Configure your wireless router

Using the network cable that came with your wireless router, you should temporarily connect your computer to one of the open network ports on your wireless router (any port that isn't labeled Internet, WAN, or WLAN). If you need to, turn your computer on. It should automatically connect to your router.
3. Configure your wireless router

Using the network cable that came with your wireless router, you should temporarily connect your computer to one of the open network ports on your wireless router (any port that isn't labeled Internet, WAN, or WLAN). If you need to, turn your computer on
4. Connect your computers, printers, and other devices to the wireless network
You can connect multiple computers, printers, and many other peripheral devices, such as an Xbox, Xbox 360, TV, cell phone, iTouch, or iPad, to your network. Before you connect them to your network, make sure that the computer or device you want to add has built-in wireless networking or a network adapter
5. Share files, printers, and more
Now that your computers and devices are connected, you can begin sharing files, printers, games, and much more. One of the top reasons for setting up a home network is to share a printer. Another is to share files. The steps for doing this, however, aren’t always obvious, so here are instructions to get you started:

2.4

Interference * All wireless networks, such as cellular telephone networks and wireless local area networks, or WLANs, rely on broadcasting stations that transmit signals. These stations, which include large cellular antenna towers as well as small wireless Internet routers, transmit signals at particular radio frequencies

Obstructions
Wireless signals travel fastest through open spaces. So if there are large or numerous obstructions between wireless transmitters and wireless receivers, signal strength suffers. For WLANs, common obstructions that come between wireless routers and wireless devices, weakening signal strength, include walls, floors, furniture and appliances.
Location
* Even when there are few obstructions between a wireless transmitter and receiver, the overall distance between them affects wireless signal strength. Wireless signals cannot travel indefinitely, as they eventually disperse and become absorbed by the surrounding environment. With a WLAN, a wireless router positioned at one end of a building may not be able to communicate with a device at the opposite end. While cellular networks provide signals that can travel farther, cellular devices can still lose reception when they stray too far from transmission towers..
Hardware
* In some instances poor wireless signal strength is the result of inadequate or dysfunctional hardware. For example, if a laptop computer has an outdated or damaged wireless network adapter card, it may struggle to receive a signal from a wireless router. Alternatively, if a wireless router has a damaged or poorly designed antenna, it may not be able to provide as strong a signal.

