NETWORK A Computer Network, or simply a Network, is a collection of computers and other hardware interconnected by communication channels that allow sharing of resources and information. A network is a group of devices connected to each other. Networks may be classified into a wide variety of characteristics, such as the medium used to transport the data, communications protocol used, scale, topology, benefit, and organizational scope.
NETWORK CLASSIFICATION A local area network (LAN) is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building using network media. A metropolitan area network (MAN) are high speed networks that connects LAN’s in a metropolitan area. Managed by a consortium of users or a single network provider. A Wide Area Network (WAN) is a network that covers a broad area i.e. any telecommunications network that links across metropolitan, regional, or national boundaries.
NETWORK TOPOLOGYNetwork topology is the arrangement of the various elements(links, nodes, etc.) of a computer or a biologicalnetwork. Essentially it is the topological structure of a networkand may be depicted physically or logically. Topologies areeither: Physical Logical
TYPES OF PHYSICAL TOPOLOGY Point to Point Bus Star Ring Mesh Tree Hybrid
POINT TO POINTPoint-to-Point topology is a point-to-point communicationchannel that appears to the user to be permanentlyassociated with the two endpoints. A tin can telephone is thebest example.
BUSAll computers and devices are connected to single cable orBUS. It consists of a main run of cable with a terminator ateach end. It is popular on LANs as they are inexpensiveand easy to install.
STARIn local area networks with a star topology, each network host isconnected to a central hub with a point-to-point connection. In Startopology every node is connected to central node called hub or switch.
RINGA network topology that is set up in a circular fashion in whichdata travels around the ring in one direction and each deviceon the right acts as a repeater to keep the signal strong as ittravels. Each device incorporates a receiver for the incomingsignal and a transmitter to send the data on to the next devicein the ring.
MESHIn mesh topology each computer is connected to each other byseparate cables. There is a point tom point connectionbetween each node.This type of topology is generally used in military area.
TREEThe type of network topology in which a central root node (the top level ofthe hierarchy) is connected to one or more other nodes that are one levellower in the hierarchy (i.e., the second level) with a point-to-point linkbetween each of the second level nodes and the top level central rootnode
HYBRIDHybrid networks use a combination of any two or moretopologies in such a way that the resulting network doesnot exhibit one of the standard topologies.
ADVANTAGES AND DISADVANTAGES OFTHE 4 MOST COMMONLY USEDNETWORK TOPOLOGIES
BUS TOPOLOGYAdvantages Easy to connect a computer or peripheral to a linear bus. Requires less cables than any other topologies. Doesn’t requires any specialized network equipment.Disadvantages Difficult to trouble shoot. Network disruption when more computers are added to it. A break in the cable will prevent all systems from accessing the network.
RING TOPOLOGYAdvantages Cable faults are easily located making trouble shooting easier Ring networks are moderately easily to install.Disadvantages Expansion to the network can cause network disruption A single break in the cable can disrupt the entire network
MESH TOPOLOGYAdvantages Provides redundant path between the devices Network can be expanded without any inconvenience to current user.Disadvantages Requires more cables than any other toplology Complicated implementations
STAR TOPOLOGY ADVANTAGES Easy to install and wire. Security can be implemented in the hub/switch. Easy to detect faults and remove parts. DISADVANTAGES Requires more cable length. If the hub or concentrator fails nodes attached are disabled More expansive due to he cost of concentrators associated with it.
NETWORKING DEVICESNetworking devices typically refers to hardware that facilitatesthe use of a computer network. Computer networkingdevices are units that mediate data in a computernetwork. Some of the networking devices are: Gateway Router Switch Bridge Hub Repeater Multiplexer Modem
GATEWAYA device sitting at a network node forinterfacing with another network that usesdifferent protocols.
ROUTER A specialized network device that determinesthe next network point to which it can forward adata packet towards the destination of thepacket.
SWITCHA device that allocates traffic from one networksegment to certain lines (intended destinations)which connect the segment to another networksegment.
BRIDGEA device that connects multiple networksegments along the data link layer.
HUBA device connects multiple Ethernet segments togethermaking them act as a single segment. When using a hub,every attached device shares the same broadcast domain andthe same collision domain. Therefore, onlyone computer connected to the hub is able to transmit at atime.
REPEATERA device to amplify or regenerate digital signalsreceived while sending them from one part of anetwork into another.
MULTIPLEXERA device that combines several electricalsignals into a single signal.
MODEMA device that modulates an analog "carrier" signal (such assound), to encode digital information, and that alsodemodulates such a carrier signal to decode the transmittedinformation, as a computer communicating with anothercomputer over the telephone network.
BROUTERBrouters are a combination of router and bridge. ABrouter transmits two types of traffic at the exact sametime: bridged traffic and routed traffic.
NETWORK INTERFACE CARDNetwork Interface Card, or NIC is a hardware card installedin a computer so it can communicate on a network. Thenetwork adapter provides one or more ports for the networkcable to connect to, and it transmits and receives data ontothe network cable. Network Card Wireless LAN Card
TRANSCEIVERSTransceiver short for transmitter-receiver, a device that bothtransmits and receives analog or digital signals. The term isused most frequently to describe the component in local-areanetworks that actually applies signals onto the network wire anddetects signals passing through the wire. For many LANs, thetransceiver is built into the network interface card.
FIREWALLFirewall is a piece of hardware and/or software whichfunctions in a networked environment to prevent somecommunications forbidden by the security policy, analogousto the function of firewalls in building construction.
PROXIES A proxy device acts as a firewall by responding to input packets (connection requests, for example) in the manner of an application, whilst blocking other packets. A proxy server acts as an intermediary for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource available from a different server and the proxy server evaluates the request as a way to simplify and control their complexity
NETWORKING CABLESNetworking cables are used to connect one networkdevice to other network devices or to connect two or morecomputers to share a printer, scanner etc. Different typesof network cables like Coaxial cable, Optical fibre cableetc. Optical fibre Ethernet cable Coaxial cable