Notes, summaries, assignments, exams, and problems for Computers

1. TCP Congestion Control

Slow Start: TCP initializes congestion window (cwnd) to a small size and doubles it every Round Trip Time (RTT) until a loss occurs (exponential growth) or the slow start threshold is reached.

Congestion Avoidance: After reaching the threshold, cwnd is incremented by one segment for each RTT, growing linearly to avoid congestion.

Fast Recovery: When triple duplicate ACKs are detected, TCP halves the cwnd and reduces the slow start threshold to half of the cwnd size before the loss, then transitions to congestion avoidance.

2. TCP RTT and Timeout

Estimating RTT: Uses Smoothed Round Trip Time (SRTT) which is a weighted average of previous RTT measurements.

Timeout Calculation: Often calculated as Timeout=SRTT+4×RTT

Understanding Linux File Management Subsystem

The Linux File Management Subsystem, an integral part of the Linux kernel and user space, meticulously handles all aspects related to files. This includes their creation, storage, retrieval, permissions, and overall structure. Its primary role is to ensure that data is stored efficiently and securely on disk, remaining readily accessible whenever needed.

Core Components of Linux File Management

File System Interface

• Provides system calls such as open(), read(), write(), and close(), which user programs utilize to interact with files.
• Abstracts the underlying complexity of physical storage devices.

Virtual File System (VFS)

• Acts as a crucial abstraction layer, offering a common interface to various file

Advantages of the System Approach

• Holistic View: Provides a comprehensive perspective of the organization, facilitating better decision-making.
• Coordination: Improves efficiency by integrating all departments and functions.

Types of Knowledge

• Explicit Knowledge: Knowledge that is documented and easily shared (e.g., manuals, reports).
• Tacit Knowledge: Personal experience-based knowledge that is difficult to express in words (e.g., skills, intuition).

Internet Protocols

• HTTP (Hypertext Transfer Protocol): Used for transferring web pages over the internet.
• FTP (File Transfer Protocol): Used for transferring files between computers on a network.

Origins of Fuzzy Logic

Fuzzy logic was proposed in 1965 by Lotfi A. Zadeh.

Functions of the CPU

• Arithmetic and Logic

Network Switches

Managed vs. Unmanaged Switches

Managed Switch: Configurable via software, supports security and communication settings. Used in large networks (enterprise, universities).

Unmanaged Switch: Fixed configuration, hardware-only, cannot be configured.

Ethernet & Speed

1. Fast Ethernet: 100 Mbps.
2. Gigabit Ethernet: 1 Gbps.

Ethernet Protocol

Divides data into frames, encapsulates IP addresses, performs error detection.

Ports

3. Console Port: Connects PC/laptop to configure switch.

Communication Modes

• Simplex (Half Duplex): One-way communication at a time.
• Duplex (Full Duplex): Two-way communication simultaneously.

Bandwidth

5. Maximum transmission speed of a network, determined by signal frequency range.

IP Addressing & Subnets

6. IP Address: Identifies

Circle Generating Algorithms

Circle generating algorithms are fundamental in computer graphics for rendering circles efficiently on raster displays. These algorithms calculate the points on the circumference of a circle and plot them. The most commonly used circle generating algorithms are the Midpoint Circle Algorithm and Bresenham's Circle Algorithm.

Midpoint Circle Algorithm Steps

The following steps outline the basic process for generating points in one octant, which are then mirrored to complete the circle:

1. Step 1: Initialization. Set starting coordinates $x = 0$ and $y = r$ (radius). Calculate the initial decision parameter $p = 1 - r$.
2. Step 2: Iteration. Repeat the following steps while $x \le y$:
   • Plot the current point $(x, y)$ and its octant

Kerberos: Secure Network Authentication Protocol

Kerberos is a network authentication protocol that allows systems and users to prove their identity to each other before accessing resources, ensuring secure communication within a network. It is a trusted third-party system that verifies user identities without sending passwords directly across the network.

Key Components and Characteristics of Kerberos

Authentication Protocol Definition

Kerberos is a protocol, meaning it is a set of rules and procedures that govern how devices and users authenticate with each other.

Trusted Third Party (KDC)

Kerberos relies on a trusted third party, known as the Key Distribution Center (KDC), to manage authentication.

Single Sign-On (SSO) Implementation

Kerberos is... Continue reading "Kerberos Protocol Authentication and Network Transmission Media Types" »

Internet Fundamentals: A Network of Networks

The Internet is often described as a "network of networks," comprising interconnected Internet Service Providers (ISPs).

Key Components of the Internet

• Hosts: End Systems for Applications

  Hosts are the end systems (clients & servers) that run applications. They connect at the edge of the Internet.

• Packet Switches: Forwarding Data

  Packet switches forward data in chunks called packets. These include:

  • Routers: Forward data between different networks.
  • Switches: Operate within the core of the Internet, not at the edge.

• Communication Links: The Data Pathways

  Communication links connect routers and can be made of:

  • Fiber optic cables
  • Copper wires
  • Radio waves
  • Satellite connections

  The transmission rate of a link is

Core Software Design Principles

• Abstraction: Removal or masking of detail and complexity.
• Modularity: Software is divided into separately named and addressable components.
• Separation of Concerns: Any complex problem can be more easily handled if it is subdivided into pieces.
• Information Hiding / Encapsulation: Hide implementation details from client components; communicate only via controlled interfaces.
• High Cohesion: Components provide specific functionality.
• Low Coupling: Components have as few dependencies as possible so they can change with minimal impact on other components.

SOLID Principles

Single Responsibility Principle

The idea here is simple: Separate the code that supports different actors (i.e., users, stakeholders, or client components)... Continue reading "Mastering Software Design Principles and SOLID Patterns" »

Keyword Research and Analysis

SEO keywords are the important words and phrases related to the developed website content. A list of keywords needs to be carefully chosen to optimize the search. Keyword Research and Analysis is an important part of Search Engine Optimization (SEO) as well as Search Engine Marketing. For Search Engine Marketing, one can pay for certain keywords. There are various online Keyword Planner tools (such as Google Ads Keyword Planner) to shortlist keywords. This is more useful to compare the cost of various keywords if the website designer opts for Paid Search Engine Marketing.

Features of PHP Scripting Language

PHP is the most popular and frequently used worldwide server-side scripting language. Following are features... Continue reading "Effective SEO Strategies and PHP Web Development Essentials" »