QUESTION3
3.1
Broadband Connections
A broadband Internet connection provides high speed internet access at transmission rates above 256kbits/sec but typically (UK) above 4Mbits/s (for ADSL).
Broadband connections can be provided by 4 main access mechanisms-
ADSL, cable and WI-FI (wireless) and GSM (mobile phones).
Broadband access can be provided by several access mechanisms: * DSL/ADSL (digital subscriber line) * Cable Internet * Wireless Internet * GSM (mobile phones) * Satellite Internet * Electric power lines- are also being considered for providing broadband internet access.
Although cable and DSL are broadband technologies ADSL is the more common, as it is carried over the standard telephone lines. For home/home office users ADSL is the standard option.
DSL/ADSL Broadband
DSL (Digital Subscriber Line)/Broadband comes in two forms: * Asymmetrical Digital Subscriber Line (ADSL), – provides different upload and download speeds (most common) * Symmetrical Digital Subscriber Line (SDSL)- provides the same speed in both directions.
Monthly Cost: Starts at approx. £13-£30 for ADSL per month
Speed: 128Kbps – 20Mbps
Hardware Requirements: ADSL modem (often included). If you want to connect multiple computers: one ADSL router (approx. £50-£200 if note included) Advantages | Disadvantages | * Always on connection * Can use a telephone and Internet simultaneously * Wide variety of speeds and prices. * Large choice of service providers (ISPs) | * Available only in limited areas but this is changing rapidly * Speed vary widely * Some providers have monthly download limits. ( 10GB per month is typical) * Requires special termination equipment to be fitted by the telecom company at both ends of the telephone line. * Exposes computer to Internet so you need to install firewall software. (Windows XP has a built in firewall). |
Wireless Broadband
Wireless broadband is of interest for mobile users. The wireless technology used is the same as is used in home wireless networking and hence if you have laptop/pda is equipped for connection to a home or office wireless network then it will also work on a public wireless network.
Monthly Cost: Often free and provided bundled by some ADSL broadband packages
Speed: 1-54 Mbps
Hardware Requirements: Wireless (Wi-FI) equipped laptop/PDA. Advantages | Disadvantages | * Always on connection when connected. * Requires you to be in a wireless hotspot. Your ISP will provide a list of sites. * Does not support wireless roaming. * Large choice of service providers (ISPs) | * Available only in limited areas usually public areas like airports, train stations etc * Speed varies depending on signal quality. * Exposes computer to Internet so you need to install firewall software. (Windows XP has a built in firewall). (see Internet computer security) |
Cable Broadband
Cable connects you to the Internet through a coaxial cable usually using the same line as your TV service. Cable connections offer very high connection speeds, 1 to 4 Mbps, but the connection may be shared with other users. This means that you can experience much slower speeds due to congestion.
Monthly Cost: £14-£50 per month
Speed: 500 Kbps to 2 Mbps
Hardware Requirements: Cable Modem (Usually included). If you have multiple computers then you might need cable router to share connection. Advantages | Disadvantages | * Wide availability on cable networks * Relatively inexpensive | * Sharing with neighbours poses some unique security risks and congestion problems * Router required for more than one computer * Primarily for home users |
.
Mobile Broadband
In the developing world were no fixed land line system is available mobile broadband is becoming the predominate method that people use to connect to the Internet..
Modern mobile phones in the UK (2012) use the 3G network (3rd generation mobile telecommunications) with speeds of several Mbit/s.
Which although much faster than the earlier 2G networks it is still much slower than typical ADSL Broadband which most home users/businesses use.
There are two main mechanism used. One uses a Internet capable mobile phone like the iphone the other uses a USB dongle (3G modem) and a laptop.
Monthly Cost: Varies considerably pay as you options are available. Speed: .6 Kbps to 7.2 Mbps
Hardware Requirements: 3G capable Mobile Phone, or USB dongle and package Advantages | Disadvantages | * Wide availability * Can be used when on the move | * Slow in comparison with ADSL * Can be expensive |
4G Broadband – This is currently in the initial phases of being rolled out in the UK. It uses HSPA+ access mechanism with speeds of upto 168 Mbit/s in the downlink and 22 Mbit/s in the uplink.
Capability is already built into Google Nexus 7 (mobile data model) and Nexus 4 mobile phone.
Dial-Up Analogue Connection -56K
Monthly Cost: Varies from 1p per minute to £13 per month (unlimited access)
Speed: Up to 56Kbps
Hardware Requirements: 56k modem included in most modern PCs (approx. £25-£50 ) Advantages | Disadvantages | * Inexpensive * Wide availability | * Using a modem ties up a phone line * Connection is not “always on” * Slowest access method * Security danger see rogue Internet diallers |
ISDN
Similar to dial-up, ISDN establishes a connection to your service provider when you access the Internet. However, ISDN circuits are 64-128K and fully digital.
ISDN is not easy to install and troubleshoot and requires you to have an ISDN box installed by your telephone company.
It is frequently used by small businesses as in addition to the ISDN line you can also use a normal telephone line at the same time . This means you can access the Internet as well as talking on the telephone.
Monthly Cost: As Analogue dial up
Speed: 64Kbps – 128Kbps
Hardware Requirements: ISDN card (£30-£60) or router ( £200-£300) Advantages | Disadvantages | * Lets you talk and surf simultaneously. * Faster than 56kbps analogue * Suitable for attaching more than 1 PC to the Internet ( 2-6 light users) | * difficult to setup * Available only in limited areas * Requires special termination equipment to be fitted by the telecom company at both ends of the telephone line * Outdated being replaced by DSL * Not practical for more than 6 computers (depending on usage) * Security danger see rogue Internet diallers |…...

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...The Wealth of Networks The Wealth of Networks How Social Production Transforms Markets and Freedom Yochai Benkler Yale University Press New Haven and London Copyright _ 2006 by Yochai Benkler. All rights reserved. Subject to the exception immediately following, this book may not be reproduced, in whole or in part, including illustrations, in any form (beyond that copying permitted by Sections 107 and 108 of the U.S. Copyright Law and except by reviewers for the public press), without written permission from the publishers. The author has made an online version of the book available under a Creative Commons Noncommercial Sharealike license; it can be accessed through the author’s website at http://www.benkler.org. Printed in the United States of America. Library of Congress Cataloging-in-Publication Data Benkler, Yochai. The wealth of networks : how social production transforms markets and freedom / Yochai Benkler. p. cm. Includes bibliographical references and index. ISBN-13: 978-0-300-11056-2 (alk. paper) ISBN-10: 0-300-11056-1 (alk. paper) 1. Information society. 2. Information networks. 3. Computer networks—Social aspects. 4. Computer networks—Economic aspects. I. Title. HM851.B457 2006 303.48'33—dc22 2005028316 A catalogue record for this book is available from the British Library. The paper in this book meets the guidelines for permanence and durability of the Committee on Production Guidelines for Book Longevity of the Council on Library Resources. 10 9 8 7 6 5 4 3 2 1...

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Network

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Network

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