Wireless Networks dor Dummies phần 4 ppsx

These devices allow for command line interaction. You do this using a program called Telnet or Secure Shell. We do not recommend using Telnet because the authentication password travels across the network in clear text and is there- fore available to anyone with access to the network and a sniffer. Secure Shell is an encrypted method of access. Unfortunately, setup and use of SSH takes more space than we are allowed for this book. You can read all about SSH at www.ssh.com. Continue using the browser to finish creating a static WEP key. To set up WEP, go to the Security page and follow the prompts. Your access point is now available for use on your network. Connect it as you would the SMC and begin enjoying the wonderful world of wireless. Testing the Signal Before you allow your users to connect, you need to make sure that the place- ment of your wireless networking components remains effective. In order to test the network, you need a wireless laptop configured to the parameters you just enabled. You may want to jump to the next chapter and find out how to set up your machine and then go to Chapter 15 for methods you can use to test the connection. You can perform a rudimentary test using the ping com- mand that we show in Figure 5-3. 102 Part II: Implementing Your Wireless Network Choosing a fail-safe password Do not use any word in the dictionary. Any dictio- nary. Such passwords are probably the easiest to attack because all you need is a brute force attacking tool and a dictionary. This book doesn’t have sufficient pages to go into the details of performing such attacks, but numerous tools are available because your primary access to the logon process is through a Web page. That is why you don’t want to allow remote access — doing so makes it too easy for hackers to attack the device. So what should you do? Use a combination of alpha (a,b,c) and numeric (1,2,3) characters. If your device permits special characters like @!$, you can combine these also to create an even stronger password. Although you can get carried away figuring out different passwords, remember that you need this password to access the device in order to administer it. The good news is that if you forget the password, all you need to do is physically reset the device, and it reverts to its original settings. Check your owner’s manual to learn how this is done. 09_575252 ch05.qxd 9/2/04 3:57 PM Page 102 Chapter 6 Connecting Your Clients In This Chapter ᮣ Adding hardware to your client ᮣ Selecting the right hardware ᮣ Installing your hardware ᮣ Upgrading your firmware or software ᮣ Connecting your Windows clients ᮣ Using AirPort ᮣ Understanding Linux clients ᮣ Testing your connection Y ou have an access point installed, but it is of little or no value without clients. You may have Linux or Mac OS clients. Also, you may have Windows 2000 Professional or XP Professional clients. This chapter provides some help on selecting the right hardware and installing the accompanying software. Some of the steps, such as acquiring and installing hardware, are the same regardless of the platform that you choose to use. But when it comes to configuring the software, you need to be aware of some subtleties for each platform. Generally, connecting your client to a wireless network is a cinch, especially when you are using a wireless-aware operating system like Windows XP, a chipset like Centrino, or a computer equipped with an Intel Pro/Wireless adapter. You will find it marginally more difficult for other platforms; where you have to use the client utility that comes with your wireless adapter. Of course, you need to read the vendor’s documentation for your particular software or hardware, but usually the first step is to install the hardware and to configure your wireless adapter. 10_575252 ch06.qxd 9/2/04 3:58 PM Page 103 Adding Hardware to the PC The first step when hooking up a client is to install the hardware. But as we spelled out in Chapter 2, you need to plan for the needs of your clients. There are many different forms that the hardware can take, and each one has a niche. When you complete your site survey, you document the types and locations of all clients. Your clients may include desktops, laptops, tablets, personal digital assistants, and printers. Basically, your client is any device that has an 802.11 interface to the wireless medium. Your Wi-Fi adapter has two major functions: ߜ Microwave software-controlled radio: This function handles the physical layer microwave reception and transmission, which includes modulation and frequency control. This is the Physical layer. ߜ Media access control and logical link