Data Communication and Networking PDF

Pimpri Chinchwad Education Trust’s Pimpri Chinchwad College of Engineering (PCCoE) (An Autonomous Institute) Affiliated to Savitribai Phule Pune University(SPPU)...

Pimpri Chinchwad Education Trust’s Pimpri Chinchwad College of Engineering (PCCoE) (An Autonomous Institute) Affiliated to Savitribai Phule Pune University(SPPU) ISO 21001:2018 Certified by TUV SUD Data Communication and Networking Fundamentals of Data Communication and Networking Process of data communication and its components: Data Communication System Components 1. Message : This is 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 form of a text file, an audio file, a video file, etc. 2. 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. 3. 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. 1  4. 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. 5. 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 Types Of Communication Systems Communication systems are divided into two categories: Analog and digital. 1. Analogue: Analog technologies transmit data between people or machines as electronic signals of various frequencies or amplitudes. Telephone and radio transmission are the most common examples of Analog technology. 2. Digital: Digital technology, information is generated and processed in two states: high and low. Digital technology stores and transmits the data in the form of 0s and 1s. There are two types of communication channels: Wired: In wired communication, it is of 4 types: Parallel wire communication Twisted wire communication Coaxial cable communication Optical fibre communication Wired communication is also known as line communication. Wireless: In this, there are 4 types of communication: Ground wave communication Skywave communication Space wave communication Satellite communication Wireless communication is also known as space communication. Types of Communication Systems: Data communication Communication modes are categorized as follows: 2 Point to point: The transmission of information from one location to another is known as point-to-point communication (P2P). When a single transmitter and receiver communicate, this is called asynchronous communication. Broadcast: Although a single transmitter provides the information, many receivers are broadcast. Television and radio are both broadcast methods of communication systems. Communication system examples: 1. Internet 2. Public Switched Telephone network 3. Intranet and Extranet 4. Television Various elements of communication system: Signal: The single-valued function of time which carries the various information, which is then converted into electrical form, so that it can be transmitted. Amplifier: The electronic device or circuit that increases the strength or amplitude of signals received by a device and which can be done anywhere from the transmitter to the receiver. Protocol Network protocols are a set of rules that are responsible for the communication of data between various devices in the network. These protocols define guidelines and conventions for transmitting and receiving data, ensuring efficient and reliable data communication. What is Network Protocol? A network protocol is a set of rules that govern data communication between different devices in the network. It determines what is being communicated, how it is being communicated, and when it is being communicated. It permits connected devices to communicate with each other, irrespective of internal and structural differences. How do Network Protocols Work? It is essential to understand how devices communicate over a network by recognizing network protocols. The Open Systems Interconnection (OSI), the most widely used model, illustrates how computer systems interact with one another over a network. The communication mechanism between two network devices is shown by seven different layers in the OSI model. Every layer in the OSI model works based on different network protocols. At every layer, one or more protocols are there for network communication. To enable network-to-network connections, the Internet Protocol (IP), for instance, routes data by controlling information like the source and destination addresses of data packets. It is known as a network layer protocol. 3 Types of Network Protocols In most cases, communication across a network like the Internet uses the OSI model. The OSI model has a total of seven layers. Secured connections, network management, and network communication are the three main tasks that the network protocol performs. The purpose of protocols is to link different devices. The protocols can be broadly classified into three major categories: Network Communication Network Management Network Security 1. Network Communication Communication protocols are really important for the functioning of a network. They are so crucial that it is not possible to have computer networks without them. These protocols formally set out the rules and formats through which data is transferred. These protocols handle syntax, semantics, error detection, synchronization, and authentication. Below mentioned are some network communication protocol: Hypertext Transfer Protocol(HTTP) It is a layer 7 protocol that is designed for transferring a hypertext between two or more systems. HTTP works on a client-server model, most of the data sharing over the web is done through using HTTP. Transmission Control Protocol(TCP) TCP layouts a reliable stream delivery by using sequenced acknowledgment. It is a connection- oriented protocol i.e., it establishes a connection between applications before sending any data. It is used for communicating over a network. It has many applications such as emails, FTP, streaming media, etc. User Datagram Protocol(UDP) It is a connectionless protocol that lay-out a basic but unreliable message service. It adds no flow control, reliability, or error-recovery functions. UPD is functional in cases where reliability is not required. It is used when we want faster transmission, for multicasting and broadcasting connections, etc. Border Gateway Protocol(BGP) BGP is a routing protocol that controls how packets pass through the router in an independent system one or more networks run by a single organization and connect to different networks. It connects the endpoints of a LAN with other LANs and it also connects endpoints in different LANs to one another. 