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Ethernet practical guide


On the face of it, networking can be somewhat intimidating. But it doesn't have to be that way. This Practical Guide to Plug-and-Play Ethernet Networks should answer any questions you have about how to get started building your own local area network.

Frequently Asked Networking Questions

Why should I invest in an Ethernet networking solution?
Networking of any kind - Ethernet or not - is a good idea. The low-tech alternative, commonly referred to as "sneakernet" - walking around with floppy disks to share, print or transfer files - is not only antiquated, it's very inefficient. Linking your company's computers, printers, servers and other peripheral equipment on a common system lets you and your co-workers share application programs, exchange files and swap data quickly, easily and reliably. Networks make electronic mail possible, they support server-based data back-ups, they provide access to the internet - in short, networks represent a highly productive way to do business that saves you considerable time and money. Plus, you always have immediate access to mission-critical information, which leads to better management and more efficient decision making - a distinct competitive advantage.

What if I already use AppleTalk or Arcnet - why should I switch to Ethernet?
Access methods such as 10 megabit-per-second (Mbps) Ethernet - as well as 16 Mbps Token Ring and 100 Mbps FDDI - are much faster than these proprietary solutions, letting you take full advantage of the performance benefits available with your computing resources. Not only that, these industry-standard protocols are widely used and supported, opening up a whole new set of options for future growth and expansion.

What is Ethernet?
Ethernet, as defined by the Institute of Electrical and Electronic Engineer's (IEEE) 802.3 standard, is an access method that determines how data, in the form of electrical signals, is transmitted across a physical cabling medium that connects computing devices. Ethernet conforms to the carrier sense multiple access with collision detection (CSMA/CD) network access protocol, which essentially allows any station on a network to transmit data at any time. If the network is busy - that is, if another station is already broadcasting - the transmitting station backs off and waits a random length of time (measured in milliseconds) before trying again. Once the network is clear, the station is free to send.

The IEEE 802.3 standard features several sub-specifications which define the specific cabling used by that particular Ethernet application. For instance, 10BASE-5 specifies the use of thick coaxial cabling; 10BASE-2 specifies thin coaxial cabling (like cable TV wire); and 10BASE-F, 10BASE-FB, 10BASE-FL and FOIRL all cover fiber optic cabling. Finally, the most popular method - IEEE 802.3I 10BASE-T - specifies the use of unshielded twisted pair data cabling with RJ45 data jacks for easy connections.

What do I need to build an Ethernet network?
At the very least, you need a network operating system that facilitates resource sharing. The network operating system defines the "language" used by the network to control input and output operations. This capability can either be built into the operating system (such as on Apple- and UNIX- based computers), or it can be an addition to the primary operating system (such as NetWare is added to DOS or MS Windows). In addition to the network operating system, you also need network interface cards (NICs) for all networked devices (PC's, servers, and others) to provide the appropriate connection to the LAN.

However, if you're just starting out, probably the most important piece of equipment you'll need is a "hub" - a device that, as the name implies, resides at the center of a network, where it provides a common link between users. Hubs come in a variety of sizes for supporting everything from small, low-density workgroups to large corporate-wide networks. You simply buy a hub that has enough connections, or "ports," to suit your current needs. As your requirements grow, you can easily add more hubs or other components such as bridges, routers or network management to keep data moving and help you maintain control over the system.

What's the benefit of using a hub?
Hubs offer a number of advantages. First, they implement networks in a "physical star" topology - just like the telephone system - in which all connections radiate out from a single location. This arrangement provides a central point for network installation, maintenance and management, allowing moves, additions and changes to be accomplished quickly and easily. The physical star topology also ensures that a problem on one device will not affect other users on the network. LED indicators on the hub alert you to these faults, helping you immediately identify and resolve problems on one link while the rest of the system continues running. Finally, hubs operate over a building's structured cabling system - in most cases, the unshielded twisted pair data cabling already installed in your office.

What exactly is a "plug-and-play" solution?
"Plug-and-play" means just what it says: a hub that requires little or no set up, preparation or configuration. Unshielded twisted pair 10BASE-T hubs are a good example; they use simple RJ45 connectors. You just install the hub in the wiring closet or on a desktop, plug in the connections (both at the hub and at the PC, server, printer or other piece of equipment) and turn it on. That's it - you're up and running. Networking doesn't get any easier.

What if my needs grow after I make my initial investment?
Then you simply expand the network by adding new hubs to support the additional load. Most hubs are designed to be "stackable" or "expandable" or "modular" - all just different ways to say that they can work together, seamlessly and transparently, to support your growing needs.

If the network grows too big and performance suffers noticeably, you can add other devices such as routers or bridges to divide, or segment, the system to give it a performance boost. If only very specific areas need the additional speed or bandwidth, you could upgrade to a new solution featuring high-speed 100 Mbps switched Ethernet, extending these capabilities to the overburdened workgroups. And if the network expands to the point that monitoring performance becomes too difficult, you can add network management to assist in the process. The key to this type of interoperability between devices is standards compatibility - adherence to industry standards that ensures everything speaks the same "language," or protocol. By using standards-based solutions, you can grow your network indefinitely - without sacrificing your original investments.

