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TCP/IP Model

The TCP/IP model is a streamlined alternative to the OSI model that more accurately reflects how modern networking protocols are structured and used in practice. It consolidates the OSI's seven layers into four, aligning closely with contemporary technologies like HTTP and Ethernet.

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About this video

The TCP/IP model is a four-layer networking framework that better represents how modern protocols function compared to the older OSI model. Where the OSI model separates communication into seven distinct layers — Application, Presentation, Session, Transport, Network, Data Link, and Physical — the TCP/IP model consolidates these into Application, Transport, Internet, and Network Access, reflecting the way contemporary technologies are actually built and deployed. The OSI model's top three layers — Application, Presentation, and Session — are merged into a single Application layer in the TCP/IP model. This consolidation makes sense for protocols like HTTP, which do not rely on separate presentation or session layer handling as older protocol suites did. The Transport layer carries over unchanged, while the OSI's Network layer is renamed Internet to more precisely reflect IP-based routing. At the bottom, the Data Link and Physical layers are grouped together as Network Access, representing local connectivity functions. Despite the TCP/IP model's more practical framing, the OSI model retains relevance because many established standards still reference its layer definitions. Ethernet, for example, spans OSI Layers 1 and 2 — the Physical and Data Link layers — and the entire IEEE 802 standards family, which covers Ethernet, wireless LAN, and wireless PAN, is organized around this two-layer boundary. Familiarity with both models provides a complete foundation for understanding how networking protocols are defined, categorized, and implemented across different environments.

What you'll learn

What's covered

TCP/IP Model Overview

Aligned to

CompTIA Network+
1.1 Explain concepts related to the Open Systems Interconnection (OSI) reference model.
Cisco CCST Networking
1.1 Identify the fundamental conceptual building blocks of networks
1.5 Describe common network applications and protocols
Cisco CCST Cybersecurity
2.1 Describe TCP/IP protocol vulnerabilities
CompTIA A+ Core 1
2.1 Compare and contrast Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) ports, protocols, and their purposes.

Key terms

Open Systems Interconnection Model
OSI
A conceptual framework that standardizes network communication into seven distinct layers.
TCP/IP
The suite of communication protocols used to interconnect network devices on the internet.
Application Layer
The topmost layer of the OSI model (Layer 7) that provides network services directly to end-user applications.
Presentation Layer
Layer 6 of the OSI model, responsible for data translation, encryption, and compression.
Session Layer
Layer 5 of the OSI model, responsible for establishing, managing, and terminating communication sessions.
Transport Layer
Layer 4 of the OSI model, responsible for end-to-end communication, flow control, and error recovery.
Network Layer
Layer 3 of the OSI model, responsible for logical addressing and routing data packets between networks.
Data Link Layer
Layer 2 of the OSI model responsible for node-to-node data transfer and error detection on a single network segment.
Physical Layer
Layer 1 of the OSI model, responsible for the transmission of raw bits over a physical medium.
Network Access Layer
The bottom layer of the TCP/IP model that combines the OSI Data Link and Physical layers, handling hardware addressing and physical transmission on a local network.
Internet Layer
The TCP/IP model layer that corresponds to the OSI Network layer, responsible for logical addressing and routing packets across networks using protocols such as IP.

Transcript

The OSI model is not the only model that explains networking. The TCP/IP model also explains networking, and it's a little more updated. So let's take a look at what the TCP/IP model looks like and how it's applied.

The OSI model is still worth knowing

There's still a lot of value in knowing the OSI model, even though the TCP/IP model might be a little updated. That is, some protocols that we work with out there are still going to fall in line with this OSI model.

Let's use Ethernet as an example. Here we have layer 3. This is the networking. This would be like IP version 4 — that would sit right here, and that doesn't change, that's relatively stable there. Then we have this data link layer here, that's layer 2. And then we have the physical layer, this is layer 1.

What I want to illustrate with this is that the data link layer is split into two different sub-layers here. And Ethernet here, we can see, spans the two different layers, layer 1 and layer 2. If you look at this, this is all related. These are all the 802s, and it defines things like the wireless LAN, Ethernet, wireless PAN, and this layer right here. So what I'm trying to say is that really we can just group this all up as being layer 1 and layer 2 — it's all kind of the same 802 arena here.

I had also mentioned the same thing with HTTP traffic. The HTTP traffic is all just an application layer, and we really don't have the presentation and session layer like we do with some of the older protocol suites that we have.

Mapping OSI onto TCP/IP

Here is the OSI model right here. We've got application, presentation, session, transport, network, data link, and physical.

Since a lot of our technologies really just group up these three, we just call this the application layer with the TCP/IP model. Notice that the transport layer stays the same. We've changed the terminology from network to the internet. And then the data link and physical are replaced with network access, so that's the local access there.

So this is the TCP/IP model. It's just a little bit different, but it really expresses some of our more recent protocols, or the more popular protocols nowadays.

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