What is networking?In the world of computers, networking is the practice of linking two or morecomputing devices together for the purpose of sharing data. Networks are builtwith a mix of computer hardware and computer software.Area NetworksNetworks can be categorized in several different ways. One approach defines thetype of network according to the geographic area it spans.Local area networks(LANs), for example, typically reach across a single home, whereas wide areanetworks (WANs), reach across cities, states, or even across the world.The Internet is the worlds largest public WAN.Network ProtocolsIn networking, the communication language used by computer devices is calledthe protocol. Yet another way to classify computer networks is by the set ofprotocols they support. Networks often implement multiple protocols to supportspecific applications. Popular protocols include TCP/IP, the most common protocolfound on the Internet and in home networks.Wired vs Wireless NetworkingMany of the same network protocols, like TCP/IP, work inboth wired and wireless networks. Networks with Ethernet cables predominated inbusinesses, schools, and homes for several decades. Recently, however, wirelessnetworking alternatives have emerged as the premier technology for buildingnew computer networks.Data communicationThe distance over which data moves within a computer may vary from afew thousandths of an inch, as is the case within a single IC chip, to as muchas several feet along the backplane of the main circuit board. Over suchsmall distances, digital data may be transmitted as direct, two-levelelectrical signals over simple copper conductors. Except for the fastestcomputers, circuit designers are not very concerned about the shape of theconductor or the analog characteristics of signal transmission.
DIFFERENT NETWORK TOPOLOGIESLAN NETWORKINGNETWORK TOPOLOGIESTOPOLOGY – defines the structure of the network. There are two parts to the topologydefinition: the physical topology which is the actual layout of the wire (media) and the logicaltopology which defines how the media is accessed by the hosts. It refers also to howcomputers are being connected with each other.The types of topologies:1. BUS TOPOLOGYIn the bus topology, the computers are connected through a common communication media. Aspecial type of central wire is used as communication media. This central wire is called Bus. Thecomputer are attached through the bus the ends of the bus are closed with the terminator .Theterminators are used to absorb signals. Bus topology use coaxial cables sections are connectedto the B. N. C connectors. B.N.C connectors are often use to connect the computer through themain cable. These connectors can connect through two section of cable with the bus extendingin both directions. The end device on the bus have the terminals on one connectors of T2.STAR TOPOLOGYThe star topology uses a separate cable for each work station as shown in fig.The cableconnects the work station to a central device typically a HUB. The configuration provides a morereliable network that is easily expended. With star there is no central point of failure in the cable.if there is a problem with the cable only the station connected to that cable is a effected .to addmore work stations simply connect another HUB3.RING TOPOLOGYIn ring topology each computer is connected to the next computer and the last computer isconnected to the first computer. Thus a ring of computers is formed as shown in figure below.4.MESH TOPOLOGYA mesh network or mesh topology uses separate cable to connect each device to every otherdevice on the network, providing a straight communication path
HOSTS – devices that connect directly to a network segment. These hosts includecomputers, both clients and servers, printers, scanners and many other devices. Thesedevices provide the users with connection to the network, with which the users share, createand obtain information.Network Interface Card (NIC) – is a printed circuit board that fits into the expansion slot of abus on a computer’s motherboard or peripheral device. It is considered to be found in Layer2 devices because each individual NIC throughout the world carries a unique code, calledthe Media Access Control (MAC) address.You can build computer networks with many different media types. Each media hasadvantages and disadvantages. What is an advantage for one media (category 5 cost) mightbe a disadvantage for another (fiber optic cost). Some of the advantages and disadvantagesare:CostEase of installationCable lengthREPEATER - is an electronic device that receives a signal and retransmits it at a higherlevel and/or higher power, or onto the other side of an obstruction, so that the signal cancover longer distances. It is used when the type of cable (CAT5 UTP) is long. CAT5 UTPhas a maximum length of 100 meters (approximately 333 feet). The purpose of a repeater isregenerate and retimes network signals at the bit level to allow them to travel a longerdistance on the media.HUB - is a device for connecting multiple twisted pair or fiber optic Ethernetdevices togetherand thus making them act as a single network segment.There are different classifications of hubs in networking:1. The first classification is active or passive. Most modern hubs are active; they take energyfrom a power supply to regenerate network signals. Some hubs are passive devicesbecause they merely split signal for multiple users, like using a “Y” cord on a CD player touse more than one set of headphones.2. Another classification of hubs is intelligent or dumb. Intelligent hubs have console ports,which mean they can be programmed to manage traffic in the network. Dumb hubs simplytake an incoming networking signal and repeat it to every port without the ability to do anymanagement.BRIDGE – refers to a device which has just two parts. It filters the frames and how this isactually accomplished.SWITCH – is to concentrate connectivity, while making data transmission more efficient. Adevice that is able to combine the connectivity of a hub with the traffic regulation of a bridgeon each port.ROUTER – the first device that you will work with that us at the OSI’s network layer, or otherknown as Layer 3. The purpose of a router is to examine incoming packets, choose the bestpath for them in a network and then switch them to the proper outgoing port
OSI modelThe Open Systems Interconnection (OSI) model is a product of the Open SystemsInterconnection effort at the International Organization for Standardization. It is a prescriptionof characterising and standardising the functions of a communications systemin termsof abstraction layers. Similar communication functions are grouped into logical layers. Alayer serves the layer above it and is served by the layer below it.OSI layersOSI ModelData unit Layer FunctionHostlayersData7. Application Network process to application6. PresentationData representation, encryption and decryption,convert machine dependent data to machineindependent data5. SessionInterhost communication, managing sessionsbetween applicationsSegments 4. TransportEnd-to-end connections, reliability and flowcontrolMedialayersPacket/Datagram 3. Network Path determination and logical addressingFrame 2. Data link Physical addressingBit 1. Physical Media, signal and binary transmissionLAN - Local Area NetworkA LAN connects network devices over a relatively short distance. A networkedoffice building, school, or home usually contains a single LAN, though sometimesone building will contain a few small LANs (perhaps one per room), andoccasionally a LAN will span a group of nearby buildings. In TCP/IP networking, aLAN is often but not always implemented as a single IP subnet.
