LAN devices
Today, LANs use sophisticated programs that permit several users to work with the same resources at the same time. This can include hard disk drives, printers, plotters, software, etc. LANs are composed of various components performing specific tasks so each user can access shared resources. Generally, every component in a network is called a node. Each node is further identified by the specific task it performs.
A user’s node is called a terminal or a workstation. This can be a “dumb” device, meaning it has no operating system, just a monitor and keyboard, or a “smart” node, meaning it can do it’s own computing because of an internal central processor.
A server is a node on the network that provides services to the users of that network. A server will manage hardware and software resources or monitor the exchange of information through a network. Each server will respond to the requests of a user and provide a service, like printing a document or retrieving a stored file. There are two basic types of servers: Dedicated and Non-dedicated. A dedicated server performs a specific task or function all the time where as a non-dedicated server functions in other capacities. A network with servers that are strictly dedicated is called a Client-Server Network. A network where services are provided by user’s workstations is a Peer-to-Peer Network.
The advantages of a Client-Server Network are better performance and Network security administration is easier to maintain. Disadvantages include users not being able to directly share resources on the workstations and network failure due to server failure. Advantages of a Peer-to-Peer Network include flexibility to share resources from any workstation and ability to distribute network applications throughout the network for better performance. Disadvantages include network security is difficult to manage and non-dedicated servers slow workstation performance down.
Servers are identified by the service they provide. A disk server might contain several CDs or Hard Drives with applications to be shared across the network. A file server usually stores files and folders and provides the core services of a network.
In order for any workstation to be able to connect to a network it will need an access point. This is normally known as a Network Interface Card (NIC). NICs provide signal and protocol conversion between network adapters and the transmission media. Signal conversion is accomplished by the Media Attachment Unit (MAU), while protocol conversion is the job of the Host Access Unit (HAU). NICs can support a variety of modes, including Ethernet, Token Ring, fiber optics, and wireless networks.
A workstation can also connect remotely via a public switched telephone network using a Modulator/Demodulator (Modem). These can be either internal or external, although they are more commonly found to be internal. Modems must always operate in pairs. A second modem must be connected to the distant end of the communications link to demodulate the signal. They must also operate under the same protocol.
Repeaters allow a network to extend to distances not normally allowable by using cabling alone. Signals sent through cables are affected by noise and will degenerate in proportion to the length of the cable. This distance varies depending on the cabling standard being used. Repeaters regenerate the signal and then retransmits it to the rest of the network. It is basically a dumb device because doesn’t modify the signal in any way, it only repeats it.
Another important node on a network is the hub, also known as a wiring hub or concentrator. These devices centralize the network’s wiring, making it easier to manage. All devices are connected via point-to-point link to the hub allowing multiple nodes to share the same connection to the network.
Routers allow intranetwork connections to take place. When connecting one or more LANs to each other, a router is used to separate them as well as to analyze current traffic conditions and determine the best route for a packet to take. Routers look at the entire address, to include the network address and the node address attached to each packet to determine it’s destination. If a router determines the packet is destined for a different type of node than what it originated from it will pass it on to a gateway. Gateways are devices that allow for dissimilar nodes on a network to be able to communicate with each other by acting as a translator or interpreter.
Of course all this hardware would be useless without the cable to connect it all together. Cables come in different standards: Ethernet, Token Ring, and ARCnet. Ethernet is, by far, the most commonly used standard in the world. It’s implementation consists of 10Base5, 10Base2, 10BaseT, 100BaseT, and 10BaseF. The first number represents the bandwidth of the cable. This is to say if you’re on a backbone that will transmit data at 10 Mbps the first number will be 10, 100 Mbps will make the first number 100, and so on. The Base means it’s a Baseband transmission method. Many people have heard of Broadband, where the signal is analog, well, Baseband is a digital signal. The last number represents the distance, in meters, the signal can travel without the need to be repeated. 2 stands for 200, 5 for 500, and T for 100. F is used for fiber optic cable and it’s effective range is 2000 meters.
LAN TOPOLOGY
After all the hardware is selected the topology must be designed. There are three basic architectures a network can be configured in. The first is the star, where all computers are connected in a point-to-point manner to a central computer or hub. The second is the bus network, the most common LAN, where each node is connected to, and shares, a backbone. The ring is the final topology. Nodes are set up in a ring formation with information passing from one computer to the other all the way around until it reaches the computer who originated the signal. This is the most advantageous of all three topologies since each node actually regenerates the signal when it is received before passing it on to the next node.
NETWORK SOFTWARE AND PROTOCOLS
After the network is complete you will need to install all necessary software to get the network up and running. Network software came along in 1984 with IBM’s Network Basic Input/Output System (NETBIOS). This was the first rationalization of a PC networking software creating a point-to-point communication between computers. Of course, each computer needed it’s own operating system. Enter MS-DOS. With the release of Microsoft’s MS-DOS 3.1 in late 1984, the concept of accessing files on a remote server, simultaneously with other users became a possibility. This, of course, led to the creation of a network operating system, necessary to use any network. Novell Netware, one of the most portable network operating systems, was the first to take advantage of the new technology. What protocols are used in a network is very important in selecting a network operating system. The most commonly used protocols are TCP/IP and IPX/SPX. Microsoft, of course, has it’s own protocol, NETBeui, but this is a non-routable protocol so it can only be used in LANs and not MANs or WANs. Today, the most commonly used network operating systems are Windows NT and 2000, as well as Sun Microsystems Solaris 8. There are advantages and disadvantages to each, but they are too extensive to go into detail. For the purpose of this paper we will consider them equal.
Well, now we have all necessary hardware and software, so putting together a network should be easy as pie, right? Right…
