Nov 2017

Internet Protocols

different types of Internet Communications Protocols


TCP and IP were developed by a Department of Defense (DOD) research project to connect a number different networks designed by different vendors into a network of networks (the “Internet”). It was initially successful because it delivered a few basic services that everyone needs (file transfer, electronic mail, remote logon) across a very large number of client and server systems. Several computers in a small department can use TCP/IP (along with other protocols) on a single LAN. As with all other communications protocol, TCP/IP is composed of layers:


IP – is responsible for moving packet of data from node to node. IP forwards each packet based on a four byte destination address (the IP number). The Internet authorities assign ranges of numbers to different organizations. The organizations assign groups of their numbers to departments. IP operates on gateway machines that move data from department to organization to region and then around the world.


TCP – is responsible for verifying the correct delivery of data from client to server. Data can be lost in the intermediate network. TCP adds support to detect errors or lost data and to trigger retransmission until the data is correctly and completely received.


Internet Hosts :

Each computer on the internet is called a host computer. The computers on the internet are millions of internet hosts, are connected by cables, phone lines and satellite connections.


Internet Protocol (IP) Addresses :

IP defines a universal addressing scheme called IP address. An IP address is a 32 bit binary addressing scheme and each standard address is unique on the internet. IP addressing scheme is used to identify networks, network devices and network connected machines. The purpose of IP address is to identify each connection to internet and to collect a group of connections to simplify routing.


Every IP address belongs to a distinct class. The class that the IP address belongs to initially determines the network ID and Host ID portion of the address. There are five different classes of address designed to meet the needs of different organizations. The various classes are given as A,B,C,D and E. the class range is presented in the table below:




First Octet




Default Subnet mask







First Octet







First 2 Octet






First 3 Octet













Finding the IP Address :

To find out your IP address on a Windows XP

On the Start Menu. Click Control Panel.

In the Control Panel window, click on Network and Internet Connections.

Click on the Network Connections

Double-click the local area connection and select Support

Local Area Connection

Connected, Firewalled

Broadcom NetXtreme 57xx Glg..


The following dialog box will appear on the screen :

Another way to find an IP address :

Open the command prompt. The command prompt is usually located within the Accessories

At the “Command Prompt” screen type ipconfig then press If this doesn’t work type in ipconfig/all.

C:\      Command Prompt
Microsoft Windows XP [V

<C> Copyright 1985-2001



  1. The IP address should appear along with other LAN details in the readout.

Windows IP Configuration

Ethernet adapter Local Area Connection:

Connection specific DNs Suffix   . :

IP Address . . . . . . . . . . . . . . . . . . . :

Subnet Mask . . . . . . . . . . . . . . . . . :

Default Gateway . . . . . . . . . . . . . . :


Note: For some computers, instead of typing ‘ipconfig’, users may have to type ‘ipconfig/all’ in the Command Prompt. Typically, ‘ipconfig/all’ shows more detailed information such as server information and the MAC address.


Domain and Host Names :

A domain name is a unique name associated with a specific IP address by a program that runs on an Internet host computer. Each part of domain is called the sub domain. The subdomains are separated by periods. The name is constructed so that each sub domain tells something about the computer. The rightmost sub domain is called the top-level domain.


Types of Domains :

Top level Domain :

The way to understand an address is to read from right to left. In general there are two types of top level domains.

  • Generic Domains/Organizational domains
  • Country Domains/Geographical domains

Generic Domains/organizational domains :

Organizational domains are based on an addressing scheme developed before the days of international networks.

.edu –Servers that provide Educational services

.gov –About the government of a country.

.mil –Servers that provide military information.

.org –Provide information about the organizations in the world.

.com –Servers providing commercial services on the Internet.

.net –Information services/network.

.int –organizations established by international treaty


Country Domains / Geographical domains :

The international top-level domain uses a 2-letter country code. Country code top-level domains are two letter designations assigned to individual countries. Each country linked to the web has a two-letter top-level domain. The following table shows the various country code top level domains.


