Applications of Computer Networks

Define: Applications of Computer Networks

Applications of Computer Networks refer to the various uses, services, and benefits that emerge from connecting computers and devices together. Networks enable a wide array of functionalities, transforming how individuals and organizations communicate, share information, and access resources.

Key Points of Network Applications:

• ⭐ Communication: Fundamentally changes how people interact remotely.
• ⭐ Resource Access: Allows distributed access to computing resources.
• ⭐ Information Sharing: Facilitates easy and fast dissemination of data.
• ⭐ Business Transformation: Drives e-commerce, cloud services, and global operations.
• ⭐ Entertainment & Education: Enables streaming, online gaming, and e-learning platforms.

Detailed Applications:

• ✨ 1. Communication (संचार):
  • Email: Asynchronous message exchange globally.
  • Instant Messaging/Chat: Real-time text, voice, and video communication.
  • Voice over IP (VoIP): Internet-based phone calls (e.g., Skype, WhatsApp calls).
  • Video Conferencing: Real-time visual and audio meetings across distances.
  • Social Media: Platforms for sharing content and connecting with people.
• ✨ 2. Resource Sharing (संसाधन साझाकरण):
  • File Sharing: Sharing documents, images, and other files across devices/users.
  • Printer Sharing: Multiple users accessing a single printer on a network.
  • Software Sharing: Centralized software deployment and updates.
  • Hardware Sharing: Sharing expensive devices like plotters, specialized servers.
  • Data Sharing: Centralized databases and distributed access to information.
• ✨ 3. E-commerce and Financial Transactions (ई-कॉमर्स और वित्तीय लेन-देन):
  • Online Shopping: Buying/selling products/services (e.g., Amazon, Flipkart).
  • Online Banking: Managing bank accounts, funds transfers, bill payments.
  • Stock Trading: Buying/selling shares and commodities online.
  • Digital Payments: Mobile wallets, UPI transactions.
  • Financial Information: Accessing real-time market data.
• ✨ 4. Entertainment and Multimedia (मनोरंजन और मल्टीमीडिया):
  • Streaming Services: On-demand movies, TV shows, music (e.g., Netflix, Spotify).
  • Online Gaming: Multiplayer games across geographical locations.
  • Video Sharing: User-generated content platforms (e.g., YouTube, TikTok).
  • Podcasts and Audiobooks: Digital content consumption.
  • Virtual Reality (VR) / Augmented Reality (AR): Network-enabled immersive experiences.
• ✨ 5. Cloud Computing and Distributed Services (क्लाउड कंप्यूटिंग और वितरित सेवाएं):
  • Cloud Storage: Storing data remotely (e.g., Google Drive, Dropbox).
  • Cloud Computing: Accessing virtual servers and computing power remotely (e.g., AWS, Azure).
  • Software as a Service (SaaS): Web-based applications (e.g., Gmail, Office 365).
  • Distributed Databases: Data spread across multiple network nodes.
  • Big Data Analytics: Processing large datasets using networked computing resources.

Concept of Layering

Define: Concept of Layering

The concept of layering (लेयरिंग की अवधारणा) in computer networks refers to the architectural design where communication tasks are broken down into several smaller, more manageable sub-tasks. Each sub-task is assigned to a distinct layer, and each layer builds upon the services provided by the layer below it, hiding the complexities of lower layers from the layers above.

Key Points of Layering:

• ⭐ Modularity: Complex network communication is broken into independent modules (layers).
• ⭐ Abstraction: Each layer performs specific functions, hiding the complexities of lower-layer operations.
• ⭐ Standardization: Promotes common interfaces between layers, allowing different technologies to be interchangeable within a layer.
• ⭐ Simplified Development: Designers can focus on one layer at a time without affecting others.
• ⭐ Ease of Maintenance: Changes in one layer do not require changes in other layers (as long as interfaces remain constant).

Applications:

• ✨ OSI and TCP/IP reference models.
• ✨ Network protocol stack design.
• ✨ Operating system’s networking subsystem.
• ✨ Hardware abstraction layers in device drivers.
• ✨ Designing complex distributed software systems.

Advantages:

• 👍 Reduces complexity by breaking down monolithic tasks.
• 👍 Enhances interoperability between different vendors’ products.
• 👍 Easier debugging and troubleshooting as issues can be isolated to specific layers.

Disadvantages:

• 👎 Overhead: Data needs to be processed at each layer, adding header/trailer info, which adds overhead.
• 👎 Redundancy: Some functionality might be duplicated across layers.
• 👎 Increased Latency: Processing at each layer can add delays to data transmission.

OSI Model

Define: OSI Model

The Open Systems Interconnection (OSI) model (ओएसआई मॉडल) is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven distinct logical layers. Developed by the International Organization for Standardization (ISO), it is a widely used reference to describe data communication processes, but not a direct implementation protocol stack.

Key Points of OSI Model:

• ⭐ 7 Layers: Organizes communication into seven specific functional layers.
• ⭐ Conceptual Model: A theoretical standard for network architecture, not an implementation.
• ⭐ Vendor Independence: Promotes interoperability between products from different manufacturers.
• ⭐ Strict Protocol Stacks: Each layer communicates only with the layer directly above and below it.
• ⭐ Protocol Encapsulation: Each layer adds its own header (and sometimes a footer) to the data unit from the layer above, then passes it down.

Functions of OSI Layers:

1. Physical Layer (परत 1: भौतिक परत)

Define: The Physical Layer (भौतिक परत) is the lowest layer of the OSI model. It deals with the physical aspects of the network medium, such as electrical, mechanical, procedural, and functional specifications for transmitting raw bit streams over a physical link. It’s about how bits are transmitted physically.

• ✨ Raw Bit Stream: Responsible for the transmission and reception of unstructured raw data bits.
• ✨ Physical Medium: Specifies the type of cabling, connectors, voltages, and data rates.
• ✨ Signal Encoding: Determines how bits are converted into electrical or optical signals.
• ✨ Device Interaction: Deals with the interface between devices and the transmission medium.
• ✨ No Error Correction: Primarily concerned with physical transmission, not error handling or framing.

Functions:

• ⚡ Specifies characteristics of physical medium (e.g., copper wire, fiber optic).
• ⚡ Defines electrical and mechanical interfaces (e.g., voltage levels, pin layouts).
• ⚡ Determines data transmission rate (e.g., bits per second).
• ⚡ Manages synchronization of bits between devices.
• ⚡ Handles topology (e.g., star, bus) and transmission mode (simplex, duplex).

