TCP - Header

What is a TCP Header?

A TCP header is the portion of a TCP segment that contains control information such as source and destination ports, sequence numbers, flags, and more — essential for reliable communication.

Why is the TCP Header useful?

It enables key TCP features like reliable delivery, ordered data transfer, flow control, and congestion management by carrying the necessary metadata for managing the connection.

How does the TCP Header work?

The TCP header is added to each TCP segment and includes fields such as sequence number, acknowledgment number, flags (like SYN, ACK, FIN), and window size. These fields coordinate communication between sender and receiver.

Where is the TCP Header used?

The TCP header is used in every TCP segment exchanged between two hosts. It plays a critical role in all TCP-based applications like HTTP, FTP, SSH, and SMTP.

Which OSI layer does the TCP Header belong to?

The TCP header is part of the Transport Layer (Layer 4) in the OSI model.

Is the TCP Header Windows specific?

No, the TCP header structure is defined by networking standards and is the same across all platforms, including Windows, Linux, and macOS.

Is the TCP Header Linux specific?

No, it is universally implemented in all systems that support the TCP/IP protocol suite.

Which Transport Protocol uses the TCP Header?

Only TCP (Transmission Control Protocol) uses the TCP header. Other protocols like UDP use their own separate header formats.

Is the TCP Header used in the client-server model?

Yes, in every TCP-based client-server interaction, the TCP header ensures reliable and structured communication between the two endpoints.

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