Computer Networks Fundamentals PDF

Created by Turbolearn AI Fundamentals of Computer Networks Introduction to Computer Networks The convergence of computers and communication has significantly reshaped the organization of computer systems. The traditional model of standalone computers serving entire organizations has been replaced...

Created by Turbolearn AI Fundamentals of Computer Networks Introduction to Computer Networks The convergence of computers and communication has significantly reshaped the organization of computer systems. The traditional model of standalone computers serving entire organizations has been replaced by interconnected computer networks. A computer network is a group of two or more computers or devices that transfer data and instructions, share information, and resources. Key Aspects: Shared communication link Facilitates communication and information sharing Consists of nodes connected by media links Nodes can send or receive data (e.g., computers, printers) Communication channels link devices Protocols: Rules governing communication between machines Examples: The Internet Network Requirements A network must meet certain criteria to be effective: Performance: How well the network operates. Reliability: The consistency of the network. Scalability: The ability for the network to grow. Need for Computer Networks Computer networks enable users to share information, services, and resources. Benefits: Page 1  Created by Turbolearn AI Cost reduction by sharing hardware and software resources High reliability through multiple sources of supply Cost reduction by using microcomputer-based networks instead of mainframes Greater flexibility due to the ability to connect devices from various vendors Increased efficiency and reduced costs Primary Ways to Achieve Goals: Sharing information (or data) Sharing hardware and software Centralizing administration and support Specific Needs and Benefits: File Sharing: Sharing data files among network users. Information Sharing: Exchanging data and information between users. Resource Sharing: Sharing expensive resources like laser printers or enterprise software. Sharing Media: Streaming music, videos, and movies across computers. Applications of Computer Networks A computer network is a collection of computing devices interconnected to achieve communication and to share available resources. Computer Network Applications: Software applications that utilize the Internet or other network hardware infrastructure. Facilitates data transfer within a network. Types of Network Applications: Pure network applications Standalone network applications Pure Network Applications Page 2  Created by Turbolearn AI These applications are developed only for use in networks, aiding in data transfer and communication within a network. They feature separate user interfaces. Examples include: Email programs: For writing and sending messages (e.g., Gmail, Outlook). File Transfer Protocol (FTP): Facilitates file transfer between computers. Downloading: Getting files from a server to a client. Uploading: Transferring files from a client to a server. TELNET: Allows a local computer to access a server for an application program. Groupware: Applications for office automation, like video conferencing and chatting. Stand Alone Applications Applications that run on standalone computers but are enhanced to operate in network environments. Examples: word processors, database management systems, spreadsheets, graphics presentations, project management. Categorization Based on Usage: Business Banking Insurance Education Marketing Health Care Engineering Design Military Communication Government Components of Computer Networks Computer networks share common devices, functions, and features. Page 3  Created by Turbolearn AI Essential Components: Network Interface Card (NIC) Hub Switches Cables and connectors Crimping Tool LAN tester Router Modem Bridge Network Interface Card (NIC) Hardware component that connects a computer to a network. It is also known as network interface controller, network adapter, LAN adapter. Hub A device used to divide a network connection into several computers. It is a distribution center typically used to connect segments of a LAN. Switches A networking device used to link network devices. A switch is like a Hub but built in with advanced features. It uses MAC addresses of each incoming messages so that it couldtransmit the message to the right destination or port. Cables & Connectors Cable is unidirectional way of transmission media that is used transmit communication signals. The wired network typology uses a special type of cable to connect computers on a network. Page 4  Created by Turbolearn AI Unshielded Twisted Pair (UTP) Cable RJ = Registered Jack Shielded Twisted Pair (STP) Cable Coaxial Cable Fiber Optic Cable Crimping Tool A crimping tool is a tool that is designed to crimp or connect a connector to the end of a cable. LAN Tester Testers assist in the installation and control of networks. LAN testers are able to determine IP addresses,connected port, identify polarity, and link connectivity. Even they can test fiber optic cables. Router A networking device that forwards data from one network to another. It forwards data packets between computer networks, creating an overlay internetwork. Modem A device that enables computers to transfer data from one location to another location via the telephone line. It modulates the (converts) digital signal to analog at the transmission end and demodulates (converts/ reverts) analog signal to digital signal. Bridge A device that connects two parts of a network together at the data link layer (layer 2 of the OSI model). Network Benefits Page 5  Created by Turbolearn AI Networks allow users to share information in various ways. Sharing Information (File Sharing, E-mail) Sharing specific files, such as documents or spreadsheets. Using messaging applications like email for communication. Holding online video conference meetings. Sharing Resources (Printer Sharing, Application Services) Sharing computer resources like printers and hard drives. Implementing shared hard drives on a central server as a storage area. Sharing the Internet connection. Facilitating Centralized Management Enables multiple users to work together on a single business application. Assists in management tasks associated with network operation and maintenance. Increases efficiency and reduces maintenance costs. Managing Software Reduces software costs through bulk purchases and discounts. Centralizes software installation, reducing operational costs. Allows remote installation of software. Maintaining the Network Reduces maintenance costs by using similar equipment across the network. Allows maintenance workers to focus on fewer types of components. Backing up data Page 6  Created by Turbolearn AI Minimizes time spent backing up necessary files. Ensures vital information and applications can be restored in case of failure. Technicians can access backup files from a central location. Benefits of Computer Networks Two benefits of computer networks are: 1. Resource Sharing: Enables sharing of resources like printers and hard disks, reducing hardware purchasing costs. 2. Easy Communication: Facilitates easy information transmission between networked computers. Computer Network Classifications Networks can be classified based on: Type of technology used Number of users and devices connected Geographic area covered Types of Networks by Geographical Area From smallest to largest: 1. Personal Area Networks (PAN) 2. Local Area Networks (LAN) 3. Campus Area Networks (CAN) 4. Metropolitan Area Networks (MAN) 5. Wide Area Networks (WAN) Personal Area Networks (PAN) Cover specific workspaces like a home office. Connect two or more devices using wireless technologies. Consist of mobile devices like cell phones, tablets, and laptops. Handle interconnection of networking devices nearby a single user. Contain appliances like wireless mice, keyboards, and Bluetooth devices. Page 7  Created by Turbolearn AI Advantages of PAN Portable: Can be carried easily and set up without wires using wireless technology. Security: Information is shared only with authorized users within the network. Disadvantages of PAN Health Issue: Wireless devices use microwave signals, which may cause health problems with prolonged exposure. Expensive: Requires devices like smartphones and laptops. Connection Quality: Sometimes has a bad connection to other networks at the same radio bands. Bluetooth Limitations: Bluetooth networks have slow data transfer speeds and distance limits. Local Area Networks (LAN) Cover limited geographical areas like a building. Usually owned and maintained by a single organization. Connect PCs and workstations at home, offices, and factories to share resources and information. Characterized by size, transmission technology, and topology. Network management is relatively easy. High data rates, fewer propagation delays, and low error rates. Use switches and servers to connect multiple computers and other networking devices. Can serve a single department, workgroups, or all users within a building. Use cable, wireless, or a combination of both. Advantages of LAN Page 8  Created by Turbolearn AI Resource Sharing: Resources like printers and modems can be shared. Software Sharing: Same software can be used within the network. Easy Communication: Information can be transmitted easily. Centralized Data: Users can save data centrally on a server. Data Security: Data is managed and secured at one place. Internet Sharing: Single internet connection can be shared. Disadvantages of LAN High Setup Cost: Initial setup cost is very high. Privacy Violations: Administrators can check personal data of users. Data Security Threat: Unauthorized users can access important data if the database is not secured. Slow Internet Speed: Shared internet connection can be slow if all computers run at once. Maintenance: Requires a full-time LAN administrator. Limited Area: Covers a small area like one office or building. Campus Area Networks (CAN) Interconnection of local area networks within a limited geographical space, like a school campus or military base. Formed by connecting LANs in two or more buildings. Connections can be done using cables or wireless devices. Also known as campus LAN. Smaller area than MAN. Uses LAN technologies like Ethernet, Token Ring, FDDI, Fast Ethernet, Gigabit Ethernet, and ATM. Metropolitan Area Networks (MAN) Page 9  Created by Turbolearn AI Connect computers in a larger geographic area than a CAN but smaller than a WAN. Formed by connecting networks located at two or more sites within the same city. Connections done using cables or wireless technologies, often optical fiber cabling. High-speed connections using fiber optical cable or other digital media. Wide Area Networks (WAN) Cover a relatively large geographical area. Connect various small networks, including LANs and MANs. Computers connected through public networks like the public telephone system. Can also be connected via leased lines or satellites. Example: The Internet. Created by linking networks over geographic distances. Telecommunications circuits link each building to facilities operated by a telecommunications provider. Use TCP/IP protocol in combination with devices like routers, switches, firewalls, and modems. Classification of Networks by Component Based on the roles that networked computers play in the network's operation: 1. Peer-to-Peer Networks 2. Server-Based Networks 3. Client-Based Networks Peer-to-Peer Network Page 10  Created by Turbolearn AI No centralized control. All computers are considered equals. Each computer controls its own information and functions as a client or server. Inexpensive and easy to install. Used in home networks and small companies. Many operating systems have built-in peer-to-peer networking capability. Security measures are typically minimal. Each peer shares its resources and allows open access. Difficult to manage if more security is added to the resources. Maximum number of peers: ten. Server-Based Network Involves centralized control. Provides centralized control and is created for secure operations. Dedicated server controls the network. Dedicated server stores data, applications, and other resources and provides access to clients. Dedicated servers control the entire network's security from one central location. Client-Based Network Refinement of server-based network. Relieves the burden on the network's capacity. Takes advantage of the powerful processors in servers and workstations. Types of Servers 1. Application Server: A component-based program that handles all application operations between users and backend applications or databases. Provides middleware services for security, state maintenance, and data access. Provides shared capabilities to software applications on client-server networks. Handles load-balancing and failover. 2. Email Server: Page 11  Created by Turbolearn AI A server or dedicated computer that controls and transfers e-mail over a network, mostly over the Internet. Receives e-mails from client computers and delivers them to other email servers. Consists of storage space for emails, user-defined rules, a database of user accounts, and communication modules. 3. File Server: A dedicated computer having central storage and management of data files, allowing users to share information within a network. Used in organization settings, schools, small organizations, and home networks. 4. Print Server: A software application, network device, or dedicated computer that manages one or more printers within a network. Manages print requests and provides printer queue status. Supports TCP/IP printing protocols like LPR/LPD, TELNET, IPP, and Microsoft print protocol. Network Topologies Introduction Network topology describes the method used to physically wire the network. Common topologies include bus, star, and ring. Definition A network topology is the pattern in which nodes (computers, printers, switches, etc.) are connected to a network via links. It is the layout of computers, cables, and other connected devices on a network. Physical Topology: The physical layout of devices on a network. Logical Topology: The way signals act on the network media or data passes through the network. Page 12  Created by Turbolearn AI Selection Criteria Factors to consider while selecting a topology: Size (no. of nodes) of the system Cost of components and service Architecture of network Cable type Expandability of the network Desired performance and reliability Scalability Bandwidth capacity Ease of installation Ease of troubleshooting Delay in routing information Available hardware resources Types of business processes Individual scalability requirements Administrative effort involved Types of Topology 1. Physical Topology 2. Logical Topology Bus Topology A network type in which every computer and network device is connected to a single cable. A single cable functions as a shared communication medium. Devices send a broadcast message onto the wire; only the intended recipient accepts it. When it has exactly two endpoints, it is called Linear Bus topology. Working: Page 13  Created by Turbolearn AI Computers communicate by addressing data to a particular computer and sending it out on the cable as electronic signals. Only one computer can send messages at a time. The number of computers affects network performance. Computers transmit signals or listen for signals. Failure of one computer does not affect the rest of the network. The signal travels from one end of the cable to the other. Terminator: A component positioned at each end of the cable to absorb free signals. Features: Transmits data only in one direction. Every device is connected to a single cable. Advantages: Cost-effective Least cable required Used in small networks Easy to understand Easy to expand by joining two cables Disadvantages: Cable failure can cause the whole network to fail. Performance decreases with heavy traffic or more nodes. Cable has a limited length. Slower than the ring topology. Ring Topology A circular loop of point-to-point links. Each computer is connected to another computer, with the last one connected to the first. Page 14  Created by Turbolearn AI Each device connects directly or indirectly through an interface device or drop cable. Every device has exactly two neighbors for communication. Messages travel through a ring in the same direction. Failure in any cable or device breaks the loop and takes down the whole network. No beginning or end needs to be terminated. Working: Computers are connected to a single circle of cable. Signals travel around the loop in one direction and pass through each computer that acts as a repeater. The failure of one computer impacts the entire network. Token Passing: A method of transmitting data around a ring. A token is a special series of bits. Network Topologies A network topology refers to the physical layout of a network, describing how devices are connected. The four basic topologies are ring, bus, star, and tree topologies. Ring Topology In a ring topology, each device is connected to exactly two other devices, forming a circular pathway for data. A special packet called a token travels around the ring. Only the device holding the token can transmit data. In a token-ring network, each network has only one token. The token is passed from computer to computer until it gets to a computer that has data to send. Page 15  Created by Turbolearn AI The sending computer modifies the token, puts an electronic address on the data, and sends it around the ring. The message passes by each computer until it finds the one with an address that matches the address on the message. The receiving computer returns an acknowledgment message to the sending computer shows that the data has been received successfully. On verification, the sending computer generates a new token and releases it on the network. The token circulates within the ring until another workstation needs it to transfer data. Features of Ring Topology Repeaters: Used to prevent data loss in large networks. Unidirectional Transmission: Data typically flows in one direction. Dual Ring Topology: Two connections between each node for bidirectional transmission and backup. Sequential Data Transfer: Data is transferred bit by bit. Advantages of Ring Topology Traffic Management: Performance is not significantly affected by high traffic or adding more nodes. Cost-Effective: Cheap to install and expand. Fault Isolation: Simplified due to constant signal circulation. Easy Device Management: Adding or deleting a device requires moving only two connections. Guaranteed Delivery Time: Fixed package delivery time because every PC has the token. No Collisions: Absence of data collisions. Disadvantages of Ring Topology Cable Requirements: Requires more cable than a bus network. Troubleshooting: Difficult to troubleshoot. Network Disturbance: Adding or deleting computers can disrupt the network. Single Point of Failure: Failure of one computer can disturb the whole network. Unidirectional Traffic: Can be a disadvantage in a simple ring. Star Topology Page 16  Created by Turbolearn AI In star topology, all nodes are individually connected to a central connection point, like a hub or a switch. Each node has a dedicated point-to-point link to the central hub, through which all communications are routed. Star network consists of one central switch, hub or computer which acts as a router to transmit messages. Features of Star Topology Dedicated Connection: Every node has its own dedicated connection to the hub. Hub as Repeater: The hub acts as a repeater for data flow. Cable Options: Can be used with twisted pair, optical fiber, or coaxial cable. Advantages of Star Topology Fast Performance: Fast performance with few nodes and low network traffic. Easy Upgrades: Hub can be upgraded easily. Easy Troubleshooting: Simplified troubleshooting. Easy Setup: Easy to setup and modify. Fault Tolerance: Only the failed node is affected. Disadvantages of Star Topology Installation Cost: High installation cost. Expensive: Can be highly expensive to use. Central Point of Failure: Failure of the central hub or switch stops the whole network. Performance Dependency: Performance depends on the capacity of the hub or switch. Mesh Topology In mesh topology, all nodes have a point-to-point connection to other nodes or devices. There are multiple paths between any two nodes in the network. All the nodes in mesh topology are connected to each other. Each node has a dedicated point to point link to every other node Page 17  Created by Turbolearn AI Types of Mesh Topology 1. Partial Mesh Topology: Some nodes are connected like mesh topology, but some are connected to only two or three nodes. 