Networking Fundamentals for Beginners: An Introduction

it courses

Welcome to our comprehensive tutorial on networking fundamentals, where you'll gain an in-depth understanding of computer networks, their types, and the importance of mastering networking fundamentals. Our goal is to equip you with the knowledge and skills to build and maintain efficient networks that can meet the demands of the modern world.

Whether you're a beginner, a seasoned IT professional, or simply someone interested in learning about computer networks, this tutorial is designed for you. We'll cover essential concepts and theories, and you'll learn how to apply them in real-world scenarios. We guarantee that by the end of this tutorial, you'll have a solid foundation in networking fundamentals.

Table of Contents:

  1. Introduction to Computer Networks
  2. Types of Networks
  3. Network Topologies and Design
  4. Networking Devices and Components
  5. Network Protocols and Standards
  6. Network Security and Best Practices

In this tutorial, we'll discuss the importance of networking fundamentals and how they serve as the backbone of our interconnected world. We'll delve into the various types of networks, such as LANs, WANs, and MANs, and their applications. You'll gain an understanding of network topologies, including bus, star, ring, and mesh, along with their respective advantages and disadvantages.

Next, we'll introduce you to the key networking devices and components, such as routers, switches, hubs, and network interface cards (NICs), which play a crucial role in connecting devices and facilitating communication. We'll also explore the world of network protocols and standards, including TCP/IP, Ethernet, and Wi-Fi, which govern how data is transmitted and received over networks.

Finally, we'll emphasize the importance of network security and provide you with best practices for protecting your networks from potential threats, such as malware, hackers, and unauthorized access.

Embark on this exciting journey with us as we explore the fascinating world of computer networks and networking fundamentals. Together, we'll unlock the secrets behind efficient, secure, and robust networks. Happy learning!

Introduction to Computer Networks

Welcome to the first section of our Networking Fundamentals tutorial, where we'll provide you with an engaging introduction to computer networks. This tutorial is designed for both beginners and advanced learners, and we'll cover everything you need to know about the fundamentals of computer networks.

What is a Computer Network?

A computer network is a system of interconnected devices that communicate with one another to share data, resources, and services. Networks can range in size from small home setups to massive global infrastructures. The primary goal of a computer network is to facilitate efficient communication and data exchange between devices.

Why Learn About Computer Networks?

The importance of learning about computer networks cannot be overstated. In today's interconnected world, computer networks have become an essential part of our daily lives. They enable us to access information, communicate with others, and use various online services. As such, having a solid understanding of networking fundamentals is crucial, whether you're a beginner or an advanced learner.

By learning about computer networks, you'll be able to:

  • Understand how data is transmitted between devices
  • Troubleshoot and resolve common network issues
  • Design and implement efficient network systems
  • Keep networks secure from potential threats

Key Concepts in Computer Networks

Throughout this tutorial, we'll explore several key concepts that are vital to understanding computer networks. These include:

  1. Data Transmission: The process of sending and receiving data between devices over a network.
  2. Network Architecture: The design and structure of a network, including its devices, connections, and protocols.
  3. Addressing: The method used to assign unique identifiers to devices on a network, enabling them to communicate with one another.
  4. Routing: The process of selecting the best path for data to travel between devices on a network.
  5. Switching: The technique used to direct data between devices on a network, ensuring that it reaches its intended destination.

The Journey Begins

Congratulations! You've now completed the first section of our Networking Fundamentals tutorial. With this introduction to computer networks under your belt, you're well on your way to mastering the world of networking.

As you continue through this tutorial, you'll learn about various types of networks, network topologies, devices, protocols, and much more. Whether you're a beginner looking to start your journey in networking or an advanced learner seeking to expand your knowledge, this tutorial is designed to help you reach your goals. So let's continue our learning journey and delve into the fascinating world of computer networks!

Types of Networks

Welcome to the second section of our Networking Fundamentals tutorial! In this section, we'll explore the different types of computer networks that exist and their various applications. This tutorial is designed to cater to both beginners and advanced learners, ensuring that everyone gains a comprehensive understanding of the types of networks.

Understanding Network Types

A computer network can be classified based on several factors, such as its geographical coverage, purpose, and the way devices are interconnected. By learning about the various types of networks, you'll be better equipped to design, implement, and troubleshoot networks based on your specific needs.

