Server

The server is a computer system or software program that is responsible for responding to user requests by providing services and distributing resources to user devices (i.e. clients). There are various types of servers that perform different functions, including data storage/backup, web hosting, email communication, security (e.g. user authentication, firewalls), and resource sharing (e.g. printers).   

Router

The role of a router is to facilitate communication between two separate networks by transferring data packets between them. In a LAN, the router establishes a connection between the internal local network to the outside network (i.e. the internet), allowing devices in different networks to communicate with each other across the internet. For example, if an email needs to be sent to a device located in another network, it must be routed from the sender’s network, through the internet, to the recipient’s mail server.

Network Interface Card (NIC)

A network interface card (NIC), also known as a network adapter, is a hardware component that enables a device to connect to a network, serving as the intermediary between the device and the network in terms of connectivity. It provides wired or wireless network connectivity through an Ethernet cable or wireless access point (WAP), respectively. NICs come in the form of a small circuit board that can be either integrated into the device or equipped externally, but most modern devices come with built-in NICs. 

Switch

The switch is essentially the central point of connection for all devices in a network, including the servers. As the central hub, its primary function is to manage the network and forward data packets between all connected devices. When a device wants to communicate with another device, it sends the data packets to the switch, which then forwards them to the intended recipient.  

Modem

The modem’s name actually describes its function. It is a modulator-demodulator that converts media signals from analogue to digital and vice versa. The conversion process from analogue to digital, known as modulation, allows computers to understand and interpret the signal, while demodulation (digital to analogue) is required for the signal to be transmitted over physical communication lines (e.g. telephone lines). These two processes are essential for devices on the network to connect to the internet through the internet service provider (ISP) and to transmit data between networks. In essence, the modem serves as a translator for these functions.

The modem and router both play a role in bringing the internet into the network and facilitating communication between networks:

• Internet Connection – the modem is responsible for signal translation by modulating analogue signals into digital ones. It then sends the translated signals to the router, which shares the internet connection with connected devices. 

• Communication – the sender first transmits data to the router, which sends it to the modem to undergo demodulation before it is able to be transmitted over cable lines. The ISP then routes the data to the destination network, where it is modulated back into digital data and forwarded by the router to the appropriate recipient device.

How it All Connects Together

A typical network is usually set up as follows:

1. The modem connects to the internet service provider (ISP) to provide internet access to the network. 

2. The router connects to the modem and acts as the gateway between the LAN and the internet, managing the traffic between the two.

3. The switch connects to the router, providing connectivity between all devices within the network.

4. The NICs, which are built-in or externally plugged into devices, connect to the switch, wired or wirelessly, to provide network connectivity for those devices. 

5. The server also connects to the switch and communicates with other devices to provide resources and services. 

Image: Network Setup, Image by Jeckmen Wu (created using EdrawMax Online)