Home Networking Bible 2nd phần 3 pps

124 Part II ✦ Planning and Setting Up Networking — Hardware and Software Checking the cabling Cables are very seldom the problem when it comes to a network connection. In only a couple of situations, the cable might be bad. If you put the ends on your cable, those could be trou- ble spots, although it’s not really the cable that is bad but the connections on the ends. Another problem area is if the cable is coiled or kinked, or if you find a nick or cut in the cable. You should make sure that the cabling is in good shape before you lay it. You should also make sure not to lay the cabling in an area where it can become damaged with nicks or cuts easily. Checking a cable connection is fairly easy. If the lights on the network card, the hub, or both are all lit, the cable connection is good. See Chapter 9 for information about cards and hubs. Deciding to Use Other Networking Hardware There are many other pieces of networking hardware you can use with your network. Some might be useful; others will not help your network at all. It’s important to determine the size and the complexity of the network before you add too much hardware. As noted previously, you can use kits to start your network. You can always add onto a kit as your network grows. You don’t need to buy everything at one time. Here are some basic rules about the hardware you need to purchase for your network. For more information, see Chapter 9. ✦ You need a network interface card (NIC) for every computer on the network. These cards can be Ethernet, wireless, phoneline, or other, but you do need a network card for each computer. You’ll need cabling or wireless access points (see Chapter 7 for more information). The cabling might be coax, Ethernet, phone line, or power line as well. ✦ If you’re connecting two computers, you can do so by using a crossover cable and the two network cards. See Chapter 7 for more information. ✦ If you want to connect three or more computers, or if you want a nice fast connection between two computers, you need a hub with Ethernet wiring. You also need a hub when you use Ethernet with wireless. That’s it. You don’t need any other hardware to start your network. Now if you want, you can add other hardware. For example: ✦ A cable modem/Digital Subscriber Line (DSL) router is something you can add to your network to enable the computers on the network to connect to the Internet. A router is a device that analyzes the network packets that come into it and direct the packets to the appropriate location, usually between network segments. ✦ Another piece of equipment you might want is a network switch. A switch is another “intelligent” device that directs packets to the appropriate computer, server, or network segment. You don’t need a switch, however, if your network is small. ✦ You’ve seen the term patch panel in this chapter. Again, that’s something you’ll only need if your network is large, as it would be in a business or corporation. A patch panel is an area where all cables come together. They are fed into a panel full of jacks, and then shorter patch cables connect the jacks to switches or routers, or the server. You will most likely not need a patch panel in your network. 125 Chapter 6 ✦ Understanding and Installing Traditional Cabling Summary In this chapter, you’ve learned about topology, technology, and network cabling. Specifically, you learned about the following topics: ✦ Understanding the methods of network cabling ✦ Considering networking topologies and technologies ✦ Understanding cabling ✦ Looking at cable connectors ✦ Considering cabling kits ✦ Installing cables In the next chapter, you learn about wireless connections, standards, products, and security. ✦✦✦ Using Wireless Network Connections W ireless technologies were originally developed to enable work- ers to roam about warehouses, manufacturing plants, and other large business facilities. Wireless LANs (WLANs) are now used in many other situations, such as corporations, small businesses, colleges and universities, and home networking. WLANs often replace wired or traditionally cabled LANs and more often work as an extension to wired LANs. What are the reasons you want to use wireless in your home network? Do you have a home in which wiring with traditional cabling would be difficult? Do you have a notebook computer you want to network yet use in different rooms of the house? Is the thought of cabling your home with traditional wiring too much? Are you curious about the technology? You can use wireless for all of these reasons and more. Considering Wireless Methods Wireless technology is all around you: radio, television, microwave ovens, telephones, personal pagers, remote controls for garage door openers and automotive keyless entry, security systems, and more. It only makes sense to use wireless technologies for networking computers. And because wireless technology is all around you, interference can also affect your wireless network. Consider where your business is located, the type of building you have, and your outside environment before using wireless in your business. Power lines, heavy machinery, microwaves or satellites, and other