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![COMPUTER NETWORKS
UNIT - I [12 Hours]
Introduction: Data Communications
Computer Networks and its applications,
Network structure, network architecture,
Topologies, LAN, WAN, MAN, The OSI reference
model, The TCP/IP reference model](https://image.slidesharecdn.com/presentation1networking-231222141934-40e35673/75/Presentation1-Networking-pptx-1-2048.jpg)
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- 1. COMPUTER NETWORKS UNIT -I [12 Hours] Introduction: Data Communications Computer Networks and its applications, Network structure, network architecture, Topologies, LAN, WAN, MAN, The OSI reference model, The TCP/IP reference model
- 2. Course Outcomes (COs): Explain the transmission technique of digital data between two or more computers and a computer network that allows computers to exchange data. Apply the basics of data communication and various types of computer networks in real world applications. Compare the different layers of protocols. Compare the key networking protocols and their hierarchical relationship in the conceptual model like TCP/IP and OSI
- 3. Agenda Definitions Applications Network Structure
- 4. DATA & INFORMATION Datarefers to the raw facts that are collected while information refers to processed data that enables us to take decisions. Ex. When result of a particular test is declared it contains data of all students, when you find the marks you have scored you have the information that lets you know whether you have passed or failed. The word data refers to any information which is presented in a form that is agreed and accepted upon by is creators and users.
- 5. DATA COMMUNICATION DataCommunication is a process of exchanging data or information, In case of computer networks this exchange is done between two devices over a transmission medium. This process involves a communication system which is made up of hardware and software. The hardware part involves the sender and receiver devices and the intermediate devices through which the data passes. The software part involves certain rules which specify what is to be communicated, how it is to be communicated and when. It is also called as a Protocol.
- 6. Characteristics The effectiveness ofany data communications system depends upon the following four fundamental characteristics: 1. Delivery: The data should be delivered to the correct destination and correct user. 2. Accuracy: The communication system should deliver the data accurately, without introducing any errors. The data may get corrupted during transmission affecting the accuracy of the delivered data. 3. Timeliness: Audio and Video data has to be delivered in a timely manner without any delay; such a data delivery is called real time transmission of data. 4. Jitter: It is the variation in the packet arrival time. Uneven Jitter may affect the timeliness of data being transmitted.
- 7. Components ofData Communication A Data Communication system has five components as shown in the diagram below:
- 8. 1.Message 2.Sender 3.Receiver 4.Transmission Medium 5.Set ofrules (Protocol)
- 9. Message : Thisis most useful asset of a data communication system. The message simply refers to data or piece of information which is to be communicated. A message could be in any form, it may be in the form of a text file, an audio file, a video file, etc. Sender : To transfer message from source to destination, someone must be there who will play role of a source. Sender plays part of a source in data communication system. It is simple a device that sends data message. The device could be in form of a computer, mobile, telephone, laptop, video camera, or a workstation, etc. Receiver : It is destination where finally message sent by source has arrived. It is a device that receives message. Same as sender, receiver can also be in form of a computer, telephone mobile, workstation, etc.
- 10. Transmission Medium: In entire process of data communication, there must be something which could act as a bridge between sender and receiver, Transmission medium plays that part. It is physical path by which data or message travels from sender to receiver. Transmission medium could be guided (with wires) or unguided (without wires), for example, twisted pair cable, fiber optic cable, radio waves, microwaves, etc. Set of rules (Protocol) : To govern data communications, various sets of rules had been already designed by the designers of the communication systems, which represent a kind of agreement between communicating devices. These are defined as protocol. In simple terms, the protocol is a set of rules that govern data communication. If two different devices are connected but there is no protocol among them, there would not be any kind of communication between those two devices. Thus the protocol is necessary for data communication to take place.
- 11. Transmission mode meanstransferring data between two devices. It is also known as a communication mode
- 12. 1. Simplex Mode– In Simplex mode, the communication is unidirectional, as on a one-way street. Only one of the two devices on a link can transmit, the other can only receive. The simplex mode can use the entire capacity of the channel to send data in one direction. Example: Keyboard and traditional monitors. The keyboard can only introduce input, the monitor can only give the output. 2. Half-Duplex Mode – In half-duplex mode, each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa. The half-duplex mode is used in cases where there is no need for communication in both directions at the same time. The entire capacity of the channel can be utilized for each direction. Example: Walkie-talkie in which message is sent one at a time and messages are sent in both directions.
