NETWORKING CONCEPTS Networking Hardware

Transmission media A medium of data transmission over a computer network is called a transmission medium. It can be guided (wired)or unguided (wireless)

Wired media Twisted pair Cable UTP(Unshielded Twisted Pair) STP(Shielded Twisted Pair) Coaxial Cable Optical Fibre Cable

Twisted pair It is widely used to transfer data over computer networks. It contains four twisted pairs covered in an outer shield . They are colour coded . These are more commonly used for connecting computers in small networks

shielded and Unshielded twisted pair cable

utp Low cost cable for small networks Thin, diameter approx 0.43cm & flexible Easy to install Can carry data upto 100cm

stp It offers better immunity against internal and external electromagnetic interferences It is expensive than UTP It is difficult to install

Co-axial cable

Co-axial cable It consists of two conductors that share a common axis. The inner conductor is a straight wire and the outer conductor is a shield that might be braided or a foil

characteristics It can carry data for a distance (185m-500m) Less susceptible to electromagnetic field Bulkier and less flexible than twisted pair Its thickness (1cm in diameter) Difficult to install.

Optical fibre cable

opticle Fibre cable Optical fibres are long and thin They are of the thickness of a human hair Used to transmit data through light signals over long distances. Core-It is the thin glass rod at the center through which the light travels Cladding- It is the outer optical material surrounding the core that reflects the light back into the core Buffer coating- It is the plastic coating that protects the cable from damage and moisture.

characteristics Not susceptible to electromagnetic fields It can carry data for a very large distance Not susceptible to electromagnetic fields Specially skilled people are required to install it Till date it is the most expensive and the most efficient cable available today for computer networks

Wireless media Electromagnetic waves are used for wireless communication networks. Based on their frequencies the waves are categorized into various categories. Radiowaves,microwaves,infrared radiation, visible light, ultraviolet ,X-rays and gamma rays.

radiowaves Frequency range 3 KHz to 3 GHz Used for communication over a distance from few meters upto covering an entire city These can penetrate through buildings easily Used in cordless phones, AM(Amplitude modulation) and FM(Frequency Modulation) radio broadcast, garage door openers etc.

characteristics Omni directional(generated in circular manner and spread all over) Inexpensive than wired media Offers ease of communication over difficult terrain Transmission can be interfered by motors or electrical equipments Less secured mode of transmission.

microwaves Frequency range of 300 MHz to 300 GHz Travel in straight lines and cannot penetrate any solid object, thats why for long distances communication ,high towers are built and microwave antennas are put on their tops.

Characteristics Relatively inexpensive than microwave media Transmission is in straight lines, antennas need to be properly aligned.

Infrared waves Frequency range of 300 GHz to 400 THz. Used for short range communication approx. 5m eg: remote control device, cordless mouse and intrusion detectors Cannot pass through solid objects or walls

characteristics It has line of sight transmission, so at a time only two devices can communicate with each other. Its performance drops with longer distances

Bluetooth Bluetooth technology uses radiowaves for the short range of communication of approx 10m CHARACTERISTICS Line of sight is not required It can connect upto eight devices together Slow data transfer rate(1Mbps)

Satellite These links are used for very long distance communication from intracity to intercontinental. Transmission from earth to a satellite is known as uplink, and transmission from satellite to earth is downlink

characteristics Satellites cover large area of earth This system is expensive

Network devices NIC(Network Interface Card)

Network Interface Card Any computer which is connected to computer network must have an NIC installed in it. A computer communicates with other computer with the help of NIC only.

HUB

hub A hub is an electronic device that connects several nodes to form a network and redirects the received information to all the connected nods in broadcast mode. Each computers NIC is connected to hub. Whenever a computer wants to send some information to other computer,NIC sends that information to hub. Then the hub retransmits this information to other computers.The intended node accepts it and others reject it.

switch A switch is an intelligent device that connects several nodes to form a network and redirects the received information only to the intended node.

repeater It is a device that is used to regenerate a signal which is on its way through a communication channel.A repeater regenerates the received signal and re- transmits it to its destination.

gateway A Gateway is a device ,which is used to connect different types of networks and perform the necessary translation so that the connected networks can communicate properly

Network topologies Node: Any device which is directly or indirectly connected to a computer network is called a node. A topology is an arrangement of physical connections among nodes in a network. Types of topologies are Bus Topology Ring Topology Star Topology Tree Topology

Bus topology

characteristics More efficient than bus Easy to install Easy to diagnose the fault Failure of hub/switch leads to failure of the system Requires more cable length than bus

bus

characteristics Easy to install Requires less cable length Failure of node does not affect the network If cable or terminator is at fault then the entire network stops working Fault diagnosis is difficult At a time only one node can transmit data.

Tree topology

characteristics Easy to expand the network If one network fails, other network is successfully working

Network protocols It is a set of rules for communication among networked devices. Protocols generally includes rules of how and when a device can send or receive the data, how is the sent data packaged and how it reaches its destination. Types of protocols are: HTTP TCP/IP PPP

http(hyper text transfer protocol) It is used to transfer all files and other data from one computer to another on the world wide web. When http client(browser) sends a request to http server(web server)

Tcp/ip(transmission control protocol) It is a basic protocol which is used by internet .It breaks into small packets and then it is reassembled at the receiving end. PPP(point to point protocol) It is a protocol for direct communication between two computers, It is direct communication between two computers. It is used for serial cable, Trunk line, Phone line, cellular phone.

Types of networks MAN PAN LAN WAN

MAC ADDRESS AND IP ADDRESS A MAC(Media Access Control) address is a unique 12 digit identifying manufacturer code(6 digits for manufacturer code and 6 digits for serial number) assigned to each NIC,MAC address of an NIC never changes. An IP address is a unique 4 digit hexadecimal number assigned to each node on a network.IP address settings of a node can be changed by the user.

Domain name resolution It is process of getting corresponding IP address from a domain name URL format http://www.cbse.nic.in

Network security Denial of Service attacks: Denial of access to information Denial of access to Application Denial of access to resources Denial of access to a website

Snooping & evesdropping Snooping is to gaining unauthorized access to another organization’s data. Evesdropping refers to gaining unauthorized access another person’s or organization’s data while the data is on its way on the network

How to protect the network login-password Firewall Anti Virus Software File permissions  Back up your files frequently.  Update your operating system regularly