devices can interfere with wireless network connectivity. Four methods of wireless networking are common —infrared, radio signals, microwaves, and laser links. For home networking, the most popular wireless connections are radio signals. More and more manufacturers and software providers are supporting wireless network connections. Small Business Tip 7 7 CHAPTER ✦✦✦✦ In This Chapter Introducing wireless technologies Considering wireless standards Choosing, configuring, and securing wireless technologies Using wireless with cabled networks ✦✦✦✦ 128 Part II ✦ Planning and Setting Up Networking — Hardware and Software ✦ Infrared works similarly to a television remote control. The connection must be line- of-sight, or point-to-point, because infrared light cannot penetrate obstacles. The narrow cone of the infrared beam enables two devices to communicate without being directly aligned. The beam itself is highly directional and ensures the infrared connection doesn’t spill to other nearby devices. The transmission distance for infrared is relatively short; depending on the hardware, the distance is usually limited to around 50 feet. Unfortunately, infrared isn’t as popular as its makers thought it would be, so choices are somewhat limited. ✦ Radio frequency, or RF, describes the number of times per second a radio wave vibrates. Two RF physical interfaces are standard: direct sequence spread spectrum and frequency hopping spread spectrum. Direct sequence spread spectrum can pass through light obstacles, such as thin walls and ceilings. Frequency hopping spread spectrum radio signals can pass through heavier walls, but the transfer rate is slow. Radio frequency connections use 900 MHz frequencies, similar to many higher-quality cordless telephones. Spread spectrum signals are fairly secure against tampering from outside sources, such as intercepting transmissions. Additionally, spread spectrum products provide 11 to 54 Mbps data rates at a range from 50 feet to 1,000 feet, depending on the building construction, interference sources, and other factors. ✦ Microwaves provide wide bandwidth, but they are susceptible to external interference and eavesdropping. Microwaves require FCC licensing and approved equipment. Microwaves can use terrestrial or satellite systems. Satellite microwave can provide links to extremely remote areas, so they’re useful in larger networks. Microwaves, however, aren’t practical for home networking because they are extremely expensive. ✦ Lasers aren’t practical for home networking, either, again because of the expense. A communication laser transmits a narrow beam of light that is modulated into pulses to carry the data. Laser light is also sensitive to atmospheric conditions and provides only a relatively short transmission distance, from 25 to 100 feet or so. Using Radio Frequency for Networking Radio signals are accessible to most users throughout the world. Radio signals penetrate light obstacles, such as walls and furniture. Popular wireless networking technologies, especially for home use, are commonly based on radio frequency principles. Figure 7-1 illustrates the ease of placement when using wireless technologies. The notebook can travel anywhere within the house and still connect to the other computers and the printer. The printer is connected to one computer, which is connected to the wireless network. The access point (also AP or WAP for wireless access point) is the device that enables wireless network cards to connect to the network. Wireless products usually use two basic components: a station adapter (SA) and an access point. The station adapter connects to the client computer as a network interface card (NIC), also called a network card or network adapter card. The access point connects to the LAN infrastructure and communicates with the station adapters to transfer data. If you set up a large wireless network or expect interference from the building structure or electrical noise sources, you may need several access points for complete coverage. More than likely, however, you’ll need only one access point for a small home network. 129 Chapter 7 ✦ Using Wireless Network Connections Figure 7-1: RF-based wireless networks are quick and easy to set up. Access points extend the range of the network. Each access point enables 15 to 50 client devices to connect to the network. Access points generally have a finite range —500 feet indoors and 1,000 feet outdoors. Figure 7-2 illustrates a large corporate network that uses multiple access points. Notebooks can roam the building and access the network from anywhere. As the user “roams,” the notebook switches access points to the one has the strongest signal. As a user roams, the NIC renegotiates with various access points to find the strongest connection to the network. The connection is not seamless, however; it takes a few seconds for the notebook, or other computer, to reconnect to the network. Although users of wireless local area networks are not required to have permits or licenses, the FCC does govern the equipment, such as transmitter power and methods of transmission. Tip Tip Tip Wireless connections Access point 130 Part II ✦ Planning and Setting Up