- 13. 3. Full-Duplex Mode– In full-duplex mode, both stations can transmit and receive simultaneously. In full_duplex mode, signals going in one direction share the capacity of the link with signals going in another direction, this sharing can occur in two ways: •Either the link must contain two physically separate transmission paths, one for sending and the other for receiving. •Or the capacity is divided between signals traveling in both directions. Full-duplex mode is used when communication in both directions is required all the time. The capacity of the channel, however, must be divided between the two directions. Example: Telephone Network in which there is communication between two persons by a telephone line, through which both can talk and listen at the same time.
- 14. NETWORK A network isa set of devices (often referred to as nodes) connected by communication links. Or a network is simply two or more computers that are linked together. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network. Benefits of a Network: Information sharing – Authorized users can use other computers on the network to access and share information and data. This could include special group projects, databases, etc. Hardware sharing – One device connected to a network, such as a printer or a scanner, can be shared by many users. Software sharing – Instead of purchasing and installing a software program on each computer, it can be installed on the server. All of the users can then access the program from a single location. Collaborative environment – Users can work together on group projects by combining the power and capabilities of diverse equipment. Network Criteria: A network must meet the following network criteria: Performance – It measured by transit time and response time[also depends on users, medium, hardware, software. Reliability – It measured by the frequency of failure. Security – It protecting data from unauthorized access.
- 16. Risks ofnetwork computing: The security of a computer network is challenged every day by: Equipment malfunctions System failures Computer hackers Virus attacks
- 17. Network Connection Types There are different types of communications connection in existence between two endpoints., Home networks, and the Internet is the one of the most commonly used examples. Many type of devices are and several different methods are used connecting to these type of network architectures. There are different advantages and disadvantages to this type of network architectures. Connecting computers to a these type of networks, we requires some networking framework to create the connections. The two different computer network connection types are getting discussed in this page are Point-to-Point Connection and multipoint connection. The main difference between them we can getting discussed with the help of below definition. Point-to-point connections allow one device to communicate with one other device. For example, two phones may pair with each other to exchange contact information or pictures. Multipoint connections allow one device to connect and deliver messages to multiple devices in parallel.
- 18.
- 19. TYPES OF COMPUTERNETWORKS There are Three main types of Computer Networks:
- 20. Local Area Network(LAN) Connection of computer in limited range(Builiding,College,Bank) Sharing the resources: Printer Software Application Data High Security Lack of Privacy
- 21. 1. Local areanetwork is a group of computers connected with each other in a small places such as school, hospital, apartment etc. 2. LAN is secure because there is no outside connection with the local area network thus the data which is shared is safe on the local area network and can’t be accessed outside. 3. LAN due to their small size are considerably faster, their speed can range anywhere from 100 to 100Mbps. 4. LANs are not limited to wire connection, there is a new evolution to the LANs that allows local area network to work on a wireless connection.
- 22. Metropolitan Area Network(MAN) MAN network covers larger area by connections LANs to a larger network of computers. In Metropolitan area network various Local area networks are connected with each other through telephone lines. The size of the Metropolitan area network is larger than LANs and smaller than WANs(wide area networks), a MANs covers the larger area of a city or town.
- 23. Wide area network(WAN) Wide area network provides long distance transmission of data. The size of the WAN is larger than LAN and MAN. A WAN can cover country, continent or even a whole world. Internet connection is an example of WAN. Other examples of WAN are mobile broadband connections such as 3G, 4G etc.
- 24. TOPOLOGY In ComputerNetwork ,there are various ways through which different components are connected to one another. Network Topology is the way that defines the structure, and how these components are connected to each other.
- 25. Types of NetworkTopology The arrangement of a network that comprises nodes and connecting lines via sender and receiver is referred to as Network Topology. The various network topologies are: Point to Point Topology Mesh Topology Star Topology Bus Topology Ring Topology Tree Topology Hybrid Topology
- 26. Mesh Topology Every deviceis connected to another via dedicated channels. These channels are known as links. •Suppose, the N number of devices are connected with each other in a mesh topology, the total number of ports that are required by each device is N-1. In Figure 1, there are 5 devices connected to each other, hence the total number of ports required by each device is 4. The total number of ports required = N * (N-1). •Suppose, N number of devices are connected with each other in a mesh topology, then the total number of dedicated links required to connect them is NC2 i.e. N(N-1)/2. there are 5 devices connected to each other, hence the total number of links required is 5*4/2 = 10.
