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4.1 Basic Networking: Definition, Types, and Topologies
· Networking is the process of connecting two or more computers or devices together to share data, files, and resources like printers or internet connections.
· It enables communication between users and systems over a wired or wireless medium.
Types of Networks
1. Personal Area Network (PAN):
o Very small network, typically within a range of a few meters.
o Used to connect personal devices such as mobile phones, laptops, tablets, Bluetooth devices, etc.
2. Local Area Network (LAN):
o Covers a small geographical area like a home, school, or office building.
o Allows multiple devices to share files and resources like printers.
o Usually faster and more secure than wide networks.
3. Metropolitan Area Network (MAN):
o Spans a city or a large campus.
o Connects multiple LANs together using high-speed connections.
o Often used by government or business organizations within a city.
4. Wide Area Network (WAN):
o Covers large geographic areas, even entire countries or continents.
o The Internet is the largest example of a WAN.
o Slower than LAN due to long-distance transmission.
5. Wireless Local Area Network (WLAN):
o Similar to LAN but uses wireless technologies like Wi-Fi.
o Commonly used in homes, cafes, schools, and public places.
6. Storage Area Network (SAN):
o A dedicated network designed to provide access to consolidated data storage.
o Often used in data centers and enterprise environments.
Network Topologies (Structure of a Network)
1. Bus Topology:
o All computers are connected to a single central cable.
o Simple and low-cost but failure in the main cable can bring down the whole network.
2. Star Topology:
o All devices are connected to a central hub or switch.
o Easy to add or remove devices.
o If the central hub fails, the entire network is affected.
3. Ring Topology:
o Each device is connected to two other devices, forming a circular path.
o Data travels in one direction.
o A failure in any one device can break the communication.
4. Mesh Topology:
o Every device is connected to every other device.
o Offers high redundancy and reliability.
o Expensive and complex to install.
5. Tree Topology:
o A combination of star and bus topologies.
o Devices are connected in a hierarchical manner.
o Scalable but harder to manage.
6. Hybrid Topology:
o Combines two or more different topologies.
o Flexible and suitable for large networks.
o Complex design and higher cost.
4.2 Client-Server and Peer-to-Peer Network
In computer networking, client-server and peer-to-peer (P2P) are two common models used to organize communication and resource sharing between devices (nodes) in a network.
1. Client-Server Network
· In this model, the network is divided into two types of devices: clients and servers.
· A server is a powerful computer that provides services or resources (such as files, printers, websites, or databases).
· A client is a device (like a PC or smartphone) that sends requests to the server to use those resources or services.
Features:
· Centralized control: The server manages and controls access to resources.
· Clients depend on the server for services like login authentication, file storage, etc.
· Common in large organizations and websites.
Examples:
· A web browser (client) requests a webpage from a web server.
· A school computer lab where all computers access files from a central server.
Advantages:
· Easier to manage and secure.
· Centralized backup and maintenance.
· Scalable for large networks.
Disadvantages:
· If the server fails, clients lose access to services.
· Requires more cost and configuration for servers.
2. Peer-to-Peer (P2P) Network
· In this model, all devices (peers) are equal and act as both clients and servers.
· Each computer can share its own resources directly with others without needing a central server.
Features:
· Decentralized: No central server controlling the network.
· All devices can initiate communication and share files or printers.
· Best suited for small networks (like home or small office).
Examples:
· Sharing files between computers in a home using LAN.
· Torrent file sharing (BitTorrent protocol).
Advantages:
· Easy and inexpensive to set up.
· No need for a dedicated server.
· Each peer contributes to the network.
Disadvantages:
· Difficult to manage in large networks.
· Less secure and harder to back up data centrally.
· Poor performance when many devices are connected.
4.3 Connectivity and Media: Network Cables and Connectors
In networking, connectivity refers to how computers and other devices are physically or wirelessly connected to exchange data. This is achieved using network media, which includes cables and connectors.
1. Network Cables
Network cables are used to physically connect devices like computers, switches, and routers in a network. The most common types are:
a. Twisted Pair Cable
· Widely used in LANs.
