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What is TCP/IP and the Internet Protocol Suite
Introduction

TCP/IP is a collection of communications protocols that are used on computer networks that use packet switching. The Internet is basically a system of computer networks (nodes) that interlink using TCP/IP. The two original protocols of the TCP/IP protocol suite are:

  1. IP - Internet Protocol
  2. TCP - Transmission Control Protocol

The Internet Protocol (IP) defines the structure of data packets, and supports an addressing system that can route the data packet from it's host to it's destination. Every device connected to a computer network - that uses TCP/IP - is assigned an IP address. The method of assigning an IP address varies across computer networks; but the format of IP addresses is defined by the Internet Protocol (IP). Data packets sent across these computer networks are formatted by the Internet Protocol. Packets have two sections: a header and it's content. The header includes the IP address of it's source (host), the IP address of it's destination, and other information that is required to route the packet from it's source to it's destination.

The Transmission Control Protocol is classified as a transportation protocol. Software applications - that are designed for use on the Internet - use a range of application protocols, such as: HTTP (World Wide Web), SMTP (Email), POP3 (Email), IMAP (Email), and FTP (Downloading). TCP is the "bridge" or "middle man" between these application protocols, and the IP Protocol (IP). TCP helps application protocols send and receive packets of data in a accurate manner: it does this through an ordered transportation procedure that includes error-checking the delivery. While the data will by delivered by the Internet Protocol (IP), TCP ensures the delivery takes place without error.

Development of TCP/IP

TCP/IP was developed as a replacement to NCP (Network Control Program); which was the original protocol used on ARPANET. ARPANET was one of the first computer networks that used packet switching, and was a computer network which was a precursor to the Internet. Robert E. Kahn and Vinton Cerf are credited as the co-inventors of TCP/IP. TCP/IP was developed in the 1970's, and was applied to ARPANET in 1983. In May, 1974, Bob Kahn and Vinton Cerf first published a paper outlining a protocol for packet switching. This paper was a seminal moment in computer networking, and was named:

  • A Protocol for Packet Network Intercommunication.

To begin with, this protocol was a single protocol, like it's predecessor the Network Control Program, and was named the Transmission Control Program. Only later was it decided that a fragmented suite of interlinking protocols would be preferable. TCP/IP evolved slowly, being tested on a number of computer networks, before it was "the" standard protocol suite for what is termed the Internet. The birth of the Internet is viewed as the 1st of January, 1983: when ARPANET adopted TCP/IP protocol as it's standard protocol.

Why was TCP/IP developed? for it's versatility. It can successfully switch packets of all shapes and sizes, and works across a varieties of networks. TCP/IP has become the backbone of the Internet and its composite LANs, VPNs and WANs. As already stated, it is due to it's ability to switch packets from any computer systems, regardless of network peculiarities, operating system differences, or, packet differences. TCP/IP does not require specific software or hardware: all it requires is that the hardware and software used by a computer network is capable of packet switching.

TCP/IP evolves into the Internet protocol suite

As already stated, TCP/IP began life as a single protocol: the Transmission Control Program. It became apparent that a fragmented suite of protocols was needed to support the growing number of application protocols. The Transmission Control Program was separated into a suite of two protocols: IP and TCP (TCP/IP). TCP/IP was adopted by ARPANET in 1983, and during the 1980's it was adopted by many prominent computer networks; which had been using their own protocol systems.

From 1990-1995, the backbone infrastructure of the Internet (major computer networks that used TCP/IP) was transitioned from the control of government agencies (US) into the hands of private commercial companies. Internet access "boomed", new technologies were developed to cater to the new users, and the overall system began to be referred to as the "Internet", rather than the "Information Superway" or "Cyberspace".

Therefore, as the backbone system was called the Internet - before 1995 there was no standard name - TCP/IP became to be named the Internet protocol suite. Present day (2014), the Internet protocol suite is maintained by the Internet Engineering Task Force (IETF). TCP and IP are still the "core" protocols of the Internet protocol suite, and the Internet could not function without them. These two protocols deal with the "nuts and bolts" processes of the Internet; which is routing data to unique (IP) addresses. However, as the Internet has evolved, more protocols were added to support new technologies. One example of the evolution of technologies on the Internet is Voice 2.0 applications that use Voice-over-Internet Protocols.

Core protocols of the Internet protocol suite

  • IP - The Internet Protocol is a network layer protocol that moves data between host computers.
  • TCP - The Transport Control Protocol is a transport layer protocol that moves multiple packet data between applications.
  • UDP - The User Datagram Protocol is a transport layer protocol - like TCP - but is less complex and more reliable than TCP.
  • ICMP - The Internet Control Message Protocol: carries network error messages and other network software requirements.

Four layer model of the Internet protocol suite

The various protocols included in the Internet protocol suite have been classified into four "loosely" defined layers. The four layers are:

  1. Application layer: protocols used by applications designed for users services.
  2. Transport layer: creates a data channel for a specific application.
  3. Internet layer: sends data(packets) across computer networks.
  4. Link layer: moves data between the Internet layers of linked hosts.

The four layers listed above are listed within the correct hierarchy. The application layer refers to the software programs that end-users use on the Internet. For example, HTTP is in the application layer, this is the protocol used on the World Wide Web. The transportation layer helps these applications send and receive data packets across the Internet. Data packets are to sent from, and to, IP addresses. The Internet layer defines the structure of these packets, and the format of the IP address. The Internet layer also sends the packet with the aid of the transport layer; the transport layer ensures the packets are sent correctly. The link layer moves packets across the physical infrastructure; and supports the physical transmission of the data. Encapsulation is used between the different layers so that they can communicate. TCP, for example, will often encapsulate: HTTP, POP3 and FTP.

Within the above layers, you can find the following protocols:

Application layer:

BGP, DHCP, DNS, FTP, HTTP, IMAP, IRC, LDAP, MGCP, NNTP, NTP, POP, RPC, RTP, RTSP, RIP, SIP, SMTP, SNMP, SOCKS, SSH, Telnet, TLS/SSL, XMPP.·

Transport layer:

DCCP, RSVP, SCTP, TCP, UDP.

Internet layer:

ECN, ICMP, IGMP, IP

Link layer:

ARP, DSL, FDDI, ISDN, NDP, OSPF, PTPP, PPPoE

 


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