- 27. Advantages of MeshTopology Communication is very fast between the nodes. Mesh Topology is robust. The fault is diagnosed easily. Data is reliable because data is transferred among the devices through dedicated channels or links. Provides security and privacy. Drawbacks of Mesh Topology Installation and configuration are difficult. The cost of cables is high as bulk wiring is required, hence suitable for less number of devices. The cost of maintenance is high. A common example of mesh topology is the internet backbone, where various internet service providers are connected to each other via dedicated channels. This topology is also used in military communication systems and aircraft navigation systems.
- 28. Star TOPOLOGY Astar topology having four systems connected to a single point of connection i.e. hub. Advantages of Star Topology If N devices are connected to each other in a star topology, then the number of cables required to connect them is N. So, it is easy to set up. Each device requires only 1 port i.e. to connect to the hub, therefore the total number of ports required is N. It is Robust. If one link fails only that link will affect and not other than that. Easy to fault identification and fault isolation. Star topology is cost-effective as it uses inexpensive coaxial cable.
- 29. Drawbacks of StarTopology If the concentrator (hub) on which the whole topology relies fails, the whole system will crash down. The cost of installation is high. Performance is based on the single concentrator i.e. hub. A common example of star topology is a local area network (LAN) in an office where all computers are connected to a central hub. This topology is also used in wireless networks where all devices are connected to a wireless access point.
- 30. Bus Topology BusTopology is a network type in which every computer and network device is connected to a single cable. It is bi-directional. It is a multi-point connection and a non-robust topology because if the backbone fails the topology crashes. In Bus Topology, various MAC (Media Access Control) protocols are followed by LAN ethernet connections like TDMA, Pure Aloha, CDMA, Slotted Aloha, etc.
- 31. Advantages of BusTopology If N devices are connected to each other in a bus topology, then the number of cables required to connect them is 1, known as backbone cable, and N drop lines are required. Coaxial or twisted pair cables are mainly used in bus-based networks that support up to 10 Mbps. The cost of the cable is less compared to other topologies, but it is used to build small networks. Bus topology is familiar technology as installation and troubleshooting techniques are well known. CSMA is the most common method for this type of topology.
- 32. Drawbacks of BusTopology A bus topology is quite simpler, but still, it requires a lot of cabling. If the common cable fails, then the whole system will crash down. If the network traffic is heavy, it increases collisions in the network. To avoid this, various protocols are used in the MAC layer known as Pure Aloha, Slotted Aloha, CSMA/CD, etc. Adding new devices to the network would slow down networks. Security is very low. A common example of bus topology is the Ethernet LAN, where all devices are connected to a single coaxial cable or twisted pair cable. This topology is also used in cable television networks
- 33. Ring Topology Ina Ring Topology, it forms a ring connecting devices with exactly two neighboring devices. A number of repeaters are used for Ring topology with a large number of nodes, because if someone wants to send some data to the last node in the ring topology with 100 nodes, then the data will have to pass through 99 nodes to reach the 100th node. Hence to prevent data loss repeaters are used in the network. The data flows in one direction, i.e. it is unidirectional, but it can be made bidirectional by having 2 connections between each Network Node, it is called Dual Ring Topology. In-Ring Topology, the Token Ring Passing protocol is used by the workstations to transmit the data.
- 34. A ring topologycomprises 4 stations connected with each forming a ring. The most common access method of ring topology is token passing. Token passing: It is a network access method in which a token is passed from one node to another node. Token: It is a frame that circulates around the network. Operations of Ring Topology One station is known as a monitor station which takes all the responsibility for performing the operations. To transmit the data, the station has to hold the token. After the transmission is done, the token is to be released for other stations to use. When no station is transmitting the data, then the token will circulate in the ring. There are two types of token release techniques: Early token release releases the token just after transmitting the data and Delayed token release releases the token after the acknowledgment is received from the receiver.