· Consists of pairs of wires twisted together to reduce interference.
· Two types:
o UTP (Unshielded Twisted Pair) – Common in homes and offices.
o STP (Shielded Twisted Pair) – Has extra shielding to reduce interference.
Example: Ethernet cable (Cat5e, Cat6, Cat7)
b. Coaxial Cable
· Has a central conductor, insulating layer, metal shield, and outer cover.
· Used in older Ethernet networks and cable TV.
Example: Used in broadband internet and CCTV.
c. Fiber Optic Cable
· Uses light to transmit data at very high speed.
· Immune to electromagnetic interference.
· Expensive but ideal for long-distance and high-bandwidth needs.
Types: Single-mode and multi-mode fiber.
2. Network Connectors
Connectors are used to connect the ends of network cables to devices.
a. RJ-45 Connector
· Most commonly used with twisted pair Ethernet cables.
· Looks like a large telephone plug.
· Connects computers to switches, routers, and network ports.
b. BNC Connector (Bayonet Neill-Concelman)
· Used with coaxial cables.
· Common in CCTV and older networks.
c. LC, SC, ST Connectors
· Used with fiber optic cables.
· Designed to connect fiber cables to networking equipment.
Wireless Media
Besides physical cables, networks can also be connected wirelessly using:
· Wi-Fi (Wireless LAN) – Uses radio waves.
· Bluetooth – Short-range communication.
· Infrared – Rarely used today.
4.4 OSI Reference Model (Open Systems Interconnection Model)
The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven different layers. It helps different networks and devices to communicate with each other regardless of their underlying architecture.
Purpose of OSI Model:
· To guide product developers and facilitate communication between different networking systems.
· To break down the complex process of data transmission into manageable layers.
· Ensures interoperability between hardware and software systems.
The 7 Layers of OSI Model (Top to Bottom):
1. Application Layer (Layer 7)
· Closest to the user.
· Provides services like email, file transfer, and web browsing.
· Examples: HTTP, FTP, SMTP, DNS
2. Presentation Layer (Layer 6)
· Translates, encrypts, or compresses data.
· Ensures data is readable by the receiving system.
· Example: Encryption like SSL, JPEG, MP3 formats
3. Session Layer (Layer 5)
· Manages sessions or connections between applications.
· Handles opening, maintaining, and closing sessions.
· Example: APIs, sockets
4. Transport Layer (Layer 4)
· Responsible for reliable data transfer.
· Provides error detection, correction, and flow control.
· Protocols: TCP (reliable), UDP (unreliable)
5. Network Layer (Layer 3)
· Determines the best physical path for data.
· Handles routing and logical addressing (IP addresses).
· Protocols: IP, ICMP, IGMP
6. Data Link Layer (Layer 2)
· Ensures error-free transfer between two connected devices.
· Deals with MAC addresses and frames.
· Protocols: Ethernet, PPP, ARP
7. Physical Layer (Layer 1)
· Concerned with the hardware and transmission of raw bits.
· Deals with cables, switches, voltage levels, and connectors.
4.5. Common TCP and UDP Ports, Protocols, and Their Purpose
In computer networking, TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are two transport layer protocols used for communication. Each protocol uses ports to identify specific services and applications on a device.
Below are the commonly used TCP and UDP ports, their associated protocols, and their purposes:
Common TCP Ports
1. Port 20 & 21 – FTP (File Transfer Protocol)
o TCP 20: Data transfer
o TCP 21: Control (commands)
o Purpose: Transfer files between client and server.
2. Port 22 – SSH (Secure Shell)
o Purpose: Secure remote login and command execution.
3. Port 23 – Telnet
o Purpose: Remote login (insecure, plain text).
4. Port 25 – SMTP (Simple Mail Transfer Protocol)
o Purpose: Sending emails.
5. Port 53 – DNS (Domain Name System)
o TCP/UDP
o Purpose: Translates domain names into IP addresses.
6. Port 80 – HTTP (HyperText Transfer Protocol)
o Purpose: Web browsing (insecure).
