OVERVIEW OF TCP / IP
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 packets 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).
TCP/IP Protocols for the Web
Web
browsers and servers use TCP/IP protocols to connect to the Internet. Common
TCP/IP protocols are:
i.HTTP - Hyper Text Transfer Protocol
HTTP
takes care of the communication between a web server and a web browser. HTTP is
used for sending requests from a web client (a browser) to a web server,
returning web content (web pages) from the server back to the client.
ii.HTTPS - Secure HTTP
HTTPS
takes care of secure communication between a web server and a web browser.
HTTPS typically handles credit card transactions and other sensitive data.
iii.FTP - File Transfer Protocol
FTP takes
care of transmission of files between computers.
TCP/IP Protocols for Email
E-mail
programs use TCP/IP for sending and receiving e-mails. The TCP/IP protocols for
email are:
i.SMTP - Simple Mail Transfer Protocol
SMTP
takes care of sending emails. Often emails are sent to an email server (SMTP
server), then to other servers, and finally to its destination. SMTP can only
transmit pure text. It cannot transmit binary data like pictures, sounds or
movies.
ii.MIME - Multi-purpose Internet Mail Extensions
The MIME
protocol lets SMTP transmit multimedia files including voice, audio, and binary
data across TCP/IP networks. The MIME protocol converts binary data to pure
text, before it is sent.
iii.POP - Post Office Protocol
The POP
protocol is used by email programs to retrieve emails from an email server. If
your email program uses POP, all your emails are downloaded to your email
program (also called email client), each time it connects to your email server.
iv.IMAP - Internet Message Access Protocol
The IMAP
protocol works much like the POP protocol. The main difference is that the IMAP
protocol will not automatically download all your emails each time your email
program connects to your email server.
The IMAP
protocol allows you to look through your email messages at the email server
before you download them. With IMAP you can choose to download your messages or
just delete them. This way IMAP is perfect if you need to connect to your email
server from different locations, but only want to download your messages when
you are back in your office.
Other TCP/IP Protocols
ARP - Address Resolution Protocol
ARP is
used by IP to find the hardware address of a computer network card based on the
IP address.
BOOTP - Boot Protocol
BOOTP is
used for booting (starting) computers from the network.
DHCP - Dynamic Host Configuration Protocol
DHCP is
used for allocation of dynamic IP addresses to computers in a network.
ICMP - Internet Control Message Protocol
ICMP
takes care of error-handling in the network.
LDAP - Lightweight Directory Access Protocol
LDAP is
used for collecting information about users and e-mail addresses from the
internet.
NTP - Network Time Protocol
NTP is
used to synchronize the time (the clock) between computers.
PPTP - Point to Point Tunnelling Protocol
PPTP is
used for setting up a connection (tunnel) between private networks.
RARP - Reverse Address Resolution Protocol
RARP is
used by IP to find the IP address based on the hardware address of a computer
network card.
SNMP - Simple Network Management Protocol
SNMP is
used for administration of computer networks.
SSL - Secure Sockets Layer
The SSL
protocol is used to encrypt data for secure data transmission.
TLS - Transport Layer Security
The TLS
protocol is a newer and more secure version of SSL.
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