What is a network?
What is a network? Why do we need network? These types of questions sometimes pop-up in our head.
So, basically here I try to explain about network from what I got inside my networking classes and some thoughts from the internet.
Hopefully this is what you are looking for.
When someone wants to build a network, he/she has to understand these 4 basic points:
- The function of a network
- The network devices
- The applications
- The network topology
1. Defining the function of a network
One simple illustration to describe a network is like this..
I want you imagine the time during the days when king use messenger to send his messages.
The king would ask the messenger to bring his proclamation to his loyal subjects, then he stamp the letter and seal it.
After that the messenger would run across the street and reading it out loudly to the people what the messages are..
Well, using that silly story I try to differentiate the application that runs across the network and what the network is.
The application is the king and his messenger running across the street to bring the messages to other people.
But the network is the road that is used by the messenger.
So, if you wanna be a network engineer someday or choosing a career like in Cisco path, you’re gonna build lots of roads!
Just to make it short.. this is my summary about what network is:
a. A collection of devices that can communicate together
b. The fabric that ties business applications together
2. Understanding the pieces of a network
As you can see what’s on the picture above, there are several stuffs that are needed in order to connect to a network. So, here i’m going to let you know just the basic use of these stuffs in a Local Area Network (LAN).
First, when you want to connect to the internet (network), of course you need a PC. The PC that you use is to give a certain command using applications to reach a server to access a certain data that you want to display on you computer screen. The pc that runs the application needs network interface card or NIC (it’s placed at the back on your pc). This NIC is a device where the ethernet cable plugged. The ethernet cable connects to the switch as the media of data transporation.
switch is a central meeting place for all of these stuffs. A switch also allows all pc’s inside the LAN to communicate each other. Switch is connected to a router, where its main goal is to connect you outside of your LAN to other networks or the internet.
So, when your LAN connects to another LAN, it is considered as a Wide Area Network (WAN).
3. Examples of applications that use networks
These are just common network applications.
a. Web browser (firefox, google chrome, opera, IE) and FTP
– Web browser is the app where you try to access a certain website, e.g. http://www.google.com. I’m sure even your 3 years old kid knows this!
So, this is how it works. The browser that you use sends a certain request through the internet to access the google’s server. And when the server grants the request, the server replies with the specific data that’s requested.
That data is the one displayed on the computer screen.
– File Transfer Protocol (FTP) is a standard network protocol used to copy a file from one host to another over a TCP/IP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server.
b. Database application
When you visit a website, and then you fill out a form starting your name, home address, phone number, etc.. then at the end you click the button ‘Save’, all this information will be kept inside the database application.
So, a database is consist of an organized collection of data for one or more uses, typically in digital form.
c. Instant messenger
Instant messenger is an application where you can send a text or message in real-time between two or more people using personal computers or other devices, along with shared software clients.
Email or e-mail, is a method of exchanging digital messages across the Internet or other computer networks. Originally, email was transmitted directly from one user to another computer.
e. Online Games
An online game needs a client-server architecture just like other application use. When a player involves to a certain game, he/she moves the character using a command from the keyboard or by clicking or moving his/her mouse.
Then the character would move according to a certain coordinate where the player wants to move the character. This can be done because the player is using an internet connection to stream to the server. And the server also streams that to the other players, so every player could see what other characters do inside the game.
4. Network topology
The network topology defines the layout of the network. It shows how devices on the network are interconnected. Devices on the network are termed nodes. A network has both a physical and a logical topology.
a. Bus topology
Commonly referred to as a linear bus, all the devices on a bus topology are connected by one single cable, which proceeds from one computer to the next. This topology is rarely used and would only be suitable for a home office or small business with only a few hosts.
– Advantages of a bus topology:
- The thinnet cabling it uses is quite inexpensive.
- It uses less cable compared to other physical topologies like star or extended star
- It works well for small networks
- It does not need a central device, such as a hub, switch, or router
– Disadvantages of a bus topology:
- It results in slower access to the network and less bandwidth due to the sharing of the same cable by all devices
- It is challenging to identify and isolate problems
- A break at any point in the bus cable can disable the entire bus network
- It needs terminators
b. Star topology
The star topology is the most commonly used architecture in Ethernet LANs and resembles spokes in a bicycle wheel.
A star topology generally costs more to implement than the bus topology because more cable is used and a central device is needed, such as a hub, switch, or router.
– Advantages of a Star Topology:
- It is upgradeable, flexible, and reliable
- It is easy to design and install
- This topology makes diagnosing problems relatively easy since the problem is localized to one computer or device
- This topology allows for more throughput than any other topology
– Disadvantages of a Star Topology:
- It requires a lot of cable to connect computers since a cable is required between each device and the central location.
- It is more expensive to build because of the additional cost of cables and devices like hubs and switch
c. Ring topology
A frame, called a token, travels around the ring and stops at each node.
If a node wants to transmit data, it adds that data and the addressing information to the frame.
The frame continues around the ring until it finds the destination node, which takes the data out of the frame.
The advantage of using this method is that there are no collisions of data packets.
With single ring all the devices on the network share a single cable, and the data travels in one direction only.
With dual ring two rings allow data to be sent in both directions.
This creates redundancy (fault tolerance), meaning that in the event of a failure of one ring, data will still be transmitted on the other ring.
The 802.5 standard is the Token Ring access method that is used.
FDDI uses light instead of electricity to transmit data over a dual ring.
d. Mesh topology
The mesh topology connects all devices (nodes) to each other for redundancy and fault tolerance.
It is used in wide-area networks (WANs) to interconnect LANs and for critical networks.
The mesh topology is expensive and difficult to implement.
e. Hybrid topology
The hybrid topology combines more than one type of topology.
When a bus line joins two hubs of different topologies, the configuration is called a star bus.
The bus line is used to transfer the data between the star topologies.