Networking

     

Network

       The ability to expend beyond the limit of a single computer in a single office has expended the reach of the PC to global proportions. Two technologies have driven this expansion: computer networking and the portable computer. In this topic, we first take a look at how the networks that link up computers on a global scale are put together. Then we examine the portable computer, whose introduction has allowed users instantaneous access to the computing and networking power of all the latest computer technology anywhere they go.

A network is defined as two or more computer linked together for the purpose of communicating and sharing information and other resources.

Basic Requirements Of a Network

            In order for a network to function, three basic requirements must be met. It must provide connections, communications and services.

Connections

            Connections include the hardware (physical components) required to hook up a computer to the network. Two terms are important to network connections.

The network medium: 

          The network hardware that physically connects one computer to another. This the cable between the computers.

The network interface: 

          The hardware that attaches a computer to the network medium and acts as an interpreter between the computer and the network. Attaching a computer to a network requires an add in board known as a network interface card (NIC)

Communications

            Communications establish the rules concerning how computers talk and understand each order. Because computers often run different software, in order to communicate with each other they must speak a “shared Language” Without communications, computers cannot exchange information and remain isolated.

Services

            A service defines those things a computer shares with the rest of the network. For example, a computer can share a printer or specific directories or files. Unless computers on the network are capable of sharing resources, they remain isolated, even though physically connected.

  Networking

            Next we look at how the basic elements of connections, communications, and services work together to make networks function property

·         The connections must operate so that any computer can send to receive electrical signals   (data) across the physical media that link them

·     Communications must function so that when one computer sends a message, the receiving  computer can listen and understand the message.

·        Computers on a network must either provide a services to other computers or make use of a service provide be other computers.

Local Area Networks

            A LAN (Local Area Network) is a network that covers a limited distance (usually a single site of facility) and allows sharing of information and resources. A LAN can be as simple as two connected computers, or as complicated as a large site. This type of network is very popular because it allows individual computers to provide processing power and utilize their own memory, while programs and data can be stored on any computer in the network. Some of the older LANs also include configurations that rely totally on the power of a mini or mainframe computer (a server) to do the entire network. In this case the workstations are no more than “dumb” terminals (a keyboard and a monitor)

Wide Area Networks

            A wide area network (WAN) spans relatively large geographical areas. Connections for these sites require the use of ordinary telephone lines, T1 lines, ISDN (Integrated Services Digital Network) lines, radio waves or satellite. WANs can be accessed though dail-up connections using a modem or leased line direct connection. The leased-line method is more expensive but can be cost effective for transmission of large volumes of data.

Types of Networks

            There are essentially two types of networks. They differ in how information is stored how security is handled, and how the computers on the network interact. In a peer to peer network, each computer acts as either a server (sharing its data or services with other computers), or a client (using data or services on another computer depending on the user’s needs. Each user, or workstation, established its own security and determines which resources are available to other users. Typically these networks are limited in size (15 to 20 workstation). MS Windows for workgroups, Windows 95, and windows 98, Windows NT workstation, Windows 2000, Novell NetWare, UNIX are Linux are some software packages available for peer-to-peer networking.

Network Topology

            LAN design is called topology. Topology describes he appearance or layout of a network and how data flows through the network. There are three basic types of topologies, Star , bus, Ring.

Star Topology

            In a star network, all devices are connected to a central point called a hub. These hubs collect and distribute the flow of data within the network. Signals from the sending computer go to hub and are then transmitted to all computers on the network. Large networks can feature several hubs. A star network is easy to troubleshoot because all information goes through the hub, making it easier to isolate problems.

Bus Topology

             In a bus network, all devices are connected to a single linear cable called a trunk (also known as a backbone or segment). Both ends of the cable must be terminated (like a SCSI bus) to stop the signal from bouncing. Because a bus network does not have a central point, it is more difficult to troubleshoot than a star network. A break or problem at any point along bus can cause the entire network to go down.

Ring Topology

            In ring topology the first computer connected with second computer. The second computer connected to with third computer similarly the last computer connected with first computer. This loop of computer is also called ring topology. In ring topology optic fiber is used.

