Tài liệu 18.3. Broadband Connections pptx

18.3. Broadband Connections If your Mac is connected wirelessly or, um, wirefully to a cable modem, DSL, or office network, you're one of the lucky ones. You have a high-speed broadband connection to the Internet that's always available, always on. You never have to wait to dial, disconnect, or download. You're connected to the Net via your Mac's Ethernet jack or AirPort antenna, leaving the dial-up era behind. 18.3.1. Automatic Configuration The real beauty of most broadband connections these days is that they require no setup whatsoever. Take a new Mac out of the box, plug in the Ethernet cable to your cable modem (or choose a wireless network from the menulet), and you can begin surfing the Web instantly. That's because most cable modems, DSL boxes, and wireless base stations automatically feed all of the necessary configuration settings to the Mac (including techie specs like IP address and DNS Server addresses), courtesy of a glorious feature called DHCP. UP TO SPEED PPPoE and DSL If you have DSL service, you may be directed create a PPPoE service. (You do that on the Network pane of System Preferences; click your Ethernet connection, and then choose Configuration Create PPPoE Service.) It stands for PPP over Ethernet, meaning that although your DSL "modem" is connected to your Ethernet port, you still have to make and break your Internet connections manually, as though you had a dial-up modem. Fill in the PPPoE dialog box as directed by your ISP (usually just your account name and password). From here on in, you start and end your Internet connections exactly as though you had a dial-up modem. This acronym means dynamic host configuration protocol, which is tech-ese for: "We'll fill in your Network pane of System Preferences automatically." 18.3.2. Manual Configuration If, for some reason, you're not able to surf the Web or check email the first time you try, it's conceivable that your broadband modem or your office network doesn't offer DHCP. In that case, you may have to fiddle with the Network pane of System Preferences, preferably with a customer-support rep from your broadband provider on the phone. On the Network pane, click either AirPort or Built-in Ethernet, depending on how your Mac is connected to the broadband modem. Now you see something like Figure 18-3 . Figure 18-3. Don't be alarmed by the morass of numbers and periods—it's all in good fun. (If you find TCP/IP fun, that is.) In this illustration, you see the setup for a cable-modem account with a static IP address, which means you have to type in all of these numbers yourself, as guided by the cable company. The alternative is a DHCP server account, which fills most of it in automatically. 18.3.3. Ethernet Connections The beauty of Ethernet connections is that they're super-fast and super-secure. No bad guys sitting across the coffee shop, armed with shareware "sniffing" software, can intercept your email and chat messages, as they theoretically can when you're on wireless. As shown in Figure 18-3 , clicking the name of an Ethernet connection in the Network pane reveals the geeky settings required for a manual Ethernet setup. For most people, the correct setting in the Configure pop-up menu is "Using DHCP," which means "Mac OS X fills in the correct settings for you." If your network geek or Internet provider has instructed you to use other settings, then you'll probably be asked to choose Manually. That is, your cable or phone company will tell you precisely which IP address (Internet address) to type in here. You'll also have to fill in all the other boxes here—Subnet Mask, Router,and so on—with cryptic numbers separated by periods. Note: But look at the bright side: You've just been given a static IP address, an Internet address that is all your own and that won't change. Because your Mac has this one reliable address, several cool Mac OS X features are available to you. For example, it's easier to access your files from anywhere in the world, as described in Chapter 22 . That's all the setup—click Apply Now. If your settings are correct, you're online, now and forever. You never have to worry about connecting or disconnecting. 18.3.4. AirPort (Wi-Fi) Connections AirPort is Apple's term for the 802.11 (Wi-Fi) wireless networking technology. If you have it, your Mac can communicate with a wireless base station up to 300 feet away, much like a cordless phone. Doing so lets you surf the Web from your laptop in the hotel room, for example, or share files with someone across the building from you. POWER USERS' CLINIC The Super-Secret, New, Hot-Spot Management Box If you open System Preferences Network, click AirPort in the left-side list, and then click Advanced, you see the cool new dialog box shown here. It lets you manage the list of Wi-Fi hot spots that Mac OS X has memorized on your travels. For example, you can delete the old ones. You can also double-click a Wi-Fi net's name to type in and store its password. Finally, you can drag the hot spots' names up and down the list to establish a priority for making connections when more than one is available. Ordinarily, Mac OS X memorizes the names of