Example:

Ethernet cable specifications (e.g., Cat5e, Cat6), fiber optic cables, connectors (RJ-45), and voltage levels for bit representation.

Applications:

• ✨ Ethernet cable connectivity.
• ✨ Fiber-optic communication links.
• ✨ Wi-Fi signal transmission characteristics.
• ✨ DSL and cable modem physical connections.
• ✨ USB connections for data transfer.

Advantages:

• 👍 Handles hardware specifics, making higher layers abstract.
• 👍 Provides the fundamental medium for all data transmission.
• 👍 Standardized interfaces for physical devices.

Disadvantages:

• 👎 No error handling at this level, susceptible to noise.
• 👎 Does not understand data structure beyond raw bits.
• 👎 Highly dependent on hardware specifics.

2. Data Link Layer (परत 2: डेटा लिंक परत)

Define: The Data Link Layer (डेटा लिंक परत) is responsible for reliable node-to-node data transfer across the physical layer. It handles error detection and correction, frames data into manageable units, and manages physical addressing (MAC addresses).

• ✨ Framing: Divides bit stream from Physical Layer into data frames.
• ✨ Physical Addressing: Uses MAC addresses for local delivery of frames.
• ✨ Error Control: Detects and sometimes corrects errors that occur on the physical link.
• ✨ Flow Control: Manages data flow to prevent fast sender from overwhelming a slow receiver.
• ✨ Medium Access Control (MAC): Regulates access to the shared physical medium for multiple devices.

Functions:

• ⚡ Provides framing, making data units recognizable.
• ⚡ Handles error detection and correction on the frame.
• ⚡ Implements flow control mechanisms.
• ⚡ Manages physical addressing (MAC address).
• ⚡ Provides mechanisms for shared media access control (e.g., CSMA/CD).

Example:

Ethernet (IEEE 802.3), Wi-Fi (IEEE 802.11), PPP (Point-to-Point Protocol).

Applications:

• ✨ Ethernet switches for local network communication.
• ✨ Wi-Fi network interface cards (NICs).
• ✨ DSL modem connection to the central office.
• ✨ Data transfer over point-to-point links (e.g., modem connection).
• ✨ Bluetooth data link connections.

Advantages:

• 👍 Ensures reliable data transfer between directly connected nodes.
• 👍 Manages shared access to the physical medium effectively.
• 👍 Detects and handles physical layer errors.

Disadvantages:

• 👎 Does not deal with routing across multiple networks.
• 👎 Limited to direct node-to-node communication.
• 👎 Error correction can add overhead.

3. Network Layer (परत 3: नेटवर्क परत)

Define: The Network Layer (नेटवर्क परत) is responsible for logical addressing (IP addresses), routing data packets across different networks, and determining the best path for data delivery from source to destination. It enables internetworking.

• ✨ Logical Addressing: Uses IP addresses to identify devices globally across networks.
• ✨ Routing: Determines the optimal path for data packets to travel from source to destination, often across multiple intermediate networks.
• ✨ Interconnection of Networks: Primary layer enabling communication between different LANs or segments.
• ✨ Packet Forwarding: Routes packets through various network devices like routers.
• ✨ Connectionless: Often operates connectionlessly, meaning packets are routed independently.

Functions:

• ⚡ Provides logical addressing (IP addresses).
• ⚡ Performs routing to find the best path for packets.
• ⚡ Handles fragmentation and reassembly of packets.
• ⚡ Implements packet forwarding mechanisms.
• ⚡ Manages congestion control at the network level.

Example:

Internet Protocol (IP), Internet Control Message Protocol (ICMP).

Applications:

• ✨ Global internet connectivity (IP routing).
• ✨ Virtual Private Networks (VPNs) using IPsec.
• ✨ Load balancing across multiple servers.
• ✨ Data forwarding through routers.
• ✨ Quality of Service (QoS) implementation over IP.

Advantages:

• 👍 Enables communication across disparate networks (internetworking).
• 👍 Determines the optimal routing paths for data delivery.
• 👍 Supports large-scale network architectures.

Disadvantages:

• 👎 Does not guarantee delivery (connectionless nature of IP).
• 👎 No error correction at this layer.
• 👎 Can be susceptible to network congestion issues.

4. Transport Layer (परत 4: ट्रांसपोर्ट परत)

Define: The Transport Layer (ट्रांसपोर्ट परत) is responsible for reliable end-to-end (process-to-process) data transfer between applications running on different hosts. It ensures data delivery, flow control, error control, and segmentation of data into segments for network transmission.

• ✨ End-to-End Delivery: Provides logical communication between processes running on source and destination hosts.
• ✨ Segmentation & Reassembly: Breaks application messages into segments and reassembles them at the destination.
• ✨ Connection-Oriented/Connectionless: Offers both reliable (TCP) and unreliable (UDP) services.
• ✨ Port Addressing: Uses port numbers to identify specific applications/processes.
• ✨ Flow Control: Prevents overwhelming the receiver by managing data rates.

Functions:

• ⚡ Performs segmentation and reassembly of data.
• ⚡ Provides port addressing for process-to-process communication.
• ⚡ Implements connection management (setup, maintenance, teardown for TCP).
• ⚡ Ensures end-to-end error control and retransmission for reliability (TCP).
• ⚡ Handles flow control and congestion control mechanisms.

Example:

Transmission Control Protocol (TCP), User Datagram Protocol (UDP).

Applications:

• ✨ Web browsing (HTTP using TCP).
• ✨ Email transfer (SMTP, POP3, IMAP using TCP).
• ✨ Video streaming (often UDP for speed over reliability).
• ✨ File Transfer Protocol (FTP using TCP).
• ✨ DNS queries (typically UDP, sometimes TCP).

Advantages:

• 👍 Ensures reliable, ordered, and error-free data delivery for applications (TCP).
• 👍 Provides multiplexing of different application streams over the same network connection.
• 👍 Adapts data flow based on network congestion.

Disadvantages:

• 👎 TCP’s reliability adds overhead and latency.
• 👎 UDP offers no reliability, susceptible to packet loss.
• 👎 Not directly aware of the network’s routing topology.

5. Session Layer (परत 5: सेशन परत)

Define: The Session Layer (सेशन परत) establishes, manages, and terminates sessions between applications. It synchronizes communication, allowing for the dialog control between communicating devices to occur and helps organize their communication.

