Network Topology

Network topology means the way computers, devices, and network connections are arranged in a network.

It describes both Physical arrangements and Logical arrangement

Physical arrangement — how cables/devices are physically connected.

Logical arrangement — how data actually flows between devices.

Types of Network Topology

1.Bus Topology

In Bus Topology all devices are connected to one main cable called backbone cable.

When one device sends data, the data travels along the main cable. Other devices can see the transmission, but the intended device processes the data.

Key points

• If the backbone cable fails, the network can be affected significantly.
• Performance decreases as more devices are added.

Working

1.If PC1 wants to send data to PC3

2.PC1 puts the data onto the backbone

3.The data is transmitted as network signals onto the shared cable.

4.The signal travels along the backbone

5.Because all devices share the same cable, the signal travels along the backbone.

6.Other devices receive/observe the transmission

7.PC2 and PC4 may see the signal on the shared medium, but the data is intended for PC3.

8.The network interface checks the destination address in the frame.

9.PC3 recognizes that the frame is addressed to it and processes it.

10.PC3 accepts the data.

11.PC2 and PC4 ignore the frame if it isn’t addressed to them.

What is Terminator

Traditional bus networks have a terminator at each end of the backbone.

The terminators absorb the signal and help prevent it from reflecting back along the cable.

When a signal reaches the end of the cable, it can reflect back. This reflection can interfere with other signals and cause communication problems.

2.Star Topology

In that topology there are many devices connected to one central device. In central sever there are usually switch and in smaller network it can be router or hub.

Working

Suppose PC1 wants to send data to PC3.

1. PC1 creates the data
2. PC1 sends the data to the switch
3. The switch check the destination MAC address of the Ethernet frame.
4. If the switch knows where PC3 is connected, it forwards the frame through PC3’s port.
5. PC3 receives the data

Suppose the connection between PC1 and the switch breaks only PC1 loses connection

3.Ring Topology

In that each devices are connected to two other devices forming a closed circular loop (ring).

Working

Suppose PC1 wants to send data to PC3.

1. PC1 sends the data to its neighboring device(PC2)
2. PC2 forwards the data towards PC3
3. PC3 receives the data
4. In some ring systems, communication can be:

PC1 → PC2 → PC3

or potentially in the opposite direction in dual-ring/redundant designs:

PC1 → PC5 → PC4 → PC3 

4.Mesh Topology

In Mesh Topology devices are connected to multiple other devices, creating multiple communication paths. Here, devices have multiple connections with each other.

Types of Mesh Topology

a.Full Mesh

In a full mesh, every device is directly connected to every other device.

For 4 devices:

• PC1 connects to PC2, PC3, PC4
• PC2 connects to PC1, PC3, PC4
• PC3 connects to PC1, PC2, PC4
• PC4 connects to PC1, PC2, PC3

b.Partial Mesh

In a partial mesh, only some devices have multiple connections. Not every device needs to connect directly to every other device.

5.Tree Topology

In Tree Topology devices are arranged in hierarchical structure, similar to the branches of a tree.

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It combines characteristics of Star topology and Bus topology.

A main/core device connects to other devices, and those devices connect to additional devices or smaller networks.

Suppose PC5 wants to communicate with PC8:

PC5 → Hub2 → Root Hub → Hub3 → PC8 

Each department can have its own network, while the core network connects all departments.

Example security issue

Suppose the intended design is:

Employee Network ──X──> Database Network

But because of an incorrect routing or firewall rule:

Employee Network ──────> Database Network

an attacker who compromises an employee machine might be able to reach systems that should have been isolated.

6.Hybrid Topology

In Hybrid Topology two or more different types of network topologies in the same network.

For example, an organization might use:

• Star topology inside each department
• Tree topology to connect departments
• Mesh topology between important network devices

Together, these form a Hybrid Topology.

7.Point-to-Point (P2P) Topology

Point-to-Point topology is the simplest network topology where two devices are directly connected to each other. There is a dedicated communication link between the two endpoints.

8.Point to Multipoint

Point-to-Multipoint (P2MP) topology is a network topology where one central device communicates with multiple other devices.

Think of it as:

One → Many

Example 1

A wireless access point can communicate with multiple clients:

                  [Wi-Fi AP]
                /     |      \
               /      |       \
          [Laptop] [Phone] [Tablet]

The AP is the central point.

Example 2

                   [Head Office]
                 /      |       \
                /       |        \
          Branch A   Branch B   Branch C

A central network can communicate with multiple remote locations.