In addition to operating in a limited space, LANs are also typically owned,controlled, and managed by a single person or organization. They also tend touse certain connectivity technologies, primarily Ethernet and Token Ring.WAN - Wide Area NetworkAs the term implies, a WAN spans a large physical distance. The Internet is thelargest WAN, spanning the Earth.A WAN is a geographically-dispersed collection of LANs. A network device calleda router connects LANs to a WAN. In IP networking, the router maintains both aLAN address and a WAN address.A WAN differs from a LAN in several important ways. Most WANs (like theInternet) are not owned by any one organization but rather exist undercollective or distributed ownership and management. WANs tend to usetechnology like ATM, Frame Relay and X.25 for connectivity over the longerdistances.Metropolitan Area Networka network spanning a physical area larger than a LAN but smaller than aWAN, such as a city. A MAN is typically owned an operated by a single entitysuch as a government body or large corporation. ADVANTAGES AND DISADVANTAGES OF ROUTERSAdvantage of Router -a) Router limits the collision domain.b) Router can function on LAN & WAN>c) Router can connects different media & architectures.d) Router can dtermine best path/route for data to reachthe destination.e) Router can filter the broadcasts.Disadvantage of Router -a) Router is more expensive than Hub, Bridge & Switch.b) Router only waork with routable protocol.c) Routing updates consume bandwidth.d) Increase latency due to greater degree of packetfiltering. ADVANTAGES AND DISADVANTAGES OF BRIDGESAdvantages of Bridge:· Simple bridges are inexpensive· Simple configuration modes· Isolate collision domains with micro-segmentation· It increase network length
· Access control and network management capabilities· Bandwidth scales as network growsDisadvantages of Bridge:· Does not limit the scope of broadcast· Does not scale to extremely large networks· Extremely large networks cannot rely on bridges· Buffering and processing introduces delays ADVANTAGES AND DISADVANTAGES OF HUBAdvantage:Hub is less expensive product.it is used for connect the multiple devices.Disadvantages:It will broadcast to all the portsIt runs half duplexIf 10 Ports in a hub it will share bandwidth of 100 MbPs.So each port share 10 MbpsMODEMA modem (modulator-demodulator) is a device that modulates an analog carrier signal toencode digital information, and also demodulates such a carrier signal to decode thetransmitted information. The goal is to produce a signal that can be transmitted easily anddecoded to reproduce the original digital data. Modems can be used over any means oftransmitting analog signals, from light emitting diodes to radio. The most familiar example isa voice band modem that turns the digital data of a personal computer intomodulatedelectrical signals in the voice frequency range of a telephone channel. Thesesignals can be transmitted over telephone lines and demodulated by another modem at thereceiver side to recover the digital data.SUBNETA subnetwork, or subnet, is a logically visible subdivision of an IP network.The practice ofdividing a network into two or more networks is calledsubnetting.All computers that belong to a subnet are addressed with a common, identical, most-significant bit-group in their IP address. This results in the logical division of an IP addressinto two fields, a network or routing prefix and the rest field or host identifier. The rest field isan identifier for a specific host or network interface.
Cisco Packet TracerCisco Packet Tracer is a powerful network simulation program that allows students toexperiment with network behavior and ask “what if” questions. As an integral part of theNetworking Academy comprehensive learning experience, Packet Tracer providessimulation, visualization, authoring, assessment, and collaboration capabilities and facilitatesthe teaching and learning of complex technology concepts. Packet Tracer supplements physical equipment in the classroom by allowingstudents to create a network with an almost unlimited number of devices,encouraging practice, discovery, and troubleshooting. The simulation-based learningenvironment helps students develop 21st century skills such as decision making,creative and critical thinking, and problem solving. Packet Tracer complements theNetworking Academy curricula, allowing instructors to easily teach and demonstratecomplex technical concepts and networking systems design.Packet Tracer featuresThe current version of Packet Tracer supports an array of simulatedApplication Layerprotocols, as well as basic routing with RIP, OSPF, and EIGRP, to the extent required by thecurrent CCNA curriculum. While Packet Tracer aims to provide a realistic simulation offunctional networks, the application itself utilizes only a small number of features foundwithin the actual hardware running a current Cisco IOS version. Thus, Packet Tracer isunsuitable for modeling production networks. With the introduction of version 5.3, severalnew features were added, including BGP. BGP is not part of the CCNA curriculum, but partof the CCNP curriculum.Packet TracerCisco Packet Tracer 5.0 in Windows 7OperatingsystemMicrosoftWindows and Debian-Like Linux