Network Fundamentals

Key Concepts

• Network Topologies
• OSI Model
• IP Addressing
• Subnetting
• Network Devices

Network Topologies

Network topologies describe the arrangement of different elements (links, nodes, etc.) in a communication network. Common topologies include:

• Bus Topology: All devices are connected to a central cable, known as the bus. This topology is simple but can suffer from a single point of failure.
• Star Topology: All devices are connected to a central hub. If the hub fails, the entire network can be affected, but individual devices can still function if the hub is operational.
• Ring Topology: Each device is connected to two other devices, forming a ring. Data travels from node to node, and each device acts as a repeater to keep the signal strong.
• Mesh Topology: Each device is connected to every other device in the network. This provides redundancy and high reliability but is complex and expensive to implement.

OSI Model

The OSI (Open Systems Interconnection) model is a conceptual framework used to understand and implement network protocols in seven layers:

1. Physical Layer: Deals with the physical connection between devices, including cables and connectors.
2. Data Link Layer: Provides node-to-node data transfer and handles error detection and correction from the physical layer.
3. Network Layer: Manages device addressing, tracks the location of devices on the network, and determines the best way to move data.
4. Transport Layer: Ensures complete data transfer and provides error recovery and flow control.
5. Session Layer: Manages sessions between applications, including setting up, controlling, and terminating connections.
6. Presentation Layer: Translates data between the application layer and the network format, including encryption and compression.
7. Application Layer: Provides network services directly to end-user applications.

IP Addressing

IP (Internet Protocol) addresses are unique identifiers for devices on a network. There are two main versions:

• IPv4: Uses 32-bit addresses, represented in decimal format (e.g., 192.168.1.1). It is widely used but has a limited address space.
• IPv6: Uses 128-bit addresses, represented in hexadecimal format (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334). It provides a much larger address space to accommodate the growing number of devices.

Subnetting

Subnetting is the process of dividing a network into smaller, more manageable subnetworks. It helps in efficient IP address allocation and improves network performance. For example, a Class C network (e.g., 192.168.1.0/24) can be subnetted into multiple subnets (e.g., 192.168.1.0/26, 192.168.1.64/26) to create smaller networks within a larger one.

Network Devices

Various devices are used to create and manage networks:

• Router: Connects different networks and forwards data packets between them. It uses routing tables to determine the best path for data.
• Switch: Connects devices within a single network and uses MAC addresses to forward data to the correct destination.
• Hub: Connects multiple devices in a network and broadcasts data to all connected devices. It is less efficient than a switch.
• Access Point: Provides wireless connectivity to devices by connecting to a wired network.
• Modem: Converts data between analog and digital formats, allowing communication over telephone or cable lines.