2. Full Mesh Topology: Each and every node is connected to each other. Formula: n(n − 1)/2 Features of Mesh Topology Fully Connected Robust Unmanageable beyond a small number of devices Not Flexible Advantages of Mesh Topology Dedicated Links: Each dedicated link carries its own data load. Robust: Failure of one link doesn’t affect the entire network. Easy Fault Diagnosis: Simplified fault diagnosis. Security and Privacy: Provides good security and privacy due to dedicated lines. Reliable: More reliable compared to other topologies. Traffic Routing: Heavy traffic data can be routed avoiding busy routes. Disadvantages of Mesh Topology Difficult Installation: Installation and configuration is difficult. Many Connections: Requires a lot of connections. High Cabling Cost: Cabling cost is more. Expensive: Very expensive. Bulk Wiring: Requires bulk wiring. Difficult to Reconfigure: Difficult to install and reconfigure. Data Transmission Techniques in Mesh Topology Page 18  Created by Turbolearn AI 1. Routing: Uses routing logic to direct data to the destination using the shortest distance. 2. Flooding: Transmits the same data to all the network nodes without using routing logic. Tree Topology Tree topology, also known as hierarchical topology, has a central or root node at the top level connected to one or more nodes at the next level, forming a hierarchy. Tree topology combines characteristics of linear bus and star topologies. Tree topology is valued for its scalability and accessibility for troubleshooting. Features of Tree Topology Hierarchical Structure: Forms a tree network. Ideal for Grouped Workstations: Ideal if workstations are located in groups. Used in WANs: Commonly used in Wide Area Networks. Advantages of Tree Topology Extension of Topologies: Combines benefits of bus and star topologies. Device Capacity: Allows more devices to be connected to the central hub. Easy Expansion: Expansion of nodes is possible and easy. Easy Management: Easily managed and maintained. Error Detection: Error detection is easily done. Disadvantages of Tree Topology Heavily Cabled: Requires heavy cabling. Expensive: More expensive. Difficult Maintenance: Maintenance becomes difficult with more nodes. Central Point of Failure: Failure of the central hub results in network failure. ibrid Topology Page 19  Created by Turbolearn AI A hybrid topology combines two or more different network topologies. a hybrid topology is a network topology which uses two or more other network topologies. Features of Hybrid Topology Combination of Topologies: It is a combination of two or more topologies. Inherited Traits: Inherits the advantages and disadvantages of the included topologies. Advantages of Hybrid Topology Reliable: Error detecting and troubleshooting is easy. Effective Scalable: Size can be increased easily. Flexible Disadvantages of Hybrid Topology Complex Design: Complex in design. Costly Network Control / Connecting Devices Network control devices are the physical entities connected to a network, enabling communication and functionality. Types of Network Devices 1. End User Devices: Computers, printers, scanners, and other devices that provide services. 2. Network Devices: Devices that connect end-user devices to communicate. End user devices that provide users with a connection to the network are also called hosts. Page 20  Created by Turbolearn AI Need for Network Control Devices Expand a single network. Extend the distance of a network. Localize network traffic. Merge existing networks. Isolate network problems. Role of Network Control Devices Network control devices operate at different layers of the TCP/IP model, and can be categorized as follows: Below the Physical Layer: Passive Hub Physical Layer: Repeater or Active Hub Physical and Data Link Layers: Bridge or Two-Layer Switch Physical, Data Link, and Network Layers: Router or Three-Layer Switch All Five Layers: Gateway Network Control Devices Connectors Connectors provide an entry point at the end segment of cabling for networking devices. It is device that provides an entry point at the end segment of cabling, for networking devices like computers, switches, hubs, and routers. Connectors are classified based on: Physical appearance and coupling properties (Jacks, Plugs, Sockets, Ports) Pinning configurations (DB9, DB15) Electrical interfaces (RS-232, V.35, RJ-45, BNC, SC, ST) Examples of Connectors: Page 21  Created by Turbolearn AI Twisted Pair cable Co-axial Cable Fiber optic cable Jacks Plugs Sockets and ports RS232 and V35 for serial interface RJ45 and BNC connectors for Ethernet SC or ST connectors for fiber optic Types of Connectors: BNC (Bayonet Neill Concelman): Used with coaxial cables like RG-58 A/U cable for 10Base-2 Ethernet. RJ-11 (Registered Jack): 6-position 2 conductor telephone connector commonly used to connect the telephone handset to the base unit. F-Type: A coaxial RF connector commonly used for cable television and satellite television. RJ-45 (Registered Jack 45): 8-position, 8-contact (8P8C) modular plug commonly used for Ethernet networking. USB (Universal Serial Bus): A computer standard designed to eliminate the guesswork in connecting peripherals to a PC. Hub A hub is a basic networking device that connects multiple computers or other network devices together. It operates at the physical layer of the OSI model. Hub is the most basic networking device that connects multiple computers or other network devices together. Hub is a device that splits a network connection into multiple computers. It is like a distribution center. Types of Hubs: Passive Hub: Does not amplify or regenerate the signal. Active Hub: Amplifies and regenerates the signal. Also known as a multiport repeater. Intelligent Hub: Combines features of active and passive hubs, and can perform bridging and routing. Page 22  Created by Turbolearn AI Applications of Hubs: Creating small home networks. Monitoring networks. Providing connectivity. Advantages of Hubs: Allows connection of clients for sharing and conversation with a network protocol analyzer. Can modulate the signal of the cable, if needed. Cost-effective compared to switches. Disadvantages of Hubs: Cannot control traffic of data. Limited port availability. Time-consuming due to query system processing. Repeater A repeater is an electronic device that operates at the physical layer. It regenerates the incoming signal over the same network before it becomes too weak or corrupted. Repeater regenerates the incoming signal over the same network before it becomes too weak or corrupted. So that the signal can be transmitted at maximum length in the network. Functionality: Extends the transmission length of cables by dividing them into segments. Operates as a two-port node in the physical layer. Advantages of Repeaters: Increases the usable distance of the network. Little impact on network performance. Connects networks using different physical media. Disadvantages of Repeaters: Page 23  Created by Turbolearn AI Cannot connect different network architectures. Does not reduce network traffic. Limited number of repeaters. Does not segment the network. Bridges A bridge operates in both the Physical and Data Link Layers. It regenerates the received signal as a Physical Layer device and checks the Physical (MAC) Addresses as a Data Link Layer device. Bridges are networking devices used connect networks working on the same protocol. Working of Bridges: Bridges work at the Media Access Control Sub-layer of the OSI model. Types of Bridges: Transparent Bridge: Appears to be transparent to other devices on the network. Source Route Bridge: The path which packet takes through the network is implanted within the packet. Translational Bridge: Converts the data format from one networking type to another (e.g., Token Ring to Ethernet). Advantages of Bridges: Extends a network by acting as a repeater. Reduces network traffic on a segment. Increases available bandwidth to individual nodes. Reduces collisions. Disadvantages of Bridges: Page 24  Created by Turbolearn AI Does not limit the scope of broadcasts. Does not scale to extremely large networks. Buffering introduces store and forward delays. Bridging of different MAC protocols introduces errors. Slower than repeaters due to extra processing. More expensive than repeaters. Switch A switch can operate at one or more OSI layers, including the physical, data link, network, or transport layer. Switch is a high-speed device that receives incoming data packets and redirects them to their destination on a LAN. Network Devices Switch A switch intelligently forwards data packets only to the port connected to the destination device. It learns MAC addresses to enhance network performance, operating in full-duplex mode, allowing simultaneous sending and receiving of data. Switch Data Transmission Methods: Cut-through transmission: Packets are forwarded immediately upon receipt, prioritizing speed but potentially overlooking error checking. Store and forward: The entire packet is received, and checked for errors before forwarding, ensuring accuracy at the cost of processing time. Fragment Free: A significant portion of the packet is examined to detect collisions before forwarding. Advantages: Increases network bandwidth Reduces workload on individual computers Enhances network performance by minimizing frame collisions Connects directly to workstations Page 25  Created by Turbolearn AI Disadvantages: Not ideal for limiting broadcasts like a router Requires inter-VLAN routing for communication between VLANs Handling multicast packets can be complex Can be vulnerable to security attacks in promiscuous mode Router A router operates at the Network Layer of the OSI model, receiving, analyzing, and forwarding packets to other networks. It can convert packets, drop them, and perform network-related actions. A router connects networks, such as two LANs, WANs, or a LAN and its ISP's network, located at gateways where networks interconnect. Functionality: 1. Determines the destination address by reading the packet header. 2. Consults its routing table to find the best path to the destination. 