Network Routing and Communication

Routing Protocols – BGP, RIP, OSPF

Learning Outcome

Apply the concept to real-world networking scenarios

Describe how routing decisions change dynamically

Explain how routers choose the best path

Differentiate between types like RIP, OSPF, and BGP

Understand what a routing protocol is and why it is needed

First, you write what you want to send.

Then the gift is packed safely and labeled correctly.

The delivery company manages the connection between you and your friend.

The package is divided into smaller boxes for easy transport.

Each box gets an address so it reaches the right place.

The delivery trucks find the best roads to travel.

Finally, the boxes move through roads, cables, or Wi-Fi signals across the internet.

Helps understand how data moves between devices step by step

Breaks complex networking into smaller, easy-to-manage parts

Makes it easier to identify and fix network problems

Ensures different devices and systems can work together properly

Helps in designing and improving network communication systems

Provides a standard structure for learning and understanding networking

Use of OSI Model

Introduction to OSI Model

The Open Systems Interconnection (OSI) model is a conceptual 7-layer framework developed by the ISO in 1984 to standardize computer networking functions, enabling diverse systems to communicate. It divides data communication into layers (physical to application) for troubleshooting and understanding network protocols.

Purpose of Layered Architecture

Layered architecture divides networking into smaller parts to make it easy to design, understand, and troubleshoot.

Why this is done?

Separation of work (Specific job for each layer)

Each layer handles only one function.
Example: One layer handles routing, another handles encryption.
This makes the system organized and efficient.

Easy to learn and understand

Breaking networking into layers helps students and engineers understand the process step-by-step instead of all at once.

Simplifies troubleshooting (Error detection)

If something goes wrong, we can identify the exact layer causing the issue.
Example:
1. No signal → Physical Layer problem
2. Wrong IP → Network Layer issue

Flexibility and independence

Changes in one layer do not affect other layers.
Example: You can upgrade hardware (Physical layer) without changing software.

Interoperability (Different systems can work together)

Devices from different companies can communicate because they follow the same layered structure.

Reusability of protocols

Same protocols (like TCP/IP) can be used in different applications without redesigning everything.

7 Layers Overview

Transmits raw bitstreams over physical mediums (cables, switches). Responsible for the transmission and reception of raw bit streams over a physical medium, including electrical, optical, or radio signals.

Deals with cables, signals, hardware

Sends raw bits (0s and 1s)

Example: Ethernet cable, Wi-Fi signals

Physical Layer (Layer 1):

The Data Link Layer makes sure data moves correctly between devices on the same network using their physical (MAC) addresses. It checks for errors and ensures the data reaches the right device nearby.

Uses MAC address

Handles switching & error detection

Example: Ensures data reaches the correct device in the same network

Data Link Layer (Layer 2):

Network Layer (Layer 3):

The Network Layer is responsible for sending data from one network to another using IP addresses. It decides the best path for data to reach its destination.

Uses MAC address

Handles switching & error detection

Example: Router deciding best path to send data

Network Layer (Layer 3):

Ensures reliable data transfer, flow control, and segmentation (TCP/UDP). Provides end-to-end communication services, including segmentation, flow control, error detection, and reliable or unreliable data delivery between hosts.

Uses TCP/UDP

Ensures data is delivered correctly

Example: Breaking data into parts and reassembling

Transport Layer (Layer 4):

Manages sessions (connections) between applications. Establishes, manages, and terminates communication sessions between applications, including synchronization and dialog control.

Manages connection (start, maintain, end)

Example: Keeping a video call connected

Session Layer (Layer 5):

Handles data encryption, decryption, and formatting. Responsible for data translation, encryption/decryption, and compression to ensure that data is presented in a standard, usable format for the application layer.

Handles encryption & formatting

Example: Converting data into readable format, encrypting passwords

Presentation Layer (Layer 6):

Interfaces directly with user applications (HTTP, FTP, SMTP). Provides network services directly to end-user applications and facilitates communication between software processes over a network.

Closest to the user

Provides services like web, email