- 35. Advantages of RingTopology The data transmission is high-speed. The possibility of collision is minimum in this type of topology. Cheap to install and expand. It is less costly than a star topology. Drawbacks of Ring Topology The failure of a single node in the network can cause the entire network to fail. Troubleshooting is difficult in this topology. The addition of stations in between or the removal of stations can disturb the whole topology. Less secure.
- 36. Tree Topology Thistopology is the variation of the Star topology. This topology has a hierarchical flow of data.
- 37. In this,the various secondary hubs are connected to the central hub which contains the repeater. This data flow from top to bottom i.e. from the central hub to the secondary and then to the devices or from bottom to top i.e. devices to the secondary hub and then to the central hub. It is a multi-point connection and a non-robust topology because if the backbone fails the topology crashes. Advantages of Tree Topology It allows more devices to be attached to a single central hub thus it decreases the distance that is traveled by the signal to come to the devices. It allows the network to get isolated and also prioritize from different computers. We can add new devices to the existing network. Error detection and error correction are very easy in a tree topology.
- 38. Drawbacks of TreeTopology If the central hub gets fails the entire system fails. The cost is high because of the cabling. If new devices are added, it becomes difficult to reconfigure. A common example of a tree topology is the hierarchy in a large organization. At the top of the tree is the CEO, who is connected to the different departments or divisions (child nodes) of the company. Each department has its own hierarchy, with managers overseeing different teams (grandchild nodes). The team members (leaf nodes) are at the bottom of the hierarchy, connected to their respective managers and departments.
- 39. Hybrid Topology This topologicaltechnology is the combination of all the various types of topologies we have studied above. Hybrid Topology is used when the nodes are free to take any form. It means these can be individuals such as Ring or Star topology or can be a combination of various types of topologies seen above. Each individual topology uses the protocol that has been discussed earlier.
- 40. it containsa combination of all different types of networks. Advantages of Hybrid Topology This topology is very flexible. The size of the network can be easily expanded by adding new devices. Drawbacks of Hybrid Topology It is challenging to design the architecture of the Hybrid Network. Hubs used in this topology are very expensive. The infrastructure cost is very high as a hybrid network requires a lot of cabling and network devices. A common example of a hybrid topology is a university campus network. The network may have a backbone of a star topology, with each building connected to the backbone through a switch or router. Within each building, there may be a bus or ring topology connecting the different rooms and offices. The wireless access points also create a mesh topology for wireless devices. This hybrid topology allows for efficient communication between different buildings while providing flexibility and redundancy within each building.
- 41. LAYERING Layering meansDecomposing the problem into more manageable components(Layers). ADVANTAGES It provides more modular design Easy to troubleshoot
- 42. Every networkconsists of a specific number of functions, layers, and tasks to perform. Layered Architecture in a computer network is defined as a model where a whole network process is divided into various smaller sub-tasks. These divided sub-tasks are then assigned to a specific layer to perform only the dedicated tasks. A single layer performs only s specific type of task. To run the application and provide all types of services to clients a lower layer adds its services to the higher layer present above it. Therefore layered architecture provides interactions between the sub- systems. If any type of modification is done in one layer it does not affect the next layer.
- 43. LAYERED ARCHITECTURES OSI REFERENCEMODEL TCP/IP MODEL
- 44. Elements of LayeredArchitecture Service: Service is defined as a set of functions and tasks being provided by a lower layer to a higher layer. Each layer performs a different type of task. Therefore, actions provided by each layer are different. Protocol: Protocol is defined as a set rules used by the layer for exchanging and transmission of data with its peer entities. This rules can consists details regarding a type of content and their order passed from one layer to another. Interface: Interface is defined as a channel that allows to transmit the messages from one layer to the another.
- 45. Features of LayeredArchitecture Use of Layered architecture in computer network provides with the feature of modularity and distinct interfaces. Layered architecture ensures independence between layers, by offering services to higher layers from the lower layers and without specifying how this services are implemented. Layered architecture segments as larger and unmanageable design into small sub tasks. In layer architecture every network has different number of functions, layers and content. In layered architecture, the physical route provides with communication which is available under the layer 1. In layered architecture, the implementation done by one layer can be modified by the another layer.
