Network Fundamentals

Study Notes

Physical Topologies:
- Bus: A single cable connects all devices in a linear sequence.
- Star: All devices connect to a central device (hub/switch).
- Ring: Devices connect in a circular configuration.
- Mesh: Each device connects to every other device.
Logical Topologies:
- Broadcast: All devices receive all messages.
- Point-to-Point: Direct connection between two devices.

Hub:
- A simple network device that connects multiple devices.
- Broadcasts incoming data to all connected devices.
Switch:
- A network device that connects multiple devices.
- Intelligently forwards data to the intended device.
Router:
- Connects multiple networks and routes data between them.
- Uses IP addresses to determine the destination network.
Repeater:
- Amplifies weak signals to extend network coverage.
- Used to connect two segments of a network.

Physical Topologies:
- Bus: A single cable connects all devices in a linear sequence, making it a simple and cost-effective topology.
- Star: All devices connect to a central device (hub/switch), allowing for easy addition or removal of devices.
- Ring: Devices connect in a circular configuration, providing high-speed data transfer but vulnerable to single point of failure.
- Mesh: Each device connects to every other device, providing maximum redundancy and reliability.

Logical Topologies:
- Broadcast: All devices receive all messages, making it a simple and efficient topology.
- Point-to-Point: Direct connection between two devices, ensuring dedicated bandwidth and reducing latency.

Layer 7: Application: Supports functions such as email, file transfer, and web browsing, providing services to end-user applications.
Layer 6: Presentation: Converts data into a format for transmission, such as encryption and compression, ensuring data integrity.
Layer 5: Session: Establishes, manages, and terminates connections between applications, controlling dialogue between devices.
Layer 4: Transport: Provides error-free transfer of data, ensuring reliable communication between devices.
Layer 3: Network: Routes data between networks, determining the best path for packet transmission.
Layer 2: Data Link: Ensures error-free transfer of data frames, providing flow control and error detection.
Layer 1: Physical: Defines physical means of data transmission, such as cable specifications and wireless transmission.

Hub: A simple network device that connects multiple devices, broadcasting incoming data to all connected devices, but lacking intelligence.
Switch: A network device that connects multiple devices, intelligently forwarding data to the intended device, reducing network congestion.
Router: A device that connects multiple networks and routes data between them, using IP addresses to determine the destination network.
Repeater: A device that amplifies weak signals to extend network coverage, used to connect two segments of a network, but not a routing device.

A switch connects multiple devices in a network, enabling communication between them.

Receives incoming data packets and directs them to the intended recipient based on the destination MAC address.
Examines incoming packets, forwards them to the correct port, and prevents data collisions by ensuring only one device can transmit at a time.
Learns and stores MAC addresses of connected devices in a table.

Unmanaged Switches: Basic switches with no configuration options, used for simple network extensions.
Managed Switches: Allow configuration of VLANs, QoS, and security features.
PoE (Power over Ethernet) Switches: Provide power to connected devices over Ethernet cables.

Cut-Through Switching: Forwards packets as soon as the destination MAC address is received.
Store-and-Forward Switching: Stores the entire packet before forwarding it to the destination.
Fragment-Free Switching: Stores the packet until the collision window is clear, then forwards it.

Advantages:
- Improves network efficiency by reducing collisions and increasing bandwidth.
- Allows for easy network expansion and scalability.
- Supports VLANs and QoS for better network management.
Disadvantages:
- Can be a single point of failure if not redundant.
- Can be vulnerable to security threats if not properly configured.