Introduction to Network Topology

When talking about topologies, sometime beginners confused with the physical and logical topologies of network. Simply Network’s physical topology means the physical connection scheme or cabling scheme among network devices. On the other hand logical topology handles the communication scheme through physical topology. But before understanding the topologies you should first look at the networking devices for better understanding.

Some physical topologies are described below:

Point to point

It is device to device direct networking scheme. In this topology two devices are connected directly and can communicate directly. Multiple connections are not possible. Some examples of point to point network topology: single pc to pc LAN scheme, when you connect two routers across WAN.

Point to point physical topology

Star topology

When network needs many devices to connect through network then star topology may be used. In this topology many devices are connected to each other through a central device which has much point to point connecting port.

10baseT Ethernet uses star topology with Hub or switch in its center. Star network capacity can increase through extended star.

In extended star several star networks are interconnected.

Star Topology

Extended Star Topology

Bus topology

In bus topology all network devices are connected through a single cable. Some older Ethernet scheme like 10base2, 10base5 use bus topology.

Bus Topology

Ring topology

In ring topology the cabling of the network complete a close ring hence it is so named. Like firs device is connected to second device, then second device connected to third device and will go on up to last and then the last device will be connected to first device and complete the ring.

Ring Topology

What is logical topology?

Logical topologies, simply the total data flow process in the network. They are strictly controlled by network protocol. Same network may have distinct physical and logical topology. Means, network with physical star topology may work on bus logical topology.

Consider a simple network connecting with star physical topology using hub. As we know hub is the least intelligent device that simply passes information or data comes to it to all others connected through it. So every connected device sees everything. We can logically simplify its physical star diagram as shown in the image below. We see it’s a typical bus topology. So though it is physically a star but logically it’s a bus topology.

Simplified Star physical topology with equivalent Logical Bus topology