3. Forwards the packet to the next hop, either the final destination or another router. Routers use software-configured network addresses for decision-making, unlike bridges and switches that use hardware-configured MAC addresses. Routing Table Information Acquisition: Static Routing: Information is manually entered into routing tables, suitable for small networks. Dynamic Routing: Uses routing protocols for communication and information exchange between routers, ideal for larger networks. Advantages: Reduces network traffic by creating collision and broadcast domains. Functions on both LAN and WAN. Connects different media and architectures. Determines the best data path using dynamic routing. Filters broadcasts. Page 26  Created by Turbolearn AI Disadvantages: More expensive than hubs, bridges, and switches. Works only with routable protocols. Dynamic router communication increases network traffic. Routing updates consume bandwidth. Slower than bridges or repeaters due to extensive packet analysis. Increases latency due to packet filtering. Gateway A gateway connects two networks that use different protocols, converting data formats without altering the data itself. A gateway functions as a messenger agent, interpreting and transferring data between systems, and can operate at any network layer. Advantages: Expands the network. Provides security. Connects different types of networks. Performs protocol conversion. Handles traffic problems effectively. Provides connections between internal and external networks. Supports user-level authentication and protection. Disadvantages: Not an intelligent device, so noise prevention is not done. Slower transmission rate due to protocol conversion. Can be hard to handle and costly. Doesn't strain out the data. Doesn't support possible kinds of linking. Modem (Modulation-Demodulation) A modem transmits data over telephone cables by converting digital information to analog signals (modulation) and vice versa (demodulation). Page 27  Created by Turbolearn AI Types of Modems: Internal Modem: Plugs into expansion slots, using a UART (universal asynchronous receiver/transmitter) to manage serial communication. External Modem: Sits outside the computer, connecting via serial or USB and powered externally. Network Software NIC Device Driver A device driver is a computer program that operates and controls a specific device connected to a computer. Network Interface Card (NIC) drivers are computerized instructions and information required for a NIC card to be operational when it is installed on or connected to a computer. Steps to verify and install NIC driver: 1. Open Control Panel and go to Device Manager. 2. Check if the NIC is listed under Network Adapters without any error icons. 3. If there's an error icon, double-click the device to view its status. 4. If the NIC is not visible, use the Add legacy hardware option to manually select and install the driver. Client-Server Architecture Client-server architecture involves clients requesting services and servers providing them. Servers manage disk drives, printers, or network traffic, while clients are PCs or workstations that rely on servers for resources. DHCP Dynamic Host Configuration Protocol (DHCP) automatically provides IP hosts with IP addresses and related configuration information. Page 28  Created by Turbolearn AI The DHCP client broadcasts a DHCPDISCOVER message to locate a Cisco IOS DHCP Server. A DHCP Server offers configuration parameters to the client in a DHCPOFFER unicast message. Benefits of DHCP: Reliable IP address configuration. Reduces network administration through centralized and automated TCP/IP configuration. Efficient handling of IP address changes. DHCP Mechanisms for IP Address Allocation: Automatic allocation: Permanent IP address. Dynamic allocation: IP address for a limited time. Manual allocation: IP address assigned by the network administrator. DHCP Server Optional Parameters Options Description domain-name Specifies the domain name for the DHCP clients. domain-name- Specifies the Domain Name System (DNS) IP servers that are servers available to the DHCP clients. router Adds the default router and gateway for the DHCP clients. subnet-mask Defines the subnet mask for the network. broadcast- Defines a broadcast address for the network. address DHCP Server CLI Commands Page 29  Created by Turbolearn AI Command Description Specifies how long, in seconds, the DHCP server command dbexpire should wait before aborting a database transfer. clear ip dhcp-server Deletes a specific, or all leases from the binding server binding binding database. ip dhcp-server Enables the DHCP server feature. enable ip dhcp-server pool Switches to pool configuration mode (config-dhcp- pool name# name prompt) and creates an address pool. show ip dhcp-server Displays a specific lease entry, or all lease entries. binding TELNET TELNET uses the TCP protocol to connect to remote computers, offering remote log- on capability. TELNET is a terminal emulator that allows a user to connect and log on to other hosts in the network from their own computer. Telnet Model: TELNET uses TCP port 23. The TELNET client acts as a terminal, accepting keystrokes and displaying output, while the TELNET server interacts with applications on the host machine, assisting in terminal emulation. Options: TELNET has a set of options that can be negotiated through a simple protocol using commands like DO, WILL, WONT, and DONT. Rules for Option Negotiation: Page 30  Created by Turbolearn AI 1. Parties may only request a change in the option. 2. If a party receives a request to enter a mode it is already in, the request should not be acknowledged. 3. If the option affects how data is processed, the command must be inserted in the data stream exactly where it should take effect. 4. Rejected requests should not be repeated until the operating environment changes.## Telnet Sub Option Negotiations Telnet sub option negotiations are needed when the option does not have only two modes: enable and disable. An example for such a sub negotiation is a terminal type negotiation. 1. The Terminal type option is first enabled with a normal 3 byte negotiation: IAC, WILL, 24 (24 = terminal type). 2. Server responds hopefully: IAC, DO, 24 3. The server then asks the terminal type of the client: IAC, SB, 24, 1, IAC, SE (SB = suboption, 24 = suboption terminal type, 1 = sent your terminal type, SE = suboptionend) 4. Client responds: IAC, SB, 24, 0, V, T, 1, 0, 0, IAC, SE (0 = my terminal type, string VT100) TELNET Commands Page 31  Created by Turbolearn AI Name Code Description EOF 236 End of file SUSP 237 Suspend process ABORT 238 Abort process EOR 239 End of record SE 240 Suboption end NOP 241 No operation DM 242 Data mark BRK 243 Break IP 244 Interrupt process AO 245 Abort output AYT 246 Are you there EC 247 Escape character EL 248 Erase line GA 249 Go ahead SB 250 Suboption WILL 251 Option negotiation WONT 252 Option negotiation DO 253 Option negotiation DONT 254 Option negotiation IAC 255 Interpret as command Telnet Syntax telnet [ host [ port ] ] host: Specifies the hostname or IP address of the remote host computer. port: Specifies the port number or service name. Examples: telnet ycmou.digitaluniversity.ac FTP: File Transfer Protocol Page 32  Created by Turbolearn AI File Transfer Protocol (FTP) is a standard network protocol used for the transfer of computer files between a client and server on a computer network. FTP is built on a client-server model architecture using separate control and data connections between the client and the server. FTP overcomes difficulties caused by various file systems used in the network, such as: File names conversion process Directories utilization process File access under restrictions process Data and the text representation process in the files In FTP: 1. The user exchanges information with a user interface in the local FTP client process. 2. A control connection is made by the local FTP client process to the remote server's FTP server protocol, located in TCP port 21. 3. The local FTP client is taken as a protocol interpreter that interprets the user commands to the acronyms which is used between the client and the server protocol. 4. The control connection is a general TELNET's NVT session. The client transmits commands across the control connection to the server, and the server replies in accordance with the server protocol. 5. If the user asks for a data transfer, a particular data connection is initiated between the server and the client, and the files are transmitted through this link. 6. Separate data transfer processes are developed for the server and the client. 7. The data connection persists until the command that it was made for is executed. For other FTP commands that need a data connection, a new connection is made. The data connection is usually used for three purposes: To send a file from the client to the server For receiving a file from the server For receiving listings of files or directories from the server FTP Commands Page 33  Created by Turbolearn AI Command Command Parameters Description USER UserId Identify user PASS Password Provide password ACCT AccountId Provide account access REIN - Reinitialize start state QUIT - Logout ABOR - Abort previous command CWD Dir name Change directory CDUP - Change to parent directory DELE Filename Delete file LIST Dir name List information about files MKD Dir name Make a directory NLST Dir name List the files in the directory PWD - Print the name of the working directory RMD Dir name Remove directory RNFR Filename Identify file to be renamed RNTO Filename Rename the file SMNT Filename Mount a different file system TYPE A, E, I, N, T, C Identify the data type for the transfer STRU F, R, S, B, C Organization of the file MODE - Transmission format ALLO No. of bytes Allocate storage for data APPE Filenames Append local file to remote file PASV - Identify IP address and port for data PORT IP Addr+port File connection transfer REST Marker value Identify restart marker RETR Filename Get a file STOR Filename Put a file STOU Filename Store unique: version of the file with unique name HELP - Information about server implementation NOOP - Ask server to return an OK reply SITE - Server specific subcommands SYST - Identify servers operating system STAT - Connection status request Transmission Media Page 34  Created by Turbolearn AI Definition Transmission media is a link that carries the information from sender to receiver. It is also known as the Communication Channel. An electrical signal is in the form of current. An electromagnetic signal is series of electromagnetic energy pulses at various frequencies. Data is transmitted normally in the form of electrical or electromagnetic signals. Electromagnetic signals travel through vacuum, air, or other transmission medium to travel from one point to another point. Electromagnetic energy includes power, voice, visible light, radio waves, ultraviolet