Overview of the Internet

The Internet’s overview is a global network of billions of computers and other electronic devices. With the Internet, it is possible to access almost any information, communicate with anyone else in the world, and do much more. You can use the Internet Technology and Web Design Forum to ask or help answer some FAQ Questions.

Table of Contents
  1. Overview of the Internet
    1. Evolution of the Internet
    2. Advantages of the Internet
    3. Disadvantages of the Internet
  2. Intranet Network
  3. Benefits of the Intranet Network
    1. Communication
    2. Time Saving
    3. Collaboration
    4. Platform Independency
    5. Cost Effective
    6. Workforce Productivity
    7. Business Management
    8. Security
    9. Specific Users
    10. Immediate Updates
  4. Issues of the Intranet Network
  5. Applications of the Intranet Network
    1. Document publication applications
    2. Electronic resources applications
    3. Interactive Communication applications
    4. Support for Internet Applications
  6. Internet Network vs Intranet Network
  7. Extranet Network
  8. Extranet Network Implementation
  9. Benefits Extranet Network
  10. Issues of the Extranet Network
    1. Hosting
    2. Security
    3. Accessing Issues
    4. Decreased Interaction
  11. Extranet Network vs Intranet Network
  12. Internet Reference Model
  13. Open System Interface Model
    1. Physical Layer
    2. Data Link Layer
    3. Network Layer
    4. Transport Layer
    5. Session Layer
    6. Presentation Layer
    7. Application Layer
  14. TCP/IP Model
    1. Application Layer
    2. Transport Layer
    3. Internet Layer
    4. Host-to-Network Layer
  15. Internet Domain Name System
  16. IP Address
  17. Uniform Resource Locator (URL)
  18. URL Types
    1. Absolute URL
    2. Relative URL
    3. Difference between Absolute and Relative URL
  19. Domain Name System Architecture
    1. Domain Names
    2. Domain Name Space
    3. Name Server
    4. Zones
  20. Types of Name Servers
    1. Root Server
    2. Primary Servers
    3. Secondary Server
  21. DNS Working
  22. Internet Service Provider
    1. Communication Services
    2. Information Retrieval Services
  23. Web Services
  24. World Wide Web (WWW)
  25. Video Conferencing
    1. Modes of Video Conferencing
    2. Point-to-Point Modes of Video Conferencing
    3. Multi-point Modes of Video Conferencing
  26. Internet Connectivity
    1. Internet Service Providers (ISP)
    2. ISP Types
    3. Access providers
    4. Mailbox Provider
    5. Hosting ISPs
    6. Virtual ISPs
    7. Free ISPs
  27. Connection Types
    1. Dial-up Connection
    2. ISDN
    3. Digital Subscriber Line (DSL)
    4. Cable TV Internet Connection
    5. Satellite Internet Connection
    6. Wireless Internet Connection
  28. Internet Protocols Network
    1. Transmission Control Protocol (TCP)
  29. TCP Services
    1. Stream Deliver Service
    2. Sending and Receiving Buffers
    3. Bytes and Segments
    4. Full Duplex Service
    5. Connection Oriented Service
    6. Reliable Service
  30. Internet Protocol (IP)
    1. User Datagram Protocol (UDP)
    2. File Transfer Protocol (FTP)
    3. Trivial File Transfer Protocol (TFTP)
  31. Difference between FTP and TFTP
  32. Telnet
  33. Hyper Text Transfer Protocol (HTTP)
    1. HTTP Request
    2. HTTP Response
  34. Internet Technology and Web Design Forum

Overview of the Internet

You can do all of this by connecting a computer to the Internet, also called going online. When someone says a computer is online, it is another way of saying it has connected to the Internet.

