Networking

Networking, in general, refers to the creation of networks. Network is a group of devices linked to one another. For example, network of telephones, or radio network or cable network etc. So, networking makes sharing of information and resources easier. 

Need for Networking

Networking is needed mainly to break the barrier of distance, time and cost. This is because communication via computers can be done to any distance in very short amount/span of time and in very cost-effective manner.

The need for networking can be summarized in these lines : the networking is needed because 

• it breaks the barriers of distance cost and time.
• it is very cost-effective as compared to telephone networks.
• all types of data viz. text, audio, pictures, graphics etc. can be transmitted through it

COMPONENTS OF NETWORK

When two persons talk to one another , one speaks and the other listens. The one who is speaking is the sender and the one who listens is the receiver of the information. But how is the data transferred in this case? What is the medium of tranmission? The medium is the the air. In networking it can be called the communication channel. So we can conclude from the above example that there are three components of the networking. These are:

• The Sender
• Communication Channel- the air
• The Receiver.

Proceeding in the same manner let us summarize the components of a computer network. 

COMPONENTS OF A COMPUTER NETWORK

A Computer network means interlinked computers. Computers can be interlinked directly also with the help of cables. In such a network there would be three components playing their roles( on the similar lines as illustrated in the figure: i) the sender computer, ii) the communication channel and, iii) the receiver computer. Computers can also be connected via telephone ao that telephone lines can work as 

communication channel for them. When computers are connected via telephones, an additional equipment called modem is required. It helps to convert the data signal generated by computers(digital signal) into the analog signal, carried by telephone cables. 

  On the receiver's end the modem first converts the received signal into computer's understable form   and then passes it to the computer.

   In such a network, there are five components playing these roles:

• Sender Computer  
• Sender eqipment (modem)    
• Communication channel (telephone cables)        
• Receiver eqipment (modem)          
• Receiver computer.

    The figure below illustrates this concept  

   

NETWORKING TRANMISSION MEDIA

In a data transmission system,the transmission medium is the physical path between transmitter and receiver.For guided media, electromagnetic waves are guided along a solid medium, such as copper twisted pair, copper coaxial cable, and optical fiber. For unguided media, wireless transmission occurs through the atmosphere, outer space, or water.The characteristics and quality of a data transmission are determined both bythe characteristics of the medium and the characteristics of the signal. In the case ofguided media, the medium itself is more important in determining the limitations oftransmission.For unguided media, the bandwidth of the signal produced by the transmittingantenna is more important than the medium in determining transmission character-istics. One key property of signals transmitted by antenna is directionality. In general, signals at lower frequencies are omnidirectional; that is, the signal propagates inall directions from the antenna. At higher frequencies, it is possible to focus the sig-nal into a directional beam.In considering the design of data transmission systems, key concerns are datarate and distance: the greater the data rate and distance the better. 

GUIDED / WIRED MEDIA

Guided Transmission Media uses a cabling system that guides the data signals along a specific path. The data signals are bound by the "cabling" system. Guided Media is also known as Bound Media or Wired Media. There are three basic types of Guided Media: 

1. Twisted Pair 
2. Coaxial Cable
3. Optical Fibre

1. Twisted Pair Cable

The most common form of wiring in data communication application is the twisted pair cable. In a twisted pair cable, wires are twisted together in pairs as shown in following figure. It may be used to transmit both analog and digital transmission. Foranalog signals, amplifiers are required about every 5 to 6 km. For digital transmis-sion (using either analog or digital signals), repeaters are required every 2 or 3 km.Compared to other commonly used guided transmission media (coaxial cable,optical fiber), twisted pair is limited in distance, bandwidth, and data rate.

                                       

                                              

2. Coaxial Cable

This type of cable consists of a solid wire core surrounded by one or more foil or wire shields, each seperated by some kind of plastic insulator. The inner core carries the signal, and the shield provides the ground. The coaxial cable has high electrical properties and is suitable for high speed communication. While it is less popular than twisted pair, it is widely used for television signals.Coaxial cable is perhaps the most versatile transmission medium and is enjoy-ing widespread use in a wide variety of applications.The most important of these are 

• Television distribution

• Long-distance telephone transmission

• Short-run computer system links

• Local area networks     

                                    

Coaxial cable is widely used as a means of distributing TV signals to individualhomes—cable TV. From its modest beginnings as Community Antenna Television(CATV), designed to provide service to remote areas, cable TV reaches almost asmany homes and offices as the telephone. A cable TV system can carry dozens oreven hundreds of TV channels at ranges up to a few tens of kilometers.Coaxial cable has traditionally been an important part of the long-distancetelephone network. 