What is network management? And when would I need it?
Network management is an all-encompassing term that describes the ability to monitor network performance and activity, via software, to detect, locate and fix problems that adversely affect the network. A number of different management applications are available, offering capabilities ranging from simple to extremely complex. At the very least, a network management system should help you rapidly detect and isolate network errors such as excessive collisions, bad packets and the like - events that could indicate or lead to potentially larger problems. Determining whether you need network management depends on your requirements.

How can I begin planning a solution that's right for my company?
A variety of solutions are available for every size company. A reputable reseller can come to your place of business, evaluate your needs and recommend a solution that not only satisfies your existing requirements, but can also grow to support your expanding business.

Glossary of Terms

Asynchronous Transfer Mode (ATM) - A type of switching technology in which the switches are small, fixed-length cells containing data.

Backbone - A segment of network that links several individual workgroup or department LANs together in a single building. It is also used to link several building LANs together in a campus environment.

Bridges - Bridges filter packets between LANs by making a simple forward/don't forward decision on each packet they receive from any of the networks to which they are connected.

Carrier Sense Multiple Access with Collision Detection (CSMA/CD) - An element defined by the 802.3 specification. It is an access method which is used by stations connected to an Ethernet LAN. In this method each station contends for access to the shared medium.

Collision - When two stations try to send packets at the same time. In Ethernet networks, collisions are considered normal events and the CSMA/CD access method is designed to quickly restore the network to normal activity after a collision occurs.

Ethernet - The most popular LAN technology in use today.

Fiber Distributed Data Interface (FDDI) - LAN technology that runs at 100 Mbps over fibre, a much higher data rate than Ethernet or Token Ring. Originally FDDI networks required fiber optic cable, but today they can be run on UTP as well.

IEEE 802.3 - An Ethernet specification commonly defined by the Institute of Electrical and Electronic Engineers (IEEE). The 802.3 specification covers rules for configuring Ethernet LANs, the types of media that can be used, and how the elements of the network should interact.

Intelligent Hubs - Intelligent hubs are wiring concentrators which can be monitored and managed by network operators.

LAN Internetwork - Connecting disparate and geographically dispersed local area networks together to form an enterprise system.

Local Area Network (LAN) - A LAN is a high-speed communications system designed to link computers and other data processing devices together within a small geographic area such as a workgroup, department, or a single floor of a multi-story building.

Manageable Hubs -Another definition for intelligent hubs. Each of the ports on the managed hub can be configured, monitored, and enabled or disabled by a network operator from a hub management console.

Modular hubs -A modular hub starts with a chassis, or card cage, with multiple card slots, each of which can accept a communications card, or module. Each module acts like a stand-alone hub; when the communications modules are placed in the card slots in the chassis, they connect to a high-speed communications backplane that links them together so that a station connected to a port on one module can easily communicate with a station on another module.

Network Interface Card (NIC) - The physical connection from the computer to the network is made by putting a network interface card (NIC) inside the computer and connecting it to the shared cable.

Open Systems Interconnect Reference Model (OSI) - A communications model developed by the International Standards Organization (ISO) to define all of the services a LAN should provide. This model defines seven layers, each of which provides a subset of all of the LAN services. This layered approach allows small groups of related services to be implemented in a modular fashion that makes designing network software much more flexible.

Packet - In a shared media network, when one stations wishes to send a message to another station it uses the network software to put the message in an envelope. This envelope is called a packet.

Routers - Routers are more complex internetworking devices and are also typically more expensive than bridges. They use Network Layer Protocol Information within each packet to route it from one LAN to another.

Shared Media - Shared media technology means that all of the devices attached to the LAN share a single communications medium, usually a coaxial, twisted pair or fiber optic cable.

Shielded twisted pair (STP)- Cable which comes with a shielding around the cable to provide more protection against electromagnetic interference (EMI).

Stackable hubs - Stackable hubs look and act like stand-alone hubs except that several of them can be "stacked" or connected together, usually by short lengths of cable. When they are linked, they act like a modular hub in that they can be managed as a single unit.

Stand-alone hubs - Single box-level products with a number of ports. Stand-alone hubs usually include some method of linking them to other stand-alone hubs - either by connecting them together with a length of 10BASE-5 coaxial cable or cascading them using twisted pair between individual ports on each hub.

10BASE-T - The specification for running Ethernet on UTP. This stands for 10 Mbps, baseband signaling (the signaling method used by Ethernet networks), over twisted pair cable.

10BASE-5 - An Ethernet specifications which uses a thick coaxial cable. 10BASE-5 is seldom installed in new Ethernet networks today.

10BASE-2 - An Ethernet specification that uses a thin coaxial cable medium. 10BASE-2 is only used in very small office networks.

Token Ring - A major LAN technology in use today. Token Ring rules are defined in the IEEE 802.5 specification. Like Ethernet, the Token Ring protocol provides services at the Physical and Data Link Layers of the OSI model. Token Ring networks can be run at two different data rates, 4 Mbps or 16 Mbps.

Unshielded twisted pair (UTP)- UTP cable is similar to telephone cable, but has somewhat more stringent specifications regarding its susceptibility to outside EMI than common telephone wire. UTP is used much more often than STP.

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