- 46. Need of LayeredArchitecture Divide and Conquer Approach: Layered architecture supports divide and conquer approach. The unmanageable and complex task is further divided into smaller sub tasks. Each sub task is then carried out by the different layer. Therefore using this approach reduces the complexity of the problem or design process. Easy to Modify: The layers are independent of each other in layered architecture. If any sudden change occurs in the implementation of one layer, it can be changed. This change does not affect the working of other layers involved in the task. Therefore layered architectures are required to perform any sudden update or change. Modularity: Layered architecture is more modular as compared to other architecture models in computer network. Modularity provides with more independence between the layers and are more easier to understand. Easy to Test: Each layer in layered architecture performs a different and dedicated task. Therefore each layer can be analyzed and tested individually. It helps to analyze the problem and solve them more efficiently as compared to solving all the problems at a time.
- 47. Layered Architecture in computerNetworks OSI Model TCP/IP Model
- 48. TCP/IP MODEL TCP/IPwas designed and developed by the Department of Defense (DoD) in the 1960s and is based on standard protocols. It stands for Transmission Control Protocol/Internet Protocol. The TCP/IP model is a concise version of the OSI model. It contains five layers, unlike the seven layers in the OSI model. The number of layers is sometimes referred to as five or four. What Does TCP/IP Do? The main work of TCP/IP is to transfer the data of a computer from one device to another. The main condition of this process is to make data reliable and accurate so that the receiver will receive the same information which is sent by the sender. To ensure that, each message reaches its final destination accurately, the TCP/IP model divides its data into packets and combines them at the other end, which helps in maintaining the accuracy of the data while transferring from one end to another end.
- 49. What is theDifference between TCP and IP? TCP and IP are different protocols of Computer Networks. The basic difference between TCP (Transmission Control Protocol) and IP (Internet Protocol) is in the transmission of data. In simple words, IP finds the destination of the mail and TCP has the work to send and receive the mail. UDP is another protocol, which does not require IP to communicate with another computer. IP is required by only TCP. This is the basic difference between TCP and IP. How Does the TCP/IP Model Work? Whenever we want to send something over the internet using the TCP/IP Model, the TCP/IP Model divides the data into packets at the sender’s end and the same packets have to be recombined at the receiver’s end to form the same data, and this thing happens to maintain the accuracy of the data. TCP/IP model divides the data into a 5-layer procedure, where the data first go into this layer in one order and again in reverse order to get organized in the same way at the receiver’s end.
- 52. Layers of TCP/IPModel Application Layer Transport Layer(TCP/UDP) Network/Internet Layer(IP) Data Link Layer (MAC) Physical Layer
- 55. As shownin the above diagram, there are five different layers. Therefore it is a five-layered architecture. Each layer performs a dedicated task. The lower level data for example from layer 1 data is transferred to layer 2. Below all the layers Physical Medium is present. The physical medium is responsible for the actual communication to take place. For the transfer of data and communication layered architecture provides with a clean cut interface.
- 56. OSI REFERENCE MODEL OSI – OPEN SYSTEM INTERCONNECTION It is a model for understanding and designing Network Architecture that is flexible, robust and interoperable It is only a guideline that is it referred as reference model OSI stands for Open Systems Interconnection. It was developed by ISO – ‘International Organization for Standardization’, in the year 1984. It is a 7- layer architecture with each layer having specific functionality to perform. All these 7 layers work collaboratively to transmit the data from one person to another across the globe.
- 61. Functions ofthe physical layer The physical layer is responsible for sending computer bits from one device to another along the network. Its role is determining how physical connections to the network are set up, as well as how bits are represented into predictable signals -- as they are transmitted either electrically, optically or by radio waves.To do this, the physical layer performs a variety of functions, including the following: Defining bits. Determines how bits are converted from zeros and ones to a signal. Data rate. Determines how fast the data flows in bits per second. Synchronization. Ensures that sending and receiving devices are synchronized. Transmission mode. Determines the direction of data transmissions and whether those are simplex (one signal is transmitted in one direction), half-duplex (data goes in both directions but not at the same time) or full-duplex (data is transmitted in both directions simultaneously). Interface. Determines how devices are connected to a transmission medium, such as Ethernet or radio waves. Configuration. Provides point-to-point configurations and multipoint configurations. Modulation. Converts data into radio waves. Switching mechanism. Sends data packets from one port to another. Signal equalization. Helps create more reliable connections and makes multiplexing easier.
