The Transmission Control Protocol, or TCP as we will refer to it from now on, is one of the most important and well-known protocols in the world on networks today. Used in every type of network world-wide, it enables millions of data transmissions to reach their destination and works as a bridge, connecting hosts with one another and allowing them to use various programs in order to exchange data.

The Need For Reliable Delivery

TCP is defined by RFC 793 and was introduced to the world towards the end of 1981. The motivation behind creating such a protocol was the fact that back in the early 80s, computer communication systems were playing a very important role for the military, education and normal office environments. As such, there was the need to create a mechanism that would be robust, reliable and complete data transmission on various mediums without great losses.

TCP was designed to be able to deliver all of the above, and so it was adopted promptly by the rest of the world.

Because TCP is not the type of protocol you can analyse in one page, it has been separated and analysed over 11 pages in order to cover all its characteristics and help you gain a better understanding of how it works and what its capabilities are.

Article 1: TCP, A Transport Protocol. This page is a brief introduction to TCP. It will show you how TCP fits into the OSI Model, by using simple diagrams. It also helps you understand the concept of a "Transport Protocol".

Article 2: Quick TCP Overview. This page is aimed for readers requiring a good and quick overview of the protocol's features without getting into too much technical detail.

Article 3: The TCP Header/Segment. Find out what the "TCP Header" and "TCP Segment" refer to. These two terms are used quite often when talking about the protocol, thus it is essential we understand what these two terms are related to.

Article 4: In-Depth TCP Header Analysis: Introduction. This subsection is a whole topic in itself and deals with the in-depth analysis of the TCP Header. We examine each field step-by-step, using plenty of examples and our well known cool-3D diagrams to make sure you understand all the material. This analysis is covered over 7 pages of hardcore information, so be prepared!

Article 5: In-Depth TCP Header Analysis: Source & Destination Port Number. Find out what ports are and how they are used in a typical data transfer.

Article 6: In-Depth TCP Header Analysis: Sequence & Acknowledgement Numbers. At last, everything you wanted to know about sequence and acknowledgment numbers. We will cover them in much detail using plenty of diagrams to ensure you are not left with unanswered questions.

Article 7: In-Depth TCP Header Analysis: Header Length. We examine the meaning of this field and how it is calculated.

Article 8: In-Depth TCP Header Analysis: TCP Flag Options. This is one of the most important pages in our in-depth analysis. Here you will learn what these flags are, how many flags the protocol supports and lastly, how they are used. We will also examine how hackers can use specific flags to gain vital information on remote systems.

Article 9: In-Depth TCP Header Analysis: Window Size, Checksum & Urgent Pointer. These fields play one of the most important roles in bandwidth utilisation. Find out how you can increase data throughput and minimise delays between WAN links by playing around with these fields! This page is highly recommended for anyone seeking details about WAN link efficiency and data throughput.

Article 10: In-Depth TCP Header Analysis: TCP Options. This page is considered to be an extension to the previous one. Here you will learn about selective acknowledgments, window scalling and several other options available to TCP that ensure data is handled the best possible way as it transits to its destination.

Article 11: In-Depth TCP Header Analysis: TCP Data. The reason for all of the above! Our last section provides an overview of TCP protocol and concludes with several good notes.

You will surely agree that there is much to cover in this fantastic protocol. So, let us not loose any more time and begin our cool analysis! If you need to grab any brain food, now's your chance cause once we start .... there is no stopping till we're done!