control: This function enables Ethernet networking over the radio system. It bridges the wired Ethernet network to the wireless 802.11 network. This is the Data Link layer. Figure 6-1 shows the components in a depiction of OSI layers 1 and 2. Look for the Wi-Fi Certified seal on any hardware you purchase. This Good Housekeeping Seal of Approval gives you confidence that your gear will interoperate with any other gear that also has the Wi-Fi certification. You can find a current list of certified gear at www.wi-fi.com/OpenSection/ certified_products.asp?TID=2 . Our search on the Wi-Fi Alliance Web site for a CompactFlash 802.11g-certified product found the ARtem CPS-BR-g prod- uct. You can look up the equipment you are looking to buy or use this site to narrow down products to evaluate. 802.2 LLC 802.11 MAC FHSSPhysical layer DSSS OFDM Data Link layer Figure 6-1: Frame format. 104 Part II: Implementing Your Wireless Network 10_575252 ch06.qxd 9/2/04 3:58 PM Page 104 Peripheral Component Interconnect (PCI) Originally, client adapters came in two flavors. You had your PC card ( www.pcmcia.org), which some people still refer to as a PCMCIA (Personal Computer Memory Card International Association) card, and your Compact Flash (CF). In the old days (perhaps reaching back as far as 2002), things were different. When you had a desktop machine, you installed a card in an empty slot and slipped a PC Card into it. Now you can buy a Peripheral Component Inter- connect (PCI) adapter with a rubber-ducky antenna. Usually, you can remove the attached antenna and use an external antenna of your choice, such as a semi-directional antenna. All new desktops have at least one PCI slot (usually four or five PCI slots) but rarely (if ever) have a PC card slot. PC Card adapters use a Type II slot, which is 5.5mm thick. PC Cards have a bulge antenna enclosed in a casing that is thicker than a typical Type II card. The antenna generally blocks the other Type II slot. If you need that other PC Card slot, you may have to go with a USB solution. However, the big problem with PC Cards is the antenna is on a horizontal plane, but most access points have vertical antennae. This causes what is known as cross polarization, which reduces the range and the bit rate of the client. Antennae work best when ori- ented vertically. Really, they work optimally when at a 90-degree angle to the ground. The patch antenna in your PC Card is oriented horizontally unless you turn your laptop on one end — great for reception, but awfully poor for typing. Some PC Cards are better than others, so make sure that your selection provides the reception your clients want and deserve. Asanté has a card (the FriendlyNet AeroLAN AL1511 PCMCIA adapter) that has a pair of hinged antenna that stows away but unfolds vertically for use. In addition, some ven- dors such as Alvarion and ORiNOCO have a small plug on the end of the card bulge that you can pop out to attach an external antenna. Last, where recep- tion is a problem, there is another solution. Whereas most client adapters are rated about 15 dBm or 32 milliwatt (mW), you can purchase PC Cards with power as high as 23 dBm or 200 mW to compensate for the bulge antenna. However, you may want to substitute an USB adapter, with its vertical anten- nae, and move the adapter closer to the access point. Regardless of what Tim the Toolman says, more power is not better. Some low-end microwave ovens use only about 500 mW. Makes you think! 105 Chapter 6: Connecting Your Clients 10_575252 ch06.qxd 9/2/04 3:58 PM Page 105 For handhelds in the old days, you needed a CF card. Now not only do you have the CF card, but you also have other flash memory products such as Memory Stick ( www.memorystick.com/en/index.html) and Secure Digital ( www.sdcard.org). CF cards, SD, and MS allow you to connect a Pocket PC or PalmOS device to your WLAN. You want versatility; at least one vendor sells an adapter for the CF card to convert it into a PC Card. Universal Serial Bus (USB) Not long ago, laptops and desktop PCs did not support Universal Serial Bus nor the USB format. Now you have difficulty finding one that doesn’t. First popularized by the Apple iMac, USB format is now ubiquitous. Starting after Windows 95 and NT, Microsoft built in support for USB. It simplifies the con- nection of one device to another device, and most operating systems now have plug-and-play (PnP) support for USB. So correspondingly, manufacturers started to sell USB models. At first, they placed a CF card in a housing and put a USB interface on it. Figure 6-2 shows a typical USB adapter with a vertical antenna and USB cable. Now they have USB models that are similar in form to a