TCP/IP is a communications protocol that is used on packet switching
computer networks. The creation of TCP/IP was funded by DARPA; DARPA
was an agency of the U.S. Department of Defense. TCP/IP was coinvented
by Bob Kahn and Vint Cerf, who worked for DARPA in the 1970's. TCP/IP
became a U.S. Department of Defense standard in 1980, and was originally
called: DoD TCP/IP.
DARPA created the Internet Architecture Board (IAB) in 1983 to
oversee the evolution of TCP/IP. TCP/IP was applied to a range of
U.S. federally funded computer networks in the 1980's, such as:
ARPANET, NSFNET, MILNET, ESNET, amongst others. TCP/IP was also
used by a range of commercially funded computer networks in the
1980's, such as: CERFnet, PSInet and UUnet.
When TCP/IP computer networks were interconnected in the 1980's,
they became the Internet (interconnected networks).
From 1992-2014 (present day), oversight and leadership of the Internet
Architecture Board (IAB) changed hands: previously DARPA (U.S. federal
government), presently the Internet Society (international organisation).
TCP and IP are now the core protocols of the Internet protocol suite,
and the Internet protocol suite is openly engineered by organisations
under charter from the Internet Society.
Development of TCP/IP
ARPA funded the creation of the first American wide area computer
networks (ARPANET) in the late 1960's. ARPA were renamed to DARPA
in the early 1970's. ARPANET used the Network Control Program (NCP)
to traffic data between it's nodes (locations). The Network Control
Program (NCP) was written by the computer scientists who created
ARPANET, and, therefore, the creation of the Network Control Program
(NCP) was funded by DARPA.
Vint Cerf had collaborated in the creation of the Network Control
Program (NCP), and Bob Kahn was part of the BBN team which built
the routers (IMPs) for ARPANET. DARPA employed Bob Kahn (he previously
worked at BBN) in 1972, and Bob Kahn had an idea for a new 'open'
network architecture which could replace the Network Control Program
(NCP). In 1973, Bob Kahn invited Vint Cerf to help develop his idea
into a working protocol. In May, 1974, Bob Kahn and Vinton Cerf
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.
The first working protocol that Kahn and Cerf developed was called
the Transmission Control Program; like it's predecessor, the Network
Control Program, it was a single protocol 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. TCP/IP eventually became a Department of Defense
(DoD) standard in 1980, and was named DoD TCP/IP. While TCP/IP was
funded by DARPA and the U.S. Department of Defense, it was implemented
on a variety of U.S. federal and commercial networks in the 1980's.
TCP/IP was implemented onto ARPANET (replacing NCP) on the 1st of
As the number of TCP/IP computer networks grew in the 1980's, the
importance of it's continuing development was apparent. In 1983,
DARPA created the Internet Activities Board (IAB) to oversee the
development of TCP/IP. The Internet Activities Board (IAB) continue
(as of 2014) to oversee the development of TCP/IP, but, leadership
of the IAB is no longer provided by DARPA: instead it is provided
by the Internet Society. TCP and IP (TCP/IP) are now the core protocols
of the Internet protocol suite.
What are TCP and IP
The Internet is basically a system of computer networks that interconnect
using a software system named TCP/IP. TCP/IP is comprised of two
- IP - Internet Protocol
- TCP - Transmission Control Protocol
The Internet Protocol (IP) defines the structure of data
packets (blocks of data sent from one location to another), and
creates an address system that can route a 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 (TCP) is classified as
a transportation protocol. Services that are designed for 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.
TCP/IP evolves into the Internet protocol suite
When TCP/IP was developed in the 1970's, the number of Internet
protocols was fairly modest. While protocols, like FTP (File Transfer
Protocol), had been created to send files across ARPANET, the amount
of protocols (services) on the Internet was limited. In the 1980's,
when TCP/IP networks began to interconnect - NSFNET, ARPANET, CSNET
- more protocols were developed to create gateways and route data
between these networks. The DNS protocol was created in the 1980's
to more easily locate resources on TCP/IP networks. By the 1990's,
due to the popularity of the Internet, new services began to be
designed for the Internet, most notable the World Wide Web (e-tailing).
By 2000, even more protocols, like Voice-over-Internet
Protocols for Voice 2.0 application
Therefore, there came a point in time that TCP and IP, while being
the core protocols of the Internet, did not accurately describe
the full collection of Internet protocols. Therefore, instead of
being referred to as the TCP/IP protocol suite, the protocols of
the Internet were named the Internet protocol suite. Present
day (2014), the Internet protocol suite is engineered by the Internet
Engineering Task Force (IETF); leadership of the IEFT is provided
by the IAB and Internet Society. TCP and IP are still the "core"
protocols of the Internet protocol suite;
the Internet could not function without them. TCP and IP protocols
deal with the "nuts and bolts" processes of the Internet:
creating a technical architecture where data can be routed from
one address to another.
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.
A computer network does not need to implement all the protocols
of the Internet protocol suite to access the Internet, but, at a
minimum, it should support the following protocols:
- Address Resolution Protocol (ARP)
- Internet Protocol (IP)
- Internet Control Message Protocol (ICMP)
- Internet Group Management Protocol (IGMP)
- Transmission Control Protocol (TCP)
- User Datagram Protocol (UDP)
Every device that is connected to the Internet is assigned an IP
address; the Domain Name System is used to locate IP addresses via
domain names. Management of IP address blocks and the Domain Name
System is managed by the Internet Assigned Numbers Authority (IANA).
Jon Postel, while working at the Information Sciences Institute
(ISI), created IANA in 1990 (although it had unofficially operated
for over a decade).
TCP and IP (TCP/IP) are the core protocols of the Internet protocol
suite. Other Internet protocols - like Telnet, FTP and SMTP - which
were originally developed for ARPANET - are also a part of the Internet
protocol suite. The Internet protocol suite is based upon a four
layer networking model. The Internet's four layer model should not
be confused with the OSI seven layer networking
model; while there are similarities between the two models, they
are different models. For more information about computer networking
models: ANSI; Daisy
Chain; Extranet's, Intranet's
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 IP addresses. 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.
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,