Internet is defined as an Information super Highway to access information over the web. However, It can be defined in many ways as follows:

  • Internet is a world-wide global system of interconnected computer networks.
  • Internet uses the standard Internet Protocol (TCP/IP).
  • Every computer in internet is identified by a unique IP address.
  • IP Address is a unique set of numbers (such as which identifies a computer location.
  • A special computer DNS (Domain Name Server) is used to give name to the IP Address so that user can locate a computer by a name.
  • For example, a DNS server will resolve a name https://eduraryhub.com to a particular IP address to uniquely identify the computer on which this website is hosted.
  • Internet is accessible to every user all over the world.
Overview of the Internet

Evolution of the Internet

Evolution of the Internet

The concept of the Internet was originated in 1969 and has undergone several technological & Infrastructural changes as discussed below:

  • The origin of Internet devised from the concept of Advanced Research Project Agency Network (ARPANET).
  • ARPANET was developed by United States Department of Defense.
  • Basic purpose of ARPANET was to provide communication among the various bodies of government.
  • Initially, there were only four nodes, formally called Hosts.
  • In 1972, the ARPANET spread over the globe with 23 nodes located at different countries and thus became known as Internet.
  • By the time, with invention of new technologies such as TCP/IP protocols, DNS, WWW, browsers, scripting languages etc.,Internet provided a medium to publish and access information over the web.

Advantages of the Internet

Internet covers almost every aspect of life one can think of. Here, we will discuss some of the advantages of the Internet:

Advantages of the Internet
  • Internet allows us to communicate with the people sitting at remote locations. There are various apps available on the wed that uses Internet as a medium for communication. One can find various social networking sites such as:
    • Facebook
    • Twitter
    • Yahoo
    • Flickr
    • Orkut
  • One can surf for any kind of information over the internet. Information regarding various topics such as Technology, Health & Science, Social Studies, Geographical Information, Information Technology, Products etc can be surfed with help of a search engine.
  • Apart from communication and source of information, internet also serves a medium for entertainment. Following are the various modes for entertainment over internet.
    • Online Television
    • Online Games
    • Songs
    • Videos
    • Social Networking Apps
  • Internet allows us to use many services like:
    • Internet Banking
    • Matrimonial Services
    • Online Shopping
    • Online Ticket Booking
    • Online Bill Payment
    • Data Sharing
    • E-mail
  • Internet provides concept of electronic commerce, that allows the business deals to be conducted on electronic systems

Disadvantages of the Internet

However, Internet has proved to be a powerful source of information in almost every field, yet there exist many disadvantages discussed below:

Disadvantages of the Internet
  • There are always chances to loose personal information such as name, address, credit card number. Therefore, one should be very careful while sharing such information. One should use credit cards only through authenticated sites.
  • Another disadvantage is the Spamming.Spamming corresponds to the unwanted e-mails in bulk. These e-mails serve no purpose and lead to obstruction of entire system.
  • Virus can easily be spread to the computers connected to internet. Such virus attacks may cause your system to crash or your important data may get deleted.
  • Also a biggest threat on internet is pornography. There are many pornographic sites that can be found, letting your children to use internet which indirectly affects the children healthy mental life.
  • There are various websites that do not provide the authenticated information. This leads to misconception among many people.

Intranet Network

Intranet is defined as a private network of computers within an organization with its Server and firewall. Moreover, we can define Intranet as:

  • Intranet is system in which multiple PCs are networked to be connected to each other. PCs in intranet are not available to the world outside of the intranet.
  • Usually each company or organization has their own Intranet network and members/employees of that company can access the computers in their intranet.
  • Every computer in internet is identified by a unique IP address.
  • Each computer in Intranet is also identified by a IP Address, which is unique among the computers in that Intranet.
Intranet Network

Benefits of the Intranet Network

Intranet is a very efficient and reliable network system for any organization. It is beneficial in every aspect, such as collaboration, cost-effectiveness, security, productivity, and much more.

Benefits of the Intranet Network


Intranet offers easy and cheap communication within an organization. Employees can communicate using chat, email, or blogs.

Time Saving

Information on Intranet is shared in real-time.


Information is distributed among the employees according to requirement, and it can be accessed by authorized users, resulting in enhanced teamwork.

Platform Independency

Intranet can connect computers and other devices with different architecture.

Cost Effective

Employees can see the data and other documents using a browser rather than printing them and distributing duplicate copies among the employees, certainly decreasing the cost.

Workforce Productivity

Data is available at every time and can be accessed using a company workstation. This helps the employees work faster.

