TCP/IP is the most pervasively used networking protocol in the history of networking. TCP stands for Transmission Control Protocol and IP stands for Internet Protocol. Every network built using any networking product today supports TCP/IP.

A networking model, sometimes also called either a networking architecture or networking blueprint. A protocol is a set of logical rules that devices must follow to communicate. The TCP/IP model both defines and references a large collection of protocols that allow computers to communicate. To define a protocol, TCP/IP uses documents called Requests For Comments (RFC).

When you buy a new computer today, it implements the TCP/IP model to the point that you can usually take the computer out of the box, plug in all the right cables, turn it on, and it connects to the network. You can use a web browser to connect to your favorite website. How? Well, the OS on the computer implements parts of the TCP/IP model. The Ethernet card, or wireless LAN card, built in to the computer implements some LAN standards referenced by the TCP/IP model. In short, the vendors that created the hardware and software implemented TCP/IP.

To help people understand a networking model, each model breaks the functions into a small number of categories called layers. Each layer includes protocols and standards that relate to that category of functions.

Now, let’s start discussing and understanding every layer one by one.

Application Layer:

TCP/IP application layer protocols provide services to the application software running on a computer. The application layer does not define the application itself, but it defines services that applications need. For example, application protocol HTTP defines how web browsers can pull the contents of a web page from a web server. In short, the application layer provides an interface between software running on a computer and the network itself.

Transport Layer:

Transport layer protocols provide services to the application layer protocols that reside one layer higher in the TCP/IP model. There two important tasks that are done by Transport layer. One is, dividing the data into smaller pieces so that, transportation of data can be handled easily. Other most important task of Transport layer is, surety of transferring of data from source to the destination. The two commonly used transport layer protocols are the Transmission Control Protocol(TCP) and User Datagram Protocol(UDP).

The main important task of this layer is to divide the data into smaller segments. The segmentation is done in order to avoid many problems. Two important reasons of segmentation are:

1- If some data is lost in between transportation then, segmentation makes troubleshooting easy.

2- Lets suppose our data is of 10 GB but the medium is capable of transferring only 10 MB then data could not pass through that medium. Here, segmentation is very important, dividing the data into segments of size <10 MB so that data can easily pass through that medium.

Network Layer:

The third-lowest layer of the TCP/IP Model is the network layer. If the data link layer is the one that basically defines the boundaries of what is considered a network, the network layer is the one that defines how internetwork (interconnected networks) function. The network layer is the lowest one in the OSI model that is concerned with actually getting data from one computer to another even if it is on a remote network; in contrast, the data link layer only deals with devices that are local to each other.

The most common network layer protocol is of course the Internet Protocol(IP). IP is the backbone of the Internet, and the foundation of the entire TCP/IP protocol suite. The network layer of the TCP/IP networking model works much like the postal service. IP defines that each host computer should have a different IP address, just as the postal service defines addressing that allows unique addresses for each house, apartment, and business. Similarly, IP defines the process of routing so that devices called routers can work like the post office, forwarding packets of data so that they are delivered to the correct destinations. Just as the postal service created the necessary infrastructure to deliver letters—post offices, sorting machines, trucks, planes, and personnel—the network layer defines the details of how a network infrastructure should be created so that the network can deliver data to all computers in the network.

Data Link Layer:

This layer is responsible for link establishment and termination, frame traffic control, sequencing, acknowledgement, error checking, and media access management. The most familiar standards used at the data link layer include IEEE 802.3 (Ethernet) Media Access Control (MAC) and Logical Link Control (LLC) sublayers. The LLC acts as an interface between the physical layer and the MAC sublayer, and the MAC sublayer provides the ability for multiple terminals (computers) to communicate over the same physical medium. Other standards examples include Asynchronous Transfer Mode (ATM), High-Level Data Link Control (HDLC), Frame Relay and the Point to Point Protocol (PPP).

Physical Layer:

Layer 1 of the TCP/IP Model is named the physical layer because it is responsible for the transmission and reception of wire level data. For example, the physical layer is where it is dictated how bits are represented across a specific networking medium. Regardless of whether the networking medium is electrical or optical in construction, the physical layer handles how data is physically encoded and decoded; examples of this would include whether a specific voltage on an electrical medium represents a 1 or 0 or another example would be how a light received at a specific wavelength would be interpreted. Standards examples include IEEE 802.3 (Ethernet), IEEE 802.11 (Wireless Ethernet) and Synchronous optical networking (SONET) among others.

Overview:

The top two layers focus more on the applications that need to send and receive data. The bottom layer focuses on how to transmit bits over each individual link, with the Internet layer focusing on delivering data over the entire path from the original sending computer to the final destination computer.

All of this must have left you scratching your head probably. Don’t worry, you will learn everything soon! I hope, this will be helpful for you!

Please comment, if I missed anything or misstated anything.

Thanks!