What is a Network Model?

To understand networking, let’s first look at human communication. People need a common language to talk to each other. Imagine someone who speaks only English trying to communicate with someone who speaks only Chinese.

Figure 1 – Communication Without a Shared Language
Without a shared language, communication is impossible. Networking devices face the same challenge: equipment from different vendors cannot talk together unless they follow a common model.
So, what is a network model?
A network model is a set of structures that allows devices from any brand to communicate with each other. It acts like a universal language that all devices can understand. Without a common language, each device would communicate in its own way. This would make communication between brands impossible.
But this structure alone isn’t enough; it needs rules to function. That’s where protocols come in.

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A protocol is a set of rules that defines how devices exchange data across a network. You can think of it as a language for computers. If two devices use different protocols, they can't understand each other. It’s just like two people who don’t share the same language.
There are many types of protocols, each with its own role. For example:
Some handle IP addressing (like IP).
Others manage data delivery (like TCP).
Others handle file transfer (like FTP).
So how do we make all these protocols work together? That’s the role of the network model: it organizes them into layers. Each layer handles a specific part of communication. It uses certain protocols to complete its task.
In short:
Protocols do the work.
The model tells them where and how to work.

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Which protocol handles file transfer?
Imagine the 1980s: no iPhones, no fiber optics, no Instagram. The first laptops were just being invented.
In the early days of networking, big companies like IBM and DEC, as well as smaller makers, built their own unique models.
Figure 2 – Proprietary Communication in the 1980s
As you can see above, proprietary models are created for each manufacturer of network devices. These models are used to design their own communication languages.
The main issue with these proprietary models was that they only let devices from the same vendor communicate.
This means that devices from one vendor couldn’t communicate with those from another because each used a unique set of rules.
The problem in the 1980s.
Imagine you buy networking gear from IBM. Later, you want to add a new device from another vendor, like DEC. These devices can't talk to each other, like an English speaker trying to talk to someone who only knows Chinese.
Figure 3 – Communication Breakdown Between Vendors in the 1980s
Without a common language, communication was impossible!
This proprietary model makes it difficult for devices to communicate with each other.
This made networking extremely difficult in the 1980s.
Challenges of Proprietary Models
Compatibility problems Devices will only be able to communicate with the same manufacturer.
Vendor Dependence: Companies had to rely on one vendor's equipment. This made upgrades costly and complex.
Added complexity: Solutions were needed to connect devices from different vendors. This made networks harder to manage.
Limited Growth: Expanding networks was hard and expensive. They needed a redesign for every change.
The Consequences
To solve these problems, the need for a vendor-neutral approach emerged. We needed a standard way to communicate. This way, devices from any maker could connect without difficulty. This created a shared understanding of a network model for the whole industry.

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What's the first challenge of proprietary models?