• ✨ Dialog Control: Manages whose turn it is to transmit (full-duplex/half-duplex).
• ✨ Synchronization: Inserts checkpoints into the data stream for recovery in case of failures.
• ✨ Session Management: Sets up, coordinates, and terminates conversations.
• ✨ Token Management: Controls access to critical resources by exchanging tokens.
• ✨ No Direct Data Transfer: Doesn’t deal with the actual transfer of data bits or packets.

Functions:

• ⚡ Establishes, maintains, and terminates sessions between applications.
• ⚡ Provides dialog control, deciding who transmits when.
• ⚡ Implements synchronization points (checkpoints) for recovery.
• ⚡ Handles token management for specific operations.
• ⚡ Maps session names to transport addresses.

Example:

NetBIOS, RPC (Remote Procedure Call), Sockets API (though sockets span transport/session).

Applications:

• ✨ Dialogue management in online multiplayer games.
• ✨ Synchronizing a remote database update process.
• ✨ Handling remote procedure calls between distributed applications.
• ✨ Managing specific web session IDs for logged-in users (though more broadly in Application layer).
• ✨ Coordinating data exchange between two systems performing complex transactions.

Advantages:

• 👍 Organizes and synchronizes dialogue between applications.
• 👍 Facilitates crash recovery with synchronization points.
• 👍 Manages flow of conversation, simplifying application development.

Disadvantages:

• 👎 Many applications often handle session management directly in the application layer, bypassing it.
• 👎 Functionality sometimes redundant with Transport or Application layers.
• 👎 Adds overhead if not strictly necessary.

6. Presentation Layer (परत 6: प्रस्तुति परत)

Define: The Presentation Layer (प्रस्तुति परत) is responsible for data translation, encryption/decryption, and compression/decompression. It ensures that the data is presented in a format that the receiving application can understand, addressing differences in data representation (e.g., character codes, data types) between systems.

• ✨ Data Translation: Translates data formats for different systems (e.g., ASCII to EBCDIC).
• ✨ Encryption/Decryption: Encrypts data for secure transmission and decrypts upon reception.
• ✨ Compression/Decompression: Reduces data size for efficient transmission and decompresses for usage.
• ✨ Syntax Layer: Concerned with the syntax and semantics of the information transmitted.
• ✨ Independence: Provides data independence from application-level data types.

Functions:

• ⚡ Data translation and formatting.
• ⚡ Data encryption and decryption.
• ⚡ Data compression and decompression.
• ⚡ Character code translation (e.g., ASCII to Unicode).
• ⚡ Syntax conversion (e.g., JPEG, MPEG).

Example:

JPEG, MPEG, TLS/SSL (partially operates here and at transport), ASCII, EBCDIC.

Applications:

• ✨ Encrypted web traffic (HTTPS) via TLS/SSL.
• ✨ Image and video format conversion (e.g., converting PNG to JPEG for transmission).
• ✨ Data compression in file transfers.
• ✨ Character encoding conversion in messaging systems.
• ✨ Remote Desktop Protocols that manage graphical output formats.

Advantages:

• 👍 Ensures data compatibility between heterogeneous systems.
• 👍 Provides encryption for enhanced security.
• 👍 Reduces network traffic through data compression.

Disadvantages:

• 👎 Adds processing overhead due to data transformation.
• 👎 Functionality often integrated into the Application layer in modern implementations.
• 👎 Can add complexity to the protocol stack if used independently.

7. Application Layer (परत 7: एप्लीकेशन परत)

Define: The Application Layer (एप्लीकेशन परत) is the top layer of the OSI model. It provides network services directly to end-user applications. This layer interacts with software applications that implement a communicating component and directly interfaces with user-level protocols to accomplish specific tasks.

• ✨ User Interaction: Direct interface for end-user applications to access network services.
• ✨ Application-Specific Protocols: Implements protocols specific to applications (e.g., HTTP for web, SMTP for email).
• ✨ Data Conversion & Formatting: Can include some presentation-level functions within the application.
• ✨ Resource Allocation: Provides services to establish distributed database management and global access.
• ✨ End-user Services: E-commerce, web browsing, email, file transfer are directly supported.

Functions:

• ⚡ Provides network access for user applications.
• ⚡ Supports application-specific protocols (HTTP, SMTP, FTP).
• ⚡ Manages data transfer for distributed applications.
• ⚡ Facilitates file transfer, virtual terminal access, remote jobs.
• ⚡ Supports database services and web browsing.

Example:

HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol), DNS (Domain Name System), SSH (Secure Shell).

Applications:

• ✨ Web browsers (HTTP/HTTPS).
• ✨ Email clients (SMTP/POP3/IMAP).
• ✨ File transfer software (FTP).
• ✨ DNS client/server interactions.
• ✨ Network management applications (SNMP).

Advantages:

• 👍 Directly interacts with end-user applications, providing vast functionality.
• 👍 Most visible layer to end-users.
• 👍 Abstracts away all lower-layer complexities from the user’s perspective.

Disadvantages:

• 👎 Highly dependent on underlying layers for basic connectivity.
• 👎 Vulnerable to application-specific security threats.
• 👎 Protocol diversity can lead to compatibility issues across applications.

Figure: The 7 Layers of the OSI Model.

TCP/IP Protocol Suite

Define: TCP/IP Protocol Suite

The TCP/IP Protocol Suite (टीसीपी/आईपी प्रोटोकॉल सूट) is a set of communication protocols used by the Internet and similar computer networks. It is the fundamental technical standard that allows computers to communicate on the Internet. It is a hierarchical protocol composed of several layers, offering a practical, implemented standard rather than a theoretical one like OSI.

Key Points of TCP/IP Protocol Suite:

• ⭐ Practical Implementation: The actual protocol suite used for the Internet, unlike the theoretical OSI model.
• ⭐ 5 Layers: Commonly described with five (or sometimes four) layers.
• ⭐ Flexibility: Less rigid than OSI, with some functionalities sometimes overlapping or being combined in practice.
• ⭐ Connectionless IP: The core Network Layer (IP) is connectionless, relying on Transport Layer for reliability.
• ⭐ Ubiquitous: The most widely adopted and used networking model globally.

Functions of TCP/IP Layers:

1. Physical Layer (परत 1: भौतिक परत)

Define: The Physical Layer in TCP/IP deals with the physical medium and hardware specifications for transmitting raw bits. Its functions are very similar to the OSI Physical Layer.