- 63. PHYSICAL LAYER Thephysical Layer is the bottom-most layer in the Open System Interconnection (OSI) Model which is a physical and electrical representation of the system. It consists of various network components such as power plugs, connectors, receivers, cable types, etc. The physical layer sends data bits from one device(s) (like a computer) to another device(s). The physical Layer defines the types of encoding (that is how the 0’s and 1’s are encoded in a signal). Source/Destination -> Data -> Signals The physical Layer is responsible for the communication of the unstructured raw data streams over a physical medium
- 64. Physical Topologies PhysicalTopology or Network Topology is the Geographical Representation of Linking devices. Following are the four types of physical topology- Mesh Topology: In a mesh topology, each and every device should have a dedicated point-to-point connection with each and every other device in the network. Here there is more security of data because there is a dedicated point-to-point connection between two devices. Mesh Topology is difficult to install because it is more complex. Star Topology: In star topology, the device should have a dedicated point-to-point connection with a central controller or hub. Star Topology is easy to install and reconnect as compared to Mesh Topology. Star Topology doesn’t have Fault Tolerance Technique. Bus Topology: In a bus topology, multiple devices are connected through a single cable that is known as backbone cable with the help of tap and drop lines. It is less costly as compared to Mesh Topology and Star Topology. Re-connection and Re-installation are difficult. Ring Topology: In a ring topology, each device is connected with repeaters in a circle-like ring that’s why it is called Ring Topology. In Ring Topology, a device can send the data only when it has a token, without a token no device can send the data, and a token is placed by Monitor in Ring Topology.
- 65. SIGNAL A signalis an electromagnetic or electrical current that carries data from one system or network to another. It is a a function that represents a variation of Physical Quantity with repect to Time. TYPES 1.Analog Analog Data Analog data refers to information which is continuous. Analog Signal Analog signals have infinitely so many levels of intensity over a period of time. When the wave moves from value A to value B, it passes through and it includes an infinite number of values along its path. 2.Digital Digital signals can have only a limited number of defined values. Although each value can be any number, it is often as simple as 0 or 1.
- 67. Transmission Media Transmissionmedia acts as a medium to transfer information from one part to the other and is defined as the communication channel to carry the data in a process. For better transmission media, there are some factors that should be taken care of as the bandwidth of the transmission media should be greater in order to have a stronger transmission media. The other factor is Interference whenever data communication flow takes place then chances of unwanted noise signals are there so to disrupt those signals interference is used. There are two types of Transmission media: Wired communication media (Also Known as Guided media) Wireless communication media (Also Known as Unguided media)
- 70. Wired/Guided Communication Media Wired communication media are also known as Guided media and are a type of Transmission media. This type of communication is the most stable which is why it is considered better than wireless. In wired communication media, wire is used to transfer data from source to destination. Wired communication media is not better for public use but can be used for professional purposes as it more relies on wires and ports which is not the case with wireless networks, data can be accessed from anywhere. Signals being transmitted are directed and confined in a narrow pathway by using physical links. Features: High Speed Secure Used for comparatively shorter distances
- 71. There are3 major types of Guided Media: (i) Twisted Pair Cable – It consists of 2 separately insulated conductor wires wound about each other. Generally, several such pairs are bundled together in a protective sheath. They are the most widely used Transmission Media. Twisted Pair is of two types: Unshielded Twisted Pair (UTP): UTP consists of two insulated copper wires twisted around one another. This type of cable has the ability to block interference and does not depend on a physical shield for this purpose. It is used for telephonic applications. Advantages: ⇢ Least expensive ⇢ Easy to install ⇢ High-speed capacity Disadvantages: ⇢ Susceptible to external interference ⇢ Lower capacity and performance in comparison to STP ⇢ Short distance transmission due to attenuation Applications: Used in telephone connections and LAN networks
- 72. Shielded TwistedPair (STP): This type of cable consists of a special jacket (a copper braid covering or a foil shield) to block external interference. It is used in fast-data-rate Ethernet and in voice and data channels of telephone lines. Advantages: ⇢ Better performance at a higher data rate in comparison to UTP ⇢ Eliminates crosstalk ⇢ Comparatively faster Disadvantages: ⇢ Comparatively difficult to install and manufacture ⇢ More expensive ⇢ Bulky Applications: The shielded twisted pair type of cable is most frequently used in extremely cold climates, where the additional layer of outer covering makes it perfect for withstanding such temperatures or for shielding the interior components.