7. Port 110 – POP3 (Post Office Protocol v3)
o Purpose: Retrieve emails from a server.
8. Port 143 – IMAP (Internet Message Access Protocol)
o Purpose: Manage and access emails on the server.
9. Port 443 – HTTPS (HTTP Secure)
o Purpose: Secure web browsing using SSL/TLS.
10. Port 3306 – MySQL
o Purpose: Database communication.
11. Port 3389 – RDP (Remote Desktop Protocol)
o Purpose: Remote desktop access to Windows systems.
Common UDP Ports
1. Port 53 – DNS
o Purpose: Quick domain resolution (usually via UDP).
2. Port 67 & 68 – DHCP (Dynamic Host Configuration Protocol)
o UDP 67: Server to client
o UDP 68: Client to server
o Purpose: Assigns IP addresses dynamically.
3. Port 69 – TFTP (Trivial File Transfer Protocol)
o Purpose: Lightweight file transfer (no authentication).
4. Port 123 – NTP (Network Time Protocol)
o Purpose: Synchronizes system time over a network.
5. Port 161 – SNMP (Simple Network Management Protocol)
o Purpose: Monitor and manage network devices.
6. Port 520 – RIP (Routing Information Protocol)
o Purpose: Routing protocol used in LAN/WAN.
1. Switch
· Function: Connects multiple devices within a local area network (LAN); uses MAC addresses to forward data to the correct destination.
· Features:
o Operates at the Data Link Layer (Layer 2) of the OSI model.
o Reduces network collisions.
o Supports VLANs for network segmentation.
· Configuration:
o Assign IP for management (optional).
o Create and assign VLANs.
o Set port speeds and enable/disable ports.
2. Router
· Function: Connects different networks together (e.g., LAN to WAN); routes data based on IP addresses.
· Features:
o Operates at the Network Layer (Layer 3).
o Supports NAT (Network Address Translation).
o Provides DHCP and firewall capabilities.
· Configuration:
o Set IP address for LAN and WAN interfaces.
o Enable routing protocols (e.g., RIP, OSPF).
o Configure static or dynamic routes.
3. Access Point (AP)
· Function: Allows wireless devices to connect to a wired network via Wi-Fi.
· Features:
o Operates at Layer 2.
o Supports multiple SSIDs and encryption methods (WPA2, WPA3).
o Can be standalone or controller-managed.
· Configuration:
o Set SSID and password.
o Configure channel and bandwidth.
o Set MAC filtering and security protocols.
4. Modem (Modulator-Demodulator)
· Function: Converts digital data from a computer into analog for transmission over telephone lines (and vice versa).
· Features:
o Used to connect to ISP via DSL, cable, or fiber.
o May include built-in router functionalities.
· Configuration:
o Set ISP login details (PPPoE, DHCP).
o Configure bridge or router mode.
o Update firmware for compatibility and security.
5. Firewall
· Function: Controls incoming and outgoing network traffic based on security rules; protects internal networks.
· Features:
o Can be hardware or software-based.
o Filters traffic by IP, port, or protocol.
o Supports Stateful Packet Inspection (SPI).
· Configuration:
o Define allow/deny rules.
o Setup NAT or DMZ if needed.
o Monitor logs and set alerts for suspicious activity.
4.7. Application of Network Utilities
Network utilities are tools used to troubleshoot and manage computer networks. They help monitor, configure, and diagnose network issues. Some commonly used utilities are:
1. IPCONFIG (Internet Protocol Configuration)
· Used in: Windows Command Prompt
· Purpose: Displays the IP configuration of the system.
· Common Uses:
o View IP address, subnet mask, and default gateway.
o Release and renew DHCP-assigned IP address.
· Examples:
o ipconfig: View IP settings.
o ipconfig /release: Release current IP address.
o ipconfig /renew: Request a new IP address from DHCP.
2. PING (Packet Internet Groper)
· Used in: Windows, Linux, macOS
· Purpose: Tests network connectivity between devices.
· Common Uses:
o Check if a website/server is reachable.
o Measure round-trip time and packet loss.