1. Local Area Network (LAN)

A Local Area Network, or LAN, is a network that spans a relatively small geographical area, typically within a single building or a group of buildings. LANs are commonly used in homes, offices, and educational institutions to connect devices such as computers, printers, and other peripherals.

Key Features of LANs:

  • Limited geographical coverage
  • High data transfer rates
  • Usually owned and controlled by a single organization

2. Wide Area Network (WAN)

A Wide Area Network, or WAN, is a network that covers a large geographical area, often connecting multiple LANs. WANs are typically used by businesses, governments, and other large organizations to connect devices and exchange data over long distances.

Key Features of WANs:

  • Large geographical coverage
  • Slower data transfer rates compared to LANs
  • Often owned and managed by multiple organizations or service providers

3. Metropolitan Area Network (MAN)

A Metropolitan Area Network, or MAN, is a network that covers a city or a large urban area. MANs are typically used by local governments, ISPs, and large organizations to provide connectivity and services within a specific geographical region.

Key Features of MANs:

  • Covers an entire city or large urban area
  • Moderate data transfer rates
  • Usually owned and managed by a single organization or consortium

4. Personal Area Network (PAN)

A Personal Area Network, or PAN, is a network that connects devices within a close proximity, typically within a range of 10 meters. PANs are commonly used to connect personal devices, such as smartphones, tablets, and wearable devices, to facilitate data transfer and communication.

Key Features of PANs:

  • Very limited geographical coverage
  • Connects personal devices
  • Can be wired or wireless (e.g., Bluetooth, Wi-Fi Direct)

5. Virtual Private Network (VPN)

A Virtual Private Network, or VPN, is a network that uses encryption and secure connections to create a private communication channel over a public network, such as the internet. VPNs are often used by organizations to securely connect remote offices or allow employees to access the company network from remote locations.

Key Features of VPNs:

  • Provides secure communication over public networks
  • Can connect devices or networks at various geographical locations
  • Uses encryption and authentication to protect data

Moving Forward

Now that you have a solid understanding of the different types of networks, you're ready to move on to the next section of our Networking Fundamentals tutorial. In the following sections, we'll delve into network topologies, networking devices and components, protocols, and more. Our goal is to provide you with the knowledge and skills needed to succeed in the world of networking, whether you're a beginner or an advanced learner. Happy learning!

Network Topologies and Design

Welcome to the third section of our Networking Fundamentals tutorial! In this section, we'll discuss network topologies and design principles that are essential for creating efficient and reliable computer networks. Whether you're a beginner or an advanced learner, this tutorial aims to provide you with a comprehensive understanding of network topologies and their applications.

Understanding Network Topologies

A network topology refers to the arrangement of devices and their connections in a computer network. It plays a crucial role in determining the performance, reliability, and scalability of a network. By understanding different network topologies, you can make informed decisions when designing and implementing networks based on your specific requirements.

Common Network Topologies

1. Bus Topology

In a bus topology, all devices are connected to a single central cable, also known as the bus or backbone. Data is transmitted along this cable, and each device listens for its own address to receive data.

Key Features of Bus Topology:

  • Simple and easy to install
  • Low cost
  • Performance degrades as more devices are added
  • Failure of the central cable results in network downtime

2. Star Topology

In a star topology, all devices are connected to a central hub or switch. Data is transmitted from one device to the central hub, which then relays the data to the destination device.

Key Features of Star Topology:

  • Easy to add or remove devices without disrupting the network
  • Failure of one device does not affect the entire network
  • Requires more cable compared to bus topology
  • Central hub or switch can be a single point of failure

3. Ring Topology

In a ring topology, each device is connected to exactly two other devices, forming a continuous loop or ring. Data is transmitted in one direction around the ring until it reaches its destination.

Key Features of Ring Topology:

  • Equal access to network resources for all devices
  • Can be easily expanded
  • Failure of one device can disrupt the entire network
  • Data transmission can be slower compared to other topologies

4. Mesh Topology

In a mesh topology, devices are connected to multiple other devices, providing multiple paths for data transmission. This topology can be either a full mesh, where each device is connected to every other device, or a partial mesh, where devices are connected to a subset of other devices.

