TCP/IP (Transmission Control Protocol/Internet Protocol) is an industry standard suite of protocols that is designedgrey cable wires to drive the Internet. It is the basic communication protocol suite that implements the protocol stack on which the commercial networks and Internet work.

It has the ability to connect a number of different networks designed by different vendors, to internet. Today, every computer with a direct connection to internet has a copy of TCP/IP program to send and receive information over internet. IPv6

How TCP/IP Works?

TCP working diagram

A header is attached at the front of each datagram and it has at least 20 octets. The most important among them are the source and destination port numbers and sequence number. A sample datagram is shown below.

With TCP header attached, the datagram looks like this.

TCP header diagram

TCP sends each of these datagrams to IP and IP finds a route for the datagram. It adds its own header with source and destination Internet address, protocol number, and another checksum. With IP attached on its header, the message now looks like this.

TCP IP attached diagram

When a packet is on the Ethernet, every machine on the network sees the packet. To avoid this Ethernet Header is attached and it has source and destination Ethernet address, and type code. Type code allows the use of several different protocol families on the same network. A checksum is added at the end.

TCP diagram

When these packets arrive at the destination, all the headers are removed. The Ethernet interface removes the internet routerEthernet header and checksum. As the type code is assigned to IP, it passes the datagram to IP. IP removes IP header. As the protocol field has TCP, the datagram is passed to TCP. Based on the sequence number and other information, the datagrams are compiled back into the original file.

TCp information diagram

The TCP/IP suite’s protocol stack has four layers as defined in RFC 1122 and each layer has several protocols working to accomplish a specific task. There is a dependency at each level with a protocol at a higher level depends on a protocol at a lower level. Also, in a Peer-level communication, every protocol communicates with its peer, an equivalent layer on a remote computer.

TCP protocol layers diagram

OSI Protocol Reference Model

OSI Protocol Reference Model table

The OSI reference model consists of seven layers for specifying the data transfer between networks. This model developed by the International Organization for Standardization (ISO) in 1984, is the architectural model for inter-computer communications. It divides the tasks into manageable chunks across seven layers. Each layer has specific task and is self-contained for implementing its task independently.

Layer table
Protocols spanning the complete range of OSI model layers

OSI layer model table

The TCP/IP suite is based on the transmission technology work of DARPA in early 1970s. The milestones in its history are given below.

  • 1970 – ARPANET used Network Control Protocol (NCP), a preliminary form of TCP.
  • 1972 – Telnet protocol for terminal emulation to connect dissimilar systems was used.
  • 1973 – File Transfer Protocol (FTP) to exchange files between dissimilar systems was used.
  • 1974 -Transmission Control Protocol (TCP) to provide reliable communication service through internet replaced NCP.
  • 1975 – A two-network TCP/IP communications test was performed between Stanford and University College London.
  • 1977 – A three-network TCP/IP test was conducted between the U.S., UK, and Norway.
  • 1978 and 1983 – Several TCP/IP prototypes were developed at multiple research centers.
  • 1981 -Internet Protocol (IP or IPv4) to provide addressing and routing functions was used.
  • 1982 – Defense Communications Agency (DCA) and ARPA established the Transmission Control Protocol (TCP) and Internet Protocol (IP) as the TCP/IP protocol suite.
  • 1983 – ARPANET switched from NCP to TCP/IP.
  • 1984 – Domain Name System (DNS) to resolve domain names to IP addresses was used.
  • 1995 – Internet service providers (ISPs) started offering Internet access to businesses and individuals.
  • 1996 -Hypertext Transfer Protocol (HTTP) was introduced.
  • 1996 – IP version 6 (IPv6) standards were published.


  • It is a standard, complete and widely accepted routable enterprise networking protocol available.
  • It provides interoperable communications between all types of hardware and all kinds of operating systems.
  • It is highly reliable, robust cross platform client/server framework.
  • It provides a way to gain access to internet.
  • It is expandable and is responsible for the phenomenal growth of Internet.

Growth of Industry

Internet usage growth graph

Within a short period of time, Internet has seen an enormous growth in the number of its users. Today, most commercial operating systems install the TCP/IP stack by default and internet has become an easy but a powerful platform to exchange communication. With a very low investment, a business on internet can reach the whole world. It saves time and money by making distances shorter. According to plunkettresearch.com, the projections for online advertising in America have been as high as $19 billion for 2007. Internet has become a significant place for business and communication offering unlimited potentials to grow in every sector and TCP/IP has made this possible.