Business Management

It is also possible to deploy applications that support business operations.


Since information shared on the Intranet can only be accessed within an organization, there is almost no chance of being stolen.

Specific Users

Intranet targets only specific users within an organization; therefore, one can exactly know whom he interacts.

Immediate Updates

Any changes made to information are reflected immediately to all the users.

Issues of the Intranet Network

Apart from several benefits of Intranet, there also exist some issues. These issues are shown in the following diagram:

Issues of the Intranet Network

Applications of the Intranet Network

Intranet applications are the same as Internet applications. Intranet applications are also accessed through a web browser. The only difference is that Intranet applications reside on a local server while Internet applications reside on a remote server. Here, we’ve discussed some of these applications:

Applications of the Intranet Network

Document publication applications

Document publication applications allow publishing documents such as manuals, software guides, employee profits, etc., without paper.

Electronic resources applications

It offers electronic resources such as software applications, templates, and tools, to be shared across the network.

Interactive Communication applications

Like on the Internet, we have email and chat-like applications for Intranet, offering interactive communication among employees.

Support for Internet Applications

Intranet offers an environment to deploy and test applications before placing them on the Internet.

Internet Network vs Intranet Network

Apart from similarities, there are some differences between the two. Following are the differences between the Internet and Intranet:

Localized Network.Worldwide Network
Doesn’t have access to IntranetHave access to the Internet.
More ExpensiveLess Expensive
SaferLess Safe
More ReliabilityLess Reliability
Intranet Network vs. Internet Network

Extranet Network

Extranet refers to a network within an organization, using the Internet to connect to outsiders in a controlled manner. It helps to connect businesses with their customers and suppliers and therefore allows working collaboratively.

Extranet Network

Extranet Network Implementation

The extranet is implemented as a Virtual Private Network (VPN) because it uses the Internet to connect to corporate organizations, and there is always a threat to information security. VPN offers a secure network in public infrastructure (Internet).

 Extranet Network Implementation

Key Points Extranet Network

  • The packet is encapsulated at boundary of networks in IPSEC complaint routers.
  • It uses an encryption key to encapsulate packets and IP addresses as well.
  • The packet is decoded only by the IPSEC complaint routers or servers.
  • The message is sent over VPN via VPN Tunnel and this process is known as tunneling.

VPN uses Internet Protocol Security Architecture (IPsec) Protocol to provide secure transactions by adding a security layer to TCP/IP protocol. This layer is created by encapsulating the I.P. packet to a new I.P. packet, as shown in the following diagram:

Internet Protocol Security Architecture (IPsec) Protocol

Benefits Extranet Network

Extranet proves to be a successful model for all kinds of businesses, whether small or big. Here are some of the advantages of an extranet for employees, suppliers, business partners, and customers:

Benefits Extranet Network

Issues of the Extranet Network

Apart from advantages, there are also some issues associated with the extranet. These issues are discussed below:


Where the extranet pages will be held, i.e., who will host the extranet pages, in this context, there are two choices:

  • Host it on your own server.
  • Host it with an Internet Service Provider (ISP) in the same way as web pages.

But hosting extranet pages on your Server requires a high bandwidth internet connection which is very costly.


Additional firewall security is required if you host extranet pages on your Server, resulting in a complex security mechanism and increased workload.

Accessing Issues

Information can not be accessed without an internet connection. However, information can be accessed on Intranet without an internet connection.

Decreased Interaction

It decreases the face-to-face interaction in the business, which results in a lack of communication among customers, business partners, and suppliers.

Extranet Network vs Intranet Network

The following table shows differences between Extranet and Intranet:

The internal network can be accessed externally.An internal network that can not be accessed externally.
An extranet is an extension of a company’s Intranet.Only limited users of a company.
For limited external communication between customers, suppliers, and business partners.Only for communication within a company.
Intranet Network vs. Extranet Network

Internet Reference Model

Reference Model offers a means of standardization that is acceptable worldwide. Since people using the computer network are located over a wide physical range, their network devices might have heterogeneous architecture.

To provide communication among heterogeneous devices, we need a standardized model, i.e., a reference model, which would give us how these devices can communicate regardless of their architecture.