Key Features of Mesh Topology:

  • Highly reliable due to multiple paths for data transmission
  • Fast data transfer and reduced latency
  • Expensive and complex to implement
  • Requires a large amount of cabling and management

Network Design Considerations

When designing a computer network, it's essential to consider factors such as performance, reliability, scalability, and cost. By understanding the advantages and disadvantages of each network topology, you can select the most suitable topology for your specific needs.

Additionally, consider using hybrid topologies, which combine two or more topologies, to create a network that meets your unique requirements.

Moving Forward

With a solid understanding of network topologies and design principles, you're now ready to advance to the next section of our Networking Fundamentals tutorial. In the upcoming sections, we'll explore networking devices and components, network protocols and standards, and network security best practices. Our goal is to equip you with the knowledge and skills needed to excel in the world of networking, regardless of your experience level. Keep learning!

Networking Devices and Components

Welcome to the fourth section of our Networking Fundamentals tutorial! In this section, we'll introduce you to the key networking devices and components that play a crucial role in connecting devices and facilitating communication within a network. This tutorial is designed to cater to both beginners and advanced learners, ensuring that everyone gains a comprehensive understanding of networking devices and their functions.

Understanding Networking Devices

Networking devices are specialized hardware components used to connect devices within a network, manage data transmission, and ensure efficient communication. By familiarizing yourself with these devices, you'll be better equipped to design, implement, and troubleshoot computer networks.

Key Networking Devices and Components

1. Network Interface Card (NIC)

A Network Interface Card, or NIC, is a hardware component that connects a device to a network. It converts data from the device into a format suitable for transmission over the network and vice versa.

Key Features of NICs:

  • Available in various forms, such as PCIe cards, USB adapters, and built-in chips
  • Supports different network types, such as Ethernet, Wi-Fi, and Bluetooth
  • Includes a unique MAC address for device identification

2. Hub

A hub is a networking device that connects multiple devices in a star topology. It receives data from one device and broadcasts it to all connected devices.

Key Features of Hubs:

  • Simple and inexpensive
  • Limited to small networks due to performance degradation with increasing devices
  • Lacks intelligence, leading to increased network traffic and collisions

3. Switch

A switch is a networking device that connects multiple devices and directs data between them based on their MAC addresses. Unlike a hub, a switch only sends data to the intended recipient, reducing network traffic and improving performance.

Key Features of Switches:

  • Can be managed or unmanaged
  • Supports VLANs and Quality of Service (QoS) features
  • More efficient and reliable than hubs

4. Router

A router is a networking device that connects multiple networks, such as a LAN and the internet. It directs data between networks based on IP addresses and uses routing protocols to determine the best path for data transmission.

Key Features of Routers:

  • Can be wired or wireless
  • Supports NAT, firewall, and VPN features
  • Manages network traffic and optimizes performance

5. Wireless Access Point (WAP)

A Wireless Access Point, or WAP, is a networking device that connects wireless devices to a wired network. It converts data from wired devices into wireless signals and vice versa, allowing wireless devices to communicate with the network.

Key Features of WAPs:

  • Supports various wireless standards, such as Wi-Fi and Bluetooth
  • Can be standalone devices or integrated into routers
  • Can be used to extend the range of a wireless network

Moving Forward

Now that you have a solid understanding of the key networking devices and components, you're ready to move on to the next section of our Networking Fundamentals tutorial. In the following sections, we'll delve into network protocols and standards, network security, and best practices. Our goal is to provide you with the knowledge and skills needed to succeed in the world of networking, whether you're a beginner or an advanced learner. Keep learning!

Network Protocols and Standards

Welcome to the fifth section of our Networking Fundamentals tutorial! In this section, we'll explore the world of network protocols and standards that govern how data is transmitted and received over networks. This tutorial is designed to cater to both beginners and advanced learners, ensuring that everyone gains a comprehensive understanding of network protocols and their significance.

Understanding Network Protocols and Standards

A network protocol is a set of rules and conventions that dictate how devices on a network communicate and exchange data. Network standards are formal specifications that define the technical requirements and characteristics of network protocols, ensuring interoperability between devices.

Key Network Protocols and Standards

1. Transmission Control Protocol/Internet Protocol (TCP/IP)

TCP/IP is a suite of protocols that serves as the foundation of the internet and most modern networks. It comprises several key protocols, such as IP, TCP, UDP, and ICMP, which work together to ensure reliable and efficient data communication between devices.

