Understanding Network Devices

To understand network devices, we should first understand how the Internet reaches our home and how we are able to share information over the World Wide Web.

Firstly, the Internet is basically a globally connected network of “Computers + Wires + Common Rules”. The information that we share using our computers follows some common rules, and this data is transferred through wires.

Now naturally, the question arises: how is data transferred inside the wires?

So the answer is: today’s optical fibre cable (which we call “wires” in day-to-day language) carries the data in the form of pulses of light, which travel via the Total Internal Reflection phenomenon happening inside the cable. That is why this incredible thing called the Internet is able to share information so fast: because optical fibre can carry data at very high speed. (The physics behind optics has contributions from many scientists, including Albert Einstein.)

Now that we understand that data is transferred inside the wires in the form of pulses, we will understand how, from our devices (which are digital), these pulses are formed and then transferred.

To understand the whole process, we have a theoretical model that helps us understand data transfer. It is called the OSI (Open Systems Interconnection) Model. This model has seven layers: Application layer, Presentation layer, Session layer, Transport layer, Network layer, Data Link layer, and Physical layer.

We will not study the OSI model in depth in this blog, but this information is helpful in getting a clear picture of which network device operates at which layer.

In this blog, we will study these devices: Modem, Router, Switch, Hub, Firewall, Load Balancer.

Modem

When the data from the server comes to us, it first meets the modem installed in our homes. A modem operates mainly at the Physical Layer. As the name suggests, it modulates and demodulates the signal. The signal comes in the form of pulses, and the modem demodulates it to convert it into digital information (binary), which can be understood by our devices.

Hub

Earlier, after the modem, digital signals used to go to the next device called a hub. A hub works at the Physical Layer and its job is to broadcast the information it receives further.

But the problem with a hub is that it transfers the data to all the systems connected to it, which is inefficient because the data should be delivered only to the system which requested it, instead of distributing it to all systems.

Switch

To solve the problem of hubs, we started using switches. Switches operate at the Data Link Layer. Unlike hubs, switches are intelligent and they transfer the data coming from the modem to the correct connected device which requested it.

Switches remember the MAC (Media Access Control) address, due to which they are able to figure out which particular connected device made the request, and then they transfer the response only to that device. This makes switches more efficient and faster in local networks.

Router

The next device we study is the router. A router operates at the Network Layer (Layer 3) of the OSI model. It basically routes data between networks using IP addresses.

Routers maintain routing tables and can use routing protocols (like OSPF, BGP) to find the most efficient path across networks. In home networks, routers also commonly perform NAT (Network Address Translation), which helps multiple devices inside your home network use one public IP address to access the Internet.

Routers often also include DHCP, which automatically assigns local IP addresses to devices on your network.

Firewall

A firewall is positioned at the network edge (between your network and the Internet), and it is often called a perimeter firewall. It performs traffic filtering, access control, threat prevention, and network segmentation.

It examines packets by checking packet headers (source and destination) and sometimes also the payload content, depending on the type of firewall and its security rules.

Traditional firewalls focus on packet filtering and stateful inspection. Next-Generation Firewalls (NGFWs) include advanced features like deep packet inspection, intrusion prevention, and application control.

Load Balancer

The last device we will see in this blog is the load balancer. This is helpful when we have multiple servers on which requests can be made. The load balancer sits before the servers, so that the request coming from the client reaches the load balancer first, and then the load balancer (based on the algorithm with which it works) decides to which server the request should go.

It continuously monitors the health of the servers and also handles server failures. The moment a server crashes, the load balancer stops sending requests to that server. Load balancers also improve response time by distributing traffic correctly.

Some common load balancing algorithms are Round Robin, Least Connection, Least Response Time, IP Hash, and Weighted Round Robin.

Conclusion

So, this was a short quick intro to the working of essential networking devices. Even having this much understanding helps us visualize the internal processes easily.