USB flash drive. Figure 6-3 illustrates the USB and other form factors. Ethernet client adapter A new entry into the client solution set is the Ethernet client adapter. A good example is the Linksys WET11 Ethernet Client Adapter. These are external devices like the USB gear. They are similar in appearance and footprint to the USB devices. The difference is the device connects to the client using a CAT5 cable and the RJ-45 jack on the computer. You can usually put up to ten feet of cable between the client and Ethernet adapter. So far, most people are using these adapters to wirelessly connect game consoles like PlayStation 2 or Xbox, but you can use it to connect a laptop, desktop, tablet, printer, and any other device that supports Ethernet. Figure 6-2: Compaq USB wireless adapter. 106 Part II: Implementing Your Wireless Network 10_575252 ch06.qxd 9/2/04 3:58 PM Page 106 The final decision Choices, choices, choices. You did do your site survey upfront, did you not? Table 6-1 lists some of the pros and cons of the various adapters. Table 6-1 Pros and Cons of Adapters Adapter Pros Cons PC Card Inside the computer Horizontal antenna and poor reception. Easy install Bulge antenna blocks other Type II slot. High-power cards eat batteries. PCI Inside your computer Require you to open computer; not flexible Flexible, external antenna Expensive Can share a PC card with another device USB Inexpensive USB 1.1 probably not ready for 802.11a Easy install and g. Give flexibility; unplug Few have dual or removable antenna. here, plug in there Connecting wire may become a nuisance. Power from the USB port Connecting wire allows you to move the device Small footprint (continued) MS SD IO PC Card Mini-PCI PCI adapter USB devices CF card Figure 6-3: USB Wireless and other form factors. 107 Chapter 6: Connecting Your Clients 10_575252 ch06.qxd 9/2/04 3:58 PM Page 107 Table 6-1 (continued) Adapter Pros Cons Ethernet Connect game consoles Not common. client Act as a wireless bridge Expensive. Plug-and-play (usually) Require external power source. Connecting wire allows you to move the device You may not find the form factor for the standard you intend to support. For instance, you may find it difficult to find USB 2.0 802.11a devices. However, every vendor has different products, different target markets and different strategies, so you really need to talk to your manufacturer or value-added reseller. (Is that an oxymoron?) Wireless print server One product also deserving of a look is the wireless print server. The D-Link DP-311P is a good example of a wireless print server with one IEEE 1284 bidi- rectional parallel port. You can use the print server to share a printer wire- lessly. The print server plugs directly into the back of your printer. Figure 6-4 shows an older HP LaserJet 4M with an attached DP-311P. This printer did not support networking and was locally attached using a serial cable. Now the printer is available for sharing through the access point — a great solution for small and home offices. Figure 6-4: Wireless print server attached to a printer. 108 Part II: Implementing Your Wireless Network 10_575252 ch06.qxd 9/2/04 3:58 PM Page 108 Installing the Wireless Hardware The steps to install your hardware are pretty straightforward. Your vendor may deviate from the following list, however, so you probably should review their documentation after you understand the basic steps. 1. Insert your CD-ROM. Most vendors want you to install the drivers for your adapter before even inserting or plugging it in. You should find drivers on the CD-ROM that came with your adapter. Usually, you just run the Setup program on the physical media that came with your adapter. Should you find you don’t have drivers or an install utility, check out the download sections of your vendor’s Web site. You have a partial list above. Operating systems such as Windows XP have many of the drivers built in. 2. Run the setup program and answer the questions with the information you gathered before starting the install. 3. Insert, plug in, install, or connect the actual adapter. Your vendor may require you to shut down the device before actually installing the physical hardware. If so, do so and power back up. Often, you will insert the PC Card when instructed to do so by the setup pro- gram. Typically, you don’t need to power down your system to install a PC Card or USB device, but you will need to shut down when you install a PCI or internal card of any kind. You have the added concern of static electricity for internal cards, but that is not a concern when adding a PC Card or USB device. 