- 73. ii) CoaxialCable – It has an outer plastic covering containing an insulation layer made of PVC or Teflon and 2 parallel conductors each having a separate insulated protection cover. The coaxial cable transmits information in two modes: Baseband mode(dedicated cable bandwidth) and Broadband mode(cable bandwidth is split into separate ranges). Cable TVs and analog television networks widely use Coaxial cables. Advantages: •High Bandwidth •Better noise Immunity •Easy to install and expand •Inexpensive Disadvantages: •Single cable failure can disrupt the entire network Applications: Radio frequency signals are sent over coaxial wire. It can be used for cable television signal distribution, digital audio (S/PDIF), computer network connections (like Ethernet), and feedlines that connect radio transmitters and receivers to their antennas.
- 74. (iii) OpticalFiber Cable – It uses the concept of refraction of light through a core made up of glass or plastic. The core is surrounded by a less dense glass or plastic covering called the cladding. It is used for the transmission of large volumes of data. The cable can be unidirectional or bidirectional. The cable can be unidirectional or bidirectional. The WDM (Wavelength Division Multiplexer) supports two modes, namely unidirectional and bidirectional mode
- 75. Advantages: Increased capacityand bandwidth Lightweight Less signal attenuation Immunity to electromagnetic interference Resistance to corrosive materials Disadvantages: Difficult to install and maintain High cost Fragile Applications: Medical Purpose: Used in several types of medical instruments. Defence Purpose: Used in transmission of data in aerospace. For Communication: This is largely used in formation of internet cables. Industrial Purpose: Used for lighting purposes and safety measures in designing the interior and exterior of automobiles.
- 76. 2. Unguided Media: Itis also referred to as Wireless or Unbounded transmission media. No physical medium is required for the transmission of electromagnetic signals. Features: The signal is broadcasted through air Less Secure Used for larger distances There are 3 types of Signals transmitted through unguided media: (i) Radio waves – These are easy to generate and can penetrate through buildings. The sending and receiving antennas need not be aligned. Frequency Range:3KHz – 1GHz. AM and FM radios and cordless phones use Radio waves for transmission.
- 77. (ii) Microwaves – Itis a line of sight transmission i.e. the sending and receiving antennas need to be properly aligned with each other. The distance covered by the signal is directly proportional to the height of the antenna. Frequency Range:1GHz – 300GHz. These are majorly used for mobile phone communication and television distribution. (iii) Infrared – Infrared waves are used for very short distance communication. They cannot penetrate through obstacles. This prevents interference between systems. Frequency Range:300GHz – 400THz. It is used in TV remotes, wireless mouse, keyboard, printer, etc.
- 78. Transmission Impairment inData Communication In communication system, analog signals travel through transmission media, which tends to deteriorate the quality of analog signal, which means that the signal at the beginning of the medium is not the same as the signal at the end of the medium. The imperfection causes signal impairment. Below are the causes of the impairment. Causes of impairment –
- 79. Attenuation – Itmeans loss of energy. The strength of signal decreases with increasing distance which causes loss of energy in overcoming resistance of medium. This is also known as attenuated signal. Amplifiers are used to amplify the attenuated signal which gives the original signal back and compensate for this loss. Distortion – It means changes in the form or shape of the signal. This is generally seen in composite signals made up with different frequencies. Each frequency component has its own propagation speed travelling through a medium. And that's why it delay in arriving at the final destination Every component arrive at different time which leads to distortion. Therefore, they have different phases at receiver end from what they had at senders end.
- 80. Noise – Therandom or unwanted signal that mixes up with the original signal is called noise. There are several types of noise such as induced noise, crosstalk noise, thermal noise and impulse noise which may corrupt the signal. Induced noise comes from sources such as motors and appliances. These devices act as sending antenna and transmission medium act as receiving antenna. Thermal noise is movement of electrons in wire which creates an extra signal. Crosstalk noise is when one wire affects the other wire. Impulse noise is a signal with high energy that comes from lightning or power lines