Key Features of TCP/IP:

  • Hierarchical addressing system using IP addresses
  • Supports both reliable (TCP) and unreliable (UDP) data transmission
  • Widely adopted and compatible with various networking devices

2. Ethernet

Ethernet is a family of networking technologies and standards used in LANs to transmit data over wired connections. It defines the physical and data link layers of the OSI model, specifying how devices connect, transmit, and receive data over the network.

Key Features of Ethernet:

  • Dominant LAN technology with various speeds, such as 10 Mbps, 100 Mbps, 1 Gbps, and 10 Gbps
  • Supports multiple topologies, such as bus, star, and ring
  • Uses MAC addresses to direct data between devices

3. Wi-Fi

Wi-Fi is a set of wireless networking technologies and standards that allow devices to connect and communicate over a WLAN. It is based on the IEEE 802.11 family of standards, which define the characteristics and requirements of wireless communication.

Key Features of Wi-Fi:

  • Supports various wireless standards, such as 802.11a, 802.11b, 802.11g, 802.11n, and 802.11ac
  • Offers wireless data transmission speeds up to several gigabits per second
  • Provides secure communication using encryption and authentication

4. Domain Name System (DNS)

DNS is a hierarchical naming system that translates human-readable domain names, such as www.computer-pdf.com, into IP addresses used by devices to locate and access resources on the internet.

Key Features of DNS:

  • Distributed database with a hierarchical structure
  • Supports various record types, such as A, AAAA, CNAME, and MX
  • Enables easy-to-remember domain names for websites and services

Moving Forward

With a solid understanding of network protocols and standards, you're now ready to advance to the final section of our Networking Fundamentals tutorial. In the next section, we'll discuss network security and best practices to protect your networks from potential threats and ensure their reliability and performance. Our goal is to provide you with the knowledge and skills needed to excel in the world of networking, whether you're a beginner or an advanced learner. Keep learning!

Network Security and Best Practices

Welcome to the final section of our Networking Fundamentals tutorial! In this section, we'll delve into the essential aspects of network security and best practices to help you safeguard your networks against potential threats and ensure their reliability and performance. This tutorial is designed for both beginners and advanced learners, providing comprehensive insights into network security measures.

Understanding Network Security

Network security is the process of protecting a network and its devices from unauthorized access, misuse, or attacks. It encompasses various measures, including policies, technologies, and tools, that aim to secure the network infrastructure, data, and devices.

Key Network Security Measures

1. Firewalls

A firewall is a security device or software that monitors incoming and outgoing network traffic and blocks unauthorized access based on predefined rules. Firewalls can be hardware-based, software-based, or a combination of both.

Key Features of Firewalls:

  • Protects the network perimeter from external threats
  • Supports packet filtering, stateful inspection, and deep packet inspection
  • Can be configured to allow or deny traffic based on IP addresses, ports, and protocols

2. Intrusion Detection and Prevention Systems (IDPS)

An IDPS is a security solution that monitors network traffic, detects potential threats or malicious activities, and takes action to prevent or mitigate them. It uses signature-based, anomaly-based, or behavior-based detection methods to identify potential threats.

Key Features of IDPS:

  • Detects and prevents network intrusions in real-time
  • Can be deployed as a standalone device or integrated into other network devices
  • Provides alerts and reports for security analysis

3. Virtual Private Networks (VPNs)

A VPN is a secure, encrypted connection between devices or networks over a public network, such as the internet. It provides confidentiality, integrity, and authentication to protect data in transit and ensure secure communication.

Key Features of VPNs:

  • Encrypts data to prevent eavesdropping and tampering
  • Supports various VPN protocols, such as PPTP, L2TP, and OpenVPN
  • Can be used to securely connect remote offices or users to a company network

4. Antivirus and Antimalware Software

Antivirus and antimalware software are security solutions that detect, prevent, and remove malware, such as viruses, worms, and Trojans, from devices and networks. They use signature-based and heuristic-based detection methods to identify and eliminate malware.

Key Features of Antivirus and Antimalware Software:

  • Provides real-time and on-demand scanning of files and devices
  • Includes regular updates to detect new malware variants
  • Can be deployed on individual devices or at the network level

Network Security Best Practices

  1. Implement a strong password policy that includes minimum length, complexity, and expiration requirements.
  2. Keep your network devices, operating systems, and software up-to-date with the latest security patches.
  3. Regularly monitor and review network logs for suspicious activities or potential threats.
  4. Implement a least-privilege access policy to restrict user and device permissions to the minimum necessary.
  5. Train employees on cybersecurity awareness and best practices to prevent social engineering attacks, such as phishing.