light, gamma rays etc. The first layer (physical layer) of Communication Networks OSI Seven layer model is dedicated to the transmission media. Need For data transmission. To transmit data safely. As transmission media decides the path of data to be transmitted between computers. Selection Criteria Different Medias have different properties like bandwidth, delay, cost and ease of installation and maintenance. The data transmission capabilities of various Media vary depending upon the various factors. Following factors are to be considered while choosing Transmission Medium Page 35  Created by Turbolearn AI Type of Media Transmission Rate Flexibility Radiation Bandwidth Cost and Ease of Installation Reliability Resistance to Environmental Conditions Noise Absorption Attenuation Distances Number of receivers Transition media Topology used Transmission Protocol Connections of nodes vis Electrical network segment can be connected Types Transmission media is broadly classified into two groups: 1. Wired or Guided Media or Bound Transmission Media 2. Wireless or Unguided Media or Unbound Transmission Media Guided Media Guided media uses physical links, such as coaxial or fibre optic cables, to transmit data to the desired connection. Most cables are made of copper and bound by some form of jacket material. Because they are tangible, this type of media is limited to a fixed location. Popular bound transmission media in use are: twisted pair cable, co-axial cable fibre optical cable. Each of them has its own characteristics like transmission speed, effect of noise, physical appearance, cost etc. Page 36  Created by Turbolearn AI Cable Characteristics Following characteristics are to be considered while choosing cable. Cable Type: It is the type of cable to be used for networking. Like (UTP, STP Coaxial or Fibre Optic) Bandwidth: The bandwidth of a communication system is the highest frequency range that it uses. Data Transfer Rate: The actual data throughput of a cable, after applying encoding and compression schemes to more efficiently use the bandwidth of the cable. Cable Cost: Cost required to purchase the cable. Installation Cost: Cost required to install the cable in the network. Electro Magnetic Interference Sensitivity: It shows the capacity of cable to tolerate electromagnetic interference. Types of Cable Guided media is further categorized in three Types: Twisted Pair Cable Coaxial Cable Fibre Optics Cable Twisted Pair Cable Twisted pair cable consists of copper core wires surrounded by an insulator. Two wires are twisted together to form a pair, and the pair forms a balanced circuit, so that voltages in each pair have the same amplitude but are opposite in phase. The twisting protects against Electromagnetic Interference(EMI) and Radio Frequency Interference(RFI). A typical cable has multiple twisted pairs, each color-coded to differentiate it from other pairs. Why twisted pair? Purpose of twisting the wire is to reduce the electrical interference from the similar pairs in surroundings. The performance of the wire improves with the increase in the number of twist per foot. Page 37  Created by Turbolearn AI If the two wires are parallel, then the electromagnetic interference from the devices such as motor can create a noise or interference on the wire that is closer to the source of noise. This results in high voltage level in one wire than the other. This further leads to uneven load and damaged signal and there will be difference at the receiver side. If two wires are twisted, then the cumulative effect of the interference on both the wires is equal. In twisted pair each wire is closer to the noise source for half of the time and farther away for the other half i.e. in one twist one wire is closer to the noise source and the other is farther; in next twist the reverse is true. So there will be no difference at the receiver side as unwanted signals are cancelled out. Types of Twisted-Pair Cable There are two basic types of twisted-pair cable: Unshielded Twisted Pair (UTP) Shielded Twisted Pair (STP) Unshielded Twisted Pair (UTP) UTP cable is a medium that is composed of pairs of wires. UTP cable is used in different types of networks. Each of the eight individual copper wires in UTP cable is covered by an insulating material. In addition, the wires in each pair are twisted around each other. UTP cable often is installed using a Registered Jack 45 (RJ-45) connector. The RJ-45 is an eight-wire connector used commonly to connect computers onto a local-area network (LAN), especially Ethernets. UTP Categories There are seven different types of UTP categories: Page 38  Created by Turbolearn AI Category Description 1 Used in telephone communications. Not used for transmitting data. Used in Token Ring networks, Transmits data at speeds up to 4 2 megabits/second. Used in Token Ring and 10BASE-T networks, Transmits data at speeds up 3 to 10 Mbps. 4 Used in Token Ring networks, Transmits data at speeds up to 16 Mbps. Used in Ethernet, Fast Ethernet and Token Ring, Transmits data at speeds 5 up to 100 Mbps. Used in Ethernet, Fast Ethernet and Gigabit Ethernet, Transmits data at 5e speeds up to 1000Mbps (1 gigabit per second [Gbps]). Used in Gigabit Ethernet and 10G Ethernet, Transmits data at speeds up 6 to 10 Gbps. UTP-CAT5e is the most popular UTP cable for networking. Features of UTP cable Physical Features: Typically uses eight wires grouped in four pairs, each composed of a solid-coloured and a stripped wire. Speed and throughput: 1 to 1000 Mbps Average cost per node: less expensive Media and connector size: Small Maximum Cable Length: 100 m (short) Advantages Installation is easy Highly Flexible Very Cheap High Speed Capacity 100-meter limit Higher grades of UTP are used in LAN technologies like Ethernet. Most compatible cabling, used in most of networking systems and need not require grounding. Disadvantages Page 39  Created by Turbolearn AI Low Bandwidth as compared to Coaxial Cable More prone to EMI interference. Shielded Twisted Pair (STP) STP is similar to UTP except with each pair covered by an additional copper braid jacket or foil wrapping. This shielding helps protect the signals on the cables from external interference. STP cable combines the techniques of shielding, cancellation, and wire twisting. Each pair of wires is wrapped in a metallic foil. The four pairs of wires then are wrapped in an overall metallic braid or foil, usually 150-ohm cable. As specified for use in Ethernet network installations, STP reduces electrical noise both within the cable and from outside the cable. Usually STP is installed with STP data connector that is specially designed for the STP cable. STP cabling may also use the same RJ connectors used by UTP. Though STP provides better interference prevention than UTP, but it is more expensive and difficult to install. Since it is expensive and have difficulty with termination, STP is hardly used in Ethernet networks. Features of STP cable Speed and throughput: 10 to 100 Mbps Average cost per node: Moderately expensive Media and connector size: Medium to large Maximum cable length: 100 m (short) STP cabling includes metal shielding over each individual pair of copper wires. This type of shielding protects cable from external EMI (electromagnetic interferences). STP cabling is used with token ring networks. Advantages Page 40  Created by Turbolearn AI Metal shield protects wires from radio and electromagnetic interference. This enhances dependability and boosts data transmission speeds at locations where EMI level is high. Installation is easy Performance is satisfactory Can used for both, Analog and Digital transmission Increases the signalling rate Higher capacity than unshielded twisted pair Disadvantages Difficult to manufacture Quite Heavy than UTP Very Expensive than UTP Coaxial Cable Coaxial cable consists of a hollow outer cylindrical conductor that surrounds a single inner wire made of two conducting elements. One of these elements, located in the centre of the cable, is a copper conductor. Surrounding the copper conductor is a layer of flexible insulation. Over this insulating material is a woven copper braid or metallic foil that acts both as the second wire in the circuit and as a shield for the inner conductor. This second layer helps in the reduction of outside interference. Coaxial cabling is the primary type of cabling used by the cable television industry and is also widely used for computer networks, such as Ethernet. Coaxial cable supports data transfer speeds up to 10 to 100 Mbps and is relatively inexpensive, it is more costly than UTP on a per-unit length.The most common connectors used with Thinnet are BNC connectors. Features of coaxial cables Speed and throughput: 10 to 100 Mbps Average cost per node: Inexpensive Media and connector size: Medium Maximum cable length: 500 m (medium) It provides better immunity than twisted pair. This cable is able to transmit data at higher rates. Page 41  Created by Turbolearn AI Other Properties of Coaxial Cable Gauge: Gauge of coaxial cable is thicker than the twisted pair. Configuration: Coaxial cables consist of a single, two- conductor wire, with a centre conductor and an outer shield (conductor), which is of solid metal Bandwidth: Very significant bandwidth, hence used in high capacity applications, such as data and image transmission. Error: Due to the outer shielding performance of Coaxial cable is exceptionally fine. Distance: Not as limited as UTP, amplifiers or other intermediate devices can be used to extend high frequency transmissions over long distances. Security: Coaxial cable is integrally quite secure, it is not easy to place physical taps on coaxial cable. Radiation of energy is also very least so intercepting it is not that easy. Cost: The acquisition, deployment, and rearrangement costs of coaxial cables are very high, as compared with UTP. Applications of coaxial cables: Coaxial cable's superior performance characteristics make it the popular medium in many short hauls, bandwidth-intensive data applications. Coaxial cable is a widely used type of wire used for carrying a wide range of transmissions from source to device. Coaxial cable is mostly use in: Analog telephone networks. Digital telephone network. Cable TV Traditional Ethernet LANs Digital transmission Thick Ethernet Types of Coaxial cables Page 42  Created by Turbolearn AI Baseband: A baseband coaxial cable transmits a single signal at a time at very high speed. A baseband cable