3. Optical Fibre

An optical fiber is a thin (2 to 125m ), flexible medium capable of guiding anoptical ray. Various glasses and plastics can be used to make optical fibers. The lowest losses have been obtained using fibers of ultrapure fused silica. Ultrapure fiber is difficult to manufacture; higher-loss multicomponent glass fibers are more econom-ical and still provide good performance. Plastic fiber is even less costly and can beused for short-haul links, for which moderately high losses are acceptable.An optical fiber cable has a cylindrical shape and consists of three concentricsections: the core, the cladding, and the jacket.The core is the inner-most section and consists of one or more very thin strands, or fibers, made of glass orplastic; the core has a diameter in the range of 8 toEach fiber is surrounded by its own cladding, a glass or plastic coating that has optical properties differentfrom those of the core. The interface between the core and cladding acts as a reflec-tor to confine light that would otherwise escape the core. The outermost layer, sur-rounding one or a bundle of cladded fibers, is the jacket. The jacket is composed of plastic and other material layered to protect against    moisture, abrasion, crushing,and other environmental dangers.                                                                        

Optical Fibre

Unguided/ Wireless Media

Unguided or Woreless Transmission Media consist of a means for the data signals to travel but nothing to guide them along a specific path. The data signals are not bound to cabling media and as such are often called Unbound Media.


1.)Microwave : Electronic waves with frequencies between 1 GHz to 300GHz are normally called microwaves.Unlike radio waves, microwaves are unidirectional, in which the sending and receiving antennas need to be aligned.Microwaves propagation is line-of-sight therefore towers withmounted antennas need to be in direct sight of each other.Due to the unidirectional property of microwaves, a pair of antennas can be placed aligned together without interfering with another pair of antennas using the same frequency.Two types of antenna are used for microwave communications. They are:      
2.) Radio Wave:  Radio waves are normally omnidirectional. When anantenna transmits radio waves, they are propagated inall directions. This means that the sending and receiving antennas do not have to be aligned.The omnidirectional characteristics of radio waves make them useful for multicasting, in which there is one sender but many receivers. Our AM and FM radio stations,cordless phones and televisions are examples of multicasting.

3.) Satellite: Satellite networking is an exciting and expanding field that has evolved significantly since the launch of the first telecommunications satellite, from telephone and broadcast to broadband ATM and Internet. With increasing bandwidth and mobility demands on the horizon, satellites have become an integral part of the Global Network Infrastructure (GNI). Satellite Networking: Principles and Protocols provides a balanced coverage of satellite topics from a network point of view, focusing on network aspects, services and applications, quality of service (QoS) and principles and protocols. 

• Introduces the basics of ATM and internet protocols, and characteristics of satellite networks and       internetworking between satellite and terrestrial networks.
• Discusses the real-time protocols including RTP, RTCP and SIP for real-time applications such as VoIP and MMC. 
• Coverage of new service and applications, internet traffic engineering and MPLS.
• Examines IPv6 over satellite using tunnelling and translation techniques, evolution of earth  stations, user terminals and network protocols, and development of satellite networking.

4.) Infrared: Infrared transmission refers to energy in the region of the electromagnetic radiation spectrum at wavelengths longer than those of visible light, but shorter than those of radio waves. Correspondingly, infrared frequencies are higher than those of microwaves, but lower than those of visible light.

Scientists divide the infrared radiation (IR) spectrum into three regions. The wavelengths are specified in microns (symbolized µ, where 1 µ = 10-6 meter) or in nanometers (abbreviated nm, where 1 nm = 10-9 meter = 0.001 5). The near IR band contains energy in the range of wavelengths closest to the visible, from approximately 0.750 to 1.300 5 (750 to 1300 nm). The intermediate IR band (also called the middle IR band) consists of energy in the range 1.300 to 3.000 5 (1300 to 3000 nm). 

Infrared is used in a variety of wireless communications, monitoring, and control applications. 

5.) Bluetooth: Bluetooth is a short-range wireless technology that lets you connect computers, mobile phones, and handheld devices to each other and to the Internet. Bluetooth technology eliminates the need for the cables that connect devices together. Bluetooth enabled devices connect wirelessly within a 10 m range. Many companies have been mulling over this idea, but it was Ericsson Mobile Communication that finally (in 1994) started the project that was named Bluetooth.The aim has been set quite hight. It is to arrive at a specification for a technology that optimizes the usage model of all mobile computing and communications devices and much more.

6.)Wi-Fi:  Wi-Fi is increasingly becoming the preferred mode of internet connection all over the world. To access this type of connection, one must have a wireless adapter on their computer. Wi-Fi provides wireless connectivity by emitting frequencies between 2.4GHz to 5GHz based on the amount of data on the network. Areas which are enabled with Wi-Fi connectivity are known as Hot Spots. One can use advanced softwares like Wirelessmon to detect and request connection to Hotspots. To start a Wireless connection, it is important that the wireless router is plugged into the internet connection and that all the required settings are properly installed.