the various hot spots that you join on your travels. It's kind of nice, actually, because it means you're interrupted less often by the "Do you want to join?" box. But if you're alarmed at the massive list of hot spots that Leopard has memorized—for privacy reasons, say— here's where you turn off "Remember any network this computer has joined." Chapter 13 has much more information about setting up an AirPort network. The real fun begins, however, when it comes time to join one. Sometimes you just want to join a friend's Wi-Fi network. Sometimes you've got time to kill in an airport, and it's worth a $7 splurge for half an hour. And sometimes, at some street corners in big cities, Wi-Fi signals bleeding out of apartment buildings might give you a choice of 20 or 30 free hot spots to join. Note: Not all attempts to join Wi-Fi hot spots are successful, even the unlocked ones. Sometimes the signal is strong enough to make the hot spot's name show up in your menu, but not enough for an actual connection. Sometimes, for security, hot spots are rigged to permit only specific computers to join (see the box on the next page), and yours isn't one of them. And sometimes wireless routers are broadcasting, but their Internet connection is down. Figure 18-4. Left: Congratulations—your Mac has discovered new Wi-Fi hot spots all around you! Double-click one to join it. But if you see a icon next to the hot spot's name, beware: It's been protected by a password. If you don't know it, then you won't be able to connect. Right: Later, you can always switch networks using the AirPort menulet. Either way, your Mac joins Wi-Fi hot spots like this: • First, it sniffs around for a Wi-Fi network that you've used before. If it finds one, it connects quietly and automatically. You're not asked for permission, a password, or anything else; you're just online. (It's that way, for example, when you come home with your laptop every day.) For details on this memorization feature, see the box on Section 18.3.4 . • If the Mac can't find a previous hot spot, but it detects a new hot spot or two, a message appears on the screen (Figure 18-4 ), displaying their names. Double-click one to connect. • If you missed the opportunity to join a hot spot when the message appeared, or if you joined the wrong one or a non-working one, then you have another chance. You can always choose a hot spot's name from the menulet, as shown in Figure 18-4 at right. A icon indicates a hot spot that requires a password—a tiny but terrific new Leopard feature—so you don't waste your time trying to join those (unless, of course, you have the password). Tip: If you don't want your Mac to keep interrupting you with its discoveries of new hot spots—it can get pretty annoying when you're in a taxi driving through a city—you can shut them off. In System Preferences, click Network, click AirPort, and then turn off "Ask to join new networks." 18.3.5. Commercial Hot Spots Choosing the name of the hot spot you want to join is generally all you have to do—if it's a home Wi-Fi network. POWER USERS' CLINIC The Secret Life of the AirPort Menulet Here's something not one Mac fan in a thousand knows about: a secret diagnostic mode in the menulet. Turns out that if you press the Option key as you open the menulet, you get a special treat: a faint gray interior menu that identifies some diagnostic details of your current wireless network. You get to see the hot spot's channel, your current data rate, and the MAC address of your AirPort card. AMAC address has nothing to do with Macs; Windows PCs have MAC addresses, too. It stands for Media Access Control, although the equivalent term, Ethernet Hardware Address, is much more descriptive. It's a unique identifier for your networking card, whether it's your Ethernet card or your AirPort circuitry. Every now and then, somebody will ask for your MAC address—usually when helping you troubleshoot network problems or get onto a really exclusive Wi-Fi hot spot. (Some hot spots are so restrictive, the network administrator has to register each MAC address that's allowed to use it.) Unfortunately, joining a commercial Wi-Fi hot spot—one that requires a credit card number (in a hotel room or airport, for example)—requires more than just connecting to it. You also have to sign into it before you can send so much as a single email message. To do that, open your Web browser. You'll see the "Enter your payment information" screen either immediately or as soon as you try to open a Web page of your choice. (Even at free hot spots, you might have to click OK on a welcome page to initiate the connection.) Supply your credit card information or (if you have a membership to this Wi-Fi chain, like Boingo or T-Mobile) your name and password. Click Submit or Proceed, try not to contemplate how this $8 per hour is pure profit for somebody, and enjoy your surfing. . account, which fills most of it in automatically. 18. 3. 3. Ethernet Connections The beauty of Ethernet connections is that they're super-fast and super-secure antenna, leaving the dial-up era behind. 18. 3. 1. Automatic Configuration The real beauty of most broadband connections these days is that they require