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
- IP - Internet Protocol
- 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
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
- 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:
- Application layer: protocols used by applications designed
for users services.
- Transport layer: creates a data channel for a specific
- Internet layer: sends data(packets) across computer networks.
- Link layer: moves data between the Internet layers of
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:
BGP, DHCP, DNS, FTP, HTTP,
IMAP, IRC, LDAP, MGCP, NNTP, NTP, POP,
RPC, RTP, RTSP, RIP, SIP, SMTP, SNMP,
SOCKS, SSH, Telnet, TLS/SSL,
DCCP, RSVP, SCTP, TCP, UDP.
ECN, ICMP, IGMP, IP
ARP, DSL, FDDI, ISDN, NDP, OSPF, PTPP,