4. If everything went well, your operating system should recognize your hardware. In Windows 2000 or XP, you should see a newly created entry in the Network Connections control panel identifying the wireless adapter. You may have to use the Found New Hardware Wizard to find the drivers for your device. 5. Upgrade the firmware or software that comes with your hardware. Upgrading the firmware or software Most wireless manufacturers implement features such as security in firmware on the adapter itself. In addition, almost all use flash-able adapters. Periodically, your vendor will post software and firmware updates on their Web site. It is your responsibility to check the site from time to time and download the update. Sometimes, the vendor labels the update as mandatory because it fixes major bugs. Other times, the vendor includes an optional feature that you may or may not use. 109 Chapter 6: Connecting Your Clients 10_575252 ch06.qxd 9/2/04 3:58 PM Page 109 We frequently caution people not to install any patch or upgrade without doing some analysis. Just because the vendor thinks the upgrade is manda- tory doesn’t mean that you must put it in. However, it does mean that you should evaluate the upgrade. You may not use the feature, so why upgrade? After you download the software upgrade, you just need to unzip and run the setup program. Pretty simple. Be aware that when you upgrade, you lose your connection. You may have to restart your system to reacquire an IP address and to reconnect. You may find that you are not so lucky. You may have to run a routine that writes new instructions to the chipset. This is known as flashing the firmware. Flashing allows you to get new instructions (read as new or enhanced capa- bilities) on the adapter without having to purchase a new adapter or having to return it to the vendor. Be warned that there is a risk in attempting to flash your firmware. You could lose power to your system and only partially update the firmware, which may also erase the original factory settings — a potentially cat- astrophic situation. With other vendors, the vendor may allow you to force a reset to the original factory settings — an inconvenience but not a catastrophe. When flashing your card, we suggest that you use the mains, not battery power. Better yet, plug your computer into a UPS with standby power and plug the UPS into the mains. You don’t want to lose power when flashing your adapter! Some upgrades are significant. When Peter installed his Proxim adapter, his wireless adapter supported no security, pre-shared keys, LEAP (Lightweight Extensible Authentication Protocol), and externally managed 802.1x keys. You can see these features in Figure 6-5. After downloading the upgrade and installing it, the card has many new fea- tures. Figure 6-6 shows the new security tab for this adapter. You can see the client now supports WPA (either shared-key or EAP versions) and more EAP versions. We cover the advantages of these new features in Chapter 11. Figure 6-5: Proxim Client Utility Version 2.3. 110 Part II: Implementing Your Wireless Network 10_575252 ch06.qxd 9/2/04 3:58 PM Page 110 Important guidelines for upgrading Whenever you intend to do an upgrade, follow these simple guidelines: ߜ Copy your current configuration. Some vendors allow you to backup the configuration to a file; others do not. If you can make the backup, do so; otherwise, capture all the information from your adapter. You may want to take screenshots. The reason you want to take a backup is that most likely flashing will erase everything you entered and take you back to the factory settings. So you will need to re-enter any pre-shared keys and profiles of sites you visit. ߜ Read the README file and follow the instructions carefully. ߜ Do not turn the power for your client off or unplug anything (especially the adapter) until the upgrade completes. If you do, pray you followed the first guideline. Perform the flash over a wired segment or USB connection and not a wireless one. This is more important when doing a flash of an access point because most assuredly, you will lose your connection to the access point when using wireless. ߜ Plan for and test your upgrade. Ensure that you can roll back the upgrade should you have the need. ߜ If you are upgrading more than one client, do one client and make sure that you can still reconnect. After you determine that the upgrade does not prevent your client from connecting, then by all means upgrade the remaining clients, but not beforehand. Better safe than sorry. Following the guidelines will take a little extra time upfront, but it may save you hours on the back end. Figure 6-6: Proxim Client Utility Version 2.4. 111 Chapter 6: Connecting Your Clients 10_575252 ch06.qxd 9/2/04 3:58 PM Page 111 [...]