Basic Networking Elements
Published: 2023-02-15 07:22:01

A **network** is a group of **interconnected** devices (PCs, Laptops, Servers, Smartphones, etc.) that can communicate (exchange information with each other (through Routers and Switches).

**1- Network Types**

- **LAN**: Local Area Network - your home network
- **MAN**: Metropolitan Area Network - extended network covering the entire surface of a city
- **WAN**: Wide Area Network - multiple networks (LANs) of an organization, which are interconnected
- **WWAN**: World Wide Area Network - Internet
- **WLAN**: Wireless LAN - aka WI-FI, which is usually created by our home Router

**2- Network Topologies**

In a typical network environment, there can be multiple representations of devices. These devices can be grouped in various ways, considering what different purposes they are serving.

**Star Topology**
If we only care for network connectivity( or Internet access), we will group the devices a star-like-topology. The problem in this scenario would be the **lack of redundancy**. 
The Interconnected devices are Switches(network devices that connect us to a LAN).

**Full Mesh Topology**
It allows for **full redundancy**. If sth bad happens with a cable or a Switch, there will be redundant ways to reach the Internet or a different destination.
Note that, Full redundancy requires more devices and cabling(more money).

**Partial Mesh**
This provides redundancy only for a part of the network

**Hub and Spoke**
Very often used in the WAN(Internet) design. Routers in this topology don’t know each other by default. One of them knows how to redirect the traffic(data) to reach its destination. This design is being used because it **scales**.

**3- Network Components**
- **End-device**: PC, Laptop, smartphone, Servers, etc.
- **Switch**: interconnects multiple end-devices within a network(LAN)
- **Router**: A network device that has the role of **multiple interconnecting networks**(LANs) and forming a larger network(WAN). The router is the main device that **connects us to the Internet** through its ability to handle packet delivery from any source( network) to any destination(network). The router achieve this by using **IP addresses** to identify the source and the destination devices.
- **Firewall**: protects network from potential cyber-attacks
- **Transmission medium**: through cable or wireless, electricity, light impulses, radio waves etc.

**4- How can we represent (or “draw”) a network?**
Usually, networks are **represented** by a **network topology**, which can be 2 types: **logical** or **physical**. 
**Logical topologies** describe the logical aspects of a network: 
- The IP addresses of the networks
- The way the devices connected
- The routing protocols that are being used, etc.

**Physical Topology** describes the physical aspect:
- Where the devices are placed
- What type of cables we are using
- How many ports we need
- On what ports/switches will be the server connected, etc.
It shows where the equipment is (physically) located and its main purpose within the network.

**5- How do computers communicate over the Internet?**
To communicate(send traffic- aka connect to Youtube, Google, etc.), the devices (PCs, Routers, Switches, etc.) must have a **unique identifier**. This identifier is known as **IP(Internet Protocol)** in the Internet world. The IP is how we identify a device in a network or on the Internet.
Components for an end device to communicate(connect) successfully on the internet:
- IP Address: uniquely identifies a device connected to a network
- Network Mask: determines the size of a network( ex: number of available IP addresses)
- Default Gateway: specifies the way out of the network( a Router connected to the internet)
- DNS Server: transform a name (I.e. google.com) into an IP address(I.e. 1773.23.85.91)