Computer Network Notes (Unit-I) PDF

COMPUTER NETWORK UNIT I  BASICS OF COMPUTER NETWORK: Computer Network tutorial provides basic and advanced concepts of Data Communication & Networks (DCN). Our Computer Networking Tutorial is designed for beginners and professionals. Our Computer Network tutorial inclu...

COMPUTER NETWORK UNIT I  BASICS OF COMPUTER NETWORK: Computer Network tutorial provides basic and advanced concepts of Data Communication & Networks (DCN). Our Computer Networking Tutorial is designed for beginners and professionals. Our Computer Network tutorial includes all topics of Computer Network such as introduction, features, types of computer network, architecture, hardware, software, internet, intranet, website, LAN, WAN, etc. What is Computer Network? A computer network is a set of devices connected through links. A node can be computer, printer, or any other device capable of sending or receiving the data. The links connecting the nodes are known as communication channels. Computer Network is a group of computers connected with each other through wires, optical fibres or optical links so that various devices can interact with each other through a network. o The aim of the computer network is the sharing of resources among various devices. o Computer Network uses distributed processing in which task is divided among several computers.  Uses of Computer Network There are multiple uses of computer network including:  Communication: Computer networks enable individuals and organizations to communicate with each other using various methods such as email, messaging, and video conferencing.  Resource sharing: Networks allow users to share resources such as printers, scanners, and files, which can improve efficiency and reduce costs.  Remote access: Networks enable users to access information and resources from anywhere in the world, providing greater flexibility and convenience.  Collaboration: Networks facilitate collaboration by enabling users to work together on projects, share ideas, and provide feedback in real time.  E-commerce: Computer networks are used extensively in e-commerce, enabling businesses to sell products and services online and process payments securely.  Education: Networks are used in educational institutions to facilitate distance learning, provide access to educational resources, and enable collaboration among students and teachers.  Entertainment: Networks are used for entertainment purposes such as online gaming, streaming movies and music, and social media. Applications of Computer Network Computer Networks: Business Applications Following are some business applications of computer networks: 1. Resource Sharing: The goal is to make all programs, equipments(like printers etc), and especially data, available to anyone on the network without regard to the physical location of the resource and the user. 2. Server-Client model: One can imagine a company's information system as consisting of one or more databases and some employees who need to access it remotely. In this model, the data is stored on powerful computers called Servers. Often these are centrally housed and maintained by a system administrator. In contrast, the employees have simple machines, called Clients, on their desks, using which they access remote data. 3. Communication Medium: A computer network can provide a powerful communication medium among employees. Virtually every company that has two or more computers now has e-mail (electronic mail), which employees generally use for a great deal of daily communication 4. eCommerce: A goal that is starting to become more important in businesses is doing business with consumers over the Internet. Airlines, bookstores and music vendors have discovered that many customers like the convenience of shopping from home. This sector is expected to grow quickly in the future. Home applications. Computer networks in the home let many electronic devices, such as laptops, desktops, game consoles, radios, clocks, and more, interact by sharing information and resources with home users. The connection between these devices brought entertainment to home users. Computer networks provide an easy way to connect multiple computer devices and share information and resources among home users. Nowadays, Every home equipment has built-in computer network systems, such as a wireless and non- wireless network that allow them to communicate with one another. Computers are bought by most people for editing text, playing games, editing pictures, and much more. Computer networks have extended the usage of computers at home. Recently Internet connectivity, Electronic news, Peer-to-Peer communication, Electronic mailing system, Social networking, E-commerce, Security system, and more are the reason for having a computer at home. The INTERNET has become an integral part of home users' lives. It allows home users to communicate with friends and family, shop, watch movies, and much more. A user at home can access and interact with information from other people in a different place, place an order online and buy products and services with e-commerce through the INTERNET with the help of a computer network. Browsing the INTERNET (WWW or World Wide Web) can improve the growth of information on sports, arts, business, travel, cooking, health, and many more. Every