• ✨ Hardware Specifics: Concerned with voltage levels, physical data rates, physical media (cables, wireless), and signal encoding.
• ✨ Bit Transmission: Handles the direct transfer of raw bit streams.
• ✨ Device Interfacing: Manages how network interface cards connect to the physical medium.
• ✨ Topology: Involved in defining physical network layouts.
• ✨ No Addressing or Flow Control: Solely focused on bit-level transmission.

Functions:

• ⚡ Converts data bits into electrical or optical signals for transmission.
• ⚡ Defines specifications for cables, connectors, and physical network devices.
• ⚡ Determines data transfer rates (bits per second).
• ⚡ Handles synchronization of bits.
• ⚡ Concerned with physical topology of the network.

Example:

Ethernet cables (Cat5e/Cat6), Wi-Fi physical standards (802.11a/b/g/n/ac/ax), fiber optic links.

Applications:

• ✨ Direct network cable connections (LANs).
• ✨ Wireless Wi-Fi communication between devices and access points.
• ✨ Transmitting data via optical fiber networks.
• ✨ Connecting devices to USB ports for network-over-USB functionality.
• ✨ Enabling data transfer through modems (DSL, cable).

Advantages:

• 👍 Provides the foundational physical medium for all digital communication.
• 👍 Hardware specific handling allows for optimization at physical level.
• 👍 High reliability of standardized physical interfaces.

Disadvantages:

• 👎 Does not manage error detection or correction.
• 👎 Limited to bit-level concerns, no understanding of data structure.
• 👎 Highly dependent on hardware choices.

2. Data Link Layer (परत 2: डेटा लिंक परत)

Define: The Data Link Layer in TCP/IP provides reliable node-to-node data transfer across a physical link, handling error detection, framing, and physical (MAC) addressing for local delivery. It is divided into Logical Link Control (LLC) and Media Access Control (MAC) sublayers.

• ✨ Framing: Encapsulates raw bits into data frames for structured transmission.
• ✨ Physical (MAC) Addressing: Uses MAC addresses for local delivery of frames within the same network segment.
• ✨ Error Detection: Adds error detection mechanisms (e.g., checksums) to frames.
• ✨ Flow Control: Manages the data rate between sender and receiver to prevent overflow.
• ✨ Media Access Control: Governs how devices share and access the physical transmission medium.

Functions:

• ⚡ Creates and recognizes frame boundaries (framing).
• ⚡ Implements physical addressing using MAC addresses.
• ⚡ Provides error detection on frames, and sometimes retransmission (error control).
• ⚡ Controls the flow of data to prevent faster sender from swamping a slower receiver.
• ⚡ Handles media access control (e.g., contention methods like CSMA/CD).

Example:

Ethernet (IEEE 802.3) frames and MAC addresses, Wi-Fi (IEEE 802.11) protocols, ARP (Address Resolution Protocol).

Applications:

• ✨ Communication between devices within a local area network (LAN) segment.
• ✨ Operating of network switches.
• ✨ Bridging of local network segments.
• ✨ Connection of devices to an access point in a wireless LAN.
• ✨ Direct point-to-point communication over modems (e.g., PPP).

Advantages:

• 👍 Ensures reliable and efficient data transfer over a direct physical link.
• 👍 Manages shared access to the network medium, avoiding collisions.
• 👍 Provides necessary physical addressing for local network communication.

Disadvantages:

• 👎 Limited to local network segments; does not perform routing across different networks.
• 👎 Errors detected at this layer require higher layers for recovery unless specifically implemented.
• 👎 Can add overhead due to frame encapsulation and control mechanisms.

3. Network Layer (परत 3: इंटरनेट परत)

Define: The Network Layer in TCP/IP, primarily defined by the Internet Protocol (IP), is responsible for host-to-host data transfer (also known as source-to-destination delivery). It provides logical addressing (IP addresses) and routes data packets across different networks to ensure that data can reach its ultimate destination on the Internet.

• ✨ Logical (IP) Addressing: Assigns unique IP addresses to devices for global identification.
• ✨ Routing: Determines the optimal path for data packets across various interconnected networks using routers.
• ✨ Connectionless Delivery: IP operates as a connectionless service, forwarding individual packets independently without prior connection setup.
• ✨ Packet Forwarding: Relies on routers to move packets efficiently from one network to the next towards their destination.
• ✨ Interconnection Backbone: Forms the backbone for the Internet’s ability to connect diverse global networks.

Functions:

• ⚡ Provides logical addressing using IP addresses for universal identification.
• ⚡ Performs routing decisions to select the best path for packets.
• ⚡ Handles fragmentation and reassembly of packets for different network MTUs.
• ⚡ Implements basic error reporting via ICMP.
• ⚡ Supports network segmentation and subnetting.

Example:

Internet Protocol (IP), ICMP (Internet Control Message Protocol).

Applications:

• ✨ Core functionality for global Internet communication.
• ✨ Operating of routers to interconnect networks.
• ✨ Enabling Virtual Private Networks (VPNs) with IPsec.
• ✨ Supporting Mobile IP for seamless mobility across different networks.
• ✨ Facilitating traceroute and ping commands for network diagnostics.

Advantages:

• 👍 Enables universal, host-to-host connectivity across the globe.
• 👍 Supports intelligent routing to ensure efficient packet delivery.
• 👍 Forms the highly scalable backbone of the Internet.

Disadvantages:

• 👎 Connectionless nature means no guarantee of delivery, order, or duplication.
• 👎 Does not inherently provide error control or retransmission mechanisms.
• 👎 Susceptible to network congestion, leading to packet loss.

4. Transport Layer (परत 4: ट्रांसपोर्ट परत)

Define: The Transport Layer in TCP/IP ensures reliable and efficient process-to-process data delivery (end-to-end communication) between applications running on different hosts. It provides segmentation of data from the application layer and adds features like flow control, error control, and multiplexing of multiple application streams.

• ✨ Process-to-Process Communication: Connects specific applications/processes (using port numbers) on different machines.
• ✨ Reliability Options: Offers both a reliable, connection-oriented service (TCP) and an unreliable, connectionless service (UDP).
• ✨ Segmentation & Reassembly: Breaks application data into smaller segments for network transmission and reassembles them at the destination.
• ✨ Port Addressing: Uses logical port numbers (e.g., Port 80 for HTTP, 443 for HTTPS) to direct data to the correct application.
• ✨ Flow & Congestion Control: Manages the sending rate to prevent both receiver overflow and network congestion.

