What is TCP / IP?

Internet Protocol (IP) serves as the internet’s fundamental addressing system, responsible for dispatching data packets from the originating device to the recipient device. IP forms the backbone of all network connections and, in essence, underpins the internet. However, IP alone does not manage the sequence of data packets nor error checking – this is where the Transmission Control Protocol (TCP) comes into play.

To better grasp the TCP/IP relationship, imagine it as sending a jigsaw puzzle with a message via mail. The message gets fragmented into multiple pieces, which then embark on different mailing routes, each with its own duration. Upon arrival, the puzzle pieces, possibly in disarray, IP ensures they reach the correct address, while TCP acts as the puzzle assembler. TCP arranges the pieces correctly, requests for missing pieces to be resent, and confirms the complete reception of the puzzle to the sender. TCP maintains the connection with the sender throughout the entire process.

Being a connectionless protocol, IP individually addresses and routes each data unit from the source device to the recipient device, bypassing the requirement for the recipient to acknowledge receipt back to the source. This is where TCP becomes invaluable. Working in tandem with IP, TCP secures a connection between the sender and receiver, ensuring the correct sequence of data packets.

Take email transmission via TCP as an instance. A connection initiates, followed by the execution of a 3-way handshake. Firstly, an SYN (Synchronization) “initial request” packet initiates dialogue from the sender to the recipient server. Following this, the recipient server sends a SYN-ACK (Synchronization-Acknowledgement) packet consenting to the communication. Subsequently, the sender confirms the process by sending an ACK (Acknowledgement) packet to the recipient. Then the email content is segmented into packets and dispatched into the internet, where they traverse through a series of gateways before landing at the recipient device. Here, TCP reassembles the packets to restore the email’s original content.

The current dominant version of IP used on the internet is Internet Protocol Version 4 (IPv4). However, due to limitations on the total number of possible IPv4 addresses, a newer protocol, the IPv6, was developed. The IPv6 offers a substantially expanded address pool and is gaining increasing acceptance.

The OSI model emphasizes a communication system divided into seven distinct layers, each built upon its predecessor. This model covers seven layers – physical, data link, network, transport, session, presentation, and application layers.