is mainly used for LANs. Baseband coaxial cable supports frequency range of a-4kHz and are used for digital signalling.50 ohm ()Baseband coaxial cables are used for digital transmission. Broadband: 75 ohm ()Broadband coaxial cables are used for analog transmission. It can transmits several simultaneous signal at different frequencies. Covers large area as compared to Baseband Coaxial Cable. Since it is used for large area, it requires amplifiers which are unidirectional. Coaxial Cable Limitations High installation cost High maintenance cost. Advantages of Coaxial Cables It can be used for both analog and digital transmission. It offers higher bandwidth as compared to twisted pair cable and can span longer distances. Because of better shielding in coaxial cable, loss of signal or attenuation is less. Better shielding also offers good noise immunity. It is relatively inexpensive as compared to optical fibres. It has lower error rates as compared to twisted pair. It is not as easy to tap as twisted pair because copper wire is contained in plastic jacket. Disadvantages of Coaxial Cables It is usually more expensive than twisted pair. Fibre Optics Cable An optical fibre is a thin (2 to 125 m), flexible medium capable of guiding an optical ray. Various glasses and plastics can be used to make optical fibres. The lowest losses have been obtained using fibres of ultrapure fused silica. Ultrapure fibre is difficult to manufacture; higher-loss multicomponent glass fibres are more economical and still provide good performance. Plastic fibre is even less costly and can be used for short-haul links, for which moderately high losses are acceptable. Page 43  Created by Turbolearn AI An optical fibre cable has a cylindrical shape and consists of three concentric sections: the core the cladding the jacket The core is the innermost section and consists of one or more very thin strands, or fibres, made of glass or plastic; the core has a diameter in the range of 8 to Each fibre is surrounded by its own cladding, a glass or plastic coating that has optical properties different from those of the core. The interface between the core and cladding acts as a reflector to confine light that would otherwise escape the core. The outermost layer, surrounding one or a bundle of cladded fibres, is the jacket. The jacket is composed of plastic and other material layered to protect against moisture, abrasion, crushing, and other environmental dangers. Applications One of the most significant technological breakthroughs in data transmission has been the development of practical fibre optic communications systems. Optical fibre already enjoys considerable use in long-distance telecommunications, and its use in military applications is growing. The continuing improvements in performance and decline in prices, together with the inherent advantages of optical fibre, have made it increasingly attractive for local area networking. The following characteristics distinguish optical fibre from twisted pair or coaxial cable: Page 44  Created by Turbolearn AI Greater Capacity: The potential bandwidth, and hence data rate, of optical fibre is immense; data rates of hundreds of Gbps over tens of kilometres have been demonstrated. Compare this to the practical maximum of hundreds of Mbps over about 1 km for coaxial cable and just a few Mbps over 1 km or up to 100 Mbps to 1 Gbps over a few tens of meters for twisted pair. Smaller Size and Lighter Weight: Optical fibres are considerably thinner than coaxial cable or bundled twisted-pair cable at least an order of magnitude thinner for comparable information transmission capacity. For cramped conduits in buildings and underground along public rights-of-way, the advantage of small size is considerable. The corresponding reduction in weight reduces structural support requirements. Lower Attenuation: Attenuation is significantly lower for optical fibre than for coaxial cable or twisted pair and is constant over a wide range. Electromagnetic Isolation: Optical fibre systems are not affected by external electromagnetic fields. Thus the system is not vulnerable to interference, impulse noise, or crosstalk. By the same token, fibres do not radiate energy, so there is little interference with other equipment and there is a high degree of security from eavesdropping. In addition, fibre is inherently difficult to tap. Greater Repeater Spacing: Fewer repeaters mean lower cost and fewer sources of error. The performance of optical fibre systems from this point of view has been steadily improving. Repeater spacing in the tens of kilometres for optical fibre is common, and repeater spacings of hundreds of kilometres have been demonstrated. Coaxial and twisted-pair systems generally have repeaters every few kilometres. Five basic categories of application have become important for optical fibre: Long-haul trunks Metropolitan trunks Rural exchange trunks Subscriber loops Local area networks Transmission Characteristics: Page 45  Created by Turbolearn AI Optical fibre transmits a signal-encoded beam of light by means of total internal reflection. Total internal reflection can occur in any transparent medium that has a higher index of refraction than the surrounding medium. In effect, the optical fib acts as a waveguide for frequencies in the range of about to this covers portions of the infrared and visible spectra. Light from a source enters the cylindrical glass or plastic core. Rays at shallow angles are reflected and propagated along the fibre; other rays are absorbed by the surrounding material. This form of propagation is called step-index multimode, referring to the variety of angles that will reflect. With multimode transmission, multiple propagation paths exist, each with a different path length and hence time to traverse the fibre. This causes signal elements (light pulses) to spread out in time, which limits the rate at which data can be accurately received. Put another way, the need to leave spacing between the pulses limits data rate. This type of fibre is best suited for transmission over very short distances. When the fibre core radius is reduced, fewer angles will reflect. By reducing the radius of the core to the order of a wavelength, only a single angle or mode can pass: the axial ray. This single-mode propagation provides superior performance for the following reason. Because there is a single transmission path with single-mode transmission, the distortion found in multimode cannot occur. Single- mode is typically used for long-distance applications, including telephone and cable television. Finally, by varying the index of refraction of the core, a third type of transmission, known as graded- index multimode, is possible. This type is intermediate between the other two in characteristics. Fiber Optic Systems Two types of light sources used in fiber optic systems: Light Emitting Diode (LED) Less costly Operates over a greater temperature range Has a longer operational life Injection Laser Diode (ILD) More efficient Can sustain greater data rates Operates on the laser principle Page 46  Created by Turbolearn AI Advantages of Fiber Optic Cables Extremely High Bandwidth: Provides bandwidth unlike any other cable-based data transmission medium. Easy to Adjust Increasing Bandwidth: Enables dynamic network bandwidth provisioning for data traffic spikes and lulls. Good Resistance to Electromagnetic Interference: Has a very low rate of bit error and is highly resistive to electromagnetic interference. Flexibility: Greater tensile strength than copper or steel fibers of the same diameter, bends easily, and resists most corrosive elements. Able to Detect Cable Damage and Provide Secure Transmissions: Secure transmission medium without the possibility of data transmission detection or leakage. Damage due to splices can be easily detected by continuous monitoring and measuring light reflection time. Low Signal Loss: Allows for longer transmission distances, requiring repeaters at very long distances. High Transmission Rate: 10 GB/sec compared to coaxial cable's 1 GB/sec. Saves Time: Small size, light weight, and flexibility provide advantages during installation. Saves Steps: No electrical conductivity, so grounding and protection are not required. Provides Safe Transmission: Secure transmission due to no light leakage. Good Ability to Work in Special Atmospheres: No electrical signals, thus no possibility of shock or other hazards, making it suitable for fiery atmospheres. Portability: Light weight and small size allow it to carry a large number of signals. Disadvantages of Fiber Optic Transmission Page 47  Created by Turbolearn AI High Installation Costs: Expensive to install, but lasts longer than copper cables. Special Test Equipments are Often Required: Traditional networking test equipment is unusable; specialized optical test equipment like Optical Time- Domain Reflectometer (OTDR) is required. Susceptible to Physical Damage: Highly susceptible to physical damage during installation or construction. Price: More costly than copper cables. Brittle in Nature: More brittle than electrical wires. Chemicals Impact: Various chemicals like hydrogen gas have adverse impacts. Opaqueness: Most fiber becomes opaque when exposed to radiation. Special Skills Required: Requires special training and accurate connecting and measurement equipment. Unguided Media Unbound transmission media that transmit data without cables, using wireless links. Also known as unbounded media or wireless media. Transmits data without physical connectors between devices, using microwave, infrared, or radio signals. Not bounded by physical geography. Transmits electromagnetic waves without a solid conductor and can travel through a vacuum. Becoming popular with wireless LANs in offices and colleges. Types of Communication Band Data transmission characteristics are determined by: Characteristics of the medium Characteristics of the signal In guided media, the medium determines transmission limitations. In unguided media, the signal's bandwidth from the transmitting antenna is more important. Directionality: Key property of signals transmitted by antenna. Lower frequencies are omnidirectional. Higher frequencies can be focused into a directional beam. Key Design Factors for Data Transmission Systems Page 48  Created by Turbolearn AI Data Transfer Rate and Distance are key concerns in data transmission system design. Higher data transfer rate means longer the distance. Bandwidth: Greater