Networking — Hardware and Software Figure 7-2: Roaming users can connect to the network via access points placed throughout the building. Another option for wireless networking is called wired bridging. When using wired bridging, you connect a wireless access point to a wired Ethernet LAN. Combining wired and wireless networking gives you more control over the wireless network, faster speeds through the wired LAN, network management functions, and so on. For more information about using wireless and wired networks together, see the section “Using Wireless in Conjunction with Cabled Networks” later in this chapter. Cross- Reference Wireless connections Access points Wireless connections About Wireless Network Topology Any computer or other device using wireless technology needs a transceiver and an antenna, and components are either a station adapter or an access point. A station adapter (also called station, SA, or STA) is the client “radio.” Usually the station adapter is incorporated into a wireless network card and installed into a computer. The wireless NIC can be a PC Card, Personal Computer Memory Card International Association (PCMCIA), universal serial bus (USB), or other form of radio that is integrated into the device, such as in some printers. The access point is the bridge between the network card and the network. You can configure the basic wireless network with either peer-to-peer or client/server. In peer-to- peer, two or more stations talk to each other without an access point; the radio frequencies connect the computers via the wireless network cards. In client/server, multiple stations connect to an access point, which acts as a bridge to a wired network. You can overlap basic services using access points that are connected to a wired network, in the case of a larger building or heavier construction materials, for instance. The ranges overlap to avoid interference or lapses in data transfer. 131 Chapter 7 ✦ Using Wireless Network Connections Advantages and Disadvantages of Wireless Technologies Wireless LANs have become popular over the last few years with many businesses; for example, wireless technologies are used in healthcare, retail, industrial parks, trade shows, aca- demic environments, corporate training facilities, and more. It’s only natural that wireless networking move into situations for more personal uses. However, as with all things, there are advantages and disadvantages to using wireless technologies. The following discussion con- centrates on the advantages and disadvantages of the use of wireless LANs in the home. Advantages of wireless One of the most popular uses for wireless networking is the advantage of using a roaming notebook, personal digital assistant (PDA), tablet computer, and the like. However, you might decide to install a wireless network even if you have nonroaming desktop computers. For one reason, the cost of deploying a wireless network is less than the traditional cabling, not only in the components and equipment but in the installation as well. Another reason you might want wireless is it is very easy to install. Wireless is also easy to use and understand. If you’re looking for a way to network your home computers quickly and easily, wireless is the ideal solution. In addition, you can start your network with wireless, and as you learn more about networking and as your network grows, you can add traditional cabling to the wireless. You can connect two PCs that are equipped with wireless network adapter cards to create a peer-to-peer (or workgroup) network. For example, suppose you use your notebook at home sometimes and you want to print to the printer connected to your desktop computer; all you have to do is connect the two with wireless NICs and bring the notebook in close proximity, and you’re ready to network. Wireless standards have been adopted all over the world to ensure regular improvements in new features and capabilities. Besides constant and consistent upgrades and revisions, there is widespread industry support for wireless technology. For more information about wireless standards, see the section “Considering Wireless Standards” later in this chapter. Because of the popularity of wireless networking, wireless networking equipment is widely available. For instance, network adapter cards come in a variety of forms to fit most computers: Peripheral Component Interface (PCI), USB, PC Card, and so on. Wireless directional antennas, extension points, and other hardware are also easily obtained. Other advantages of wireless networking include the following: ✦ Intuitive to use ✦ Convenient to install and use ✦ Economical ✦ A large number of hardware manufacturers from which to choose Tip 132 Part II ✦ Planning and Setting Up Networking — Hardware and Software Disadvantages of wireless What are some other questions you might ask before choosing wireless networking? Will you be sharing only files and printers, or will you be sharing applications? What type of applications will run over the WLAN? It’s important to remember that wireless networking is a shared medium, not a switched medium. This means that some applications running over a wireless network do not run as efficiently