4 Address Resolution Protocol(ARP) ARP is a protocol that helps in mapping logical addresses to the physical addresses acknowledged in a local network. For mapping and maintaining a correlation between these logical and physical addresses a table known as ARP cache is used. Internet Protocol(IP) It is a protocol through which data is sent from one host to another over the internet. It is used for addressing and routing data packets so that they can reach their destination. Dynamic Host Configuration Protocol(DHCP) it’s a protocol for network management and it’s used for the method of automating the process of configuring devices on IP networks. A DHCP server automatically assigns an IP address and various other configurational changes to devices on a network so they can communicate with other IP networks. it also allows devices to use various services such as NTP, DNS, or any other protocol based on TCP or UDP. 2. Network Management These protocols assist in describing the procedures and policies that are used in monitoring, maintaining, and managing the computer network. These protocols also help in communicating these requirements across the network to ensure stable communication. Network management protocols can also be used for troubleshooting connections between a host and a client. Internet Control Message Protocol(ICMP) It is a layer 3 protocol that is used by network devices to forward operational information and error messages. ICMP is used for reporting congestions, network errors, diagnostic purposes, and timeouts. Simple Network Management Protocol(SNMP) It is a layer 7 protocol that is used for managing nodes on an IP network. There are three main components in the SNMP protocol i.e., SNMP agent, SNMP manager, and managed device. SNMP agent has the local knowledge of management details, it translates those details into a form that is compatible with the SNMP manager. The manager presents data acquired from SNMP agents, thus helping in monitoring network glitches, and network performance, and troubleshooting them. Gopher It is a type of file retrieval protocol that provides downloadable files with some description for easy management, retrieving, and searching of files. All the files are arranged on a remote computer in a stratified manner. Gopher is an old protocol and it is not much used nowadays. File Transfer Protocol(FTP) FTP is a Client/server protocol that is used for moving files to or from a host computer, it allows users to download files, programs, web pages, and other things that are available on other services. 5 Post Office Protocol(POP3) It is a protocol that a local mail client uses to get email messages from a remote email server over a TCP/IP connection. Email servers hosted by ISPs also use the POP3 protocol to hold and receive emails intended for their users. Eventually, these users will use email client software to look at their mailbox on the remote server and to download their emails. After the email client downloads the emails, they are generally deleted from the servers. Telnet It is a protocol that allows the user to connect to a remote computer program and to use it i.e., it is designed for remote connectivity. Telnet creates a connection between a host machine and a remote endpoint to enable a remote session. 3. Network Security These protocols secure the data in passage over a network. These protocols also determine how the network secures data from any unauthorized attempts to extract or review data. These protocols make sure that no unauthorized devices, users, or services can access the network data. Primarily, these protocols depend on encryption to secure data. Secure Socket Layer(SSL) It is a network security protocol mainly used for protecting sensitive data and securing internet connections. SSL allows both server-to-server and client-to-server communication. All the data transferred through SSL is encrypted thus stopping any unauthorized person from accessing it. Hypertext Transfer Protocol(HTTPS) It is the secured version of HTTP. this protocol ensures secure communication between two computers where one sends the request through the browser and the other fetches the data from the web server. Transport Layer Security(TLS) It is a security protocol designed for data security and privacy over the internet, its functionality is encryption, checking the integrity of data i.e., whether it has been tampered with or not, and authentication. It is generally used for encrypted communication between servers and web apps, like a web browser loading a website, it can also be used for encryption of messages, emails, and VoIP. Some Other Protocols Internet Message Access Protocol (IMAP) ICMP protocol is used to retrieve message from the mail server. By using ICMP mail user can view and manage mails on his system. 6 Session Initiation Protocol (SIP) SIP is used in video, voice, and messaging application. This protocol is used to initiating, Managing, Terminating the session between two users while they are communicating. Real-Time Transport Protocol (RTP) This protocol is used to forward audio, video over IP network. This protocol is used with SIP protocol to send audio, video at real-time. Rout Access Protocol (RAP) RAP is used in network management. It helps to user for accessing the nearest router for communication. RAP is less efficient as compared to SNMP. Point To Point Tunnelling Protocol (PPTP) It is used to implement VPN ( Virtual Private Network ). PPTP protocol append PPP frame in IP datagram for transmission through IP based network. Trivial File Transfer Protocol (TFTP) TFTP is the simplified version of FTP. TFTP is also used to transfer file over internet Resource Location Protocol (RLP) RLP is used to assign the resource such as server, printer, or other devices over the internet to the user. It is used to locate the resource to the client for broadcast query. Standard organizations Computer Networking Standards Bodies Computer networking relies on standardized protocols and technologies to ensure interoperability and seamless communication between devices. Several organizations play a crucial role in developing and maintaining these standards. Here are some key standard organizations in computer networking: 1. IEEE (Institute of Electrical and Electronics Engineers): A US-based professional organization that develops and publishes standards for electrical, electronics, and computer engineering, including networking protocols such as Ethernet (802.3) and Wi-Fi (802.11). 