home user in the group can communicate with one or more other people. If users at home need to share files with others, they should install a Peer-to-Peer file transfer software application. Home users use the attachment file system found in the email to transfer text file, computer programs, audio, video, and more between one another. Computer networks allow the user at home and groups of people to work together in creating educational content. E-learning refers to a type of learning that takes place online. It includes courses, videos, podcasts, blogs, wikis, forums, and other forms of content that can be accessed through an internet connection. Mobile Users Mobile computers often incorporate wireless technologies, which allow users to connect to the internet and each other without being tethered to a physical connection. Mobile computers, such as laptops and handheld computers, are the fastest-growing segment of the computer industry, having overtaken desktop sales. People use mobile devices to read and send an email, tweet, watch movies, download music, play games, and surf the web. Internet connectivity The computer network enables the connectivity of mobile devices to the internet through wireless networks. Since wire connection is impossible in an automobile system such as cars, boats, and airplanes. The computer and mobile devices industry shows interest in wireless networks. They are implementing a wireless network in many devices because of their portability. There are two types of commonly used wireless networks; The first type is a cellular network operated by a telephone company. They provide coverage for mobile phones. The second type of network is a wireless hotspot based on the 802.11 standards. A wireless hotspot network connects mobile computers to the internet. They are found in many public places, like cafes, hotels, airports, schools, trains, and planes. If you have a laptop computer with a wireless modem, you can connect to the internet with a hotspot by turning on your computer. Hotspots are now considered places where people can access the internet wirelessly. Portability/Mobility Networking is one of the factors that provide mobility to mobile devices. Mobile computing implements both wireless and non-wireless networking. For example, pc or mac computer can be plugged into the wired network jack in a hotel room, providing mobility without a wireless network. Some wireless computers are not mobile and can be more convenient to connect to desktop computers or media players wirelessly than to install wires. Mobile communication Wireless applications are the widespread use of mobile phones. Text messaging has become a huge trend, as it allows mobile phone users to type a short message and then deliver it by the cellular network to another mobile subscriber. Educational resources Other consumer electronics devices can also use cellular and hotspot networks to stay connected to remote computers. Electronic book readers can download a newly purchased book and the next edition of a magazine or today's newspaper wherever they roam. These educational resources will help the mobile user increase in knowledge. Mobile commerce application (m-commerce) The mobile phone's usefulness has now dominated the area of m-commerce (mobile- commerce). Instead of using cash or credit cards, people can authorize payments for food in vending machines and movie tickets by sending short text messages from their mobile phones. And the charge then appears on the mobile phone bill. Mobile devices are now implementing a technology called NFC (Near Field Communication), which makes them act as an RFID smart card and interact with a nearby reader for payment. With this technology, Customers can pay for items in a store by waving their phone at the cash register. The computer network is the main backbone behind m- commerce. Transportation Wireless networks offer many advantages to transport companies, including the ability to stay in contact with customers. For example, in many cities, taxi drivers are independent individuals rather than employees of a taxi company. In these cities, the taxis have a display that directs the driver and gives him some clue about the location. An example of how wireless networks can be beneficial is that many cities have taxi drivers who are independent businessmen. In some cities, taxis have a display that tells the driver where to pick up the next customer. Social Issues Of Computer Networks The extensive overview of networking has introduced new social, ethical, and political hitches. Some of the social issues just briefly mentioned a few of them; a popular feature of numerous networks and newsgroups or bulletin boards whereby people can give-and-take messages and communications with like as of the one- minded individual. The issues come up when newsgroups are set up on issues that people essentially care about, like politics, religion, or sex. Messages could not be limited to text. High-resolution color photographs and even short video clips can easily be transmitted over communication and computer networks. Another social issue area is employee rights as opposed to an employer’s rights. A lot of people write and read an e-mail at work. Many employers have applied for the right to read and perhaps censor employee communications, as well as messages