We have two reference models such as OSI model and the TCP/IP reference model. However, the OSI model is a hypothetical one, but the TCP/IP is an efficient model.

Open System Interface Model

OSI is the acronym for Open System Interface. This model was developed by the International organization of Standardization (ISO) and is also referred to as ISO-OSI Model.

The OSI model consists of seven layers, as shown in the following diagram. Each layer has a specific function. However, each layer provides services to the layer above.

Open System Interface Model

Physical Layer

The Physical layer is responsible for the following activities:

  • Activating, maintaining and deactivating the physical connection.
  • Defining voltages and data rates needed for transmission.
  • Converting digital bits into electrical signal.
  • Deciding whether the connection is simplex, half duplex or full duplex.

The data link layer performs the following functions:

  • Performs synchronization and error control for the information which is to be transmitted over the physical link.
  • Enables error detection, and adds error detection bits to the data which are to be transmitted.

Network Layer

Following are the parts of the Network Layer:

  • To route the signals through various channels to the other end.
  • To act as the network controller by deciding which route data should take.
  • To divide the outgoing messages into packets and to assemble incoming packets into messages for higher levels.

Transport Layer

The Transport layer performs the following functions:

  • It decides if the data transmission should take place on parallel paths or single path.
  • It performs multiplexing, splitting on the data.
  • It breaks the data groups into smaller units so that they are handled more efficiently by the network layer.

The Transport Layer guarantees transmission of data from one end to other end.

Session Layer

The Session layer performs the following functions:

  • Manages the messages and synchronizes conversations between two different applications.
  • It controls logging on and off, user identification, billing and session management.

Presentation Layer

The Presentation layer performs the following functions:

  • This layer makes it sure that the information is delivered in such a form that the receiving system will understand and use it.

Application Layer

The Application layer performs the following functions:

  • It provides different services such as manipulation of information in several ways, retransferring the files of information, distributing the results etc.
  • The functions such as LOGIN or password checking are also performed by the application layer.

TCP/IP Model

TCP/IP model is a practical model and is used on the Internet. TCP/IP is an acronym for Transmission Control Protocol and Internet Protocol.

The TCP/IP model combines the two layers (Physical and Data link layer) into one layer, i.e., Host-to-Network layer. The following diagram shows the various layers of the TCP/IP model:

TCP/IP Model

Application Layer

This layer is the same as that of the OSI model and performs the following functions:

  • It provides different services such as manipulation of information in several ways, retransferring the files of information, distributing the results etc.
  • The functions such as LOGIN or password checking are also performed by the application layer.

Protocols used: TELNET, FTP, SMTP, DN, HTTP, NNTP are the protocols employed in this layer.

Transport Layer

It does the same functions as that of the transport layer in the OSI model. Here are the key points regarding the transport layer:

  • It uses TCP and UDP protocol for end to end transmission.
  • TCP is reliable and connection oriented protocol.
  • TCP also handles flow control.
  • The UDP is not reliable and a connection less protocol also does not perform flow control.

Protocols used: TCP/IP and UDP protocols are employed in this layer.

Internet Layer

The function of this layer is to allow the host to insert packets into the network and then make them travel independently to the destination. However, the order of receiving the packet can be different from the sequence they were sent.

Protocols used: Internet Protocol (IP) is employed in Internet layer.

Host-to-Network Layer

This is the lowest layer in the TCP/IP model. The host has to connect to the network using some protocol to send I.P. packets over it. This protocol varies from host to host and network to network.

Protocols used: ARPANET, SATNET, LAN, packet radio are the protocols which are used in this layer.

Internet Domain Name System

When DNS was not in existence, one had to download a Host file containing hostnames and their corresponding I.P. address. But with an increase in the number of hosts on the Internet, the size of the host file also increased. This resulted in increased traffic on downloading this file. To solve this problem, the DNS system was introduced.

Domain Name System helps to resolve the hostname to an address. It uses a hierarchical naming scheme and distributed database of I.P. addresses and associated names.