2. ITU-T (International Telecommunication Union - Telecommunication Standardization Sector): A specialized agency of the United Nations responsible for setting global standards for telecommunications, including data transmission, networking, and internet protocols. 3. ANSI (American National Standards Institute): A private, non-profit organization that coordinates the development of voluntary national standards in the United States, including standards for data communication and networking. 7  4. ETSI (European Telecommunications Standards Institute): A non-profit organization that develops and publishes standards for telecommunications, including wireless and fixed networks, in Europe and globally. 5. 3GPP (3rd Generation Partnership Project): A collaboration of seven telecommunications standards organizations (ARIB, ATIS, CCSA, ETSI, TSDSI, TTA, and TTC) that develops standards for cellular telecommunications technologies, including radio access, core network, and service capabilities. 6. ISO (International Organization for Standardization): A global organization that develops and publishes standards for a wide range of industries, including information technology, telecommunications, and data communication These organizations work together to ensure that standards are compatible and interoperable, enabling seamless communication between devices and networks worldwide. Some notable standards developed by these organizations include: Ethernet (IEEE 802.3) Wi-Fi (IEEE 802.11) TCP/IP (ITU-T and ISO) ISDN (ITU-T) GSM and LTE (3GPP) Broadband ISDN (ITU-T) X.25 and X.75 (ITU-T) These standard organizations play a vital role in maintaining the stability and consistency of computer networking, ensuring that devices and networks from different manufacturers can communicate effectively and efficiently. Bandwidth Bandwidth, or precisely network bandwidth, is the maximum rate at which data transfer occurs across any particular path of the network. Bandwidth is basically a measure of the amount of data that can be sent and received at any instance of time. That simply means that the higher the bandwidth of a network, the larger the amount of data the network can be sending to and from across its path. Be careful not to confuse bandwidth with closely related terms such as the data rate and the throughput. Bandwidth is something that deals with the measurement of capacity and not the speed of data transfer. Units of Measurement Bandwidth is usually measured in bits transferred per second through a path or link. The common units of bandwidth we come across are as follows. bps (Bits per second) Mbps (Megabits per second) Gbps (Gigabits per second) 8 Example: Here, a bandwidth of 10 bps for a channel, is just another way of saying that a maximum of 10 bits can be transferred using that link for any given time. It has no relation with the transfer speed of the channel. Physical Layer Property in OSI Model The physical Layer in the OSI Model as we know comes as the bottom-most layer in the Open System Interconnection (OSI) Reference Model. And since this layer deals with communication of the raw data streams across a physical transmission medium bandwidth is an essential parameter of the layer. Nature of Bandwidth If we closely understand the concept of bandwidth and the information we get from the bandwidth measurement of a network link we can clearly see that it is more of a theoretical (or not real-time value) concept in terms of communication taking place across the network. It is the maximum capacity possible that might not be achieved during most instances of communication. Bandwidth does not depend on the sender and receiver components and is solely determined by the communication media employed to carry the information. Hence, bandwidth is never affected by any physical obstruction as it is a theoretical measurement parameter in a way. Importance of Bandwidth It is the bandwidth of a web page that determines how quickly it will load in a browser. When choosing a web hosting platform, this is arguably the most important factor to consider. It is important to consider how the website and internet connection will impact bandwidth. The bandwidth requirement for a website with a lot of graphics can reach 10 gigabytes or more. The bandwidth usage of a simpler website will also be lower. A faster internet connection will allow you to download web pages and movies smoothly, just as a higher bandwidth will improve the user experience. 9 Bandwidth Difference between Bandwidth and Speed Bandwidth and Speed can be differentiated on the basis that Bandwidth tells the quantity whereas Speed tells the fastness of the information. Bandwidth is the quantity whereas Speed is the fastness, how early the information is receiving its destination. For more, refer to Difference Between Bandwidth and Speed. Difference between Bandwidth and Latency Latency can be easily defined as How late the information is coming to the user and Bandwidth is simply the data coming to the user. This is the main characteristic difference between Bandwidth and Latency. An example of latency that we suffer almost every day is Buffering and Bandwidth can be referred to as simply the amount of data received. Difference between Bandwidth and Throughput Throughput is simply the data that is finally reaching the destination or in simple words, the product data and Bandwidth is the data coming to the user. This is the main difference between Bandwidth and Throughput. There are some factors that impact the Throughput is that Network Speed, Packet Loss, etc. Data Transmission Data transmission rate, also known as data transfer rate, refers to the amount of data transmitted from one device to another within a specified time frame. It is typically measured in bits per second (bit/s), 10 kilobits per second (kbit/s), megabits per second (Mbit/s), gigabits per second (Gbit/s), or terabits per second (Tbit/s). Units of Measurement Common data rate units include: 1 bit/s 1 Kbit/s (1,000 bit/s) 1 Mbit/s (1,000,000 bit/s) 1 Gbit/s (1,000,000,000 bit/s) 1 Tbit/s (1,000,000,000,000 bit/s) Calculating the data transmission rate can involve different methods depending on the context, but here are some common approaches: 1. Basic Formula The fundamental formula for calculating data transmission rate is: Total Data Transmitted is typically measured in bits, bytes, kilobytes, etc. Total Time Taken is measured in seconds. 