sent from a personal computer after work. Other key social issues are government against the citizen. The government does not have a monopoly on threatening peoples or public secrecy. The private sector does it a too bit. For example, minor or small documents and files called as cookies that web browsers or search engine stored at user’s computer permit companies and organization to track the user’s activities in cyberspace and also might be permit credit card numbers, social security and secrecy numbers, and many of other confidential info to leak all over the internet. Computer networks are allowed to send potential and hidden messages. In some situations, this ability might be desired. Individuality robbery is becoming a serious issue as robs gather enough information materials about a victim to gain catch credit cards and many other additional information and documents in the victim’s name. Lastly, being able to transfer music and video in numerical form has opened the door to massive copyright violations that are firm to catch and enforce. A lot of these issues have been solved if the computer corporation and organization took computer security seriously. If all the conversations or messages will be encrypted and authenticated, it would be harder to commit mischief. What is Network Topology? Topology defines the structure of the network of how all the components are interconnected to each other. There are two types of topology: physical and logical topology. Types of Network Topology Physical topology is the geometric representation of all the nodes in a network. There are six types of network topology which are Bus Topology, Ring Topology, Tree Topology, Star Topology, Mesh Topology, and Hybrid Topology. 1) Bus Topology o The bus topology is designed in such a way that all the stations are connected through a single cable known as a backbone cable. o Each node is either connected to the backbone cable by drop cable or directly connected to the backbone cable.  o When a node wants to send a message over the network, it puts a message over the network. All the stations available in the network will receive the message whether it has been addressed or not. o The configuration of a bus topology is quite simpler as compared to other topologies. o The backbone cable is considered as a "single lane" through which the message is broadcast to all the stations. o The most common access method of the bus topologies is CSMA (Carrier Sense Multiple Access). Advantages of Bus topology: o Low-cost cable: In bus topology, nodes are directly connected to the cable without passing through a hub. Therefore, the initial cost of installation is low. o Moderate data speeds: Coaxial or twisted pair cables are mainly used in bus-based networks that support upto 10 Mbps. o Familiar technology: Bus topology is a familiar technology as the installation and troubleshooting techniques are well known, and hardware components are easily available. o Limited failure: A failure in one node will not have any effect on other nodes. Disadvantages of Bus topology: o Extensive cabling: A bus topology is quite simpler, but still it requires a lot of cabling. o Difficult troubleshooting: It requires specialized test equipment to determine the cable faults. If any fault occurs in the cable, then it would disrupt the communication for all the nodes. o Signal interference: If two nodes send the messages simultaneously, then the signals of both the nodes collide with each other. o Reconfiguration difficult: Adding new devices to the network would slow down the network. o Attenuation: Attenuation is a loss of signal leads to communication issues. Repeaters are used to regenerate the signal. 2) Ring Topology o Ring topology is like a bus topology, but with connected ends. o The node that receives the message from the previous computer will retransmit to the next node. o The data flows in one direction, i.e., it is unidirectional. o The data flows in a single loop continuously known as an endless loop.  o It has no terminated ends, i.e., each node is connected to other node and having no termination point. o The data in a ring topology flow in a clockwise direction. Advantages of Ring topology: o Network Management: Faulty devices can be removed from the network without bringing the network down. o Product availability: Many hardware and software tools for network operation and monitoring are available. o Cost: Twisted pair cabling is inexpensive and easily available. Therefore, the installation cost is very low. o Reliable: It is a more reliable network because the communication system is not dependent on the single host computer. Disadvantages of Ring topology: o Difficult troubleshooting: It requires specialized test equipment to determine the cable faults. If any fault occurs in the cable, then it would disrupt the communication for all the nodes. o Failure: The breakdown in one station leads to the failure of the overall network. o Reconfiguration difficult: Adding new devices to the network would slow down the network. o Delay: Communication delay is directly proportional to the number of nodes. Adding new devices increases the communication delay. 