IP Address

The I.P. address is a unique logical address assigned to a machine over the network. An I.P. address exhibits the following properties:

  • IP address is the unique address assigned to each host present on Internet.
  • IP address is 32 bits (4 bytes) long.
  • IP address consists of two components: network component and host component.
  • Each of the 4 bytes is represented by a number from 0 to 255, separated with dots. For example

An I.P. address is a 32-bit number, while on the other hand, domain names are easy to remember names. For example, when we enter an email address, we always enter a symbolic string such as webmaster@tutorialspoint.com.

Uniform Resource Locator (URL)

Uniform Resource Locator (URL) refers to a web address that uniquely identifies a document over the Internet.

This document can be a web page, image, audio, video, or anything else present on the web.

For example, https://eduraryhub.com/overview-of-the-internet/ is an URL to the index.html, stored on the eduraryhub web server under the overview-of-the-internet directory.

URL Types

There are two forms of URL as listed below:

  • Absolute URL
  • Relative URL

Absolute URL

An absolute URL is a complete address of a resource on the web. This completed address comprises the protocol used, server name, pathname, and file name.

For example, https://eduraryhub.com/overview-of-the-internet/ where:

  • http is the protocol.
  • eduraryhub.com is the server name.
  • index.htm is the file name.

The protocol part tells the web browser how to handle the file. Similarly, we have some other protocols also that can be used to create URLs are:

  • FTP
  • https
  • Gopher
  • mailto
  • news

Relative URL

A relative URL is a partial address of a webpage. Unlike absolute URLs, the protocol and server parts are omitted from the relative URLs.

Relative URLs are used for internal links, i.e., to create links to a file part of the same website as the WebPages on which you are placing the link.

For example, to link an image on tutorialspoint.com/internet_technology/internet_referemce_models, we can use the relative URL, which can take the form like https://eduraryinstoftech.com/wp-content/uploads/2021/10/Internet-Technology-and-Web-Design-1.jpg.

Difference between Absolute and Relative URL

Absolute URLRelative URL
Used to link web pages on different websitesThey are used to connect web pages within the same website.
Difficult to manage.Easy to Manage
Changes when the server name or directory name changesIt remains the same even if we change the server name or directory name.
Take time to accessComparatively faster to access.
Difference between Absolute and Relative URL

Domain Name System Architecture

The Domain name system comprises Domain Names, Domain Name Space, Name Server that have been described below:

Domain Names

Domain Name is a symbolic string associated with an I.P. address. Several domain names are available; some are generic such as com, edu, gov, net, etc., while some country-level domain names, such as au, in, za, us, etc.

The following table shows the Generic Top-Level Domain names:

Domain NameMeaning
ComCommercial business
GovU.S. government agency
IntInternational entity
MilU.S. military
NetNetworking organization
OrgNonprofit organization

The following table shows the Country top-level domain names:

Domain NameMeaning
usUnited States
zaSouth Africa
UKUnited Kingdom
HKHong Kong

Domain Name Space

The domain name space refers to a hierarchy in the internet naming structure. This hierarchy has multiple levels (from 0 to 127), with a root at the top. The following diagram shows the domain name space hierarchy:

Domain Name Space

In the above diagram, each subtree represents a domain. Each domain can be partitioned into sub-domains, and these can be further partitioned and so on.

Name Server

A name server contains the DNS database. This database comprises various names and their corresponding I.P. addresses. Since a single server can’t maintain the entire DNS database, the information is distributed among many DNS servers.

  • Hierarchy of server is same as hierarchy of names.
  • The entire name space is divided into the zones


A zone is a collection of nodes (subdomains) under the main domain. The Server maintains a database called zone file for every zone.


If the domain is not divided into sub-domains, then domain and zone refer to the same thing.

The information about the nodes in the subdomain is stored in the servers at the lower levels. However, the original Server references these lower levels of servers.

Types of Name Servers

Following are the three categories of Name Servers that manages the entire Domain Name System:

  • Root Server
  • Primary Server
  • Secondary Server

Root Server

Root Server is the top-level Server that consists of the whole DNS tree. It does not contain the information about domains but delegates the authority to the other Server

Primary Servers

Primary Server stores a file about its zone. It has the power to create, maintain, and update the zone file.