or as quickly as they would over a traditionally wired network. Consider the application question before choosing wireless. In home networking, the only applications you might share are games for the kids. Check the minimum requirements for the games you buy to see if they can run on a wireless network. Other applications you might want to run over a network include accounting programs, pay- roll, point of sale, and other such “business” programs. For more information about applications and the network, see Chapter 20. Another question you need to ask yourself is this: Will there be roaming computers on your network? If so, how far will they roam? Range is important to wireless networking, because if a roaming computer, such as a tablet or notebook, roams away from the RF range, the computer becomes disconnected from the network. Radio frequencies disperse as the distance from the transmitter increases. Also, as data rates increase, range decreases. Question three: How fast do you want your network to transmit data? RF networks generally come in two speeds: 11 Mbps and 54 Mbps. Some manufacturers have begun to introduce 60 Mbps in recent months. Cross- Reference Tip What Are Hotspots? Hotspots are all the rage now in many cities and towns. A hotspot is any commercial business — cafés, hotels, restaurants, bars, airports, and so on —that has a high-speed Internet connection. Many of these businesses have wired access, but even more have wireless. The business provides you with a hookup to check your mail or surf the Net while you eat, drink, or otherwise patronize the business. The standard 802.11b is currently the most popular standard for wireless networks at hotspots (see the section “Considering Wireless Standards” later in this chapter for more information about 802.11b). Public hotspots might be free or pay-for-use. Private hotspots also exist, located in a workplace or even a home where a private group of people create and use the hotspot. There are also community hotspots, often free and open to the public. Some community hotspots are offered by public organizations; other hotspots are affiliated with nonprofit organizations. You can use a hotspot to access the Internet with a PDA or a notebook computer with a wireless adapter. Find hotspots in your area by checking colleges, hotels, restaurants, and such, or go to the Wi-Fi Zone at www.wi-fizone.org. 133 Chapter 7 ✦ Using Wireless Network Connections Looking at performance As I’ve indicated, the most popular wireless networking hardware is radio-based technology. Because of the technology, some performance issues do exist. Some issues have solutions that are acceptable to the user; others do not. Radio waves can be absorbed by furniture, walls, plastic, water, and other materials. For example, sometimes objects create interference with the signal, causing dead spots for the radio signal. If you find a dead spot, a spot in a room where a wireless device cannot attach to the network, you generally just move to another area. Dead spots often cover only small areas. You can, alternatively, move the wireless access points to cover the dead spots. Wireless devices are meant to keep a reliable and consistent connection between two devices; however, connection speed varies as range and signal strength vary. Performance degrades with increased distance between devices (NIC and access point). As performance degrades, wireless technology institutes a fallback. A fallback is when the wireless technology slows the speed of the connection in order to maintain a more reliable connection. If, for instance, the range increases and the signal strength varies, the connection slows to make sure that transferred data is more accurate and consistent. Radio waves grow weaker as they expand from the initial source. If, for example, your notebook computer is in the room beside the access point, it will receive data transmissions bet- ter than if the notebook is three or four rooms away from the access point. Figure 7-3 shows an example of signal strength as it relates to range between wireless devices. Two access points, one upstairs and one downstairs, radiate waves of RF. The closer a computer —notebook, PDA, desktop, or other —is to the access point, the more reliable and sta- ble the connections. However, a computer can roam to other rooms, and perhaps outside of the house, and still connect to the network. Each wireless device clearly defines a range in which it works most efficiently. You can purchase wireless devices that have a range of 25, 75, 100, or 150 feet indoors. (There are some devices that offer higher ranges, such as 1,000 feet; however, these devices are quite expensive and not really for home networks.) You can also purchase signal boosters, repeaters, and a host of additional hardware to increase the signal of the wireless devices. For your home, though, you’ll probably need only one or two access points. If you require high performance from your wireless connection, place that device closer to the access point. Considering interference The range of radio frequencies that wireless networking uses is known as an unlicensed band; the FCC does not require the use of a license for these RF ranges. Therefore, other devices also use the same frequencies, resulting in interference with RF wireless networking. Cordless telephones are a prime example of another RF device that can jam, or interfere, with RF networking. Microwave ovens are another device that can interfere with your wireless network. The good news is that cordless telephones and microwave ovens use slightly different frequencies within the RF range; so neither is a huge threat to your wireless network, and your wireless network isn’t a huge threat to your telephone or microwave system. Tip [...]