TCP /IP PROTOCOL

TCP/IP (Transmission Control Protocol/
Internet Protocol) is the basic
communication language or protocol of
the Internet. It can also be used as a
communications protocol in a private
network (either an intranet or an
extranet ). When you are set up with
direct access to the Internet, your
computer is provided with a copy of the
TCP/IP program just as every other
computer that you may send messages to
or get information from also has a copy of
TCP/IP.
TCP/IP is a two-layer program. The higher
layer, Transmission Control Protocol,
manages the assembling of a message or
file into smaller packet s that are
transmitted over the Internet and
received by a TCP layer that reassembles
the packets into the original message.
The lower layer, Internet Protocol ,
handles the address part of each packet
so that it gets to the right destination.
Each gateway computer on the network
checks this address to see where to
forward the message. Even though some
packets from the same message are
routed differently than others, they'll be
reassembled at the destination.
TCP/IP uses the client/server model of
communication in which a computer user
(a client) requests and is provided a
service (such as sending a Web page) by
another computer (a server) in the
network. TCP/IP communication is
primarily point-to-point, meaning each
communication is from one point (or host
computer) in the network to another
point or host computer. TCP/IP and the
higher-level applications that use it are
collectively said to be "stateless" because
each client request is considered a new
request unrelated to any previous one
(unlike ordinary phone conversations that
require a dedicated connection for the
call duration). Being stateless frees
network paths so that everyone can use
them continuously. (Note that the TCP
layer itself is not stateless as far as any
one message is concerned. Its connection
remains in place until all packets in a
message have been received.)
Many Internet users are familiar with the
even higher layer application protocols
that use TCP/IP to get to the Internet.
These include the World Wide Web's
Hypertext Transfer Protocol ( HTTP), the
File Transfer Protocol (FTP), Telnet
( Telnet ) which lets you logon to remote
computers, and the Simple Mail Transfer
Protocol ( SMTP). These and other
protocols are often packaged together
with TCP/IP as a "suite."
Personal computer users with an analog
phone modem connection to the Internet
usually get to the Internet through the
Serial Line Internet Protocol (SLIP) or the
Point-to-Point Protocol (PPP ). These
protocols encapsulate the IP packets so
that they can be sent over the dial-up
phone connection to an access provider's
modem.
Protocols related to TCP/IP include the
User Datagram Protocol ( UDP ), which is
used instead of TCP for special purposes.
Other protocols are used by network host
computers for exchanging router
information. These include the Internet
Control Message Protocol ( ICMP), the
Interior Gateway Protocol (IGP ), the
Exterior Gateway Protocol (EGP), and the
Border Gateway Protocol (BGP ).