2. Example Calculation If you transfer 500 megabytes of data in 10 seconds: 1. Convert megabytes to bits: 500MB =500 × 8 megabits = 4000 megabits 2. Use the formula: Data Rate= 4000 megabits / 10 Seconds = 400 Mbps 11 3. Using Network Protocols In networking, data rates can be affected by the protocol used (TCP, UDP, etc.) and the overhead involved. Throughput Calculation: You can calculate throughput using: Throughput=Effective Data Transferred÷Time\text{Throughput} = \text{Effective Data Transferred} \div \text{Time}Throughput=Effective Data Transferred÷Time Take into account the protocol overhead to get the effective data rate. 4. Tools and Software Network monitoring tools can also measure data rates by analyzing packet flows, often providing real- time statistics and averages over time. 5. Considering Factors When calculating practical data rates, consider: Latency: Higher latency can decrease effective throughput. Packet Loss: Lost packets require retransmission, lowering the effective data rate. Network Conditions: Congestion and noise can impact speeds. Baud Rate Computers communicate by transmitting bits of digital data from one device to another device through transmission media. You can send and receive data without worrying about setting up the details. However, for some devices, we need to supply baud rates and other details. Old devices use parallel and serial communication ports, though their speeds would be considered slow in today’s time. All the devices that are used today handle all the coordination of communication in the background of the computer. For example, when you plug a new device in your computer, it prompts a message like “installing device drivers” after they are installed and the device is configured you never have to repeat this process. Though for industrial devices it could be different they might ask you to provide information such as Baud rate, communication ports to route the information, etc. People often confuse baud rate with bit rate, though they are completely different. The baud rate can be higher or lower than the bit rate depending upon the type of encoding scheme used (Such as NRZ, Manchester, etc.). 1. Bit rate : Bit rate is the number of binary bits (1s or 0s) transmitted per second. Bit rate = number of bits transmitted/ total time (in seconds) The bit rate can also be defined in terms of baud rate: 12 Bit rate = Baud rate x bits per signal or symbol 2. Baud rate : Baud rate is the rate at which the number of signal elements or changes to the signal occurs per second when it passes through a transmission medium. The higher a baud rate is the faster the data is sent/received. Baud rate = number of signal elements/total time (in seconds) For Example: Image 1 In Image 1, Number of signal elements (marked in red color) = 3, Number of bits transmitted (1, 0, 1) = 3. So, Here Bit rate = 3/1 = 3 bits per second. And, Baud rate = 3/1 = 3 baud per second. Image 2 In Image 2, Number of signal elements (marked in red color) = 6, Number of bits transmitted (1, 1, 0) = 3. So, Here Bit rate = 3/1 = 3 bits per second. and, Baud rate = 6/1 = 6 baud per second. Signal element: A signal element is the smallest unit of a digital signal. A signal is one of several voltages, phase changes, or frequencies. For Digital signals 1 signal element is a signal with constant amplitude. For Analog signals, 1 signal element is a signal with the same amplitude, phase, and frequency. Why baud rate is important ? Baud rate is important because: 13  Baud rate can determine the bandwidth requirements for transmission of the signal. Baud rate is also used for the calculation of the Bit rate of a communication channel. It is a tuning parameter (i.e., it adjusts the Network congestion in data networking) for the transmission of a signal. It specifies how fast data can be sent over a serial line or serial interface (it’s an interface that sends data as a series of bits over a single wire.). Understanding Baud Rate 1. Definition: Baud rate measures the number of signal changes (symbols) per second in a communication channel. A symbol can represent one or more bits of information depending on the encoding scheme used. 2. Baud Rate vs. Bit Rate: Baud Rate: The number of signal changes per second. Bit Rate: The number of bits transmitted per second. In simple binary systems (one bit per symbol), the baud rate equals the bit rate. In systems using modulation techniques (e.g., QAM), one symbol may represent multiple bits, making the bit rate higher than the baud rate. Applications of Baud Rate 1. Serial Communication: Common in devices like modems, UARTs (Universal Asynchronous Receiver- Transmitters), and other serial interfaces (e.g., RS-232, RS-485). Typical baud rates include 300, 1200, 2400, 9600, 115200, etc. 2. Telecommunications: Used in data transmission over telephone lines, where modems convert digital signals to analog signals for transmission. 3. Data Logging and Monitoring: In industrial applications, sensors communicate data over serial connections at specific baud rates to ensure reliable data transfer. 4. Embedded Systems: Many microcontrollers use specific baud rates to communicate with peripherals, ensuring compatibility and reliability in data transmission. Implications of Baud Rate 1. Performance: 14  Higher baud rates allow for faster data transmission but may introduce errors if the channel cannot support the increased speed due to noise or distance limitations. 2. Distance: As baud rates increase, the maximum distance for reliable communication typically decreases. This is due to increased susceptibility to noise and signal degradation. 3. Error Handling: Higher baud rates may necessitate more robust error detection and correction mechanisms to maintain data integrity. 