... learned about using wireless networking in the home Specifically, you’ve learned about the following: ✦ Using wireless standards ✦ Configuring wireless access points ✦ Setting up a wireless workgroup ✦ Using wireless networking with cabled networking In the next chapter, you learn about using alternative cabling methods, such as phone line networking and using the house wiring for networking computers ✦... of this writing available for working with 802.11a Looking at HomeRF Another wireless protocol is available yet limited in scope and practice HomeRF Shared Wireless Access Protocol (SWAP) is designed to transmit voice and data in the home HomeRF is a wireless network solution that carries data up to 1.6 Mbps for a distance of up to 150 feet HomeRF is also on the 2.4 GHz band, so remember, you can and... networks together Figure 7-6 illustrates network adapter cards, access points, and antennas in use in a home networking environment 139 140 Part II ✦ Planning and Setting Up Networking — Hardware and Software Antennas Access points Wireless adapter card Figure 7-6: Everything is connected through wireless networking Tip You can definitely use wireless with most Linux distributions (distros), but you have... Small Business Tip If you plan to use wireless networking in your small business, be especially careful about placement of the access points Keep the points closer to the center of the building so the outside range is less Security issues are another reason you might want to use wired networking for your small business 135 136 Part II ✦ Planning and Setting Up Networking — Hardware and Software Figure 7-5... women can send documents back and forth between their homes Chapter 7 ✦ Using Wireless Network Connections Hub Access point Figure 7-16: Two network segments — wireless and wired — share resources 1 53 154 Part II ✦ Planning and Setting Up Networking — Hardware and Software Antennas Wireless connection Access points Hubs Figure 7-17: Two different home networks share data through wireless antennas acting... requirements for using AirPort with various Mac OSs Table 7-1: AirPort Compatibility Software OS Required Base Station Firmware AirPort 2.0.2 Mac OS 9.0.4 or later 3. 84/4.0.2 AirPort 2.0.5 Mac OS X 10.1.5 3. 84/4.0.7 AirPort 3. 0.4 Mac OS X 10.2 3. 84/4.0.8/5.0.1 Firmware Update AirPort 4.0.7 Windows 98, 2000, XP Utilities for Windows AirPort Admin Windows 98, 2000, XP AirPort adapter cards AirPort’s Extreme... you each have a network in your home You can use wireless antennas to bridge the two networks together Small Business Tip If you have only one employee located upstairs or in another, smaller office building and you need to connect that one employee to the wired network, you can use wireless networking to accomplish it Figure 7-17 illustrates two networked homes The home on the left uses a hub to connect... example, you may purchase two antennas that cover up to 30 0 feet; or you may look for antennas that cover up to a mile Remember that information sent over RF can be picked up by other wireless devices, so you want higher security when transmitting data outside Also, make sure you’re using the same IEEE standard 1 43 144 Part II ✦ Planning and Setting Up Networking — Hardware and Software Rotated antennas... least ✦ 802.11b is in the 2.4 GHz band, which also includes cordless phones and microwave ovens ✦ This standard is available in most airports, hotels, college campuses, and so on 137 138 Part II ✦ Planning and Setting Up Networking — Hardware and Software Using the 802.11a standard The 802.11a standard provides data rates to 54 Mbps, thus making this wireless standard faster and more efficient than... 134 Part II ✦ Planning and Setting Up Networking — Hardware and Software Access point Access point Radio waves Figure 7 -3: Depending on the size of your house, you might need two access points Other interference might occur with metal objects close to the access . networks. Microwaves, however, aren’t practical for home networking because they are extremely expensive. ✦ Lasers aren’t practical for home networking, either, again because of the expense. A communication. 802.11a. Looking at HomeRF Another wireless protocol is available yet limited in scope and practice. HomeRF Shared Wireless Access Protocol (SWAP) is designed to transmit voice and data in the home. HomeRF is. a home networking environment. Small Business Tip Tip Note Tip 140 Part II ✦ Planning and Setting Up Networking — Hardware and Software Figure 7-6: Everything is connected through wireless networking. You

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