Conclusion

Congratulations on completing our Networking Fundamentals tutorial! You should now have a solid foundation in computer networks, their types, topologies, devices, protocols, and security measures. As you continue your journey in the world of networking, remember to stay up-to-date with the latest advancements and best practices to ensure the security, reliability, and performance of your networks. Keep learning and growing in your networking expertise!

Networking Fundamentals for Beginners: An Introduction PDF eBooks

Networking Fundamentals

The Networking Fundamentals is a beginner level PDF e-book tutorial or course with 56 pages. It was added on December 31, 2012 and has been downloaded 12538 times. The file size is 1.44 MB. It was created by BICSI.


Networking : Principles, Protocols and Practice

The Networking : Principles, Protocols and Practice is an advanced level PDF e-book tutorial or course with 272 pages. It was added on January 12, 2021 and has been downloaded 20348 times. The file size is 4.85 MB. It was created by Olivier Bonaventure.


Configuration Basic Networking

The Configuration Basic Networking is a beginner level PDF e-book tutorial or course with 44 pages. It was added on January 1, 2013 and has been downloaded 14270 times. The file size is 654.35 KB. It was created by unknown.


Linux Networking

The Linux Networking is an intermediate level PDF e-book tutorial or course with 294 pages. It was added on February 20, 2016 and has been downloaded 7351 times. The file size is 2.28 MB. It was created by Paul Cobbaut.


Basics of Computer Networking

The Basics of Computer Networking is a beginner level PDF e-book tutorial or course with 140 pages. It was added on September 19, 2017 and has been downloaded 10869 times. The file size is 606.8 KB. It was created by Thomas G. Robertazzi.


Computer Network

The Computer Network is a beginner level PDF e-book tutorial or course with 36 pages. It was added on December 12, 2013 and has been downloaded 15274 times. The file size is 805.5 KB. It was created by Mrs.Vasanthi Muniasamy, M.Phil Rank.


Introduction to Networking: How the Internet Works

The Introduction to Networking: How the Internet Works is a beginner level PDF e-book tutorial or course with 119 pages. It was added on November 9, 2021 and has been downloaded 5109 times. The file size is 1.95 MB. It was created by Charles Severance.


Microsoft Windows 7 Advanced

The Microsoft Windows 7 Advanced is an advanced level PDF e-book tutorial or course with 237 pages. It was added on December 6, 2013 and has been downloaded 15132 times. The file size is 5.55 MB. It was created by unknown.


Android Developer Fundamentals Course

The Android Developer Fundamentals Course is a beginner level PDF e-book tutorial or course with 566 pages. It was added on November 12, 2021 and has been downloaded 2138 times. The file size is 6.66 MB. It was created by Google Developer Training Team.


IP Addressing a simplified tutorial

The IP Addressing a simplified tutorial is a beginner level PDF e-book tutorial or course with 69 pages. It was added on January 1, 2013 and has been downloaded 7722 times. The file size is 377.15 KB. It was created by Avaya Labs.


Basic Networking Tutorial

The Basic Networking Tutorial is a beginner level PDF e-book tutorial or course with 21 pages. It was added on January 1, 2013 and has been downloaded 42869 times. The file size is 265.77 KB. It was created by Sangay Yeshi.


Procreate: The Fundamentals

The Procreate: The Fundamentals is a beginner level PDF e-book tutorial or course with 38 pages. It was added on April 4, 2023 and has been downloaded 300 times. The file size is 2.45 MB. It was created by Procreate.


Fundamentals of Cryptology

The Fundamentals of Cryptology is an intermediate level PDF e-book tutorial or course with 503 pages. It was added on December 9, 2021 and has been downloaded 1897 times. The file size is 2.35 MB. It was created by Henk C.A. Tilborg.