4. Device Compatibility: Devices communicating over a serial connection must agree on the baud rate for successful communication. Mismatched baud rates can lead to data corruption or loss. 5. Trade-offs: Selecting an optimal baud rate often involves balancing speed, reliability, and hardware capabilities. Lower baud rates might be more reliable over longer distances, while higher rates are beneficial for short-range, high-speed applications. Transmission Modes in Computer Networks (Simplex, Half-Duplex and Full-Duplex) Transmission modes also known as communication modes, are methods of transferring data between devices on buses and networks designed to facilitate communication. They are classified into three types: Simplex Mode, Half-Duplex Mode, and Full-Duplex Mode. In this article, we will discuss we will discuss Transmission Modes. What is Transmission Modes? Transmission mode means transferring data between two devices. It is also known as a communication mode. Buses and networks are designed to allow communication to occur between individual devices that are interconnected. There are three types of transmission modes: 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. 15 Advantages of Simplex Mode Simplex mode is the easiest and most reliable mode of communication. It is the most cost-effective mode, as it only requires one communication channel. There is no need for coordination between the transmitting and receiving devices, which simplifies the communication process. Simplex mode is particularly useful in situations where feedback or response is not required, such as broadcasting or surveillance. Disadvantages of Simplex Mode Only one-way communication is possible. There is no way to verify if the transmitted data has been received correctly. Simplex mode is not suitable for applications that require bidirectional communication. 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. Advantages of Half Duplex Mode Half-duplex mode allows for bidirectional communication, which is useful in situations where devices need to send and receive data. It is a more efficient mode of communication than simplex mode, as the channel can be used for both transmission and reception. 16  Half-duplex mode is less expensive than full-duplex mode, as it only requires one communication channel. Disadvantages of Half Duplex Mode Half-duplex mode is less reliable than Full-Duplex mode, as both devices cannot transmit at the same time. There is a delay between transmission and reception, which can cause problems in some applications. There is a need for coordination between the transmitting and receiving devices, which can complicate the communication process. 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. Advantages of Full-Duplex Mode Full-duplex mode allows for simultaneous bidirectional communication, which is ideal for real-time applications such as video conferencing or online gaming. It is the most efficient mode of communication, as both devices can transmit and receive data simultaneously. Full-duplex mode provides a high level of reliability and accuracy, as there is no need for error correction mechanisms. Disadvantages of Full-Duplex Mode Full-duplex mode is the most expensive mode, as it requires two communication channels. It is more complex than simplex and half-duplex modes, as it requires two physically separate transmission paths or a division of channel capacity. 17  Full-duplex mode may not be suitable for all applications, as it requires a high level of bandwidth and may not be necessary for some types of communication. Difference Between Simplex, Half duplex, and Full Duplex Transmission Modes Parameters Simplex Half Duplex Full Duplex Half Duplex mode is a Full Duplex mode is a Simplex mode is a uni- The direction of two-way directional two-way directional directional communication communication but one communication communication. at a time. simultaneously. In simplex mode, In Half Duplex mode, In Full Duplex mode, Sender and Sender can send the Sender can send the data Sender can send the data Receiver data but that sender and also can receive the and also can receive the can’t receive the data. data but one at a time. data simultaneously. Usage of one channel Usage of one channel Usage of two channels Channel usage for the transmission of for the transmission of for the transmission of data. data. data. The simplex mode The Half Duplex mode Full Duplex provides provides less provides less better performance than Performance performance than half performance than full simplex and half duplex duplex and full duplex. duplex. mode. Bandwidth Simplex utilizes the The Half-Duplex The Full-Duplex doubles Utilization maximum of a single involves lesser the utilization of bandwidth. utilization of single transmission bandwidth. bandwidth at the time of transmission. It is suitable for those It is suitable for those It is suitable for those transmissions when transmissions when there transmissions when there is requirement of is requirement of sending Suitable for there is requirement of sending data in both and receiving data full bandwidth for directions, but not at the simultaneously in both delivering data. same time. directions. 18  Parameters Simplex Half Duplex Full Duplex Example of simplex Example of half duplex Example of full duplex Examples mode are: Keyboard mode is: Walkie-Talkies. mode is: Telephone. and monitor. Analog Signal and Digital Signal Digital Signal A digital signal is a signal that represents data as a sequence of discrete values. A digital signal can only take on one value from a finite set of possible values at a given time. With digital signals, the physical quantity representing the information can be many things: Variable electric current or voltage. Analog Signals An analog signal is a continuous signal that varies over time and can take on any value within a given range. Unlike digital signals, which represent information in discrete binary form, analog signals are characterized by their smooth and continuous waveforms. Importance of Analog to Digital Conversion The main role of ADC in modern technology development process is the transition of voice communication systems from outdated analogue signal processing to the more advanced voice over IP, or VoIP, systems of today is largely due to the contribution. The teletypewriters and other computer input devices needed to be connected to a modem which was connected to a mainframe or