The Basic of Networking devices

Cables
Hubs and Switches
Routers
Servers and Clients

Cables

Connect different devices to each other, allowing data to be transmitted over them

Copper and Fiber(Fiber-optic Cables):The two categories are the most network cables used today.

Copper

Computers communicate in binary, which people represent with ones and zeros. The sending device communicates binary data across these copper wires by changing the voltage between two ranges. The system at the receiving end is able to interpret these voltage changes as binary ones and zeros, which can then be translated into different forms of data.The most common forms of copper twisted pair cables used in networking, are Cat 5, Cat 5e, and Cat 6 cables(Category 5 or 6).Cat 5e cables have mostly replaced those older Cat 5 cables because their internals reduce crosstalk.
Crosstalk is when an electrical pulse on one wire is accidentally detected on another wire.Cat 6 cables, following even more strict specification to avoid crosstalk, making those cables more expensive. Cat 6 cables can transfer data faster and more reliably than Cat 5e cables can, but because of their internal arrangement, they have a shorter maximum distance when used at higher speeds.

Fiber

Fiber cables contain individual optical fibers, which are tiny tubes made out of glass about the width of a human hair.

These tubes of glass can transport beams of light. Unlike copper, which uses electrical voltages, fiber cables use pulses of light to represent the ones and zeros of the underlying data. Fiber is even sometimes used specifically in environments where there's a lot of electromagnetic interference from outside sources because this can impact data being sent across copper wires.
Fiber cables can generally transport data quicker than copper cables can, but they're much more expensive and fragile. Fiber can also transport data over much longer distances than copper can without suffering potential data loss.

Comparison

Category	Mechanism
Copper	Using electrical voltages
Fiber	Using pulses of light

Hubs and Switches

Hubs 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 device that allows for connections from many computers at once.

How the hub work below:

All the devices connected to a hub will end up talking to all other devices at the same time. It's up to each system connected to the hub to determine if the incoming data was meant for them, or to ignore it if it isn't. This causes a lot of noise on the network and creates what's called a collision domain as below.

Collision domain is a network segment where only one device can communicate at a time. If multiple systems try sending data at the same time, the electrical pulses sent across the cable can interfere with each other.

Switch

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

The difference is that while a hub is a layer one or physical layer device, a switch is a layer two or data link device. This means that a switch can actually inspect the contents of the ethernet protocol data being sent around the network. Determine which system the data is intended for and then only send that data to that one system. This reduces or even completely eliminates the size of collision domains on the network.

Routers

Hubs and switches are the primary devices used to connect computers on a single network, usually referred to as a LAN, or local area network. But we often want to send or receive data to computers on other networks, this is where routers come into play.

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

While a hub is a layer 1 device and a switch is a layer 2 device, a router operates at layer 3, a network layer as below. Just like a switch can inspect Ethernet data to determine where to send things, a router can inspect IP data to determine where to send things. Routers store internal tables containing information about how to route traffic between lots of different networks all over the world.

How the router works:

Once traffic is at the ISP(Internet service provider), a way more sophisticated type of router takes over. These core routers form the backbone of the Internet, and are directly responsible for how we send and receive data all over the Internet every single day. Core ISP routers don't just handle a lot more traffic than a home or small office router, they also have to deal with much more complexity in making decisions about where to send traffic. A core router usually has many different connections to many other routers.

Border Gateway Protocol(BGP)

Routers share data with each other via a protocol known as BGP, or border gateway protocol, that let's them learn about the most optimal paths to forward traffic.

Servers and Clients

The simplest way to think of a server, is as something that provides data to something requesting that data. The thing receiving the data, is referred to as a client.

A server is anything that can provide data to a client, but we also use the words to refer to the primary purpose of various nodes on our network

References:
https://www.coursera.org/learn/computer-networking
https://www.multicominc.com/training/technical-resources/copper-vs-fiber-which-to-choose/
https://www.dignited.com/58676/fiber-optic-vs-copper-cables/

Week1-02_The Basic of Networking devices