Sonia Manoubi
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[ Devops : Back to Basics ] : Introduction to Networking

This article is part of a serie called [ Devops : Back to Basics ] where i document what i'm learning on my journey to become a Devops Engineer from my current position as a Backend Engineer.

Definitions

Network: Interconnection of computers

Computer networking : the full scope of how computers communicate with each other.

Protocol : a defined set of standards that computers must follow in order to communicate properly.

Computers in a network can talk to each other and send data to one another.

Computers are using protocols to communicate with each other.

The TCP/IP Five-Layer Network Model

Here is a representation of the TCP/IP Model

tcp_ip model.png

Let's start at the bottom

  • The Physical Layer: Represents the physical devices that interconnect computers.
  • The Data Link Layer: Responsible for defining a common way of interpreting signals from the physical layer so network devices can communicate.
  • The Network Layer: Allows different networks to communicate with each other through devices known as routers

The most known protocol in the network layer is IP (for Internet Protocol). IP is the heart of the Internet and most smaller networks around the world.

  • The Transport Layer: Sorts out which client and server programs are supposed to get the data

The most known protocol used in the transport layer is TCP (Transmission Control Protocol).

  • The Application Layer: Highest abstraction layer of the TCP/IP model that provides the interfaces and protocols needed by the users

The Basics of Networking Devices

Cables

Cables connect different devices to each other, allowing data to be transmitted over them.

Most cables used in networking can be splitted in two categories:

  • Copper : the most common forms of copper twister-pair cabled used in networking are Cat5, Cat5e and Cat6 cables.

copper-cat6.png

  • Fiber : contain individual optical fibers, which are tiny tubes made out of glass. fibre-optic-cable.jpeg

Hubs and Switches

Hub and switches are the primary devices used to connect computers on a single network, usually referred to as a LAN or local area network.

Hub

A Hub is a physical layer that allows connections from many computers at once.

All devices connected to the Hub will end up talking to every other computer connected to the Hub.

Every device must determine if the incoming data is for them or not, and in that case to ignore it.

This causes a lot of noise on the network and creates what's called a collision domain.

A collision domain : a network segment where only one device can communicate at a time.

If multiple systems try to send data at the same time, the electrical pulses sent across the cables can interfere with each other.

It means each system has to wait for a certain amount of time before sending data, so it slows down the network, so people prefer using switches.

Switch

A switch is very similar to a hub since you can connect many devices to it.

The difference is while a Hub is on the Layer 1 (the Physical layer) of the TCP/IP model, a switch is on the Layer 2 (the Data link layer).

This means that the switch can inspect the content of the ethernet protocol data being sent around the network and determine which system the data is intended for and then only send that data to that one system.

This reduce / eliminate the size of collision domain on a network.

Routers

A router is a device that knows how to forward data between independent networks.

A router is a Layer 3 (Network Layer) device.

Just like a switch can inspect ethernet data, a router can inspect IP data to know where to send the data.

Routers store internal tables containing informations about how to route traffic between lots of different networks all over the world

The most common router you'll see is the one for your home network or a small office. These devices generally don't have detailed routing tables.

The purpose of these devices is to take the traffic generated from inside the home or the office LAN and forward it to the ISP (Internet Service Provider).

Once traffic is at the ISP, a more sophisticated type of router takes over.

These core routers form the backbone of the internet and are directly responsible of how we send and receive data all over the internet.

Core ISP routers don't just handle a lot more traffic than a home router. They also have to deal with much more complexity in making decisions about where to send traffic.

Border Gateway Protocol (BGP) : Routers share data with each other via this protocol, which lets them learn about the most optimal paths to forward traffic.

hub & switch & router@2x.png

Conclusion

That's it !

Don't hesitate to comment to point out some mistakes or make some precisions.

As i said in the beginning, i am still studying these concepts :)

See you in the next one !

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