... Right-click the Wireless Network Connection icon in the System Tray and select View Available Wireless Networks from the contextual menu Chapter 6: Connecting Your Clients 2 From the Wireless Network Connection dialog box, select the network where you want to connect 3 Click the Advanced button 4 From the Wireless Network Connection Properties dialog box, click the Add button shown under the Preferred Networks. .. zone increases your chances for success at whatever you do In wireless networks, multiple zones might allude to the number of locations where you provide wireless access or commercial hot spots that advertise themselves as Wireless Zones This chapter shows how connecting to multiple locations seamlessly is the goal, whether it is using a Wireless Metropolitan Area Network (WMAN) like that in Fredericton,... with the software To choose from the available networks, follow these steps: 1 Select Network List from the menu You see a picture showing available networks, their names, BSSIDs, Channels, Encryption, and signal strength Of course, you could use this to roam around looking for wireless networks You see this clearly in Figure 7-2 Figure 7-2: Available networks using the Segue Roaming Client 2 Click... others offer similar services NetMotion Wireless NetMotion Mobility (www.nmwco.com/default_ swf.asp) is another vendor product that provides seamless roaming between wireless networks for Pocket PC-based devices and Windows machines Reassociation — Getting back together as you move from AP to AP Setting up multiple access points allows you to form a larger wireless network, which should be fairly... lunch room, conference room, and a few other locations where you might need wireless access Then add an authentication process for the wireless machines before allowing them to access the rest of your network using 802.1x protocols This way you are in effect setting up a Wireless DMZ Vendor concerns You may find that some vendors increase security within a single access point, but then lose the ability... them all eventually Luckily, the trend is reversing with wireless access leading the way Choice Hotels International, Inc., which owns 370 Comfort Suites and 140 Clarion properties, plans to roll out free wireless Internet access in public areas and their guest rooms this year Marriott International has wireless high-speed Internet access at 40 0 hotels in the United States, the United Kingdom, and... license terms and then click Next 4 Select Express and then click Next Then click Next again to start the install 5 Click Finish to end the installation and open the client software 127 128 Part II: Implementing Your Wireless Network After the client software is loaded and running, it automatically checks your wireless network card and uses it to discover available networks If you install both a GPRS... Wireless Network Using Boingo to access the network Boingo is the brainchild of Sky Dayton, EarthLink’s founder Sky aggregated ISPs to create EarthLink Now, Sky is trying to do the same with WISPs (wireless Internet service providers) Boingo provides a fee-based service and acts as a wireless aggregator, but that’s not why it is mentioned here The brains behind Boingo decided to distribute a free wireless. .. and then focus on what you can do now to achieve roaming for your business users Currently, it is difficult and expensive to connect between vendors’ wireless networks This is less because of technical reasons than pure marketing and cost-sharing issues Vendors such as T-Mobile and Boingo are starting to offer reciprocity agreements, but there is a long way to go for a truly transparent connection... one part of the network to another, the wireless network card will automatically select the strongest signal, changing as one nears and another falls away 129 130 Part II: Implementing Your Wireless Network The wireless city If you travel a lot and like to remain connected, visit Fredericton, New Brunswick, Canada The city has installed one of the first WMAN networks, with free (yes, we wrote free) . offices. Figure 6 -4: Wireless print server attached to a printer. 108 Part II: Implementing Your Wireless Network 10_575252 ch06.qxd 9/2/ 04 3:58 PM Page 108 Installing the Wireless Hardware The. DSSS OFDM Data Link layer Figure 6-1: Frame format. 1 04 Part II: Implementing Your Wireless Network 10_575252 ch06.qxd 9/2/ 04 3:58 PM Page 1 04 Peripheral Component Interconnect (PCI) Originally,. steps: 1. Right-click the Wireless Network Connection icon in the System Tray and select View Available Wireless Networks from the contextual menu. 112 Part II: Implementing Your Wireless Network 10_575252