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Transmission Control Protocol (TCP)

By Kinza Yasar

What is Transmission Control Protocol (TCP)?

Transmission Control Protocol (TCP) is a standard that defines how to establish and maintain a network conversation by which applications can exchange data.

One of the main communication protocols of the IP suite, TCP resides at the transport layer of the Open Systems Interconnection (OSI) model. It works with the IP, which defines how computers send packets of data to each other. Together, TCP and IP are the basic rules that define the internet and ensure the successful delivery of messages over networks.

History of TCP

The emergence of the internet is intertwined with the history of the transmission control protocol. The following is a brief timeline of the key events in the history of TCP:

TCP is still being developed and standardized, with continual efforts to handle new challenges, improve performance and adapt to evolving networking environments.

Four layers of TCP/IP

TCP/IP is composed of four layers, each of which handles a certain function in the data transmission process.

The four layers of the TCP/IP stack include the following:

How Transmission Control Protocol works

TCP is a connection-oriented protocol, which means a connection is established and maintained until the applications at each end have finished exchanging messages.

TCP performs the following actions:

In OSI communication model, TCP covers parts of Layer 4, the transport layer, and parts of Layer 5, the session layer.

When a web server sends an HTML file to a client, it uses the HTTP to do so. The HTTP program layer asks the TCP layer to set up the connection and send the file. The TCP stack divides the file into data packets, numbers them and then forwards them individually to the IP layer for delivery.

Although each packet in the transmission has the same source and destination IP address, packets may be sent along multiple routes. The TCP program layer in the client computer waits until all packets have arrived. It then acknowledges those it receives and asks for the retransmission of any it does not, based on missing packet numbers. The TCP layer then assembles the packets into a file and delivers the file to the receiving application.

TCP vs. UDP

TCP and UDP are two different protocols used for transmitting data over the internet. The key differences between TCP and UDP include the following:

What TCP is used for?

TCP is used for organizing data in a way that ensures secure transmission between the server and the client. It guarantees the integrity of data sent over the network, regardless of the amount. For this reason, it is used to transmit data from other higher-level protocols that require all transmitted data to arrive.

Examples of these protocols include the following:

These examples all exist at the application layer of the TCP/IP stack and send data downwards to TCP on the transport layer.

Some important use cases of TCP include the following:

Why is TCP important?

TCP is important because it establishes the rules and standard procedures for the way information is communicated over the internet. It is the foundation for the internet as it currently exists and ensures that data transmission is carried out uniformly, regardless of the location, hardware or software involved.

TCP is flexible and highly scalable, meaning new protocols can be introduced to it. It will accommodate them. It is also nonproprietary, meaning no one person or company owns it.

Advantages and disadvantages of TCP

TCP provides the following advantages:

Along with its many benefits, TCP also comes with a few drawbacks. Common disadvantages of TCP include the following:

Location in the TCP/IP stack

The TCP/IP stack is a model that represents how data is organized and exchanged over networks using the TCP/IP protocol. It depicts a series of layers that represent the way data is handled and packaged by a series of protocols as it makes its way from client to server and vice versa.

TCP exists in the transport layer with other protocols, such as UDP. Protocols in this layer ensure the error-free transmission of data to the source, except for UDP because it has a more limited error-checking capability.

Like the OSI model, the TCP/IP stack is a conceptual model for data exchange standards. Data is repackaged at each layer based on its functionality and transport protocols.

Requests come down to the server through the stack, starting at the application layer as data. From there, the information is broken into packets of different types at each layer. The data moves in the following ways:

TCP/IP vs. OSI model

The OSI model and TCP/IP have a lot in common. For instance, they both offer a foundation for comprehending how various protocols interact with one another and with network communication. Both models support the idea of encapsulation, in which data is packaged into headers and trailers at each layer for transmission and have levels that define certain functionalities.

However, both models also have many differences:

11 Dec 2023

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