Part-1 What is Networking?

Networking refers to the practice of connecting computers, devices, or systems together to enable communication and data exchange between them. It involves the use of hardware, software, and protocols to establish these connections and facilitate the flow of information.

In the context of computer networking, the primary purpose is to allow computers and other devices to share resources, such as files, printers, and internet connections. Networking enables users to access information, services, and applications that may reside on remote systems, making it an essential component of modern communication and information sharing.

Type of Networks (LAN, WAN, MAN, WLAN, CAN, PAN, SAN, VPN, Internet and Extranet.)

A network refers a collection of interconnected devices or nodes that can communicate with each other and share resources. Networks can be physical, where devices are connected with cables, or wireless, where devices communicate over radio waves.

The primary purpose of a network is to enable data transmission, resource sharing, and communication between devices. networks can vary in size and complexity, from small local area networks (LANs) within homes or offices to wide area networks (WANs) that span across cities, countries, or even the globe.

1. Local Area Network (LAN):

• A LAN is a network that covers a relatively small geographical area, such as a home, office, or a single building.
• It connects computers, printers, and other devices within the same physical location, allowing them to share resources like files and printers.
• LANs typically have high transfer rates and low latency.

2. Wide Area Network (WAN):

• A WAN is a network that spans a large geographical area, often connecting multiple LANs across cities, states, or countries.
• It uses public or private telecommunication networks, like leased lines or the Internet, to connect remote locations.
• WANs enable data and resource sharing between distant sites.

3. Metropolitan Area Network (MAN):

• A MAN is a network that covers a larger geographical area than a LAN but is smaller than a WAN, typically encompassing a city or a metropolitan area.
• It interconnects multiple LANs and may use technologies like fiber optics or wireless connections.

4. Wireless Local Area Network (WLAN):

• A WLAN is a type of LAN that uses wireless communication to connect devices within a limited area, such as a home, office, or public hotspot.
• WLANs typically utilize Wi-Fi technology to enable wireless connectivity.

5. Campus Area Network (CAN):

• A CAN is a network that spans a limited geographical area, such as a university campus, industrial complex, or military base.
• It connects multiple buildings and LANs within the campus, facilitating seamless communication and resource sharing.

6. Personal Area Network (PAN):

• A PAN is the smallest type of network, designed for personal use or connection between devices in close proximity to an individual.
• Bluetooth and infrared are common technologies used in PANs.

7. Storage Area Network (SAN):

• A SAN is a specialized network that provides high-speed access to storage resource, such as disk arrays and tape libraries, and multiple servers.
• It allows for efficient centralized data storage and management.

8. Virtual Private Network (VPN):

• A VPN is a secure network connection established over a public network, typically the Internet. 
• It enables remote users to access a private network securely as if they were physically present at the network's location.

9. Intranet and Extranet:

• An intranet is a private network within an organization that allows employees to access internal resources like company information, tools, and applications.
• An extranet extends parts of an intranet to external users, such as customers, suppliers, or partners, providing limited access to specific resources.
• These network types serve various purposes and are tailored to meet specific communication needs, depending on the scale of the area to be covered and the required functionalities.

Network Topologies (Bus, Star, Ring, Mesh, Tree, Hybrid)

Network topologies refer to the physical or logical arrangement of devices and communication links in a computer network. Each topology has its advantages and disadvantages in terms of cost, scalability, fault tolerance, and ease of implementation, here are some common network topologies:

1. Bus Topology:

• In a bus topology, all devices are connected to a single communication channel or backbone, resembling a linear bus.
• Each device on the network can transmit data, and all other devices receive and process the data, but only the intended recipient accepts the data.
• The main advantage of a bus topology is its simplicity and cost-effectiveness for small networks.
• However, it can suffer from a single point of failure if the main cable is damaged or disconnected.

2. Star Topology:

• In star topology, each device connects directly to a central hub or switch.
• All communication between devices goes through the central hub, which helps in easier management and fault isolation.
• If a device fails, it doesn't affect the rest of the network, making star topology more reliable than bus topology. 
• The main drawback is that the central hub becomes a single point of failure, and the cost of implementation can be higher due to the requirement of the hub.