3) Star Topology o Star topology is an arrangement of the network in which every node is connected to the central hub, switch or a central computer. o The central computer is known as a server, and the peripheral devices attached to the server are known as clients. o Coaxial cable or RJ-45 cables are used to connect the computers. o Hubs or Switches are mainly used as connection devices in a physical star topology. o Star topology is the most popular topology in network implementation. Advantages of Star topology o Efficient troubleshooting: In a bus topology, the manager has to inspect the kilometers of cable. In a star topology, all the stations are connected to the centralized network. Therefore, the network administrator has to go to the single station to troubleshoot the problem. o Network control: Complex network control features can be easily implemented in the star topology. Any changes made in the star topology are automatically accommodated. o Limited failure: As each station is connected to the central hub with its own cable, therefore failure in one cable will not affect the entire network. o Familiar technology: Star topology is a familiar technology as its tools are cost-effective. o Easily expandable: It is easily expandable as new stations can be added to the open ports on the hub. o Cost effective: Star topology networks are cost-effective as it uses inexpensive coaxial cable. o High data speeds: It supports a bandwidth of approx 100Mbps. Ethernet 100BaseT is one of the most popular Star topology networks. Disadvantages of Star topology o A Central point of failure: If the central hub or switch goes down, then all the connected nodes will not be able to communicate with each other. o Cable: Sometimes cable routing becomes difficult when a significant amount of routing is required. 4) Tree topology o Tree topology combines the characteristics of bus topology and star topology. o A tree topology is a type of structure in which all the computers are connected with each other in hierarchical fashion. o The top-most node in tree topology is known as a root node, and all other nodes are the descendants of the root node. o There is only one path exists between two nodes for the data transmission. Thus, it forms a parent-child hierarchy. Advantages of Tree topology o Support for broadband transmission: Tree topology is mainly used to provide broadband transmission, i.e., signals are sent over long distances without being attenuated.  o Easily expandable: We can add the new device to the existing network. Therefore, we can say that tree topology is easily expandable. o Easily manageable: In tree topology, the whole network is divided into segments known as star networks which can be easily managed and maintained. o Error detection: Error detection and error correction are very easy in a tree topology. o Limited failure: The breakdown in one station does not affect the entire network. o Point-to-point wiring: It has point-to-point wiring for individual segments. Disadvantages of Tree topology o Difficult troubleshooting: If any fault occurs in the node, then it becomes difficult to troubleshoot the problem. o High cost: Devices required for broadband transmission are very costly. o Failure: A tree topology mainly relies on main bus cable and failure in main bus cable will damage the overall network. o Reconfiguration difficult: If new devices are added, then it becomes difficult to reconfigure. 5) Mesh topology o Mesh technology is an arrangement of the network in which computers are interconnected with each other through various redundant connections. o There are multiple paths from one computer to another computer. o It does not contain the switch, hub or any central computer which acts as a central point of communication. o The Internet is an example of the mesh topology. o Mesh topology is mainly used for WAN implementations where communication failures are a critical concern. o Mesh topology is mainly used for wireless networks. Advantages of Mesh topology: Reliable: The mesh topology networks are very reliable as if any link breakdown will not affect the communication between connected computers. Fast Communication: Communication is very fast between the nodes. Easier Reconfiguration: Adding new devices would not disrupt the communication between other devices. Disadvantages of Mesh topology o Cost: A mesh topology contains a large number of connected devices such as a router and more transmission media than other topologies. o Management: Mesh topology networks are very large and very difficult to maintain and manage. If the network is not monitored carefully, then the communication link failure goes undetected. o Efficiency: In this topology, redundant connections are high that reduces the efficiency of the network. 