IT- Solution: Computer Network Topologies By Md. Farrukh Asif

A Network Topology is the arrangement with which computer systems or network devices are connected to each other. Topologies may define both physical and logical aspects of the network. Both logical and physical topologies could be the same or different in the same network.

1. Point-to-Point:

Point-to-point networks contain exactly two hosts such as computers, switches,, or routers, and servers connected back to back using a single piece of cable. Often, the receiving end of one host is connected to the sending end of the other and vice-versa.

If the hosts are connected point-to-point logically, then may have multiple intermediate devices. However, the end hosts are unaware of the underlying network and see each other as if they are connected directly.

2. Bus Topology:

In the case of Bus topology, all devices share a single communication line or cable. Bus topology may have a problem when multiple hosts send data at the same time. Therefore, Bus topology either uses CSMA/CD technology or recognizes one host as the Bus Master to solve the issue. It is one of the simple forms of networking where a failure of a device does not affect the other devices. However, failure of the shared communication line can make all other devices stop functioning.

Both ends of the shared channel have a line terminator. The data is sent in only one direction and as soon as it reaches the extreme end, the terminator removes the data from the line.

3. Star Topology:

All hosts in Star topology are connected to a central device, known as a hub device, using a point-to-point connection. That is, there exists a point-to-point connection between the hosts and the hub. The hub device can be any of the following:

Layer-1 devices such as a hub or repeater

Layer-2 devices such as switch or bridge

Layer-3 device such as router or gateway

As in Bus topology, the hub acts as a single point of failure. If the hub fails, connectivity of all hosts to all other hosts fails. Every communication between hosts takes place through only the hub. Star topology is not expensive as to connect one more host, only one cable is required and configuration is simple.

4. Ring Topology:

In ring topology, each host machine connects to exactly two other machines, creating a circular network structure. When one host tries to communicate or send a message to a host that is not adjacent to it, the data travels through all intermediate hosts. To connect one more host in the existing structure, the administrator may need only one more extra cable.

Failure of any host results in failure of the whole ring. Thus, every connection in the ring is a point of failure. Some methods employ one more backup ring.

5. Mesh Topology:

In this type of topology, a host is connected to one or multiple hosts. This topology has hosts in point-to-point connection with every other host or may also have hosts that are in point-to-point connection to a few hosts only.

Hosts in Mesh topology also work as relays for other hosts that do not have direct point-to-point links. Mesh technology comes into two types:

Full Mesh: All hosts have a point-to-point connection to every other host in the network. Thus for every new host n(n-1)/2 connections are required. It provides the most reliable network structure among all network topologies.

Partially Mesh: Not all hosts have a point-to-point connection to every other host. Hosts connect to each other in some arbitrary fashion. This topology exists where we need to provide reliability to some hosts out of all.

6. Tree Topology:

Also known as Hierarchical Topology, this is the most common form of network topology in use presently. This topology imitates an extended Star topology and inherits properties of bus topology.

This topology divides the network into multiple levels/layers of the network. Mainly in LANs, a network is bifurcated into three types of network devices. The lowermost is the access layer where computers are attached. The middle layer is known as the distribution layer, which works as a mediator between the upper layer and the lower layer. The highest layer is known as the core layer and is the central point of the network, i.e. root of the tree from which all nodes fork.

All neighboring hosts have a point-to-point connection between them. Similar to the Bus topology, if the root goes down, then the entire network suffers even. though it is not the single point of failure. Every connection serves as a point of failure, the failure of which divides the network into unreachable segments.

7. Daisy Chain:

This topology linearly connects all the hosts. Similar to Ring topology, all hosts are connected to two hosts only, except the end hosts. This means, that if the end hosts in the daisy chain are connected then it represents Ring topology.

Each link in the daisy chain topology represents a single point of failure. Every link failure splits the network into two segments. Every intermediate host works as a relay for its immediate hosts.

8. Hybrid Topology:

A network structure whose design contains more than one topology is said to be a hybrid topology. Hybrid topology inherits the merits and demerits of all the incorporating topologies.

The above picture represents an arbitrarily hybrid topology. The combining topologies may contain attributes of Star, Ring, Bus, and Daisy-chain topologies. Most WANs are connected using Dual-Ring topology and networks connected to them are mostly Star topology networks. Internet is the best example of the largest Hybrid topology

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Tuesday, July 16, 2024

Computer Network Topologies By Md. Farrukh Asif

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