Network Fundamentals: Protocols, Addressing, and Security Concepts

Posted on Sep 30, 2025 in Contemporary Music Composition

1. Core Network Protocols: WWW and HTTP

Protocol Definition

A protocol is a set of rules and conventions that govern the communication between devices in a network.

It ensures data is sent, received, and understood properly between computers or network devices.

World Wide Web (WWW)

The WWW is a system of interlinked hypertext documents and resources accessed via the internet using a web browser. It uses the HTTP protocol to transfer web pages from the server to the client. Components of the WWW include: Web browsers, web servers, and web pages.

Hypertext Transfer Protocol (HTTP)

HTTP is the application layer protocol used for transferring web pages. It uses client-server architecture: the client sends a request, and the server sends back a response. It is a stateless protocol, meaning each request is processed independently.

2. Transmission Impairment and Causes

What is Transmission Impairment?

Impairment refers to the degradation of signal quality during data transmission over a medium.

It causes loss, distortion, or corruption of the transmitted signal.

Causes of Impairments

1. Attenuation:

   Signal loses strength over distance.

   • It requires amplifiers or repeaters to maintain signal quality.

2. Noise:

   • Unwanted electrical signals that interfere with the original signal.
   • Examples: Thermal noise, crosstalk, impulse noise.

3. Distortion:

   • Occurs when the shape of the signal changes due to different propagation speeds for each signal component.

4. Latency and Jitter:

   • Delay in transmission or variation in delay affects real-time communication (like video calls).

3. IP Addressing and IPv4 Classes

IP Address Definition

• An IP address is a 32-bit numeric address used to identify a device on a network.
• It is written in dotted-decimal format, e.g., 192.168.1.1.

IPv4 Address Classes

4. Subnetting Definition and Calculation Example

What is Subnetting?

• Subnetting is the process of dividing a large network into smaller sub-networks (subnets).
• It helps in efficient IP address utilization and improved security/performance.

Subnet Calculation Example

Given:

• IP: 192.168.10.0 (Class C)
• Subnet mask: 255.255.255.240 → CIDR: /28

Calculation:

1. Number of subnet bits = 28 – 24 = 4 bits
2. Number of subnets = 2⁴ = 16 subnets
3. Number of host bits = 32 – 28 = 4 bits
4. Number of hosts per subnet = 2⁴ – 2 = 14 hosts

5. The TCP/IP Reference Model

Model Structure

The TCP/IP model is a 4-layer model used to understand and design network systems.

Features of TCP/IP

• Based on standard protocols used in the Internet.
• Supports inter-networking, routing, and addressing.
• More practical than OSI; forms the foundation of the Internet.

6. Necessity of Layered Network Architecture

Layered architecture is essential in computer networks due to the following reasons:

• Simplifies Network Design: Each layer handles a specific function, making complex design manageable.
• Modularity: Developers can modify or replace one layer without affecting others.
• Interoperability: Standardized layers ensure different systems and vendors can communicate seamlessly.
• Simplified Debugging and Testing: Issues can be traced to specific layers, making troubleshooting easier.
• Ease of Development and Maintenance: Clear separation of concerns allows parallel development and easier upgrades.

Example: The OSI model has 7 layers, each performing distinct functions (e.g., transport, data link, application).

7. Switching Methods and Types

Definition of Switching

Switching is a method used in networks to forward data from the source to the destination efficiently. It selects the best path for data transmission through intermediate nodes.

Types of Switching

Circuit Switching:

• A dedicated communication path is established between sender and receiver before transmission starts.
• Example: Traditional telephone networks.
• No other data can use the path until the session ends.

Packet Switching:

• Data is broken into small packets, each transmitted independently over the network.
• Uses shared network resources, improving efficiency.
• Example: The Internet.

Message Switching:

• The entire message is sent to a switching node, stored temporarily, and then forwarded to the next node.
• Works like postal mail.
• Introduces delay but doesn’t require a dedicated path.

8. ALOHA Protocol and Performance Analysis

What is ALOHA?

ALOHA is a random access protocol designed for wireless communication in networks like satellite and LANs.

Types of ALOHA

Pure ALOHA:

• Stations transmit whenever they have data.
• If a collision occurs, they wait a random time and retransmit.
• Efficiency: Maximum 18.4% (throughput = G × e^(-2G)).

Slotted ALOHA:

• Time is divided into equal slots, and transmission can begin only at the start of a slot.
• Reduces chances of collision.
• Efficiency: Maximum 36.8% (throughput = G × e^(-G)).

Conclusion: Slotted ALOHA improves performance by synchronizing transmissions and reducing collisions.

9. High-Level Data Link Control (HDLC)

HDLC Definition

• HDLC is a bit-oriented protocol developed by ISO for point-to-point and multipoint communication.
• It provides error detection, flow control, and supports both half and full duplex communication.

HDLC Frame Types

1. Information Frame (I-Frame):

   • Carries user data and control information.
   • Used for bidirectional data transmission.

2. Supervisory Frame (S-Frame):

   • Provides control information like acknowledgment and flow control.
   • Used to pause/resume transmissions or request retransmissions.

3. Unnumbered Frame (U-Frame):

   • Used for control purposes such as establishing and terminating a connection.