· Example:
o ping www.google.com
Sends ICMP packets to Google and shows response time.
3. TRACERT (Trace Route)
·
Used in:
Windows (tracert),
Linux/macOS (traceroute)
· Purpose: Traces the route that a packet takes to reach a destination.
· Common Uses:
o Diagnose where network delays or failures occur.
· Example:
o tracert
www.facebook.com
Displays all routers/hops between your computer and Facebook.
4. NSLOOKUP (Name Server Lookup)
· Used in: Windows, Linux, macOS
· Purpose: Queries DNS servers to obtain domain name or IP address mapping.
· Common Uses:
o Check DNS resolution issues.
o Find IP address of a domain.
· Example:
o nslookup
www.microsoft.com
Returns the IP address of Microsoft’s server.
4.8. Network Cabling and Cable Testing
Network Cabling
Network cables are physical media used to connect and transfer data between computers, switches, routers, and other devices in a network.
Types of Network Cables
1. Twisted Pair Cable (Ethernet Cable)
o Most commonly used in LAN.
o Types:
§ UTP (Unshielded Twisted Pair)
§ STP (Shielded Twisted Pair)
o Categories: Cat5, Cat5e, Cat6, Cat6a, Cat7.
o Connector: RJ45
2. Coaxial Cable
o Single copper conductor at the center.
o Used in cable internet and CCTV.
o Connector: BNC
3. Fiber Optic Cable
o Uses light instead of electricity.
o High-speed and long-distance transmission.
o Types:
§ Single-mode (long distance)
§ Multi-mode (short distance)
o Connector: SC, LC, ST
Cable Testing
Cable testing ensures that the network cable is working properly and is free of faults.
Common Cable Tests
1. Continuity Test
o Checks if each wire inside the cable is connected end-to-end.
o Tool: Cable Tester or Continuity Tester
2. Wire Map Test
o Verifies correct pinout arrangement (straight-through or crossover).
3. Length Test
o Measures cable length to detect breaks.
4. Signal Loss (Attenuation)
o Checks if the signal weakens over distance.
5. Crosstalk
o Ensures there is no signal interference between wires.
6. Certification Test
o High-end testing to meet industry standards (mainly for enterprise environments).
Tools Used in Cable Testing
· Cable Tester: Basic tool to test continuity and pinout.
· Tone Generator & Probe: Locates cables in a bunch.
· TDR (Time Domain Reflectometer): Advanced tool to locate exact break or fault.
· Certification Tester: Used by professionals for formal cable validation.
4.9. IP Addressing and Related Concepts
1. IP Addressing
An IP address is a unique identifier assigned to each device connected to a network.
·
IPv4 Example: 192.168.1.10
·
IPv6 Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334
It consists of two parts:
· Network portion – identifies the network.
· Host portion – identifies the specific device on the network.
2. Subnet Mask
A Subnet Mask determines which portion of the IP address is the network and which is the host.
·
Example:
255.255.255.0
It means the first 3 parts are the network, and the last part is for the host.
3. Default Gateway
The Default Gateway is the IP address of a router that connects your device to other networks, including the internet.
·
Example:
If your PC’s IP is 192.168.1.10, the gateway might be 192.168.1.1.
4. DNS (Domain Name System)
DNS converts human-readable domain names
(like www.google.com) into IP addresses (like 142.250.77.206).
· Without DNS, you'd need to remember IPs to visit websites.
5. WINS (Windows Internet Name Service)
WINS resolves NetBIOS names to IP addresses, mainly used in older Windows-based networks.
·
Example:
Instead of using an IP, a computer named SALES-PC is resolved by WINS.
6. Static vs Automatic IP Address Assignment
Static IP Address
· Manually assigned by the user or network admin.
· Doesn't change.
· Useful for printers, servers, routers.
Example:
IP Address: 192.168.1.100Subnet Mask: 255.255.255.0Gateway: 192.168.1.1DNS: 8.8.8.8Automatic IP Address (DHCP)
· Given by DHCP server.
· Changes from time to time.