3. Ring Topology:

• In a ring topology, each device is connected to exactly two other devices, creating a circular loop.
• Data travels in one direction around the ring until it reaches the intended recipient.
• Ring topologies are relatively simple and work well for small networks.
• However, if a single link or device fails, the entire network can be disrupted since there is no alternate path for data transmission.

4. Mesh Topology:

• In a mesh topology, each device is connected directly to every other device on the network, creating multiple redundant paths for data transmission.
• Mesh networks offer high fault tolerance and robustness, as there are multiple paths for data to travel, reducing the risk of network failure.
• They are particularly useful in critical systems where reliability is crucial.
• However, implementing a full mesh can be expensive and complex, especially as the number of devices grows.

5. Tree Topology:

• A tree topology combines the characteristics of bus and star topologies. It has a central root (main hub) connected to several secondary hubs, and each secondary hub can have its own set of devices connected to it.
• Tree topologies are effective for larger networks and are known for their scalability and fault isolation.
• However, the reliance on a central hub means that its failure can disrupt connectivity to its branches.

6. Hybrid Topology:

• Hybrid topologies are combinations of two or more basic topologies.
• for example, a network might combine elements of a star and ring topology to benefit from their respective advantages.

Each network topology has its pros and cons, and the choice of topology depends on the specific requirements of the network, the number of devices, the distance between them, fault tolerance needs, and budget constraints.

OSI and TCP/IP Models

The OSI (Open Systems Interconnection) model and the TCP/IP (Transmission Control Protocol/Internet Protocol) model are two different conceptual frameworks used to understand and standardize how different networking protocols and communication technologies interact in computer networks. Both models describe the layers of protocols that work together to enable communication between devices on a network. Let's take a brief look at each model:

OSI Model:

1. Application Layer (Layer 7): This layer deals with user interfaces and application-level interactions. It provides services to end-user software applications and enables network services like email (SMTP), file transfer (FTP), and web browsing (HTTP).
2. Presentation Layer (Layer 6): The presentation layer handles data formatting, encryption, and compression. It ensures that data exchanged between applications can be understood by both sides by translating data into a standard format.
3. Session Layer (Layer 5): The session layer manages sessions or connections between applications. It establishes, maintains, and terminates communication sessions, ensuring reliable data transfer.
4. Transport Layer (Layer 4): The transport layer is responsible for end-to-end communication and data flow control between devices. It handles error detection. retransmission, and flow control. Examples of transport layer protocols include TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).
5. Network Layer (Layer 3): The network layer handle routing and forwarding of data packets between devices across different networks. It deals with logical addressing and packet routing. IP (Internet Protocol) is a primary network layer protocol.
6. Data Link Layer (Layer 2): The data link layer facilitates data transfer between devices on the same network segment. It is responsible for framing, addressing, and error detection. Ethernet is an example of a data link layer protocol.
7. Physical Layer (Layer 1): The physical layer deals with the physical medium through which data is transmitted. It involves electrical signals, cables, switches, and network interface cards.

TCP/IP Model:

The TCP/IP model is a practical implementation of networking protocols used in the internet and most modern computer networks. It consist of four layers, which correspond to some of the layers of the OSI model but are not an exact match:

1. Application Layer: This is equivalent to the combination of the OSI application, presentation, and session layers. It deals with user-facing applications and services.
2. Transport Layer: The transport layer is similar to the OSI transport layer, responsible for end-to-end communication and data flow control. It includes TCP and UDP protocols.
3. Internet Layer: This layer corresponds to the OSI network layer, handling packet routing and logical addressing using IP (Internet Protocol).
4. Link Layer: The link layer encompasses the OSI data link and physical layers, handling data transfer between devices on the same local network segment.

The TCP/IP model is widely used in modern networking, especially in internet communication, while the OSI model is more of a theoretical framework for understanding networking concepts and standardization. Despite their differences, both models aim to ensure seamless communication between devices and networks by defining how different protocols work together at various levels of abstraction.