Secondary Server

Secondary Server transfers complete information about a zone from another server, a primary or secondary server. The secondary Server does not have the authority to create or update a zone file.

DNS Working

DNS translates the domain name into I.P. address automatically. The following steps will take you through the measures included in the domain resolution process:

  • When we type www.eduraryhub.com into the browser, it asks the local DNS Server for its IP address.
  • When the local DNS does not find the IP address of requested domain name, it forwards the request to the root DNS server and again enquires about IP address of it.
  • The root DNS server replies with delegation that I do not know the IP address of www.eduraryhub.com but know the IP address of DNS Server.
  • The local DNS server then asks the com DNS Server the same question.
  • The com DNS Server replies the same that it does not know the IP address of www.eduraryhub.com but knows the address of eduraryhub.com.
  • Then the local DNS asks the tutorialspoint.com DNS server the same question.
  • Then eduraryhub.com DNS server replies with IP address of www.eduraryhub.com.com.
  • Now, the local DNS sends the IP address of www.eduraryhub.com to the computer that sends the request.

Internet Service Provider

Internet Services
 providers allow us to access a massive amount of information such as text, graphics, sound, and software over the Internet. The following diagram shows the four different categories of Internet Services.

Internet Service Provider

Communication Services

There are various Communication Services available that offer the exchange of information with individuals or groups. The following table gives a brief introduction to these services:

S.N.Service Description
1Electronic Mail
It is used to send an electronic message over the Internet.
It is used to log on to a remote computer that is attached to the Internet.
It offers a forum for people to discuss topics of common interest.
4Internet Relay Chat (IRC)
Allows people from all over the world to communicate in real-time.
5Mailing Lists
They are used to organize a group of internet users to share standard information through email.
6Internet Telephony (VoIP)
Allows the internet users to talk across the Internet to any P.C. equipped to receive the call.
7Instant Messaging
Offers real-time chat between individuals and groups of people. E.g. Yahoo messenger, MSN messenger.
Communication Services

Information Retrieval Services

There exist several Information retrieval services offering easy access to information present on the Internet. The following table gives a brief introduction to these services:

S.N.Service Description
1File Transfer Protocol (FTP)
Enable the users to transfer files.
It’s an updated database of public FTP sites and their content. It helps to search a file by its name.
Used to search, retrieve, and display documents on remote sites.
4Very Easy Rodent Oriented Netwide Index to Computer Achieved (VERONICA)
VERONICA is a gopher-based resource. It allows access to the information resource stored on gopher’s servers.
Information Retrieval Services

Web Services

Web services allow the exchange of information between applications on the web. Using web services, applications can easily interact with each other.

The web services are offered using the concept of Utility Computing.

World Wide Web (WWW)

WWW is also known as W3. It offers a way to access documents spread over several servers over the Internet. These documents may contain texts, graphics, audio, video, hyperlinks. The hyperlinks allow the users to navigate between the documents.

Video Conferencing

Video conferencing or Video teleconferencing is a method of communicating by two-way video and audio transmission with the help of telecommunication technologies.

Modes of Video Conferencing

Point-to-Point Modes of Video Conferencing

This mode of conferencing connects two locations only.

Point-to-Point Modes of Video Conferencing

Multi-point Modes of Video Conferencing

This mode of conferencing connects more than two locations through Multi-point Control Unit (MCU).

Multi-point Modes of Video Conferencing

Internet Connectivity

This tutorial will discuss connecting to the Internet, i.e., internet service providers, software and hardware requirements, configuring internet connection, etc.

Internet Service Providers (ISP)

Internet Service Provider (ISP) is a company offering access to the Internet. They provide various services:

  • Internet Access
  • Domain name registration
  • Dial-up access
  • Leased line access

ISP Types

ISPs can broadly be classified into six categories, as shown in the following diagram:

Internet Service Providers (ISP)

Access providers

They provide access to the Internet through telephone lines, cable WiFi, or fiber optics.

Mailbox Provider

Such providers offer mailbox hosting services.