· Used for general devices like laptops and mobile phones.
Example:
Your computer requests IP → DHCP assigns IP like 192.168.1.105 automatically.
4.10 Data Encryption Standards
Data encryption is the process of converting plain data into a coded form to prevent unauthorized access. It ensures confidentiality and security of data during storage or transmission.
Data Encryption Standards
1. DES (Data Encryption Standard)
o Developed in the 1970s by IBM.
o Uses a 56-bit key for encryption.
o Symmetric key algorithm (same key for encryption and decryption).
o Now considered insecure due to short key length and vulnerability to brute-force attacks.
2. 3DES (Triple DES)
o Enhancement of DES.
o Applies DES encryption three times with three different keys.
o Provides better security than DES but slower.
o Still used in some legacy systems.
3. AES (Advanced Encryption Standard)
o Developed by the U.S. National Institute of Standards and Technology (NIST).
o Uses key sizes of 128, 192, or 256 bits.
o Symmetric key encryption.
o Highly secure and widely used in modern systems (e.g., Wi-Fi, VPNs).
4. RSA (Rivest-Shamir-Adleman)
o Asymmetric encryption (uses public and private keys).
o Used mainly for secure key exchange rather than bulk data encryption.
o Based on the difficulty of factoring large prime numbers.
o Common in SSL/TLS for secure web browsing.
5. Blowfish
o Symmetric key algorithm.
o Variable key length (32 to 448 bits).
o Designed as a fast alternative to DES.
o Used in some encryption software.
6. Twofish
o Successor to Blowfish.
o Uses 128-bit block size and key sizes up to 256 bits.
o Designed for high security and efficiency.
Symmetric vs Asymmetric Encryption
· Symmetric Encryption: Same key for encrypting and decrypting (e.g., AES, DES).
· Asymmetric Encryption: Uses a pair of keys – public key to encrypt, private key to decrypt (e.g., RSA).
4.11 Multiplexing and Multiple Access Techniques, Switching Techniques and Systems
1. Multiplexing
· Definition: Technique that combines multiple signals into one medium/channel to optimize resource use.
· It enables simultaneous transmission of multiple data streams over a single physical link.
Types of Multiplexing:
· Frequency Division Multiplexing (FDM):
o Divides the total bandwidth into frequency bands.
o Each signal uses a unique frequency band.
o Used in radio and TV broadcasting.
· Time Division Multiplexing (TDM):
o Divides time into slots.
o Each signal transmits in its assigned time slot.
o Common in digital telephony.
· Wavelength Division Multiplexing (WDM):
o Used in fiber optics.
o Different signals are sent at different light wavelengths.
2. Multiple Access Techniques
· Allow multiple users or devices to share the same communication channel without interference.
Common Techniques:
· TDMA (Time Division Multiple Access):
o Divides time into slots and assigns slots to different users.
o Used in 2G cellular networks.
· FDMA (Frequency Division Multiple Access):
o Assigns different frequency bands to users.
o Used in traditional radio systems.
· CDMA (Code Division Multiple Access):
o Uses unique codes to separate users.
o Used in 3G cellular networks.
· OFDMA (Orthogonal Frequency Division Multiple Access):
o Splits the frequency into sub-carriers assigned dynamically.
o Used in 4G and 5G networks.
3. Switching Techniques
Switching determines how data is transmitted from source to destination in a network.
Types:
· Circuit Switching:
o Establishes a dedicated communication path for the duration of the session.
o Used in traditional telephone networks.
o Pros: Constant transmission rate.
o Cons: Inefficient if the channel is idle.
· Packet Switching:
o Data is broken into packets; each packet may take a different path.
o Used in the Internet.
o Pros: Efficient use of resources, robust.
o Cons: Variable delays, possible packet loss.
· Message Switching:
o Entire message is sent to the switching system, stored temporarily, then forwarded.
o Less common today.
4. Switching Systems
· Devices or systems that perform switching:
o Telephone switches (circuit switching).
o Routers and packet switches (packet switching).
o Store-and-forward systems (message switching).