other front end computer system to communicate with the required 19 computer systems. In contrast to the ultrahigh-speed networks of today, modem transmission speeds were modest to process. The systems for smaller office applications and the digital private branch exchange, or PBX, were developed by using ADC technology as the foundation to process properly. Techniques of Analog-to-Digital Conversion The following techniques can be used for Analog to Digital Conversion – a. PULSE CODE MODULATION The most common technique to change an analog signal to digital data is called pulse code modulation (PCM). A PCM encoder has the following three processes: 1.Sampling 2.Quantization 3.Encoding Low pass filter : The low pass filter eliminates the high frequency components present in the input analog signal to ensure that the input signal to sampler is free from the unwanted frequency components. This is done to avoid aliasing of the message signal. 1.Sampling – The first step in PCM is sampling. Sampling is a process of measuring the amplitude of a continuous-time signal at discrete instants, converting the continuous signal into a discrete signal. There are three sampling methods: (i) Ideal Sampling: In ideal Sampling also known as Instant sampling pulses from the analog signal are sampled. This is an ideal sampling method and cannot be easily implemented. (ii) Natural Sampling: Natural Sampling is a practical method of sampling in which pulse have finite width equal to T. The result is a sequence of samples that retain the shape of the analog signal. (iii) Flat top sampling: In comparison to natural sampling flat top sampling can be easily obtained. In this sampling technique, the top of the samples remains constant by using a circuit. This is the most common sampling method used. 20 Nyquist Theorem: One important consideration is the sampling rate or frequency. According to the Nyquist theorem, the sampling rate must be at least 2 times the highest frequency contained in the signal. It is also known as the minimum sampling rate and given by: Fs =2*fh 2.Quantization – The result of sampling is a series of pulses with amplitude values between the maximum and minimum amplitudes of the signal. The set of amplitudes can be infinite with non- integral values between two limits. The following are the steps in Quantization: 1.We assume that the signal has amplitudes between Vmax and Vmin 2.We divide it into L zones each of height d where, d= (Vmax- Vmin)/ L 3.The value at the top of each sample in the graph shows the actual amplitude. 4.The normalized pulse amplitude modulation(PAM) value is calculated using the formula amplitude/d. 5.After this we calculate the quantized value which the process selects from the middle of each zone. 6.The Quantized error is given by the difference between quantized value and normalised PAM value. 7.The Quantization code for each sample based on quantization levels at the left of the graph. 3.Encoding – The digitization of the analog signal is done by the encoder. After each sample is quantized and the number of bits per sample is decided, each sample can be changed to an n bit code. Encoding also minimizes the bandwidth used. Note that the number of bits for each sample is determined from the number of quantization levels. If the number of quantization levels is L, the number of bits is n bit = log 2 L. 21 b. DELTA MODULATION Since PCM is a very complex technique, other techniques have been developed to reduce the complexity of PCM. The simplest is delta Modulation. Delta Modulation finds the change from the previous value. Modulator – The modulator is used at the sender site to create a stream of bits from an analog signal. The process records a small positive change called delta. If the delta is positive, the process records a 1 else the process records a 0. The modulator builds a second signal that resembles a staircase. The input signal is then compared with this gradually made staircase signal. Following rules for output: 1.If the input analog signal is higher than the last value of the staircase signal, increase delta by 1, and the bit in the digital data is 1. 2.If the input analog signal is lower than the last value of the staircase signal, decrease delta by 1, and the bit in the digital data is 0. Demodulator – The demodulator takes the digital data and, using the staircase maker and the delay unit, creates the analog signal. The created analog signal, however, needs to pass through a low-pass filter for smoothing. c. ADAPTIVE DELTA MODULATION The performance of a delta modulator can be improved significantly by making the step size of the modulator assume a time-varying form. A larger step-size is needed where the message has a steep slope of modulating signal and a smaller step-size is needed where the message has a small slope. The size is adapted according to the level of the input signal. This method is known as adaptive delta modulation (ADM). 22 Applications Digital Signal Processing: In this process, the systems for processing, storing, or transporting almost any analogue signal into digital format require ADCs to perform well. Let’s an example, in TV tuner cards this is use as fast video analog-to-digital converters. Recording Music System: The modern digital audio workstation-based sound recording and music reproduction technologies both are basically rely heavily on analog-to-digital converters. Scientific Instruments or Projects: The digital imaging systems are normally use analog-to-digital converters for digitizing the instruments and projects pixels. Digital to Analog Conversion Digital Signal – A digital signal is a signal that represents data as a sequence of discrete values; at any given time it can only take on one of a finite number of values. Analog Signal – An analog signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity i.e., analogous to another time varying signal. Digital-to-analog conversion is the process of changing one of the characteristics of an analog signal based on the information in digital data. The following techniques can be used for Digital to Analog Conversion: 1. Amplitude Shift keying – A digital modulation technique in which the amplitude of the carrier wave is altered according to the modulating signal (bitstream) is known as Amplitude Shift Keying (ASK). It is the easiest and straightforward digital modulation scheme. ASK is sometimes known as On-Off keying because the carrier wave swings between 0 and 1 according to the low and high level of input signal respectively. (Coherent and Decoherent technique) Amplitude Shift Keying is a technique in which carrier signal is analog and data to be modulated is digital. The amplitude of analog carrier signal is modified to reflect binary data. The binary signal when modulated gives a zero value when the binary data represents 0 while gives the carrier output when data is 1. The frequency and phase of the carrier signal remain constant. 