TCP/IP Overview
Tags: model, network, beginners
Published: 2021-12-30 11:36:39

## TCP/IP model
Transmission Control Protocol and Internet Protocol (TCP/IP) is a network model using current internet architecture to standardize computer networking, just like the Open System Interconnection (OSI) model. OSI is widely referenced but TCP/IP is a more recommended model. The main idea of TCP/IP is to allow an application on a computer to send data packets or communicate to another application running on a different computer.

## Layers of TCP/IP
4 Application layer
3 Transport layer
2 Internet layer
1 Data link and physical layer

These are the original layers numbered from the bottom up just like the OSI model. However the layers have been updated to:

5 Application layer
4 Transport layer
3 Network layer
2 Data link layer
1 Physical layer

One splitted layer and one renamed layer. The application, presentation and session layers of the OSI model are compressed to form just the application layer for the TCP/IP model.

**Layer 5/Application:** This is mainly used for data representation and application interface. Here we have application protocols such as Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP) and Simple Mail Transfer Protocol (SMTP).

**Layer 4/Transport:** This s a process to process communication with the use of port addresses (source and destination) to identify services or applications. The two most common transport protocols are Transmission Control Protocol (TCP) and User Data-gram Protocol (UDP).

**Layer 3/Network:** This is a node to node communication with the help of IP address to identify devices on a network, routers operate on this layer.

**Layer 2/Data link:** This contains Ethernet and switches. Ethernet also has source and destination addresses but they’re physical addresses, that means they are burned addresses from the company that can’t be changed by user. This layer also helps with flow control and error control.

**Layer 1/Physical:** This is every device that we can felt and touched, like network interface cards and cables. Physical layer takes bits and produces a signal to carry them.


## How the layers work.
As we send data, each layer will add it’s own bit of information, this is the encapsulation process, where the physical layer transmits the data over to the receiving device, the receiving device then starts to decapsulate the data.
Staring from the application layer which is simply the data, it is passed down to the next layer where the transport information is added, an example could be a TCP header, the data has now been transformed into a segment by breaking the data into pieces, then it moves to the network layer where the IP header is added, causing the segment to become a packet, then moves to the data link layer, Here it’s given a header and a trailer, The header contains mainly the source and destination MAC address and the trailer contains some error checking information to make sure the receiver receives the data correctly, and our packet has been made a frame. Lastly the physical layer, the data is then physically transmitted, thereby completing the encapsulation process.
The encapsulation process has been completed once the data has been transmitted to the receiving computer. To start the decapsulation process, It will check the destination MAC address for that frame and if the frame is correct it will process further to checks the IP information of the packets, again if the packet is correct it will process further to the transport information where it is read and the application data is sent to the receiving application.

## How some protocols work efficiently well with the TCP/IP model:
Application protocol HTTP shows how web browsers can get contents of a web page from a web server, HTTP has the functionality to ask for contents of web pages by enabling the web browser to request files from the server and giving the server a way to return the contents of those files with the help of uniform resource locators (URL) or universal resource identifiers (URI). This HTTP header includes the request to get a file, the request typically contains the name of the file.

Transport protocol TCP is widely know for it’s feature of error recovery, it’s works as the error recovery service provided to application layer. TCP/IP needs a mechanism to guarantee successful delivery of data across a network. the TCP header shows a sequence number (SEQ) with each message the network has a problem and fails to deliver the TCP message called a segment with example sequence number7, message7 was lost, that realization by TCP logic causes TCP to send a TCP segment back to the server asking to resend message7. 

Network protocol IP provides several features most importantly addressing and routing. Routers are networking devices that connect the parts of the TCP/IP network together for the purpose of routing IP packets to the correct destination. Routers receive IP packets on various physical interfaces, make decisions based on the IP address included with the packet and then physically forward the packet out to other network interfaces. The TCP/IP network layer using the IP protocol provides a service of forwarding IP packets from one device to another. Sending data back and forth to IP addresses is called IP routing.

Data link layer and physical layers define the protocols and hardware required to deliver data across some physical network. The physical layer defines the electrical signals that flow over the cables, rules and conventions exist when sending data over the cable however those rules exist in the data link layer, when a host or router’s IP process chooses to send an IP packet to another router or host, the host or router then uses data link layer details to send that packet to the next host/router.


## Conclusion
TCP/IP  is very modular, this makes it easy to add additional protocols and hardware when they are developed. TCP/IP was produced to make sure that data is reliable on the Internet because with ARPANET everything was very sensitive. This model shows a grand overview of how systems on a network behaves. It helps make everything user-friendly, It also avoids repeating work already done by  some other standards body or vendor consortium by simply referring to standards or protocols created by those groups.
Layer 7, 6 and 5 of the OSI model are grouped in to produce PDU for the transport layer of the TCP/IP model called data. The PDU is mostly in the form of binary. PDU is the data that is broken into segments. We segment our data for security and multiplexing.