Ten Network Gizmos Only Big Networks Need

Gigabit Ethernet Most small networks operate just fine with standard 100BaseT Ethernet connections. However, if your network is large enough to merit a high-speed backbone connection, you may want to look into Gigabit Ethernet. Gigabit Ethernet is a relatively new version of Ethernet, which runs at 1000 Mbps instead of 100 Mbps. Gigabit Ethernet, also known as 1000BaseX, was initially designed to operate over fiber-optic cables but will eventually be able to work over Category-5 UTP cable as well. That’s one of the reasons you should take care to install only top-quality Category-5 cable and keep the cable lengths under 100 meters. Of course, Gigabit Ethernet is more expensive than 10BaseT or 100BaseT. A Gigabit Ethernet switch can cost several thousand dollars, and you need one at each end of the backbone. Storage Area Networks A storage area network, also called SAN, is designed for managing very large amounts of network storage — in some cases, downright huge amounts. A SAN consists of three components: storage devices possibly hundreds of them, a separate high-speed network usually fiber-optic that directly con- nects the storage devices to each other, and one or more SAN servers that connect the SAN to the local area network. The SAN server manages the stor- age devices attached to the SAN and allows users of the LAN to access the storage. Setting up and managing a Storage Area Network is a job for a SAN expert. If you’re interested, you can find more information about storage area net- works at the home page of the Storage Networking Industry Association at www.snia.org . Protocol Analyzer A protocol analyzer is a device that attaches to your network and examines all of the packets that are zipping along inside the cables. In the hands of a seasoned pro, a protocol analyzer can help diagnose all kinds of networking problems — performance problems, security breaches, broken connections, and so on. 375

Chapter 29: Ten Network Gizmos Only Big Networks Need

But to use a protocol analyzer, you need a low-level understanding of how networking works. You need to understand about protocols, the differences between the Data Link and MAC Layers of the OSI Model, and the details that lurk inside the packets that make up your network traffic. So although a protocol analyzer can be a nifty tool, it’s usually found only in the hands of network technicians who work with large networks. 376 Part VI: The Part of Tens Gadgets that used to be in this chapter Over the years, as I’ve revised this book to keep up with current technology, I’ve had the privi- lege of dropping items from this chapter. I’ve dropped some items because they aren’t even used in large networks anymore. Others I’ve dropped because their cost has come down so dramatically that they are now used in even the smallest networks or because their usefulness has grown to the point that they’re essential for almost every network. Here are a few of the goodies that I’ve retired from this chapter: ⻬ Fast Ethernet. When 100Mbps Ethernet was new, it was expensive enough that only large organizations could justify it. Now it’s dirt-cheap. Even the least expensive network cards and components support 100BaseT. So I’ve retired Fast Ethernet from this chapter. Gigabit Ethernet is another story. Most networks are fine with 100 Mbps; only really large networks need 1,000 times that much speed. ⻬ Switches. In the old days, inexpensive 10BaseT networks used cheap hubs, and switches were used only for large networks where network performance was a driving factor. However, the price of switches has come down so much lately that I now rec- ommend you build all 10BaseT networks using switches rather than hubs. ⻬ Routers. Routers were once required only for large networks. However, now that broad- band Internet access is the norm, many small networks — even networks with just two or three computers — use inexpensive routers to connect to the Internet. ⻬ Firewalls. Again, because of the prolifera- tion of cheap and fast Internet access, I can no longer say that only large networks need firewalls. Nowadays, any network that has a broadband Internet connection needs a firewall. ⻬ Superservers. This is one of my favorite archaic buzzwords. Once upon a time, com- puter makers coined this phrase to refer to big servers with multiple processors that could handle work that used to require sev- eral servers. The idea was that network servers would become more like the main- frame computers of old, where a single computer handled the workload for an entire organization. Fortunately, this idea didn’t catch on. Imagine if somebody pulled the plug . . . I almost dropped RAID from this chapter this time around. As the price of disk drives contin- ues to drop, RAID is becoming more and more common on smaller networks. Even inexpensive servers you can order over the Internet from companies such as Dell can be configured with built-in RAID. Chapter 30 Ten Layers of the OSI Model In This Chapter 䊳 The Physical Layer 䊳 The Data Link Layer 䊳 The Network Layer 䊳 The Transport Layer 䊳 The Lemon-Pudding Layer 䊳 The Session Layer 䊳 The Presentation Layer 䊳 The Application Layer O SI sounds like the name of a top-secret government agency you hear about only in Tom Clancy novels. What it really stands for, as far as this book is concerned, is Open System Interconnection, as in the Open System Interconnection Reference Model, also known as the OSI Reference Model or OSI Model depending on how pressed for time you are. The OSI Model breaks the various aspects of a computer network into seven distinct layers. These layers are kind of like the layers of an onion: Each suc- cessive layer envelops the layer beneath it, hiding its details from the levels above. The OSI Model is also like an onion in that if you start to peel it apart to have a look inside, you’re bound to shed a few tears. The OSI Model is not itself a networking standard in the same sense that Ethernet and TCPIP are. Rather, the OSI Model is a framework into which the various networking standards can fit. The OSI Model specifies what aspects of a network’s operation can be addressed by various network standards. So, in a sense, the OSI Model is sort of a standard’s standard. The first three layers are sometimes called the lower layers. They deal with the mechanics of how information is sent from one computer to another over a network. Layers 4 through 7 are sometimes called the upper layers. They deal with how applications relate to the network through application pro- gramming interfaces.