Network Topology

Network Topology Definition

Topology refers to the arrangement of nodes within a network. Two or more links between nodes make a topology.

The devices making a network can be within a building, city or country. But definitely there must be a pattern of connections between them.

Network Topology types

1. Mesh Topology

In a mesh network topology every node in a data communication network is connected to every other node in the network. (See Fig-1)

Fig-1: Mesh Topology Diagram

Mesh Topology Advantages

• Every two nodes have dedicated link so they can utilize the full capacity of the channel
• The connection is secure because no third node in the network sharing the link
• This is robust. If one link goes down then other links still work
• Delivery to correct destination is guaranteed
• Due to point-to-point link the fault identification is easy for network administrator

Mesh Topology Disadvantages

• Due to connections of all nodes with each other we need large number of I/O ports
• Cables are required in a large length. Imagine if you want to make a mesh network between 100 computers within a building. How much cable you do you need? Secondly it will become messy to connect 100 computers with each other. Definitely you don’t have much space in your walls or room
• It is expensive too. Because you need network cards for so many links

2. Star Topology

In star topology the devices are not connected to each other directly. But there is a central hub or controller between them. (See fig-2)

Fig-2: Star Topology Diagram

You can see, the devices cannot share data without hub. The devices first send data to hub and then hub send data to respective devices or device.

Star Topology Advantages

• As devices are only connected to central hub so less number of I/O ports required as compared to mesh topology
• It’s easy to add new device in the network. Just connect device with the central controller
• If one link fails then other links will not be affected

Star Topology Disadvantages

• The main disadvantage is that if hub fail, all the system will go down

3. Bus Topology

One long cable is the core component of bus topology. Signal moves in the main cable. The nodes are connected with the main cable with connectors or taps. (See fig-3)

Fig-3: Bus Topology Diagram

Bus Topology Advantages

• Deployment of the network is easy. Main cable is deployed on the best possible path and other nodes are attached to it
• Less cabling is required as compared to star and mesh

Bus Topology Disadvantages

• Taps create interference so difficult to add new device
• Signal becomes week with length of main cable
• Fault detection is difficult
• A breakage in the main cable stops the nodes beyond that

4. Ring Topology

In ring topology the devices are connected in a closed loop or ring shape. So every device is connected with two other adjacent devices. One on left side and other on right side. (See fig-4)

Fig-4: Ring Topology Diagram

The message travels in the form of token. This is why it is also called token ring network. Token passes from every device on its way until it reaches to correct destination. Every node check the token and acts as a repeater if token is not for it. Ring topology can be uni-directional or bi-directional.

Ring Topology Advantages

• Every node can send and receive data
• No need of network server
• Because every node works as repeater too so ring can be expanded to any length
• Fault detection is easy due to point-to-point connection

Ring Topology Disadvantages

• Breakage in the ring can stop the network to some extent
• Addition of new device slows the things. Because every node check the token on token’s way
• Every node should be switched on

5. Hybrid Topology

This is basically the combination of two or more topologies we talked above. For example if one department of your office has star topology and bus topology is deployed in another department. Then combining these two will make hybrid topology.

Types of Hybrid Topology

1. Star-Bus Topology

In start-bus topology the main or backbone cable like a bus topology connects multiple start topologies. (See Fig-5)

Fig-5: Star-Bus Topology Diagram

2. Star-Ring Topology

This topology is a combination of star and ring topologies. (See fig-6)

Fig-6: Star-Ring Topology Diagram

Hybrid Topology Advantages

• Can be designed according to requirements
• Fault detection is easy
• Use the capabilities of two topologies rather than one

Hybrid Topology Disadvantages

• Difficult to design its architecture
• This is costly because need precise hubs which can manage a huge and complex architecture