Functions:

• ⚡ Provides segmentation, dividing application messages into manageable units.
• ⚡ Implements multiplexing and demultiplexing using port numbers.
• ⚡ For TCP: Establishes, maintains, and terminates connections; provides reliable data transfer through retransmission and acknowledgments.
• ⚡ For UDP: Offers simple, fast, unreliable data transmission without overhead.
• ⚡ Manages flow control and congestion control for effective network utilization.

Example:

Transmission Control Protocol (TCP), User Datagram Protocol (UDP).

Applications:

• ✨ Web Browsing (HTTP built on TCP for reliable page loading).
• ✨ Email (SMTP, POP3, IMAP built on TCP for reliable mail delivery).
• ✨ Video Conferencing & Online Gaming (often use UDP for speed, tolerating minor packet loss).
• ✨ File Transfer (FTP uses TCP for reliable file transfer).
• ✨ Domain Name System (DNS) queries (primarily UDP for speed, uses TCP for large responses).

Advantages:

• 👍 Ensures reliable, ordered, and error-free data delivery for applications (TCP).
• 👍 Provides multiplexing, allowing multiple applications to share the same network connection.
• 👍 Adapts data flow based on receiver’s capacity and network congestion (TCP).

Disadvantages:

• 👎 TCP’s reliability features (handshakes, retransmissions) introduce overhead and latency.
• 👎 UDP’s unreliability makes it unsuitable for applications requiring guaranteed delivery.
• 👎 It is process-to-process, not directly responsible for overall network routing beyond its host’s interaction.

5. Application Layer (परत 5: एप्लीकेशन परत)

Define: The Application Layer in TCP/IP is the top-most layer, encompassing the functionalities of the OSI’s Session, Presentation, and Application layers. It provides the interface for user applications to access network services directly. It implements specific protocols that allow end-user applications to exchange data and accomplish specific tasks.

• ✨ End-User Services: Directly supports common user-facing applications and services like web browsing, email, and file transfer.
• ✨ Protocol Integration: Incorporates application-specific protocols (e.g., HTTP, SMTP) that dictate how data is formatted and exchanged at the highest level.
• ✨ Presentation/Session Functionalities: Features like data encryption, compression, and session management are often handled within the application protocol itself.
• ✨ Abstraction of Lower Layers: Presents a user-friendly interface by abstracting away the complexities of the underlying network infrastructure.
• ✨ Direct Communication: Acts as the bridge between software applications and the underlying network.

Functions:

• ⚡ Provides services like file transfer, email, and remote login for applications.
• ⚡ Implements application-specific protocols (HTTP, SMTP, FTP, DNS, Telnet).
• ⚡ Manages data transfer for distributed applications.
• ⚡ Facilitates file transfer, virtual terminal access, remote jobs.
• ⚡ Supports database services and web browsing.

Example:

HTTP (Hypertext Transfer Protocol), FTP (File Transfer Protocol), SMTP (Simple Mail Transfer Protocol), DNS (Domain Name System), Telnet, SSH (Secure Shell).

Applications:

• ✨ Web browsers (e.g., Chrome, Firefox) for accessing websites (HTTP/HTTPS).
• ✨ Email clients (e.g., Outlook, Gmail app) for sending and receiving mail (SMTP, POP3, IMAP).
• ✨ File transfer clients (e.g., WinSCP) for transferring files between computers (FTP).
• ✨ Online gaming platforms for real-time multiplayer interactions.
• ✨ Instant messaging and video conferencing applications (e.g., WhatsApp, Zoom).

Advantages:

• 👍 Directly serves the needs of end-user applications, enabling a wide array of functionalities.
• 👍 Highly flexible as developers can create new protocols for new applications without altering lower layers.
• 👍 Provides the most visible layer to users, enabling interactive network services.

Disadvantages:

• 👎 Highly dependent on all underlying layers for connectivity and reliability.
• 👎 Vulnerable to application-specific security threats.
• 👎 Protocol diversity can lead to compatibility issues across applications.

Transmission Mode

Define: Transmission Mode

Transmission mode (संचरण मोड) refers to the direction of data flow between two linked devices in a communication system. It defines how data can be sent or received on a communication link, determining whether communication is unidirectional or bidirectional, and if bidirectional, whether it’s simultaneous or alternating.

Key Points of Transmission Mode:

• ⭐ Direction of Flow: Defines whether data travels in one direction or both.
• ⭐ Bidirectional Capability: Determines if communication is two-way.
• ⭐ Simultaneous/Alternating: Specifies if bidirectional flow can occur concurrently.
• ⭐ Impacts System Design: Crucial for designing appropriate hardware and software for communication.
• ⭐ Efficiency & Cost: Affects link utilization, complexity, and overall cost of communication.

Types of Transmission Mode:

1. Simplex Mode (सिंप्लेक्स मोड)

Define: Simplex mode is a communication mode where data flows in only one direction from the sender to the receiver. Communication is unidirectional, meaning only one device can transmit, and the other can only receive.

• ✨ Unidirectional: Data moves strictly in one direction.
• ✨ Dedicated Link: The entire channel capacity is used for one-way transmission.
• ✨ Simple: Easiest to implement as no return path or coordination is needed.
• ✨ No Feedback: The receiver cannot send back acknowledgments or requests for retransmission.
• ✨ Limited Use: Best for scenarios where only one-way information flow is sufficient.

Example:

Traditional radio broadcasting, where the radio station transmits, and your radio receiver only listens. Or, a keyboard sending input to a computer.

Applications:

• ✨ Traditional TV/Radio broadcasting.
• ✨ Keyboard input to a computer.
• ✨ Computer output to a traditional printer.
• ✨ Paging systems (e.g., sending out an emergency alert).
• ✨ Security cameras transmitting live video feed without return audio/control.

Advantages:

• 👍 Simple and cost-effective to implement.
• 👍 The entire channel bandwidth is dedicated to one-way transmission.
• 👍 No coordination issues between sender and receiver.

Disadvantages:

• 👎 No interactive communication possible.
• 👎 No error detection or correction mechanism (as receiver can’t send feedback).
• 👎 Inefficient for bidirectional communication needs.

