Original subtitles

We'll be discussing typologies and a lot more details throughout the course.

But I want to introduce you to the concept of physical versus logical typologies.

We've mentioned that networks have both a physical and logical typology.

The physical topology of a network refers to the physical layout of the devices and cabling you mismatch

the appropriate physical typology to the top of cabling that you will install which may be twisted pay

correctible cabling or fiber cabling as an example.

Understanding the type of cabling used is important in each type of physical typology.

The logical topology however defines the logical path that data will travel from one point to another.

In the past we had devices called hubs.

These devices were connected in what was called a star physical topology but logically the topology

was a bus.

So let's look at some of these typology types.

The first type is bus in early bus typologies computers and other network devices were cobbled together

in a line using coaxial cable modern bus typologies establish the bus in a hardware device and connect

the host devices to the bus using twisted pay wiring.

A ring was used by technology such as token ring and FDDI.

In the past in a ring topology the computers and network devices were cobbled together with the last

device connected to the first device which formed a circle or ring.

Each device is connected to exactly two neighbors and doesn't have a connection to a third device.

The physical connection used here was either co-axial or fiber cabling in a star topology which is one

of the most common physical implementations a central device has other devices connected to it.

So a switch would have PCs connected to it in a star topology physical cabling these days is typically

done using twisted pair wiring in a mesh.

Every device is connected to multiple other devices.

This increases reliability and provides for self-healing because of the redundant lengths the physical

connection could be made using fiber or twisted pay wiring.

The logical topology however is different as it shows where data travels to get from one end point to

another which may be very different to a physical implementation.

Later in this course I'm going to show you how a hub is physically a start apology but logically acts

as a bus topology.

It's important in networking to not just look at the physical topology of a network but to also view

the logical topology because that may be very different to the physical design and may affect network

throughput reliability and scalability.

One of the skills that you'll need to gain as a network engineer is how to interpret a network diagram

a network diagram captures network related information and the amount of information varies from one

organization to another.

A network diagram is essentially a map of the network and illustrates the logical representation of

the devices in the network and helps clarify how the devices are interconnected.

In addition a well-designed network diagram provides information such as the interface IDs of devices

device identifiers as well as network addressing common network icons that you may come across include

work group line switches routers wireless access points servers and use a desktop PCs and use the laptops

Ethernet links serial links wireless links and networks which could be used to represent the internet

and access network or a lab network.