6) Hybrid Topology o The combination of various different topologies is known as Hybrid topology. o A Hybrid topology is a connection between different links and nodes to transfer the data. o When two or more different topologies are combined together is termed as Hybrid topology and if similar topologies are connected with each other will not result in Hybrid topology. For example, if there exist a ring topology in one branch of ICICI bank and bus topology in another branch of ICICI bank, connecting these two topologies will result in Hybrid topology. Advantages of Hybrid Topology o Reliable: If a fault occurs in any part of the network will not affect the functioning of the rest of the network. o Scalable: Size of the network can be easily expanded by adding new devices without affecting the functionality of the existing network. o Flexible: This topology is very flexible as it can be designed according to the requirements of the organization. o Effective: Hybrid topology is very effective as it can be designed in such a way that the strength of the network is maximized and weakness of the network is minimized. Disadvantages of Hybrid topology o Complex design: The major drawback of the Hybrid topology is the design of the Hybrid network. It is very difficult to design the architecture of the Hybrid network. o Costly Hub: The Hubs used in the Hybrid topology are very expensive as these hubs are different from usual Hubs used in other topologies.  o Costly infrastructure: The infrastructure cost is very high as a hybrid network requires a lot of cabling, network devices, etc.  signal is a way of communicating by sending information from one system to other system. In other words signal is a function that represents information or data. Signal is an electromagnetic wave that carries information through physical medium. Signals are divided into two categories based on their nature. Signals which are  Signal which are Continuous as time varying in nature are analog signals  Signal which are discrete are called digital signals. Analog Signals Analog signal is a form of electrical energy (voltage, current or electromagnetic power) for which there is a linear relationship between electrical quantity and the value that the signal represents. The signal whose amplitude takes any value in a continuous range is called analog signal. Analog Signals are continuous in nature which vary with respect to time. They can be periodic or non-periodic. Voltage, current, frequency, pressure, sound, light, temperature are the physical variables that are measured with respect to their changes with respect to time to obtain information. These signals are more subjected to noise as they travel through the medium. Examples of analog signals: The signals include audio signals transmitted through wires, video signals broadcasted using older technology, radio signals, and analog watches. Digital Signals The signal, whose amplitude takes only limited values is called Digital signal. Digital signal are discrete, they contain only distinct values. Digital signals carry binary data i.e. 0 or 1 in form of bits, it can only contain one value at a period of time. Digital signals are represented as square waves or clock signals. Nowadays usage of digital signals for transmitting information has increased rapidly in every field of usage as the applications and properties of digital signals are more productive compared to analog signals. Examples of digital signals:  Smart transmitters using various protocols transmit data through analog and digital signals.  Digital watches.  Digital video signals.  CD’s.  DVD’s.  Computer. Transmission impairment Signal quality is compromised due to imperfections in the transmission medium. This is called transmission impairment. There are three main types of transmission impairment: signal distortion, attenuation, and noises. 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 – Attenuation – It means 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. 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. Noise – The random 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  Data rate limits and performance in computer networks Data rate limits A very important consideration in data communications is how fast we can send data, in bits per second, over a channel. Data rate depends on three factors: The bandwidth available The level of the signals we use The quality of the channel (the level of noise) Digital Transmission Data can be represented either in analog or digital form. The computers used the digital form to store the information. Therefore, the data needs to be converted in digital form so that it can be used by a computer. DIGITAL-TO-DIGITAL CONVERSION Digital-to-digital encoding is the representation of digital information by a digital signal. When binary 1s and 0s generated by the computer are translated into a sequence of voltage pulses that can be propagated over a wire, this process is known as digital-to-digital encoding. Digital-to-digital encoding is divided into three categories: o Unipolar Encoding o Polar Encoding o Bipolar Encoding Unipolar o Digital transmission system sends the voltage pulses over the medium link such as wire or cable.  