2. Half-Duplex Mode (हाफ-डुप्लेक्स मोड)

Define: Half-duplex mode allows data to flow in both directions between two devices, but not simultaneously. At any given time, only one device can transmit data, and the other can only receive. The roles reverse periodically.

• ✨ Bidirectional (Alternating): Communication can occur in both directions, but not at the same time.
• ✨ Single Channel: Uses a single communication channel, which is shared by both directions.
• ✨ “Turn-Taking”: Devices take turns sending data, like a walkie-talkie.
• ✨ Less Complex than Full: Simpler to implement than full-duplex, more complex than simplex.
• ✨ Collision Potential: Can suffer from collisions if both attempt to transmit simultaneously (though managed by protocols).

Example:

A walkie-talkie, where one person speaks, and the other listens; then the roles reverse.

Applications:

• ✨ Walkie-talkies.
• ✨ Citizens Band (CB) radio.
• ✨ Hub-based Ethernet LANs (older Ethernet standards).
• ✨ Fax machines sending and receiving documents over a single line.
• ✨ Shared buses in computer systems.

Advantages:

• 👍 Allows two-way communication, unlike simplex.
• 👍 More efficient than simplex for interactive tasks.
• 👍 Cheaper than full-duplex systems (fewer channels/circuits).

Disadvantages:

• 👎 Communication is not simultaneous, which can lead to delays.
• 👎 Potential for collisions if both try to transmit at once.
• 👎 Requires a mechanism for managing turns.

3. Full-Duplex Mode (फुल-डुप्लेक्स मोड)

Define: Full-duplex mode allows data to flow in both directions simultaneously between two devices. This mode uses two distinct communication paths or channels, one for sending data and one for receiving data, enabling simultaneous two-way communication.

• ✨ Bidirectional (Simultaneous): Both devices can send and receive data at the same time.
• ✨ Dual Channels: Requires two separate channels or sub-channels for simultaneous transmission.
• ✨ Most Efficient: Provides maximum link utilization and highest throughput for two-way communication.
• ✨ More Complex: Hardware and protocols are more complex than simplex or half-duplex.
• ✨ No Collisions: Since channels are separate, there are no collision issues between transmitted signals.

Example:

A standard telephone conversation, where both parties can speak and hear at the same time.

Applications:

• ✨ Telephone conversations.
• ✨ Modern Ethernet networks (using switches).
• ✨ DSL/Cable modem internet connections.
• ✨ Mobile phone communication.
• ✨ Video conferencing systems for interactive discussions.

Advantages:

• 👍 Provides simultaneous two-way communication, maximizing throughput.
• 👍 Highly efficient for interactive and high-bandwidth applications.
• 👍 Eliminates the need for turn-taking, reducing latency.

Disadvantages:

• 👎 More complex to implement due to dual channels/circuitry.
• 👎 More expensive than simplex or half-duplex modes.
• 👎 Requires twice the bandwidth if implemented with separate physical lines.

Figure: Transmission Modes ke prakar (Simplex, Half-Duplex, Full-Duplex).

Physical Topology

Define: Physical Topology

Physical topology (भौतिक टोपोलॉजी) refers to the literal physical layout or arrangement of interconnected devices and cables within a computer network. It defines how devices are actually wired or connected to each other, forming the geographical representation of the network infrastructure.

Key Points of Physical Topology:

• ⭐ Layout: Describes the physical arrangement of devices and cables.
• ⭐ Wiring Scheme: Specifies how network nodes are physically linked.
• ⭐ Hardware Setup: Deals with the actual cabling and device placement.
• ⭐ Cost & Reliability Impact: Affects installation cost, fault tolerance, and network performance.
• ⭐ Distinct from Logical Topology: A physical topology can be different from a logical topology (how data flows).

Types of Physical Topology:

1. Mesh Topology (मेश टोपोलॉजी)

Define: In a Mesh topology, every device in the network is connected to every other device with a dedicated point-to-point link. This creates a fully redundant network where multiple paths exist between any two devices.

• ✨ Full Redundancy: Each device has a dedicated connection to every other device.
• ✨ Many Links: For ‘N’ devices, there are N(N-1)/2 physical links.
• ✨ High Fault Tolerance: If one link fails, communication can still occur through other paths.
• ✨ Complex Cabling: Requires extensive cabling, making it costly and complex for large networks.
• ✨ Point-to-Point Traffic: Supports simultaneous data transmission between multiple pairs of devices.

Example:

Connecting all 5 routers in a small critical network so that each router has a direct connection to every other router.

Applications:

• ✨ Small, highly critical networks (e.g., backbone of long-distance telephone networks).
• ✨ Highly fault-tolerant industrial control systems.
• ✨ Networks where reliability is paramount.
• ✨ Distributed computing clusters for dedicated communication paths.
• ✨ Experimental networks for high bandwidth point-to-point communication.

Advantages:

• 👍 Extremely reliable and highly fault-tolerant (redundant paths).
• 👍 High traffic capacity, as multiple simultaneous transmissions are possible.
• 👍 Easier fault isolation; problems can be quickly localized to a specific link.

Disadvantages:

• 👎 Very complex and costly to install and configure due to excessive cabling.
• 👎 Requires many I/O ports on each device (N-1 ports per device).
• 👎 Difficult to scale as number of connections grows quadratically.

2. Star Topology (स्टार टोपोलॉजी)

Define: In a Star topology, all network devices are connected individually to a central connecting device (like a hub, switch, or router). Data is sent from a transmitting device to the central device, which then forwards it to the destination device.

• ✨ Central Hub/Switch: All devices connect directly to a single central device.
• ✨ Point-to-Point Links (Logical): Each device has a dedicated cable segment connecting it to the central hub.
• ✨ Easy Management: Simpler to install, manage, and add/remove devices.
• ✨ Central Point of Failure: The central device is a single point of failure; if it fails, the entire network fails.
• ✨ Widely Used: Most common topology in modern LANs.

Example:

A home Wi-Fi network where all devices connect to a central wireless router, or computers in an office connected to a central switch.

Applications:

• ✨ Home and small office networks (LANs).
• ✨ Office environments connecting PCs to a central switch.
• ✨ School computer labs.
• ✨ Client-server networks.
• ✨ Most wireless local area networks (WLANs).

Advantages:

• 👍 Easy to install and wire.
• 👍 Easy to add new devices without disrupting the network.
• 👍 Fault isolation is simple (a single cable fault only affects one device).

