Communication

# Network Topology and Types of network topology

The arrangements of network including the physical or logical description of how the nodes are related with each other are network topology. Network topology like bus star, ring, tree, mesh and hybrid. In this tutorial, we will also understand what are the advantages and disadvantages of network topology. The network topology diagrams are shown below.

## What is network topology?

In network technology, how various devices and node are connected with each other in physical and logical arrangement? There is several ways to arrange a device. Each network topology has advantages and disadvantages and depending upon which type of network topology required in a company. The certain advantage can give a greater degree of security and connectivity.

We have some nodes and we have to arrange these nodes so that we can establish communication among all the nodes. Topology means arrangement of nodes of a computer network, say I have to arrange all these nodes so that I can establish communication among all the nodes, topology can be viewed as a layout of a computer network. Topology can be viewed as a physical topology and logical topology. Physical topology means where I am going to place all these nodes this is what physical topology.

Say I can place all these three nodes in ground floor of my building I can also take these two nodes to the first floor of my building and the placement of these nodes is called as physical topology. Logical topology means how the data is going to flow from this node to this node. This node may be in ground flow this node may be in first floor. How I am going to deal with the data flow in the network that is viewed as the logical topology. Simply topology means the arrangement of nodes in such a way that we have to make communication among all the nodes. We will see what the various topologies are.

### Types of network topology

The connection of node in a various manner is comes in the categories of types of network topology.

• Star Topology
• Bus Topology
• Ring Topology
• Mesh Topology

Let us discuss types of topology one by one below.

### Bus topology

In bus topology there is a common transmission medium and all nodes are connected to this transmission medium. Suppose if node gave wants to send some data to node B and it can send the data over this transmission medium and all nodes will receive this transmission. That is the data. Now the problem with this approach is if you want to send some data to B everyone will receive a copy of the data signal including B but all others will deny or reject this packet. Why because this data signal is intended to the recipient B and not to anyone else in the network. So, now we will see what a bus topology as per the definition is.

All data transmitted between nodes in the network is transmitted over this common transmission medium, and all nodes will receive the signal simultaneously. This transmission medium is capable of sending as well as receiving the data. So, the data flow in this transmission medium is bi-directional. It means data can flow in both directions.

• Since there is only one wire or the cable involved this transmission it is less expensive. The same time if you are going to construct a temporary Network where this is not going to last for a long then you can go for bus topology.
• Another advantage of having this network is that if any node failure does not affect others. and these are all bus topology

This is obviously not a fault tolerant Network we have already seen what is a fault tolerant network. Fault tolerance means if there is a failure and this failure should not affect others but if this link this transmission medium is failed obviously the entire network goes down. At the same time if this node wants to send some data to this node and there is a problem in this line so communication here can take place but the communication between this places will not happen. why because this is not dealing with any alternative technique.

The only way for this computer to reach this computer is this line and there is no redundant line. Then that is why this network is not a fault tolerant network. if this node wants to send some data to this node everyone participating in this network will receive a copy of the signal. So, there is no security in this approach.

### Ring topology

A ring topology is a bus topology but in a closed loop. If you observe this is a bus topology but this is a closed loop. So, here the nodes involved are peer-to-peer and LAN topology nodes. It means there is no one in superior in this network and there is no one inferior in this network. All nodes are with equal rights and that is why we call these nodes are peer-to-peer nodes and every node will have two connections one to each of its nearest neighbors and the communication is always unidirectional. Suppose, if this node wants to send some data to this node and the network is set up like the flow of data should be in this direction and this node will send this data to this node and this node will forward the data to this node this node this node and finally it will be received by this node.

The communication will not happen directly like this the communication will be like this because the communication pattern of ring topology is always unidirectional and you may ask me how this communication will happen. It is with the help of a token that is why we call this topology as a token ring topology. Now we will see how sending and receiving happens with the help of this token. It means it’s their turn to send data. for example if this node has the token. It means it’s the turn of this node to send the data. After some time the token will be moved on to the next node. it means that it’s this computer’s turn to send the data after some point of time the token will be passed on and this token will be circulated throughout this network it means whoever holds this token it’s their time to send their data and this is how all nodes gets opportunity to send or receive the data.

It has better performance than bus topology because it is in a close loop, but the problem is if this link is a weak link this ring topology causes some bottleneck in the network because of this weak link at the same time all nodes are having equal access which is considered to be one of the advantages of ring topology.

If transfer of data from one node to other nodes. It is very easy to send this way but link topology is a unidirectional communication pattern. It has to send the data by crossing these many nodes and finally reach the destination. One of the disadvantages is being unidirectional. Single points of failure say this link is failed. So, the entire network is disrupted because of this. A node failure or a link failure will definitely affect the entire network. This is what the primary disadvantage of a ring topology. If there is very high load in the network then the performance of the network is getting degraded. If this is going to send some confidential data to this computer but again this has to cross so many intermediary nodes in order to reach the destination and obviously there is no security in this ring topology.

### Star topology

In star topology every node is connected to each other not directly but with the help of a central node. This central node can be a hub or a switch. This is going to do the entire centralized administration. All traffic must pass through the hub or a switch. Suppose, if this node wants to send some data to this node so obviously this is going to send the data to the central node which is the hub or the switch here. It is the responsibility of this hub or switch to forward the data to this node. that is the destination if you observe keenly in the previous cases there were chances for other nodes to receive a copy of the data but here if this node wants to send some data to this node and this is going to be the path of this communication and there is no way for others to hear this communication or see this communication.

It is definitely very easy to design and implement. We have a centralized administrator. This is the hub or a switch. For example, if the switch has 24 ports. You can connect 24 computers to the switch. if you find that 24 computers are not sufficient you have 50 more computers you bring another switch and connect all the computers to that switch and again make a communication between this switch and this switch so that this network becomes a scalable network. So star topology is easy to design and implement and there is a centralized administration. It is a scalable Network.

Star topology has a serious disadvantages to a failure in this central node will affect the entire network. If this node that is the switch or the hub is failed no communication can take place.  if this node is overloaded with lot of traffic and lot of processing then the communication or the performance is affected. That is what we call as a bottleneck. You have to spend some money for purchasing this hub or a switch.

So, obviously it is going to increase the cost. So, there are some disadvantages a single point failure is going to affect the whole network. There can be bottlenecks due to a overloaded hub or switch. You have to spend more for purchasing this hub or a switch. We can also have a variation of a star topology like this is one star topology another star topology you can connect these to start apology’s with the help of a repeater.

### Mesh topology

If you observe there are five nodes and if you observe this node is having a link to all other nodes. Likewise, this node is having link to all other nodes. So, if you observe cleanly this is the topology where each node is directly connected to every node of network. Thereby it provides 100% fault tolerant and reliability. Suppose, if there is a link failure encounter here and this computer has another way to reach the destination. If this link is failed this computer has so many ways to reach the destination. This is one way this is another way and this is another way and this is another way there are so many ways for a node to reach the destination.

It is fault tolerant it means a failure is not going to affect the network. You can rely upon this network because somehow your data will definitely reach the destination. Even if there are link failures.