   Domain Country
.af Afghanistan
.aq Antarctica
.at Austria
.bd Bangladesh
.bm Bermuda
.br Brazil
.bt Bhutan
.ca Canada
.ch Switzerland
.cn China
.co Colombia
.cu Cuba
.de Germany
.dk Denmark
.eg Egypt
.fr France
.hu Hungary
.in India
.it Italy
.is Island
.jp Japan
.kw Kuwait
.lk Sri lanka
.ly Libya
.ma Morocco
.mn Magnolia
.mx Mexico
.ng Nigeria
.nl Netherland
.nz New Zealand
.om Oman
.pk Pakistan
.qa Qatar
.sa Saudi Arabia
.sd Sudan
.se Sweden
.sg Singapore
.th Thailand
.tw Taiwan
.us United States
.uk United Kingdom


Example :



Servers and Clients :

Server :

Computer connected to a network that other computers may or may not access. Unlike other computers on a network, a server is a dedicated computer set up for one or more purposes. For example, a user may setup a server to authenticate and allow or prohibit users from accessing a network, send/receive e-mail, manage print jobs, or host a website.


Clients :

A client is a computer that retrieves information from or uses resources provided by a server or main computer. Many corporate networks are comprised of a client computer at each of the employees’ desks. Each of these computers connects to a central server or mainframe, which allows a lot of the processing to be done on the client side instead of the server side and reduces the processing requirements of the server


Here are some types of servers and clients that you may encounter:

Mail Servers:

Mail servers are used to receive email from local users and send the email to other users over the Internet. Mail servers use the SMTP (Simple Mail Transfer Protocol) or ESMTP (extended SMTP) to send mail and either POP 3 (Post Office Protocol 3) or IMAP (Internet Message Access Protocol) to receive email. Mail can be downloaded from the Internet into a email program such as Outlook or Evolution, or it can be accessed directly on line with sites such as Gmail or Hotmail.


Web Servers:

A web server accepts HTTP (hypertext transfer protocol) requests from a client and returns the appropriate HTML document. The web server maps the URL provided by the client to the specific document or program located on the server. It is the typical type of server that is accessed through a web browser. The most popular web servers, according to the August, 2009 Netcraft survey are the Apache Web server and Microsoft’s IIS (Internet Information Services).


FTP Servers:

FTP Servers are used to transfer files from one computer to another over the Internet. FTP servers allow for user authentication, file transfer policies and activity logging. FTP servers are accessed by a ftp client which allows the user to move the files between the server computer and the client computer. The client software can be a graphical application or, more traditionally, a command line application. FTP server software includes VSFTP, BulletProof FTP, and SurgeFTP. All operating systems have a command line FTP client available. Graphical FTP clients include FileZilla and SmartFTP.


News Servers :

They work as source of distribution and delivery for hundreds of available public news groups accessible over the USENET news network. USENET is global bulletin board system that can be approached via internet or via a variety of online services.


IRC Servers :

Internet Relay Chat is comprised of various independent networks of servers that allow users to connect to each other via an IRC network. It is an option for those who are seeking real time competence.


Port and Port Numbers :

A port is an additional 16-bit number that uniquely identifies the particular service on any given machine on the Internet. Port numbers are 16 bit wide, therefore each computer on the Internet has a maximum number of 216 or 65,536 ports. The particular application is identified by its unique port number in the same way that a specific television station has a unique channel number.


Port numbers are divided into three ranges:

  • Well-known ports are those from 0 through 1,023.
  • Registered ports are those from 1,024 through 49,151.
  • Dynamic and private ports are those from 49,152 through 65,535.

Well-known ports, those ranging from 0 through 1,023 are where most common services on the Internet are residing. These ports are controlled and assigned by the Internet Assigned Number Authority (IANA) and on most systems can be used only by system (root) processes or by programs executed by privileged users


The following table shows the protocolport numbers :

Port Number Protocol
21 File Transfer Protocol (FTP)
25 Simple Mail Transfer Protocol(SMTP)
80 Hyper Text Transfer Protocol(HTTP)
110 Post Office Protocol 3 (POP3)


Domain Name System and DNS Servers :

The domain address is converted into number internally. The part of the Internet that keeps track of addresses is called the DNS Domain Name System.


DNS server is a computer that translates the domain name of another computer into an IP (Internet Protocol) address and vice versa on request. Every computer in the network has an IP address, which specifies its physical network connection. To locate the information in Internet two kinds of addresses can be used. These are domain names and IP addresses. Domain names follow a format called Domain Name system.



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