TCP / IP (Transmission Control Protocol / Internet Protocol) is the communication protocol for communication between computers on the Internet.
It defines how electronic devices (like computers) should be connected to the Internet, and how data should be transmitted between them. Inside the TCP/IP standard there are protocols for handling data communication :
- TCP (Transmission Control Protocol) communication between applications
- UDP (User Datagram Protocol) simple communication between applications
- IP (Internet Protocol) communication between computers
- ICMP (Internet Control Message Protocol) for errors and statistics
- DHCP (Dynamic Host Configuration Protocol) for dynamic addressing
TCP takes care of the communication between your application software (browser) and your network software. It's responsible for breaking data down into IP packets before they are sent, and for assembling the packets when they arrive.
IP takes care of the communication with other computers. It's responsible for sending the packets to the correct destination.
Each computer must have an IP address before it can connect to the Internet.
Each IP packet must have an address before it can be sent to another computer.
This is an example of IP address : 173.194.38.178
This address have the same IP address : www.google.com
You can check an IP address using cmd by ping it
IP Address Consist of 4 Numbers.
Each computer have a unique IP address.
TCP/IP uses 4 numbers to address a computer. The numbers are between 0 and 255.
IP addresses are normally written as four numbers separated by a period, like this : 192.168.1.20.
32 Bits = 4 Bytes
In computer terms, TCP/IP uses 32 bits addressing. One byte is 8 bits. TCP/IP uses 4 bytes.
One byte can contain 256 different values:
00000000, 00000001, 00000010, 00000011, 00000100, 00000101, 00000110, 00000111, 00001000 .......up to 11111111.
Domain Names
A name is much easier to remember than a 12 digit number.
Names used for TCP/IP addresses are called domain names.
google.com is a domain name.
When you address a web site, like http://www.google.com, the name is translated to a number by a Domain Name Server (DNS).
All over the world, DNS servers are connected to the Internet. DNS servers are responsible for translating domain names into TCP/IP addresses.
When a new domain name is registered together with a TCP/IP address, DNS servers all over the world are updated with this information.
Some protocols used in the network :
TCP - Transmission Control Protocol
TCP is used for transmission of data from an application to the network. It's responsible for breaking data down into IP packets before they are sent, and for assembling the packets when they arrive.
IP - Internet Protocol
IP takes care of the communication with other computers. It's responsible for the sending and receiving data packets over the Internet.
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.
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.
SSL - Secure Sockets Layer
The SSL protocol is used for encryption of data for secure data transmission.
SMTP - Simple Mail Transfer Protocol
SMTP is used for transmission of e-mails.
MIME - Multi-purpose Internet Mail Extensions
The MIME protocol lets SMTP transmit multimedia files including voice, audio, and binary data across TCP/IP networks.
IMAP - Internet Message Access Protocol
IMAP is used for storing and retrieving e-mails.
POP - Post Office Protocol
POP is used for downloading e-mails from an e-mail server to a personal computer.
FTP - File Transfer Protocol
FTP takes care of transmission of files between computers.
NTP - Network Time Protocol
NTP is used to synchronize the time (the clock) between computers.
DHCP - Dynamic Host Configuration Protocol
DHCP is used for allocation of dynamic IP addresses to computers in a network.
SNMP - Simple Network Management Protocol
SNMP is used for administration of computer networks.
LDAP - Lightweight Directory Access Protocol
LDAP is used for collecting information about users and e-mail addresses from the internet.
ICMP - Internet Control Message Protocol
ICMP takes care of error-handling in the network.
ARP - Address Resolution Protocol
ARP is used by IP to find the hardware address of a computer network card based on the IP address.
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.
BOOTP - Boot Protocol
BOOTP is used for booting (starting) computers from the network.
PPTP - Point to Point Tunneling Protocol
PPTP is used for setting up a connection (tunnel) between private networks.
Email
When you write an email, you use an email program like Lotus Notes, Microsoft Outlook or Netscape Communicator.
Your email program uses different TCP/IP protocols:
It sends your emails using SMTP
It can download your emails from an email server using POP
It can connect to an email server using IMAP
SMTP - Simple Mail Transfer Protocol
The SMTP protocol is used for the transmission of e-mails. SMTP takes care of sending your email to another computer.
Normally your email is sent to an email server (SMTP server), and then to another server or servers, and finally to its destination.
SMTP can only transmit pure text. It cannot transmit binary data like pictures, sounds or movies.
SMTP uses the MIME protocol to send binary data across TCP/IP networks. The MIME protocol converts binary data to pure text.
POP - Post Office Protocol
The POP protocol is used by email programs (like Microsoft Outlook) 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.
IMAP - Internet Message Access Protocol
The IMAP protocol is used by email programs (like Microsoft Outlook) just like the POP protocol.
The main difference between the IMAP protocol and the POP protocol 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.