o In most types of encoding, one voltage level represents 0, and another voltage level represents 1. o The polarity of each pulse determines whether it is positive or negative. Polar o Polar encoding is an encoding scheme that uses two voltage levels: one is positive, and another is negative. o By using two voltage levels, an average voltage level is reduced, and the DC component problem of unipolar encoding scheme is alleviated. o Bipolar o Bipolar encoding scheme represents three voltage levels: positive, negative, and zero. o In Bipolar encoding scheme, zero level represents binary 0, and binary 1 is represented by alternating positive and negative voltages. ANALOG-TO-DIGITAL CONVERSION o When an analog signal is digitalized, this is called an analog-to-digital conversion. o Suppose human sends a voice in the form of an analog signal, we need to digitalize the analog signal which is less prone to noise. It requires a reduction in the number of values in an analog message so that they can be represented in the digital stream. o In analog-to-digital conversion, the information contained in a continuous wave form is converted in digital pulses. Analog Transmission To send the digital data over an analog media, it needs to be converted into analog signal.There can be two cases according to data formatting. Bandpass:The filters are used to filter and pass frequencies of interest. A bandpass is a band of frequencies which can pass the filter. Low-pass: Low-pass is a filter that passes low frequencies signals. When digital data is converted into a bandpass analog signal, it is called digital-to-analog conversion. When low-pass analog signal is converted into bandpass analog signal, it is called analog-to-analog conversion. Digital-to-Analog Conversion When data from one computer is sent to another via some analog carrier, it is first converted into analog signals. Analog signals are modified to reflect digital data. An analog signal is characterized by its amplitude, frequency, and phase. Analog-to-Analog Conversion Analog signals are modified to represent analog data. This conversion is also known as Analog Modulation. Analog to analog conversion can be done in three ways:  Amplitude Modulation In this modulation, the amplitude of the carrier signal is modified to reflect the analog data.  Frequency Modulation In this modulation technique, the frequency of the carrier signal is modified to reflect the change in the voltage levels of the modulating signal (analog data).  Phase Modulation In the modulation technique, the phase of carrier signal is modulated in order to reflect the change in voltage (amplitude) of analog data signal. Computer Network Types A computer network is a group of computers linked to each other that enables the computer to communicate with another computer and share their resources, data, and applications. A computer network can be categorized by their size. A computer network is mainly of four types: o LAN(Local Area Network) o MAN(Metropolitan Area Network) o WAN(Wide Area Network) LAN(Local Area Network) o Local Area Network is a group of computers connected to each other in a small area such as building, office. o LAN is used for connecting two or more personal computers through a communication medium such as twisted pair, coaxial cable, etc. o It is less costly as it is built with inexpensive hardware such as hubs, network adapters, and ethernet cables. o The data is transferred at an extremely faster rate in Local Area Network. o Local Area Network provides higher security. MAN(Metropolitan Area Network) o A metropolitan area network is a network that covers a larger geographic area by interconnecting a different LAN to form a larger network. o Government agencies use MAN to connect to the citizens and private industries. o In MAN, various LANs are connected to each other through a telephone exchange line. o The most widely used protocols in MAN are RS-232, Frame Relay, ATM, ISDN, OC-3, ADSL, etc. o It has a higher range than Local Area Network(LAN). Uses of Metropolitan Area Network: o MAN is used in communication between the banks in a city. o It can be used in an Airline Reservation. o It can be used in a college within a city. o It can also be used for communication in the military. WAN(Wide Area Network) o A Wide Area Network is a network that extends over a large geographical area such as states or countries. o A Wide Area Network is quite bigger network than the LAN. o A Wide Area Network is not limited to a single location, but it spans over a large geographical area through a telephone line, fibre optic cable or satellite links. o The internet is one of the biggest WAN in the world. o A Wide Area Network is widely used in the field of Business, government, and education. Examples of Wide Area Network: o Mobile Broadband: A 4G network is widely used across a region or country. o Last mile: A telecom company is used to provide the internet services to the customers in hundreds of cities by connecting their home with fiber. o Private network: A bank provides a private network that connects the 44 offices. This network is made by using the telephone leased line provided by the telecom company. Advantages of Wide Area Network: Following are the advantages of the Wide Area Network: o Geographical area: A Wide Area Network provides a large geographical area. Suppose if the branch of our office is in a different city then we can connect with them through WAN. The internet provides a leased line through which we can connect with another branch. o Centralized data: In case of WAN network, data is centralized. Therefore, we do not need to buy the emails, files or back up servers. o Get updated files: Software companies work on the live server. Therefore, the programmers get the updated files within seconds. o Exchange messages: In a WAN network, messages are transmitted fast. The web application like Facebook, Whatsapp, Skype allows you to communicate with friends. o Sharing of software and resources: In WAN network, we can share the software and other resources like a hard drive, RAM. o Global business: We can do the business over