Disadvantages:

• 👎 Single point of failure (central device).
• 👎 Requires more cabling than bus or ring topologies.
• 👎 Central device cost can increase the overall network cost.

3. Bus Topology (बस टोपोलॉजी)

Define: In a Bus topology, all network devices are connected to a single, common communication cable (called the backbone or bus) that runs through the network. Data is sent along this shared cable, and devices monitor the cable for data intended for them.

• ✨ Single Backbone Cable: All devices share one main cable segment.
• ✨ Simple Cabling: Requires the least amount of cabling.
• ✨ Terminators: Electrical signals must be terminated at both ends of the cable to prevent signal reflection.
• ✨ Shared Medium: All devices contend for access to the same shared medium.
• ✨ Easy Failure: A break in the main cable can bring down the entire network.

Example:

An older Ethernet network (e.g., 10BASE2 or 10BASE5 coax Ethernet), where multiple computers connect directly to a shared coaxial cable segment.

Applications:

• ✨ Early Ethernet networks (e.g., Thinnet, Thicknet).
• ✨ Very small, temporary networks.
• ✨ Internal connections within a computer (e.g., internal bus structure).
• ✨ Connecting a few devices in a lab setting.
• ✨ Sensor networks with linear data collection path.

Advantages:

• 👍 Simple and cost-effective for small networks.
• 👍 Requires minimum cabling compared to other topologies.
• 👍 Easy to understand conceptually.

Disadvantages:

• 👎 A single break in the main cable takes down the entire network.
• 👎 Troubleshooting can be difficult (hard to isolate cable breaks).
• 👎 Performance degrades significantly with increasing number of devices or traffic.

4. Ring Topology (रिंग टोपोलॉजी)

Define: In a Ring topology, each network device is connected to exactly two other devices, forming a single continuous circular loop or ring. Data travels in one direction (either clockwise or counter-clockwise) around the ring, passing through each device until it reaches its destination.

• ✨ Circular Layout: Devices are connected in a closed loop.
• ✨ Unidirectional Flow (Typically): Data usually flows in a single direction around the ring.
• ✨ No Terminators: The loop eliminates the need for terminators.
• ✨ Repeater Functionality: Each device on the ring acts as a repeater, passing the data along.
• ✨ Single Point of Failure: A single cable break or device failure can disrupt the entire ring.

Example:

Token Ring networks (e.g., IBM Token Ring), or FDDI (Fiber Distributed Data Interface) networks.

Applications:

• ✨ IBM Token Ring networks (historically significant).
• ✨ Fiber Distributed Data Interface (FDDI).
• ✨ Used in some industrial control systems requiring sequential data passing.
• ✨ Smaller campus backbones for older networks.
• ✨ Specific sensor loops where data collection needs to be sequential.

Advantages:

• 👍 No data collisions, as data flows in one direction.
• 👍 Relatively high data transfer rates can be achieved in dedicated ring systems.
• 👍 Data packages travel from one device to the next on the loop.

Disadvantages:

• 👎 A single device failure or cable break can take down the entire network.
• 👎 Adding or removing devices disrupts the entire network temporarily.
• 👎 Troubleshooting issues in a ring can be complex.

5. Hybrid Topology (हाइब्रिड टोपोलॉजी)

Define: A Hybrid topology is a network structure that combines two or more different basic network topologies (like Star, Bus, Ring, or Mesh) into a larger, composite network. It leverages the advantages of each component topology while minimizing their individual drawbacks.

• ✨ Combination: Comprises two or more fundamental topologies.
• ✨ Scalability: Highly scalable and can be tailored for large, complex organizations.
• ✨ Flexibility: Offers great flexibility in design, allowing optimal choice for different parts of a network.
• ✨ Increased Complexity: Design, installation, and management can be complex due to the varied components.
• ✨ Most Common in Large Networks: Many large-scale real-world networks are hybrid in nature.

Example:

A “Star-Bus” topology where several Star networks (each connected to a central switch) are connected to a central Bus backbone. For instance, multiple departments (each a Star LAN) in a large company connected via a common Bus line.

Applications:

• ✨ Large corporate networks with multiple departments.
• ✨ University campuses with different departmental LANs.
• ✨ Wide-area banking networks connecting branches.
• ✨ Cloud data centers combining various connectivity patterns.
• ✨ Modern internet service provider (ISP) networks.

Advantages:

• 👍 Highly flexible and adaptable to specific network requirements.
• 👍 Inherits the benefits of its component topologies (e.g., resilience from mesh, easy management from star).
• 👍 Provides high scalability for expanding complex networks.

Disadvantages:

• 👎 Design and implementation are more complex than simple topologies.
• 👎 Troubleshooting can be challenging due to multiple interconnections.
• 👎 Can be costly due to specialized equipment for linking different topologies.

Multiplexing

Define: Multiplexing

Multiplexing (मल्टीप्लेक्सिंग) is a technique that allows multiple analog or digital signals to be combined and transmitted over a single shared communication medium (channel or link). The purpose is to share the bandwidth or time of a high-capacity link among multiple users, thereby reducing transmission costs and improving efficiency.

Key Points of Multiplexing:

• ⭐ Resource Sharing: Enables sharing a single communication channel among multiple data streams.
• ⭐ Efficiency: Improves utilization of available bandwidth and reduces cost.
• ⭐ Multiplexer (Mux): Device that combines signals at the sending end.
• ⭐ Demultiplexer (Demux): Device that separates combined signals at the receiving end.
• ⭐ Transparent: Multiplexing and demultiplexing are transparent to the end-users.

Types of Multiplexing:

1. Frequency Division Multiplexing (FDM – फ़्रीक्वेंसी डिविज़न मल्टीप्लेक्सिंग)

Define: Frequency Division Multiplexing (FDM) is an analog multiplexing technique that divides the total bandwidth of a single wide-band communication channel into multiple smaller, non-overlapping frequency sub-channels. Each sub-channel is assigned to a different signal, allowing multiple signals to transmit simultaneously over the same medium without interference.

• ✨ Analog Multiplexing: Primarily used for analog signals.
• ✨ Frequency Bands: Divides bandwidth into different frequency ranges.
• ✨ Guard Bands: Small unused frequency ranges placed between sub-channels to prevent interference.
• ✨ Simultaneous Transmission: All signals transmit at the same time but on different frequencies.
• ✨ Requires Modulators: Each input signal requires a separate modulator to shift it to a specific carrier frequency.