bandwidth = higher data rate. Transmission Losses: Attenuation limits distance. Interference: Competing signals can distort or wipe out a signal. Number of Receivers: Each attachment introduces attenuation and distortion, limiting distance and data rate. Electromagnetic Spectrum Used for wireless communication and divided into sub-bands: Abbreviation Full Name ELF Extremely Low Frequency VF Voice Frequency VLF Very Low Frequency LF Low Frequency MF Medium Frequency HF High Frequency VHF Very High Frequency UHF Ultrahigh Frequency SHF Super High Frequency EHF Extremely High Frequency Signal Propagation Methods A signal radiated from an antenna propagates along one of three routes: Ground Wave (GW) Sky Wave (SW) Line of Sight (LOS) Page 49  Created by Turbolearn AI Frequency Band Wavelength Typical Use Characteristics Range Power line 10,000 to 1000 to 100 frequencies; used by ELF 30 Hz km some home control systems Used by the 300 to 3000 1000 to 100 telephone system for VF Hz km analog subscriber lines Long-range GW; low attenuation day 3 to 30 kHz VLF 100 to 10 km navigation; submarine and night; high communication atmospheric noise level Long-range GW; slightly less reliable 30 to 300 navigation; marine LF 10 to 1 km than VLF; absorption in kHz communication time daytime radio beacons GW and night SW; Maritime radio; direction Maritime radio; 300 to 3000 1000 to 100 finding; AM broadcasting; MF direction finding; AM kHz m attenuation low at night, broadcasting high in day; atmospheric noise Amateur radio; SW quality varies with international time of day, season, and 3 to 30 MHz HF 100 to 10 m broadcasting, military frequency distance aircraft communication and ship communication VHF television; FM LOS; scattering because of 30 to 300 broadcast and two- VHF 10 to 1 m temperature inversion; MHz way radio, AM aircraft cosmic noise communication UHF television; 300 to 3000 cellular telephone; UHF 100 to 10 cm LOS; cosmic noise MHz radar; microwave links 3 to 30 GHz SHF 10 to 1 cm Satellite LOS; rainfall attenuation communication; radar; above 10 GHz; atmospheric attenuation Page 50  Created by Turbolearn AI terrestrial microwave due to oxygen and water links vapor LOS; atmospheric 30 to 300 Experimental; EHF 10 to 1 mm attenuation due to oxygen GHz wireless local loop and water vapor Infrared LANs; 300 GHz to 1 mm to 770 Infrared consumer electronic LOS 400 THz nm applications 400 to 900 Visible 770 to 330 Optical LOS THz light nm communication Wired and Wireless Data Communication Frequencies Type Frequencies Wired Twisted Pair 0-100MHz Coaxial Cable 1 KHz-1GHz Optical Fiber 100 THz-1PHz Wireless AM Radio 530 KHz-1600KHz FM Radio 88 MHz-108Hz Terrestrial/Satellite 1 GHz-1THz Infrared 1 THz-100THz Signal Propagation Methods Explained Page 51  Created by Turbolearn AI Ground Propagation Radio waves travel through the lowest part of the atmosphere, following the curvature of the Earth. Effective up to about 2 MHz. Factors: Wave induces current in the Earth's surface, slowing the wave front. Diffraction scatters waves, preventing penetration of the upper atmosphere. Example: AM radio. Sky Propagation High-frequency radio waves radiate into the ionosphere and are reflected back to Earth. Used for amateur radio, CB radio, and international broadcasts. Signal can travel through multiple hops, bouncing between the ionosphere and Earth. Line-of-Sight Propagation Very high-frequency signals transmitted in straight lines. Above 30 MHz, ground wave and sky wave modes do not operate. Microwaves are bent by the atmosphere, propagating farther than the optical line of sight. Types of Wireless Communication Microwave Communication Radio Wave Communication Terrestrial Microwave Satellite Microwave Infrared Communication Microwave Communication Information is transmitted by electromagnetic waves with short wavelengths (1 mm to 30 cm). Frequencies range from 1.0 GHz to 300 GHz. Ideal for radio and television broadcasting and transmitting data over long distances without physical wires. Helpful in rural mountainous regions where physical transmission lines are difficult and expensive to install. Page 52  Created by Turbolearn AI Microwave Transmission Types Terrestrial Microwave: Employs Earth-based transmitters and receivers. Frequencies used are in the low-gigahertz range. Limited to line-of-sight. Uses radio frequency spectrum ranging from 2 to 40 GHz. Common antenna: parabolic dish (about 3 m in diameter). Used for long-distance telecommunication services. Point-to-point links between buildings. Cellular systems. Power utilities use microwaves to remotely manage the power grid. Satellite Microwave: Uses a communication satellite as a microwave relay station. Links ground-based microwave transmitter/receivers (earth stations). Satellite receives transmissions on one frequency band (uplink), amplifies or repeats the signal, and transmits it on another frequency (downlink). Satellite remains stationary with respect to its position over the Earth at a height of 35,863 km at the equator. Applications: Television Distribution Long-Distance Telephone Transmission Private Business Networks Satellite radio Satellite internet access Satellite Types Communication Satellite Weather satellite Remote- Sensing Satellite Scientific Satellite Principal Satellite Transmission Bands Page 53  Created by Turbolearn AI C band: 4 (downlink) - 6 (uplink) GHz Ku band: 12 (downlink) -14 (uplink) GHz Rain interference is the major problem Ka band: 19 (downlink) - 29 (uplink) GHz Equipment needed to use the band is still very expensive Radio Wave Communication Radio wave is omnidirectional, unlike microwave. Does not require dish-shaped antennas or precise alignment. Electromagnetic waves ranging in frequency between 3 kHz and 1 GHz. Can penetrate walls. Applications AM and FM radio Television Maritime radio Cordless phones and paging Infrared Communication Uses transmitters/receivers (transceivers) that modulate non-coherent infrared light. Transceivers must be within the line of sight of each other directly or via reflection. Does not penetrate walls, so security and interference problems encountered in microwave systems are not present. No frequency allocation issue. Frequencies from 300 GHz to 4 THz. Applications TV Remote control Guidance in weapon system Wireless keyboards and mouse Advantages Page 54  Created by Turbolearn AI Security: High directionality, maintaining high confidentiality. Effect on the human body: No harmful effect. Data communication speed: Potential of 1 Gbps, optimal for large-volume data such as video. Bluetooth Architecture Developed to provide a wireless interconnect between small mobile devices and their peripherals. Designed to connect mobile devices over a personal and private connection. Uses radio frequency for communication and maintains a high level of security. Robustness, low power and low cost are some of the key features of Bluetooth technology. Uniform structure is defined for a wide range of devices to connect and communicate with each other. Bluetooth architecture defines two types of networks: Piconet Scatternet Piconet Piconet is a Bluetooth network that consists of one primary (master) node and seven active secondary (slave) nodes. Up to eight active nodes (1 master and 7 slaves) within 10 meters. Only one primary or master station in each piconet. Communication is between master and a slave. Up to 255 parked nodes (secondary or slave stations) that cannot take part in communication until moved from parked state to active state. Scatternet Scattemet is formed by combining various piconets. Page 55  Created by Turbolearn AI A slave in one piconet can act as a master or primary in other piconet. Node can receive messages from the master in the first piconet and deliver the message to its slaves in other piconet where it is acting as master (bridge slave). A station cannot be a master in two piconets. Bluetooth Layers and Protocol Stack Bluetooth standard has many protocols organized into different layers. The layer structure of Bluetooth does not follow OSI model, TCP/IP model or any other known model. Radio Layer Corresponds to the physical layer of the OSI model. Deals with radio transmission and modulation. Moves data from master to slave or vice versa. Low power system that uses 2.4 GHz ISM band in a range of 10 meters. Uses Frequency Hopping Spread Spectrum (FHSS) to avoid interference. Hops 1600 times per second. Uses GFSK (FSK with Gaussian bandwidth filtering). Baseband Layer Equivalent to the MAC sublayer in LANs. Uses a form of TDMA called TDD-TDMA (time division duplex TDMA). Master and slave stations communicate with each other using time slots. The master in each piconet defines the time slot of 625 µsec. Communication is half duplex. If piconet has only no slave, the master uses even numbered slots (0, 2, 4...) and the slave uses odd-numbered slots (1, 3, 5...). If piconet has more than one slave, the master uses even numbered slots. The slave sends in the next odd-numbered slot if the packet in the previous slot was addressed to it. Bluetooth Communication Page 56  Created by Turbolearn AI Bluetooth communication involves two types of links established between a master and a slave device: 1. Asynchronous Connection-less (ACL): Used for packet-switched data at irregular intervals. Delivers traffic on a best-effort basis. Frames can be lost and may require retransmission. A slave can have only one ACL link to its master. Emphasizes correct delivery over fast delivery. Achieves a maximum data rate of 721 kbps using one or more slots. 2. Synchronous Connection Oriented (SCO): Used for real-time data, such as sound. Prioritizes fast delivery over accurate delivery. A physical link is created between the master and slave by reserving specific slots at regular intervals. Damaged packets are not retransmitted. A slave can have up to three SCO links with the master. Data can be sent at 64 Kbps. Logical Link Control Adaptation Protocol Layer (L2CAP) The Logical Link Control Adaptation Protocol (L2CAP) is equivalent to the logical link control sublayer of LAN. The ACL link uses L2CAP for data exchange, but the SCO channel does not. L2CAP's functions include: Page 57  Created by Turbolearn AI 1. Segmentation and Reassembly: Receives packets up to 64 KB from upper layers. Divides them into frames for transmission. Adds extra information to define the frame's location in the original packet. Reassembles frames into packets at the destination. 