the internet globally. o High bandwidth: If we use the leased lines for our company then this gives the high bandwidth. The high bandwidth increases the data transfer rate which in turn increases the productivity of our company. Disadvantages of Wide Area Network: The following are the disadvantages of the Wide Area Network: o Security issue: A WAN network has more security issues as compared to LAN and MAN network as all the technologies are combined together that creates the security problem. o Needs Firewall & antivirus software: The data is transferred on the internet which can be changed or hacked by the hackers, so the firewall needs to be used. Some people can inject the virus in our system so antivirus is needed to protect from such a virus. o High Setup cost: An installation cost of the WAN network is high as it involves the purchasing of routers, switches. o Troubleshooting problems: It covers a large area so fixing the problem is difficult. What is Client-Server Network? A client-server network is also known as a network computing model. In this, we have clients and servers. A client includes a device or a program. Using this, end users can access the web. There are various examples of clients such as web browsers, laptops, desktops, smartphones, etc. A server includes a program or device that replies to the clients with the services. It offers databases, files, web pages, and shared resources based on their type. In a client-server network, the client requests services from the server. The server reacts to client requests by rendering the necessary service after listening to their queries. A client-server network's key benefit is that it is safer because the server constantly controls access and security. Additionally, making backups is simpler. However, it is not very dependable because a server failure will impair the clients' ability to work. Additionally, the setup and maintenance costs are high. Client-Server Network Example The World Wide Web consortium is one of the most well-known examples of client-server architecture. In this, internet users, people like us, act as clients requesting information from the servers, and the servers reply by providing the precise information that was asked for. Advantages of Client Server Network The following are the advantages of client server network: o The client-server network offers a good user interface, and can handle files easily. o In a client-server network, we can share the resources easily. o Users have the freedom to access files stored in the central storage from any location. o The client-server network has complete control over all network processes and activities because it is a centralised network. o The main focus of the Client-Server Network is on information sharing. However, the server can distribute its resources such as computing power or hard drive space with the network. o Client-Server Network is more scalable and stable. o In order to store data in a client-server network, a centralized server is used. Data backup and protection are made simpler by centralised file storage. o In Client-Server Network, client and server are distinct, and there are particular servers and clients. o In Client-Server Network, the client requests a service, and the server provides it. o It costs a lot of money to implement client-server. A separate computer must be used to serve as the server, and because a server needs more processing power, a high-performance machine is necessary. o The access time for a service is longer in client-server networks because more client's requests services from a server. Peer-to-Peer Network This model does not distinguish between clients and servers; each node acts as both a client and server. Every node in a peer-to-peer network has the ability to request and provide service. A node is also called a peer. In a peer-to-peer network, a node joins the network and begins offering services, and then asks other nodes for services. Communication occurs between the service-providing and service-requesting nodes. In the alternative technique, a node that needs particular services can broadcast a message to all other nodes that need the same service. The node with the necessary service responds to the node making the request by giving the desired service. Peer-to-Peer networks have a number of benefits. It is simpler to keep up. To maintain the network, no specialist expertise is required. One machine is not the only thing that the network depends on. Peer-to-Peer Network Example One of the most well-known peer-to-peer networks is torrent. All computer in this kind of network is linked to the internet, allowing users to download resources shared by any one computer. The local area network (LAN), which is typically preferred by small workplaces for the purpose of resource sharing, is another frequently used example of the peer-to-peer network. Advantages of Peer-to-Peer Network The following are the advantages of peer-to-peer networks: o Each device linked to the peer-to-peer network exchanges resources with other network nodes. o The setup of a peer-to-peer network is easily established with the help of specialized software. o Peer-to-peer networks are very reliable because other systems continue to function even when a server fails. Synchronous Transmission: In Synchronous Transmission, data is sent in form of blocks or frames. This transmission is the full-duplex type. Between sender and receiver, synchronization is compulsory. In Synchronous transmission, There is no gap present between data. It is more efficient and more reliable than asynchronous transmission to transfer a large amount of data. Example:  Chat Rooms  Telephonic Conversations  Video Conferencing  Asynchronous Transmission: In Asynchronous Transmission, data is sent in form of byte or character. This transmission is the half-duplex type transmission. In this  transmission start bits and stop bits are added with data. It does not require synchronization.  