Example:

Traditional radio and TV broadcasting, where multiple radio/TV stations transmit simultaneously on different frequencies via the airwaves. Or, a cable TV system distributing many channels over a single coaxial cable.

Applications:

• ✨ Analog radio and television broadcasting.
• ✨ Cable TV systems.
• ✨ Old telephone trunk lines for analog voice channels.
• ✨ Cellular radio (early generations) and satellite communications.
• ✨ Simultaneous transmission of voice, data, and video over a single link.

Advantages:

• 👍 Allows simultaneous transmission of multiple signals.
• 👍 Relatively simple to implement for analog signals.
• 👍 Does not require strict timing synchronization.

Disadvantages:

• 👎 Requires guard bands, wasting some bandwidth.
• 👎 Limited number of channels can be created if original bandwidth is limited.
• 👎 Susceptible to crosstalk (interference between adjacent channels).

2. Time Division Multiplexing (TDM – टाइम डिविज़न मल्टीप्लेक्सिंग)

Define: Time Division Multiplexing (TDM) is a digital multiplexing technique that divides the total time available on a shared communication channel into multiple short, fixed-length time slots. Each time slot is assigned to a different signal, allowing multiple signals to transmit sequentially (taking turns) over the same medium, sharing the entire bandwidth but at different times.

• ✨ Digital Multiplexing: Primarily used for digital signals.
• ✨ Time Slots: Divides time into recurring slots, with each signal assigned its own slot.
• ✨ Sequential Transmission: Signals transmit one after another in a rotating fashion.
• ✨ Full Bandwidth (Alternating): Each signal gets the full bandwidth of the channel, but only for its assigned time slot.
• ✨ Strict Synchronization: Requires precise synchronization between the multiplexer and demultiplexer to assign and recover time slots correctly.

Example:

A digital telephone network (e.g., T1 lines in North America) where multiple phone calls share the same line, each using a distinct, repeating time slot. Or, a single elevator carrying multiple people by sequentially stopping at different floors.

Applications:

• ✨ Digital cellular networks (TDMA).
• ✨ T1/E1 digital phone lines (PSTN backbone).
• ✨ ISDN (Integrated Services Digital Network).
• ✨ Multiplexing various data streams onto a single fiber optic line.
• ✨ Sharing a processor’s time among multiple users/processes (CPU scheduling).

Advantages:

• 👍 No guard bands, leading to higher bandwidth utilization than FDM for digital.
• 👍 Utilizes the entire channel bandwidth for each signal’s turn.
• 👍 More robust against crosstalk compared to FDM.

Disadvantages:

• 👎 Requires precise synchronization between sender and receiver.
• 👎 Can have wasted capacity if an assigned time slot is empty.
• 👎 Inflexible if input data rates vary significantly.

3. Wavelength Division Multiplexing (WDM – वेवलेंथ डिविज़न मल्टीप्लेक्सिंग)

Define: Wavelength Division Multiplexing (WDM) is an optical multiplexing technique that allows multiple data streams to be transmitted simultaneously over a single optical fiber, using different wavelengths (colors) of light. Each distinct wavelength acts as a separate communication channel.

• ✨ Optical Multiplexing: Specifically for fiber optic cables and light signals.
• ✨ Different Wavelengths/Colors: Uses various colors (wavelengths) of light to carry different data streams.
• ✨ High Bandwidth: Enables extremely high data capacities over a single fiber.
• ✨ Similar to FDM: Conceptually similar to FDM but applied in the optical domain.
• ✨ Transceivers Required: Requires specialized optical transceivers at both ends.

Example:

A single optical fiber carrying 80 separate data channels, where each channel operates at a different wavelength of light (e.g., one channel uses red light, another blue, another green, etc.).

Applications:

• ✨ Backbone of the Internet infrastructure (transoceanic and terrestrial).
• ✨ Long-haul fiber optic communication networks.
• ✨ Data center interconnections (high-speed).
• ✨ High-bandwidth metro and access networks.
• ✨ Providing high-capacity communication for large corporations.

Advantages:

• 👍 Achieves extremely high bandwidth and data rates over a single fiber.
• 👍 Cost-effective as it utilizes existing fiber infrastructure more efficiently.
• 👍 Allows for future capacity expansion by adding more wavelengths.

Disadvantages:

• 👎 Requires expensive specialized optical equipment (lasers, multiplexers, demultiplexers).
• 👎 Vulnerable to signal attenuation over very long distances without amplification.
• 👎 Installation and maintenance require specialized optical expertise.

4. Code Division Multiplexing (CDM – कोड डिविज़न मल्टीप्लेक्सिंग)

Define: Code Division Multiplexing (CDM) is a spread-spectrum technique where multiple signals share the same communication channel and bandwidth simultaneously, at the same frequency, without interfering with each other. Each signal is assigned a unique code, and these codes are used to encode the signals before transmission and decode them at the receiver.

• ✨ Spread Spectrum: Spreads signals across a wide frequency band.
• ✨ Unique Codes: Each signal uses a distinct, orthogonal coding sequence (chipping code).
• ✨ Simultaneous Transmission: All users transmit simultaneously at the same frequency.
• ✨ Receiver Decoding: Receiver uses the sender’s specific code to extract the desired signal from the mixed stream.
• ✨ Resistant to Interference: Robust against noise and interference due to spread spectrum properties.

Example:

Second and Third-generation (2G and 3G) cellular phone systems like CDMA (Code Division Multiple Access), where multiple callers share the same radio frequency by using different unique codes.

Applications:

• ✨ CDMA (Code Division Multiple Access) mobile phone systems (2G & 3G cellular).
• ✨ GPS (Global Positioning System) signal transmission.
• ✨ Some specialized wireless local area networks.
• ✨ Military communication for secure and robust transmission.
• ✨ Spread spectrum radio applications.

Advantages:

• 👍 Allows multiple users to share the same frequency band simultaneously.
• 👍 Offers enhanced security due to the unique coding and spread spectrum nature.
• 👍 Highly resistant to interference, jamming, and eavesdropping.

Disadvantages:

• 👎 Requires complex signal processing and coding at both ends.
• 👎 The number of simultaneous users is limited by interference from other codes (Near-Far problem).
• 👎 Power control is critical for effective operation.

Figure: Frequency, Time, aur Wavelength Division Multiplexing ke Concepts.