HDLC Frame Format Structure

| Flag | Address | Control | Information | FCS | Flag |
|-----|---------|---------|-------------|-----|------|

• Flag: Marks the start/end of the frame (01111110).
• Address: Identifies the destination station.
• Control: Specifies the frame type and control functions.
• FCS (Frame Check Sequence): Used for error detection.
• Information: Optional field, used only in I-frames.

10. Point-to-Point Protocol (PPP) and Frame Format

PPP Definition

• PPP is a data link layer protocol used to establish a direct connection between two nodes.
• Commonly used in dial-up internet, DSL, and VPNs.
• Supports authentication, encryption, and compression.

PPP Frame Format

• Flag (1 byte): Marks the beginning and end of the frame (01111110).
• Address (1 byte): Default broadcast address (0xFF).
• Control (1 byte): Usually 0x03, used for control purposes.
• Protocol (2 bytes): Specifies the type of payload (e.g., IP, LCP).
• Payload: Actual data being transmitted.
• FCS (2 or 4 bytes): Frame Check Sequence for error detection.

11. Domain Name System (DNS) Operation

DNS Definition

• DNS is a naming system that translates domain names (e.g., www.google.com) into IP addresses (e.g., 142.250.190.14).
• It allows users to access websites using human-readable names instead of numeric IPs.

How DNS Works

1. User enters a URL in the browser.

2. The browser sends a request to the DNS resolver (often provided by the ISP).

3. If the resolver has the mapping cached, it returns the IP address.

4. If not, the resolver queries the hierarchy:

   • Root DNS server
   • TLD server (e.g., for .com)
   • Authoritative DNS server (holds the actual IP for the domain)

5. The resolver receives the IP and returns it to the browser.

6. The browser uses this IP to contact the web server and load the page.

12. Digital Signatures: Mechanism and Verification

Digital Signature Definition

• A digital signature is a cryptographic technique used to verify the authenticity, integrity, and non-repudiation of digital data.
• It is often described as an electronic fingerprint of the sender.

Working Mechanism

Step 1: Sender Side (Signing)

1. The sender applies a hash function to the message to get a message digest.
2. The digest is encrypted with the sender’s private key, which forms the digital signature.
3. The message plus the digital signature are sent to the receiver.

Step 2: Receiver Side (Verification)

1. The receiver decrypts the signature using the sender’s public key to retrieve the original digest (Digest A).
2. The receiver applies the same hash function on the received message to generate a new digest (Digest B).
3. If Digest A and Digest B match, the message is authentic and untampered.

13. Bit and Byte Stuffing Mechanisms

Bit Stuffing

Bit stuffing is a technique used to ensure that the flag sequence (e.g., 01111110) does not appear accidentally within the data payload.

• It adds an extra ‘0’ after 5 consecutive ‘1’s in the data stream.
• Example: Data 01111110 becomes 011111010 (the stuffed bit is removed by the receiver).

Byte Stuffing

Byte stuffing is used when frames are delimited by specific control characters (bytes).

• It adds a special escape character (ESC) before any control character (like FLAG or ESC itself) that appears in the data payload.
• Example: If FLAG = 0x7E and ESC = 0x1B, then the data byte 0x7E becomes 0x1B7E.

14. User Datagram Protocol (UDP) and Datagram Format

UDP Definition

UDP is a connectionless transport protocol. It is faster than TCP but does not ensure reliability, order, or error checking.

UDP Datagram Format

+-----------------+-----------------+
| Source Port (16) | Destination Port (16) |
+-----------------+-----------------+
| Length (16)     | Checksum (16)   |
+-----------------+-----------------+
| Data (Payload)                    |
+-----------------------------------+

UDP Operations

• Used in real-time applications like video streaming, DNS lookup, and VoIP.
• No connection setup (handshake) is needed.
• The receiver processes packets as they arrive, regardless of order.

15. Key Networking and Security Concepts (Short Notes)

a) RSA (Rivest–Shamir–Adleman)

RSA is a public key cryptographic algorithm used to secure data transmission over the internet. It is based on the mathematical difficulty of factoring large prime numbers. In RSA, two keys are used: a Public key (for encryption) and a Private key (for decryption). It is commonly used in SSL/TLS protocols, digital signatures, and secure email communication.

b) CRC (Cyclic Redundancy Check)

CRC is an error-detecting technique used in digital networks and storage devices. It uses polynomial division to generate a checksum based on the data bits. At the receiver side, the same CRC calculation is performed to check for data integrity. It is widely used in Ethernet, USB, and storage systems.

c) Firewall

A firewall is a network security device or software that filters incoming and outgoing traffic based on predefined security rules. It acts as a barrier between trusted internal networks and untrusted external networks (like the Internet). Firewalls can be hardware-based, software-based, or both, helping prevent unauthorized access, malware, and network attacks.

d) FDDI (Fiber Distributed Data Interface)

FDDI is a high-speed network protocol using fiber-optic cables arranged in a dual-ring topology. It provides data transfer rates of up to 100 Mbps and is used for LANs and MANs. It offers fault tolerance through a secondary ring that takes over if the primary ring fails. It operates on the token-passing method, ensuring fair access to the network.

e) IPSEC (Internet Protocol Security)

IPSEC is a suite of protocols that ensures secure communication over IP networks. It provides confidentiality, integrity, and authentication at the IP layer. It consists of two main protocols: AH (Authentication Header) – ensures data integrity and origin authentication; and ESP (Encapsulating Security Payload) – provides encryption and optional authentication. It is primarily used in VPNs and secure data transmission over public networks.