Example:  Email  Forums  Letters Synchronous communication, a definition Synchronous communication is the exchange of information between 2 or more people in real-time. It may be in person but it certainly doesn’t have to be. In addition to in-person conversations or meetings, phone calls and video meetings are also examples of synchronous communication. There are many situations in which synchronous communication will be your best choice – these include, but are not limited to  Discussions of sensitive projects or issues  Providing critical feedback  Brainstorming or conversations with a lot of unknowns  Project kickoffs or other instances where everyone needs to be quickly brought up to speed or a lot of dynamic variables need to be shared  Rapport needs to be built  A crisis has happened and immediate attention is required Synchronous communication, a definition Synchronous communication is the exchange of information between 2 or more people in real-time. It may be in person but it certainly doesn’t have to be. In addition to in-person conversations or meetings, phone calls and video meetings are also examples of synchronous communication.  Emails  Direct messages  Shared document comments What is asynchronous communication? Asynchronous communication means interaction without real-time conversation — replies can be delayed. A great example is email. In this approach, people aren't scheduling meetings and responses are less time-sensitive. In this scenario, instead of asking your employees to be online at the same time, you give your teammates the flexibility to choose their working hours, irrespective of their location. For example, if you’ve sent an email requesting a document from a team member, rather than expecting an immediate response, you’re patient and wait for them to respond later on. Types of synchronous vs asynchronous communication Learning Synchronous learning happens in real-time, with students and teachers together. Alternatively, teachers can share information asynchronously. Learners explore on their own time, for example by watching videos, reading, and listening. Teachers use a learning management system (LMS) to share learning materials. Programming In coding, synchronous operations are performed one at a time. One task finishes, the next step begins. Asynchronous operations can happen at the same time — you can move to the next step while another step finishes. Communication The key difference between synchronous and asynchronous communication is synchronous communications are scheduled, real-time interactions by phone, video, or in- person. Asynchronous communication happens on your own time and doesn’t need scheduling. Examples of asynchronous communication Messaging software: Messaging software like Microsoft Teams and Slack is helpful for employee communication and collaboration. You send a message and the recipient replies when they come online. Email: There’s no pressure to respond instantly to work emails. Employees can reply at a convenient time with tools like Gmail and Outlook. Video recording: Video recordings or demos work great when you need to explain a process. Popular video recording tools include Zoom   What is Client-Server Architecture in Computer Network? In this architecture, a specific computer is known as a server, specially designated to provide various services to other computers known as clients. In simple terms, the server can be defined as a provider of services, and the client can be a requester to services. The client requests any information from the server, and the server, in turn, responds to the client request, as shown in the below figure − The most common client-server arrangement method is a LAN made out of micro computers linked to a network server, which serves all LAN clients. Classifications of Client/Server Architecture Following is the classification of Client/Server Architecture − Two Tier-Architecture In the two-tier architecture, there exists only two parties; one is the client, and the other is the server. The main benefit of the client/server model is its simplicity. But there is a major problem when 100s of clients request the data from the server simultaneously. Every client will have to wait for its turn to come. Three-Tier Architecture It is also referred to as multi-tier architecture. In this architecture, there is a middle layer within the client and the server. It clarifies the difficulty of waiting time by clients. It maintains a queue of requests by different clients, and the client can do their work; meanwhile, the server is busy processing other client’s request. The middle layer forwards the request, and the server, in turn, replies to the client.