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What’s TCP IP? A further look into the protocol suite and model

Written by

greg jorgensen

Date published

July 29, 2023

Welcome! Firstly, TCP/IP stands for Transmission Control Protocol/Internet Protocol, a concatenation of two acronyms that create a larger, more complex acronym. At its core, it's a collection of protocols utilized for connecting devices on the internet. A protocol is simply defined as a set of rules that data follows.

Why is TCP/IP Important?

TCP/IP not only forms the backbone of the Internet, but it also provides a means of communication between various hardware and software systems. This aspect is crucial for the proper functioning of the internet.

Understanding the TCP/IP Model

The TCP/IP model is a conceptual framework that simplifies the process of sending and receiving data by dividing it into four distinct layers. This approach aids in understanding the role of each protocol and their interactions within the system.

The TCP/IP Stack

The TCP/IP model, also known as the TCP/IP stack, is akin to the 'rules of the road' for data on the internet. Systems need to adhere to these rules to send and receive data successfully. TCP/IP is composed of layers that build upon each other, each layer responsible for a different aspect of the data transmission process.

The Four Layers of the TCP/IP Model

The TCP/IP model comprises of:

Application Layer: This is where web browsers or email clients access network services. This layer hosts a wide range of protocols, including:

Hypertext Transfer Protocol (HTTP)
File Transfer Protocol (FTP)
Simple Mail Transfer Protocol (SMTP)
Domain Name System (DNS)
Telnet
Simple Network Management Protocol (SNMP)

Transport Layer: This layer handles the reliability aspect of data transmission. The primary protocols at this layer are:

Transmission Control Protocol (TCP)
User Datagram Protocol (UDP)
Datagram Congestion Control Protocol (DCCP)
Stream Control Transmission Protocol (SCTP)

Internet Layer: Also known as the Network Layer, this layer is used primarily for routing. It uses Internet Protocol (IP) addresses to route packets. This layer includes:

Internet Protocol (IP) - both IPv4 and IPv6
Internet Control Message Protocol (ICMP)
Internet Group Management Protocol (IGMP)
Address Resolution Protocol (ARP)
Routing Information Protocol (RIP)
Open Shortest Path First (OSPF)

Network Interface Layer: Also referred to as the Link Layer, this layer interfaces with network hardware. This layer consists of protocols that operate at the link level, such as:

Ethernet
Wi-Fi
Frame Relay
Point-to-Point Protocol (PPP)
Asynchronous Transfer Mode (ATM)

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Remember, the Internet layer and Network Interface layer can also be referred to as the Network layer and Link layer, respectively, due to the terminology used in the Internet Engineering Task Force's document RFC 1122. However, these original names were provided by the US Department of Defence, which initially developed this model, and are widely used.

How Does Data Flow in the TCP/IP Model?

Data always flows from the top (Application layer) to the bottom (Network Interface Layer) of the system sending the data and from the bottom to the top of the system receiving the data.

TCP/IP Model vs OSI Model

You may already be familiar with the OSI model, another network protocol framework. However, the OSI model has seven layers, compared to TCP/IP's four. The TCP/IP model is simpler, and some of its layers encompass multiple layers from the OSI model. While I personally find the TCP/IP model more practical for network troubleshooting and real-world applications, the OSI model may be more useful for a comprehensive understanding of all networking protocols.

The Journey of Data in the TCP/IP Model

Here's a simplified breakdown of how data travels using the TCP/IP model:

Starting at the Application Layer: The user interacts with an application that needs to send data over the network, like sending an email, opening a webpage, or streaming a video. The application layer prepares the data for the Transport layer through a process known as encapsulation.
Transport Layer: Here, data is divided into smaller pieces called segments. Each segment is assigned a source port number and a destination port.
Internet Layer: At this layer, segments are packaged into packets and assigned source and destination IP addresses, allowing routers to direct the packets.
Network Interface Layer: Packets are turned into frames and transmitted over the physical network, whether that's through an Ethernet cable, Wi-Fi, or something else. At this layer, the frames are encoded into bits (1s and 0s).

Once data reaches its destination, the process is reversed to de-encapsulate the data.

Summary of TCP/IP Model

To summarize, the TCP/IP model consists of four layers, each with a specific function, and can be remembered with the phrase: All Tech Is Needed. It's a much cooler model than the OSI model. It's important to note that multiple protocols can operate at each layer simultaneously, such as HTTP and DNS when browsing a website.

However, not all protocols fit neatly into the TCP/IP model as they do in the OSI model. Protocols like SSL or TLS might appear to fit between layers, which is why the TCP/IP model is sometimes expanded into five layers, though it typically contains four.

Thank you for reading.

I’ve made a youtube video using this article. Check it out if you’d like.