 Network Cabling

            All networks need cables. The three main type are twisted pair cable (TP), coaxial cable, and fiber optic cable (FDDI-Fiber Distributed Data interface).

Twisted Pair Cable

          

  Twisted Pair Cable consists of two insulated of copper wire twisted around each other to form a pair one or more twisted pairs are used in a twisted pair cable. The purpose of twisting the wires is to eliminate electrical interference from other wires and outside sources. Twisted pair wiring comes in two types: shielded (STP) and unshielded (UTP). STP has a foil or wire braid wrapped around the individual wires of the pairs; UTP does not the STP cable uses a woven-copper braided jacket, which is a higher quality, more protective jacket than UTP.

            Of the two types, UTP is the most common. UTP cables can be further divided into six categories.

Ø  Traditional telephone cable. Carries voice but not data.

Ø  Certified UTP for data transmission of up to 4 Mbps (megabits per seconds). It has four twisted pairs.

Ø  Certified UTP for data transmission of up to 10 Mbps. It has four twisted pairs

Ø  Certified UTP for data transmission up to 16 Mbps. It has four twisted pairs.

Ø  Certified UTP for data transmission up to 100 Mbps. It has four twisted pairs.

Ø  Certified UTP for data transmission up to 1000 Mbps. (Gigabit Ethernet)  It has four twisted pairs.

CAT 5 Cabling Issues

            

          Distance Limitations

                        Ethernet networks use unshielded twisted pair (UTP) category 5 cables. CAT 5 cable runs should not exceed 100 meters.

CAT 6 Cabling Issues

            Distance Limitations

                        CAT 6 used to carry Ethernet 10base-T, 100Base-T, and 1000Base-T (Gigabit Ethernet) connections. Cat 6 cable is backed with more stringent specifications for crosstalk and system noise than earlier cabling standards.

Connectors

            There are two different types of RJ 45 connectors. There is the “bent tyne” connector intended for use with solid core CAT5, and then there is the “aligned tyne” connector for use with stranded CAT5 cable.

Wiring/Color Coding for CAT5 and CAT6 Cable

CAT5 cables are typically terminated with RJ-45 connectors. Two types of RJ-45 connectors.

Two wires color-code standard apply: EIA/TIA 568A and EIA/TIA 568B. The codes are commonly dedicated with RJ-45 jacks as follows (the view is from the front of the jacks).

Coaxial Cable

           

Coaxial cable is made of two conductors that share the same axis; the center is a copper wire that is insulated by a plastic coating and then wrapped with an outer conductor (usually a wire braid). This outer conductor around the insulation serves as electrical shielding for the signal being carried by the inner conductor. Outside the outer conductor is a tough insulating plastic tube that provides physical and electrical protection. At one time, coaxial cable was the most widely used network cabling. However, with improvements and lower cost of twisted pair cables, it has lost its popularity.

Coaxial cable is found in two types thin (Thin Net) and thick (Thick Net). Of the two Thin Net is the easiest to use. It is about one quarter of an inch in diameter, making it flexible and easy to work with (it is similar to the material commonly used for cable TV). Thin Net can carry a signal about 605 feet (185 meters) before the signal strength begins to suffer. Thick Net on the other hand is about three eigths of an inch in diameter. This makes it a better conductor it can cary a signal about 1640 feet (500 meters) before signal strength begins to suffer.

Fiber Optic Cable

            Fiber Optic cable is made of light conducting or plastic fibers. It can carry data signals in the form of modulated pulses of light. The plastic core cable are easier to install, but do not carry signals as far as glass core cables. Multiple fiber cores can be bundled in the center of the protective tubing.

Fiber Optic Cable

       When both material and installation costs are taken into account, fiber optic cable can prove to be no more expensive than twisted pair or coaxial cable. Fiber has some advantage a reliable and secure transmission media. It also supports very high bandwidths (the amount of information the cable can carry), so it can handle thousands of times more data than twisted pair or coaxial cable.

Cable lengths can run from .25 to 2.0 kilometers depending on the fiber optic cable and network. If you need to network multiple buildings, this should be the cable of choice. Fiber optic cable systems require the use of fiber compatible NICs.