Fourth Chapter Lesson-3: IP address, Web address or URL

At the end of this lesson-

  • 1. You will be able to explain IP address.
  • 2. You will be able to differentiate IPV4 and IPV6.
  • 3. You will be able to describe different parts of URL or web address.


IP address: An Internet Protocol address (IP address) is a logical numeric address that is assigned to every single computer, printer, switch, router or any other device of a TCP/IP-based network. An IP address is a logical address that is used to uniquely identify every node in the network. Because IP addresses are logical, they can change.

The numerals in an IP address are divided into 2 parts:

  • The network part specifies which networks this address belongs to and
  • The host part further pinpoints the exact location.

There are two primary types of IP address formats used today — IPv4 and IPv6.

IPv4: IPv4 uses 32 binary bits to create a single unique address on the network. An IPv4 address consist of four sets of numbers from 0 to 255, separated by three dots. Each number is the decimal (base-10) representation for an eight-digit binary (base-2) number, also called an octet. For example:

The total number of IPv4 addresses ranges from to There are 232 or 4,294,967,296 possible IP addresses. While this may seem like a large number, it is no longer enough to cover all the devices connected to the Internet around the world. Therefore, many devices now use IPv6 addresses.

IPv6: IPv6 uses 128 binary bits to create a single unique address on the network. An IPv6 address is expressed by eight groups of hexadecimal (base-16) numbers separated by colons, as in 2001:cdba:0000:0000:0000:0000:3257:9652. Groups of numbers that contain all zeros are often omitted to save space, leaving a colon separator to mark the gap (as in 2001:cdba::3257:9652).

There are 2128 or 3.4 x 1038or 340 undecillion) possible IPv6 addresses, meaning we shouldn’t run out of IPv6 addresses anytime soon.


Static Versus Dynamic IP Addresses:

IP addresses are assigned in two different ways. They may be dynamically assigned (they can change automatically) or statically assigned (they’re intended not to change, and must be changed manually). Most home networks use dynamic allocation.

An IP address can be static or dynamic. A static IP address will never change and it is a permanent Internet address. A dynamic IP address is a temporary address that is assigned each time a computer or device accesses the Internet.


IP address classes:

With an IPv4 IP address, there are five classes of available IP ranges: Class A, Class B, Class C, Class D and Class E, while only A, B, and C are commonly used. Each class allows for a range of valid IP addresses, shown in the following table.

ClassAddress rangeSupports
Class A1.0.0.1 to 16 million hosts on each of 127 networks.
Class B128.1.0.1 to 65,000 hosts on each of 16,000 networks.
Class C192.0.1.1 to 254 hosts on each of 2 million networks.
Class D224.0.0.0 to for multicast groups.
Class E240.0.0.0 to for future use, or research and development purposes.

Ranges 127.x.x.x are reserved for the loopback or localhost, for example, is the loopback address. Range broadcasts to all hosts on the local network.


Web address or URL: A web address, also known as a URL (Uniform Resource Locator), is a reference to a web resource that points to a location where a file, directory or website page is hosted. Website addresses can represent the home page of a website, a script, image, photo, movie or other file made available on a server for viewing, processing or download. A website address begins with the protocol, a unique name and the domain and ends with a port number. Website addresses are entered into the address bar of an Internet browser. This name translates, through a DNS server to a unique number called an IP address.

Different parts of a URL:

  • 1. Protocol (http)
  • 2. Domain (
    1. Sub-domain (www)
    2. Domain Name (edupointbd)
    3. Top-level Domain (.com)
      1. Generic Domain (.com)
      2. Country Domain (say .bd)
  • 3. Directory (/ict)
  • 4. File Name or Document Name (robotics.html)


Protocol: A protocol or scheme is a set of rules and guidelines for communicating data. Rules are defined for each step and process during communication between two or more computers.

HTTP of the above URL is the underlying protocol used by the World Wide Web and this protocol defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands.There are also other protocols such as-

  • HTTP – Hyper Text Transfer Protocol
  • HTTPS- Hyper Text Transfer Protocol Secure
  • FTP – File Transfer Protocol
  • IP – Internet Protocol
  • TCP- Transmission Control Protocol


Domain: A domain is the textual address by which Internet users can access websites.  A domain that represents IP address. A domain is used for finding and identifying computers on the Internet. Computers use IP addresses, which are a series of number. However, it is difficult for humans to remember series of number. Because of this, domains were developed and used to identify entities on the Internet rather than using IP addresses. The domain name must be registered before you can use it. Every domain name is unique. No two websites can have the same domain name.

Every domain has three parts. They are:

  • 1. Sub-domain 
  • 2. Domain Name 
  • 3. Top-level Domain 

Sub-domain: A sub-domain is an additional part to the main domain. Sub-domains are created to organize and navigate to different sections of the website. You can create multiple sub-domains or child domains on your main domain. It is considered a third-level domain used to organize site content. For example – is a domain and is a sub-domain of it.

Top-level Domain: Top-level domain (TLD) refers to the last segment of a domain name, or the part that follows immediately after the “dot” symbol. TLDs are mainly classified into two categories: generic TLDs and country-specific TLDs.

A top-level domain recognizes a certain element regarding the associated website, such as its objective (business, government, education), its owner, or the geographical area from which it originated.

Generic Domain: It recognizes a certain element regarding the associated website, such as its objective business, government, education etc.

Generic DomainType of Institute
.milLimited to the U.S. military only
.netNetwork service
.orgNonprofitable organization

Country Domain:
It recognizes websites owner, or the geographical area from which it originated. It is an optional part of a domain.

Country DomainCountry Name
.ukUnited Kingdom
.usUnited States


Directory or path: The path identifies the specific resource in the host that the web client wants to access. For example, /software/htp/cics/index.html.

File Name or Document Name: It indicates the name of web pages or web resources. In the above URL, robotics.html is the name of a web page.


DNS Server: DNS (Domain Name System) server is an Internet service that translates domain names into IP addresses. Because domain names are alphabetic, they’re easier to remember. The Internet however, is really based on IP addresses. For example, when a Web address (URL) is typed into a browser, DNS servers return the IP address of the Web server associated with that name

The DNS system is, in fact, its own network. If one DNS server doesn’t know how to translate a particular domain name, it asks another one, and so on, until the correct IP address is returned.


Lesson Evaluation-

Knowledge Based Questions:

  • a. What is web address / URL?
  • a. What is IP address?
  • a. What is domain name?
  • a. What is protocol?
  • a. What is HTTP/HTTPS/FTP/TCP? 
  • a. What is DNS server? 

Comprehension Based Questions:

  • b. Why domain name needs to be registered? explain.
  • b. Explain the importance of domain name.
  • b. “Domain name should be related to the institute” explain.
  • b. Why there is WWW in domain name? explain.
  • b. Explain top-level domain.
  • b. “It is not possible a web address without top-level domain”-explain.
  • b. “Domain name is more convenient to use than IP address” explain.
  • b. Explain .

Creative Questions:

Multiple Choice Questions:


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