2. Multiplexing: Performs multiplexing at the sender side and demultiplexing at the receiver side. At the sender site, it accepts data from upper layer protocols, frames them, and delivers them to the Baseband layer. At the receiver site, it accepts frames from the baseband layer, extracts data, and delivers them to the appropriate protocol layer. 3. Quality of Service (QoS): Handles quality of service requirements during link establishment and normal operation. Enables devices to negotiate the maximum payload size during connection establishment. Bluetooth Frame Format The Bluetooth frame format consists of the following fields: Page 58  Created by Turbolearn AI 1. Access Code: A 72-bit field containing synchronization bits. Identifies the master. 2. Header: A 54-bit field containing an 18-bit pattern repeated three times. Subfields: Address: A 3-bit field that can define up to seven slaves (1 to 7). An address of zero is used for broadcast communication from the primary to all secondaries. Type: A 4-bit field that identifies the type of data from upper layers. F: The flow bit, used for flow control. Set to 1 when the device cannot receive more frames. A: The acknowledgement bit. S: Contains the sequence number of the frame to detect retransmission. One bit is sufficient due to the use of the stop-and- wait protocol. Checksum: An 8-bit field containing a checksum to detect header errors. 3. Data: A variable-length field (0 to 2744 bits). Contains data or control information from upper layers. Wi-Fi Wi-Fi (Wireless Fidelity) is a popular wireless networking technology that provides wireless high-speed Internet and network connections using radio waves. In Wi-Fi networks, there is no physical connection between sender and receiver; they connect using radio frequency (RF). Access Point (AP): The foundation of any wireless network. Its primary job is to transmit a wireless signal for computers to detect and connect to. Wireless Network Adapters: Computers and devices need these to connect to an access point and join a wireless network. Wi-Fi is compatible with many applications and devices like video game consoles, home networks, PDAs, mobile phones, major operating systems, and other consumer electronics. It has a range of about 100m and allows for faster data transfer rates between 10 and 54 Mbps. Page 59  Created by Turbolearn AI Wi-Fi Standards There are three different wireless standards under Wi-Fi, set by The Institute of Electrical and Electronic Engineers (IEEE): 802.11a 802.11b 802.11g Wi-Fi is used to create wireless Local Area Networks (WLAN). 802.11b: The most widely used standard. 802.11g: Expected to grow rapidly due to its speed. These two standards are relatively inexpensive and provide wireless connectivity in public areas such as airports, railway stations, cafes, bars, and restaurants. The main difference between 802.11b and 802.11g is the speed. 802.11b: Data transfer rate of up to 11 Mbps. 802.11g: Data transfer rate of up to 54 Mbps. 802.11a is more expensive and less available for public access. WiMAX WiMAX (Worldwide Interoperability for Microwave Access) is a broadband wireless technology based on the IEEE 802.16 set of standards, providing multiple physical layer and Media Access Control options. WiMAX systems are expected to deliver broadband access services to residential and enterprise customers economically. It is a wireless technology optimized for delivering IP-centric services over a wide area and a scalable wireless platform for constructing alternative and complementary broadband networks. It is also a certification that denotes interoperability of equipment built to the IEEE 802.16 or compatible standard. The IEEE 802.16 Working Group develops standards that address two types of usage models: Page 60  Created by Turbolearn AI A fixed usage model (IEEE 802.16-2004) A portable usage model (IEEE 802.16e) WiMAX network design is based on the following major principles: Spectrum: Capable of being deployed in both licensed and unlicensed spectra. Topology: Supports different Radio Access Network (RAN) topologies. Interworking: Provides an independent RAN architecture to enable seamless integration and interworking with Wi-Fi, 3GPP, and 3GPP2 networks and existing IP operator core networks. IP Connectivity: Supports a combination of IPv4 and IPv6 networks to interconnect clients and application servers. Mobility Management: Extends fixed access to mobility and broadband multimedia services delivery. WiMAX Wireless Services WiMAX provides two forms of wireless service: 1. Non-line-of-sight service: Similar to Wi-Fi. A small antenna on a computer connects to the WiMAX tower. Uses a lower frequency range from 2 GHz to 11 GHz, similar to Wi-Fi. 2. Line-of-sight service: A fixed dish antenna points straight at the WiMAX tower from a rooftop or pole. Provides a stronger and more stable connection, enabling the transmission of a lot of data with fewer errors. Uses higher frequencies, with ranges reaching a possible 66 GHz. WiMAX operates on two frequency bands (2-11 GHz and 10-66 GHz), has a range of about 50km, and speeds of up to 80 Mbps. This enables smaller wireless LANs to be interconnected by WiMAX, creating a large wireless MAN (Metropolitan Area Network). It also achieves networking between cities without the need for expensive cabling and provides high-speed wireless broadband access to users. Page 61  Created by Turbolearn AI WiMAX can work by line-of-sight and non-line-of-sight. At the 2-11 GHz frequency range, it works by non-line-of-sight, where a computer inside a building communicates with a tower/antenna outside the building. Short frequency transmissions are not easily disrupted by physical obstructions. Higher frequency transmissions are used for non-line-of-sight service, enabling towers/antennas to communicate with each other over a greater distance. Due to infrastructure and costs involved, it is more suited to provide the backbone services for ISPs and large corporations providing wireless networking and internet access. Comparison of Wireless Technologies Technology Bluetooth Wi-Fi (a) Wi-Fi (b) Wi-Fi (g) WiMAX Standard 802.15 802.11a 802.11b 802.11g 802.16 Frequency (GHz) 2.45 5 2.4 2.4 2-66 Speed (Mbps) 0.72 54 11 54 80 Range 10m 50m 100m 100m 50km Advantages Low Cost Speed Low Cost Speed Speed, Range Disadvantages Range Cost Speed Cost, Range Cost Cellular (Mobile) Telephone Cellular communication is designed to provide communication between two moving units or between a mobile unit and a stationary land unit (PSTN). The entire network coverage area is divided into cells based on the principle of frequency reuse. Cell: A basic geographical unit of a cellular network; the area around an antenna where a specific frequency range is used. Represented graphically as a hexagonal shape but irregular in reality. Cluster: A group of adjacent cells, usually 7 cells, with no frequency reuse within a cluster. In heavy traffic zones, cells are smaller, while in isolated zones, cells are larger. Page 62  Created by Turbolearn AI Band in Cellular Telephony Analog transmission is used for cellular telephony. Frequency modulation is used for communication between the mobile phone and cell office. Two frequency bands are allocated for this purpose. One band is for communication initiated by the mobile phone, and the other band is for the land phone. Each channel requires a full-duplex dialog. To prevent interference, adjacent channels are rarely allocated, with some reserved for control purposes. This reduces the number of channels available for each cell. GSM uses FDMA and TDMA to transmit voice and data: Uplink Channel: Between the cell phone and the BTS (Base Transceiver Station) uses FDMA. Downlink Channel: Between the BTS and the cell phone uses TDMA. Uplink and downlink channels each have a bandwidth of 25 MHz. Each band is further split into: Control Channel: Used to set up and manage calls. Traffic Channel: Used to carry voice. GSM Frequency Bands: Frequency Band Uplink/BTS Transmit Downlink/BTS Receive 900 MHz 935-960 MHz 890-915 MHz 1800 MHz 1805-1880 MHz 1710-1785 MHz 1900 MHz 1930-1990 MHz 1850-1910 MHz The same frequency band can be used for multiple non-adjacent cells. Calls Using Mobile Phones Page 63  Created by Turbolearn AI 1. A call is made from the mobile phone by entering a 10-digit phone number. 2. The mobile phone scans the band and seeks a channel for setting up the call. 3. After seeking, it sends this number to the closest cell office, which sends it to the CTO (Central Telephone Office). 4. If the called party is available, the CTO lets the MTSO (Mobile Telephone Switching Office) know. 5. At this point, the MTSO allocates an empty voice channel to the cell to establish the connection. 6. The mobile phone adjusts its tuning to the new channel, and the dialog begins. Call from Land Phone to a Mobile Phone: 1. The telephone central office sends the number to the MTSO. 2. The MTSO performs a lookup to see where the mobile phone is currently placed by sending appropriate query signals to all the cells (paging). 3. The cell where the mobile phone is currently located responds to the MTSO. 4. To start, an idle phone continuously listens to the paging channel to detect messages directed at it. 5. The MTSO then transmits the incoming call signal to that mobile phone, and when the mobile phone is answered, the connection is established. Transmitting/Receiving/Handoff Operations Handoff is the process where a mobile moves into a different cell while a conversation is in progress, and the MSC (Mobile Switching Center) automatically transfers the call to a new channel belonging to the new base station. This involves identifying a new base station and allocating voice and control signals to channels associated with the new base station. Processing handoffs is an important task in any cellular radio system. When a mobile user is engaged in a conversation, the MS (Mobile Station) is connected to a BS (Base Station) via a radio link. If the mobile user moves to the coverage area of another BS, the radio link to the old BS is eventually disconnected, and a radio link to the new BS should be established to continue the conversation. This process is referred to as automatic link transfer, handover, or handoff. Types of Handoff Page 64  Created by Turbolearn AI 1. Hard Handoff: A mobile station only communicates with one base station at a time. When the MS moves from one cell to another, communication must first