23 Advantages of amplitude shift Keying – It can be used to transmit digital data over optical fiber. The receiver and transmitter have a simple design which also makes it comparatively inexpensive. It uses lesser bandwidth as compared to FSK thus it offers high bandwidth efficiency. Disadvantages of amplitude shift Keying – It is supersensitive to noise interference and entire transmissions could be lost due to this. 2. Frequency Shift keying – In this modulation the frequency of analog carrier signal is modified to reflect binary data. The output of a frequency shift keying modulated wave is high in frequency for a binary high input and is low in frequency for a binary low input. The amplitude and phase of the carrier signal remain constant. 24 What is frequency? Alternating current (ac) frequency is the number of cycles per second in an ac sine wave. Frequency is the rate at which current changes direction per second. It is measured in hertz (Hz), an international unit of measure where 1 hertz is equal to 1 cycle per second. Hertz (Hz) = One hertz is equal to one cycle per second. Cycle = One complete wave of alternating current or voltage. Alternation = One half of a cycle. Period = The time required to produce one complete cycle of a waveform. At its most basic, frequency is how often something repeats. In the case of electrical current, frequency is the number of times a sine wave repeats, or completes, a positive-to-negative cycle. The more cycles that occur per second, the higher the frequency. Example: If an alternating current is said to have a frequency of 3 Hz (see diagram below), that indicates its waveform repeats 3 times in 1 second. Advantages of frequency shift Keying – Frequency shift keying modulated signal can help avoid the noise problems beset by ASK. It has lower chances of an error. It provides high signal to noise ratio. The transmitter and receiver implementations are simple for low data rate application. Disadvantages of frequency shift Keying – 25  It uses larger bandwidth as compared to ASK thus it offers less bandwidth efficiency. It has lower power efficiency. 3. Phase Shift keying – In this modulation the phase of the analog carrier signal is modified to reflect binary data.The amplitude and frequency of the carrier signal remains constant. It is further categorized as follows: 1.Binary Phase Shift Keying (BPSK): This is also called as 2-phase PSK or Phase Reversal Keying. In this technique, the sine wave carrier takes two phase reversals such as 0° and 180°. BPSK is basically a Double Side Band Suppressed Carrier (DSBSC) modulation scheme, for message being the digital information. BPSK also known as phase reversal keying or 2PSK is the simplest form of phase shift keying. The Phase of the carrier wave is changed according to the two binary inputs. In Binary Phase shift keying, difference of 180 phase shift is used between binary 1 and binary 0. This is regarded as the most robust digital modulation technique and is used for long distance wireless communication. 2.Quadrature phase shift keying: This is the phase shift keying technique, in which the sine wave carrier takes four phase reversals such as 0°, 90°, 180°, and 270°. If this kind of techniques are further extended, PSK can be done by eight or sixteen values also, depending upon the requirement. 26 This technique is used to increase the bit rate i.e we can code two bits onto one single element. It uses four phases to encode two bits per symbol. QPSK uses phase shifts of multiples of 90 degrees. It has double data rate carrying capacity compare to BPSK as two bits are mapped on each constellation points. Advantages of phase shift Keying – It is a more power efficient modulation technique as compared to ASK and FSK. It has lower chances of an error. It allows data to be carried along a communication signal much more efficiently as compared to FSK. Disadvantages of phase shift Keying – It offers low bandwidth efficiency. The detection and recovery algorithms of binary data is very complex. It is a non coherent reference signal. Phase Phase is the fraction of a period (i.e., the time required to complete a full cycle). 27 Network Architecture: Client Server Network, Peer To Peer In the world of network architecture, two fundamental models are widely utilized to structure data exchange and resource sharing. For the purpose of this discussion, two types of networks are available; the Client-Server Network and the Peer-to-Peer Network. All the models have their strengths, weaknesses, and appropriate applications that make them suitable for use. An understanding of these differences will assist in choosing suitable approaches for different networking requirements. 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. This model are broadly used network model. In the Client-Server Network, Clients and servers are differentiated, and Specific servers and clients are present. In Client-Server Network, a Centralized server is used to store the data because its management is centralized. In Client-Server Network, the Server responds to the services which is requested by the Client. 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: The client-server network offers a good user interface, and can handle files easily. In a client-server network, we can share the resources easily. 28  Users have the freedom to access files stored in the central storage from any location. The client-server network has complete control over all network processes and activities because it is a centralised network. What We Need to Know About Client-Server Network The following is the list of some important things which we need to know about the client-server network: 1.