Mac OS X Help Desk Essentials

The Mac OS X Help Desk Essentials is level PDF e-book tutorial or course with 528 pages. It was added on December 7, 2013 and has been downloaded 1467 times. The file size is 6.39 MB.


jQuery Fundamentals

The jQuery Fundamentals is a beginner level PDF e-book tutorial or course with 108 pages. It was added on October 18, 2017 and has been downloaded 2849 times. The file size is 563.78 KB. It was created by Rebecca Murphey.


Interconnecting Cisco Networking Devices (ccna) Part1

The Interconnecting Cisco Networking Devices (ccna) Part1 is a beginner level PDF e-book tutorial or course with 99 pages. It was added on October 13, 2017 and has been downloaded 9546 times. The file size is 868.75 KB. It was created by Firebrand.


Oracle Database 11g: SQL Fundamentals

The Oracle Database 11g: SQL Fundamentals is a beginner level PDF e-book tutorial or course with 499 pages. It was added on December 10, 2013 and has been downloaded 70083 times. The file size is 2.12 MB. It was created by Puja Singh - Brian Pottle.


TCP/IP Tutorial and Technical Overview

The TCP/IP Tutorial and Technical Overview is a beginner level PDF e-book tutorial or course with 1004 pages. It was added on May 10, 2023 and has been downloaded 1451 times. The file size is 6.4 MB. It was created by Lydia Parziale.


Fundamentals of Python Programming

The Fundamentals of Python Programming is a beginner level PDF e-book tutorial or course with 669 pages. It was added on January 6, 2019 and has been downloaded 22702 times. The file size is 3.3 MB. It was created by Richard L. Halterman.


Fundamentals and GSM Testing

The Fundamentals and GSM Testing is an advanced level PDF e-book tutorial or course with 54 pages. It was added on December 8, 2016 and has been downloaded 1687 times. The file size is 784.04 KB. It was created by Marc Kahabka.


TCP/IP Networking Basics

The TCP/IP Networking Basics is a beginner level PDF e-book tutorial or course with 24 pages. It was added on January 1, 2013 and has been downloaded 14777 times. The file size is 146.6 KB. It was created by unknown.


Linux Fundamentals

The Linux Fundamentals is a beginner level PDF e-book tutorial or course with 365 pages. It was added on October 17, 2018 and has been downloaded 28181 times. The file size is 2.68 MB. It was created by Paul Cobbaut.


AngularJS Fundamentals in 60 Minutes

The AngularJS Fundamentals in 60 Minutes is a beginner level PDF e-book tutorial or course with 102 pages. It was added on December 16, 2014 and has been downloaded 10709 times. The file size is 3.65 MB. It was created by Dan Wahlin.


Interconnecting Cisco Networking Devices (ccna) Part2

The Interconnecting Cisco Networking Devices (ccna) Part2 is an intermediate level PDF e-book tutorial or course with 99 pages. It was added on October 13, 2017 and has been downloaded 6631 times. The file size is 1.09 MB. It was created by Firebrand.


Computer Fundamentals

The Computer Fundamentals is a beginner level PDF e-book tutorial or course with 86 pages. It was added on August 17, 2017 and has been downloaded 13738 times. The file size is 772.52 KB. It was created by Dr Steven Hand.


The Promise and Peril of Big Data

The The Promise and Peril of Big Data is an advanced level PDF e-book tutorial or course with 61 pages. It was added on December 2, 2021 and has been downloaded 177 times. The file size is 333.48 KB. It was created by David Bollier.


Fundamentals of C++ Programming

The Fundamentals of C++ Programming is a beginner level PDF e-book tutorial or course with 766 pages. It was added on February 5, 2019 and has been downloaded 35389 times. The file size is 3.73 MB. It was created by Richard L. Halterman School of Computing Southern Adventist University.


Excel Fundamentals

The Excel Fundamentals is a beginner level PDF e-book tutorial or course with 60 pages. It was added on March 30, 2020 and has been downloaded 60185 times. The file size is 7.03 MB. It was created by St. George’s Information Services.


Fundamentals of Computer Programming with C#

The Fundamentals of Computer Programming with C# is a beginner level PDF e-book tutorial or course with 1122 pages. It was added on December 27, 2016 and has been downloaded 9417 times. The file size is 8.57 MB. It was created by Svetlin Nakov & Co.


Introduction to Linux

The Introduction to Linux is level PDF e-book tutorial or course with 223 pages. It was added on December 6, 2013 and has been downloaded 6648 times. The file size is 1.05 MB.


it courses