This tutorial explains network topologies (Bus, Star, Ring, Mesh, Point-to-point, Point-to-multipoint, and Hybrid) in detail with their advantages and disadvantages.
Network topology is the layout of a network. It consists of two parts; physical and logical. The physical part describes the physical layout of a network while the logical part describes how the data flows in that network. Both, physical and logical parts are also known as the physical topology and the logical topology.
Physical part (topology) + Logical part (topology) = Network topology
Types of network topology
The popular types of network topology are; Bus, Star, Hybrid, Ring, Mesh, point-to-point, and point-to-multipoint. Let’s understand each of these types in detail.
In this topology, all computers connect through a single continuous coaxial cable. This cable is known as the backbone cable.
Both ends of the backbone cable are terminated through the terminators. To connect a computer to the backbone cable, a drop cable is used.
To connect the drop cable to the computer and backbone cable, the BNC plug and BNC T connector are used respectively.
The following image shows the bus topology.
When a computer transmits data in this topology, all computers see that data over the wire, but only that computer accepts the data to which it is addressed. It is just like an announcement that is heard by all but answered only by the person to whom the announcement is made.
For example, if in the above network, PC-A sends data to the PC-C then all computers of the network receive this data but only the PC-C accepts it. The following image shows this process.
If PC-C replies, only the PC-A accepts the return data. The following image shows this process.
The following table lists the advantages and disadvantages of the bus topology.
|It is very simple to install.||It is very difficult to troubleshoot.|
|It uses less cable than other topologies.||It provides slow data transfer speed.|
|It is relatively inexpensive.||A single fault can bring the entire network down.|
This topology is no longer used. But there was a time when this topology used to be the first choice among the network administrators. The concept that this topology uses to transmit the data is also used in the other topologies.
In this topology, all computers connect to a centralized networking device.
Usually, a networking switch or a Hub (in earlier days) is used as the centralized device.
Each computer in the network uses its own separate twisted pair cable to connect to the switch. Twisted pair cable uses RJ-45 connectors on both ends.
The following image shows an example of the star topology.
To transmit data, the star topology uses the same concept which the bus topology uses. It means,
if you build a network using the star topology, then that network will use the bus topology to transmit the data.
The following table lists the advantages and disadvantages of the star topology.
|It is easy to install.||It uses more cables than other topologies.|
|Relocating of computers is easier than other topologies.||If the centralized device fails, it brings the entire network down.|
|Since each computer uses its own separate cable, a fault in cable does affect other computers of the network.||The total installation cost is higher than the other topologies.|
|Troubleshooting is relatively easy.||Use the twisted pair cable which is prone to break.|
|It provides higher data transfer speed.||Too many cables make the network messy.|
In modern computer networks, the star topology is the king. Nearly all new network installations, including small home and office networks, use some form of the star topology.
This topology is a mix of two or more topologies. For example, there are two networks; one is built from the star topology and another is built from the bus topology. If we connect both networks to build a single large network, the topology of the new network will be known as the hybrid topology.
You are not restricted to the bus and star topologies. You can combine any topology with another topology. In modern network implementations, the hybrid topology is mostly used to mix the wired network with the wireless network.
The following image shows an example of the hybrid network topology.
Unlike a wired network, a wireless network does not use cables to connect computers. A wireless network uses radio spectrum to transmit data.
In this topology, all computers connect in a circle. Each computer directly connects to two other computers in the network. Data moves down a one-way path from one computer to another. When data signals pass from one computer to the next, each computer regenerates the signals. Since the signals are regenerated on each passing computer, the quality of the signals remains constant throughout the ring.
The following image shows a typical ring topology.
The following table lists the advantages and disadvantages of the ring topology.
|It does not uses terminators.||It uses more cables.|
|It is relatively easy to troubleshoot.||It is too expensive.|
|Since data flows only in one direction, there is no collision in the network.||A single break in the cable can bring the entire network down.|
Like the bus topology, this topology is also no longer used in modern networks. This topology was originally developed by IBM to overcome the existing drawbacks of the bus topology.
In this topology, multiple paths exist between end devices. Based on paths, a mesh topology can be divided into two types; fully meshed and partially meshed. If a direct path exists from each end device to every other end devices in the network, it’s a fully meshed topology. If multiple paths exist between the end devices in the network, it’s a partially meshed topology.
To know how many connections require to make a network fully meshed, we can use the following formula.
Required connections = n * (n-1)/2
Here, n is the number of end devices or locations.
For example, to make a fully meshed network of 4 end devices, we need 4*(4-1)/2 = 6 connections.
We can also use this formula to figure out whether a network is fully meshed or partially meshed. If the number of connections in a network is less than the total required number of the connections then the network is considered as the partially meshed network. For example, a network of 4 end devices has less than 6 connections, then it will be considered as the partially meshed network.
The following image shows an example of both types.
Mesh topology is commonly used in the WAN network for backup purposes. This topology is not used in the LAN network implementations.
In this topology, an end device connects directly to multiple end devices in the network. Just like mesh topology, this topology is also used in the WAN network to connect multiple remote sites/locations/offices with a central site/location/office.
The following image shows an example of the point-to-multipoint topology.
Partially meshed topology and the point-to-multipoint topology are the same except the number of connections. In partially meshed topology number of connections are higher the point-to-multipoint topology.
This is the simplest form of network topology. In this topology, two end devices directly connect with each other. The following image shows a few examples of this topology.
That’s all for this tutorial. If you like this tutorial, please don’t forget to share it with friends through your favorite social network.
Prerequisites for 200-301
200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.
The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.
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