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. 2.Client-Server Network is more scalable and stable. 3.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. 4.In Client-Server Network, client and server are distinct, and there are particular servers and clients. 5.In Client-Server Network, the client requests a service, and the server provides it. 6.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. 7.The access time for a service is longer in client-server networks because more client's requests services from a server. 8.If the number of clients increases, there are no performance issues with the client-server setup. This is because the server handles most of the heavy lifting and the clients are not needed to share their computing resources. 9.When compared to peer-to-peer networks, client-server networks are far more secure. This is due to the server's ability to authenticate a client's access to any network resource. 10.The clients in a client-server network reply on the server. The operation of every client will be interfered with if the server fails. Hence it is unreliable. What is 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. 29 In a peer-to-peer network, a node joins the network and begins offering services, and then asks other nodes for services. Which node offers which service can be determined using one of two ways. The service that a node offers is registered with a centralised lookup service. Any node that needs a service consults the centralised lookup to determine which node offers particular facilities. Then, 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. Additionally, the network setup doesn't call for a lot of hardware. Peer-to-peer networks, on the other hand, lack security significantly. Keeping an ordered file structure might be challenging as well. Additionally, users are responsible for managing their own backups. 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: Each device linked to the peer-to-peer network exchanges resources with other network nodes. The setup of a peer-to-peer network is easily established with the help of specialized software. Between several devices, resources are exchanged without any issues. Peer-to-peer networks are very reliable because other systems continue to function even when a server fails. Being a part of a peer-to-peer network makes it simple for nodes to share resources like a What You Need to Know About Peer-To-Peer Network 1.The main focus of the peer-to-peer groups is on connectivity. We can mostly find it in small offices and homes where centralized access to files or services is unnecessary. 2.In a peer-to-peer network, every pair contains its own data, and the server is decentralized. 3.It is less expensive to implement the peer-to-peer network. The simplest peer-to-peer networks can be created by connecting two computers tother using an Ethernet cable. 30  4.If the number of peers increases then, the peer-to-peer network would be less stable, 5.In this network, the client and server cannot be distinguished. 6.In a peer-to-peer network, each node is able to request and respond to the services. 7.Compared to a client-server network, the peer-to-peer network is less secure, and it becomes trickier if the number of clients increases. 8.In a peer-to-peer network, there are multiple services-providing nodes hence it is more reliable. 9.Since all resources in a peer-to-peer network are shared, performance issues are quite likely to arise in the case of a large number of clients. 10.Because the service-providing nodes in a peer-to-peer network are dispersed, the service- requesting nodes do not have a wait very long. Basis of Client-Server Network Peer-to-Peer Network Comparison In a client-server network, we have a In a peer-to-peer network, clients are Basic specific server and specific clients not distinguished; every node act as a connected to the server. client and server. A Client-Server network is more A Peer-to-Peer is less expensive to Expense expensive to implement. implement. It is less stable and scalable, if the It is more stable and scalable than a peer- Stability number of peers increases in the to-peer network. system. In a client-server network, the data is stored In a peer-to-peer network, each peer Data in a centralized server. has its own data. A server is not bottlenecked since the A server may get overloaded when many services are dispersed among Server customers make simultaneous service numerous servers using a peer-to- requests. peer network. Focus Sharing the information. Connectivity. The server provides the requested service in Each node has the ability to both Service response to the client's request. request and delivers services. Because the server does the bulk of the Because resources are shared in a big Performance work, performance is unaffected by the peer-to-peer network, performance growth of clients. will likely to suffer. A Client-Server network is a secured The network's security deteriorates, network because the server can verify a Security and its susceptibility grows as the client's access to any area of the network, number of peers rises. making it secure. 31 Key Differences Between Client-Server and Peer-to-Peer Network The main distinction between client-server and peer-to-peer networks is that client-server networks have a dedicated server and specialised clients, whereas peer-to-peer networks allow any node to operate as both a client and a server. The importance of connectivity between peers is greater in the peer-to-peer architecture than in the client-server approach. In the client-server network, each peer has its own data, in contrast to the client-server network, where data is stored on a single server. In the client-server network, the server gives the client services. Peer-to-peer, on the other hand, allows each peer to both requests and deliver services. The client-server network is more stable and scalable than a peer-to-peer, The client-server network is more costly than peer-to-peer network. Peer-to-peer systems have distributed servers, which reduces the likelihood that a server would become bottlenecked. Client-server systems, on the other hand, have a single server that serves all the clients, increasing the likelihood that a server will become bottlenecked. 32