Hosting ISPs

Hosting ISPs offers email and other web hosting services such as virtual machines, clouds, etc.

Virtual ISPs

Such ISPs offer internet access via other ISP services.

Free ISPs

Free ISPs do not charge for internet services.

Connection Types

There exist several ways to connect to the Internet. Following are these connection types available:

  1. Dial-up Connection
  2. ISDN
  3. DSL
  4. Cable TV Internet connections
  5. Satellite Internet connections
  6. Wireless Internet Connections

Dial-up Connection

The dial-up connection uses a telephone line to connect the P.C. to the Internet. It requires a modem to set up a dial-up connection. This modem works as an interface between the P.C. and the telephone line.

There is also a communication program that instructs the modem to call a specific number provided by an ISP.

The dial-up connection uses either of the following protocols:

  1. Serial Line Internet Protocol (SLIP)
  2. Point to Point Protocol (PPP)

The following diagram shows the accessing Internet using modem:

Serial Line Internet Protocol (SLIP)
Point to Point Protocol (PPP)


ISDN is the acronym of Integrated Services Digital Network. It establishes the connection using the phone lines, which carry digital signals instead of analog signals.

There are two techniques to deliver ISDN services:

  1. Basic Rate Interface (BRI)
  2. Primary Rate Interface (PRI)

Key points:

  • The BRI ISDN consists of three distinct channels on a single ISDN line: t1o 64kbps B (Bearer) channel and one 16kbps D (Delta or Data) channels.
  • The PRI ISDN consists of 23 B channels and one D channels with both have operating capacity of 64kbps individually making a total transmission rate of 1.54Mbps.

The following diagram shows accessing the Internet using an ISDN connection:

Basic Rate Interface (BRI)
Primary Rate Interface (PRI)

Digital Subscriber Line (DSL)

DSL is an acronym of Digital Subscriber Line. It is a form of a broadband connection as it provides a connection over ordinary telephone lines.

Following are the several versions of the DSL technique available today:

  1. Asymmetric DSL (ADSL)
  2. Symmetric DSL (SDSL)
  3. High bit-rate DSL (HDSL)
  4. Rate adaptive DSL (RDSL)
  5. Very high bit-rate DSL (VDSL)

As mentioned earlier, all of the technologies differ in their upload and download speed, bit transfer rate, and level of service.

The following diagram shows that how we can connect to the Internet using DSL technology:

Digital Subscriber Line

Cable TV Internet Connection

Cable T.V. Internet connection is provided through Cable T.V. lines. It uses a coaxial cable capable of transferring data at a much higher speed than a standard telephone line.

Key Points:

  • A cable modem is used to access this service, provided by the cable operator.
  • The Cable modem comprises of two connections: one for internet service and other for Cable TV signals.
  • Since Cable TV internet connections share a set amount of bandwidth with a group of customers, therefore, data transfer rate also depends on number of customers using the internet at the same time.

The following diagram shows that how the Internet is accessed using a Cable T.V. connection:

Cable TV Internet Connection

Satellite Internet Connection

Satellite Internet connection offers a high-speed connection to the Internet. There are two types of satellite internet connection: one-way connection or two-way connection.

In a one-way connection, we can only download data, but we need dial-up access through ISP over the telephone line if we want to upload.

In two way connection, we can download and upload the data by the satellite. It does not require any dial-up connection.

The following diagram shows how the Internet is accessed using a satellite internet connection:

Satellite Internet Connection
Satellite Internet Connection

Wireless Internet Connection

Wireless Internet Connection uses radiofrequency bands to connect to the Internet and offers a very high speed. Either WiFi or Bluetooth can obtain a wireless internet connection.

Key Points:

  • Wi Fi wireless technology is based on IEEE 802.11 standards which allow the electronic device to connect to the internet.
  • Bluetooth wireless technology makes use of short-wavelength radio waves and helps to create personal area network (PAN).

Internet Protocols Network

The Internet Protocol (I.P.) is the network layer communications protocol for relaying datagrams across network boundaries in the Internet protocol suite. Its routing function enables internetworking and essentially establishes the Internet.

I.P. has the task of delivering packets from the source host to the destination host solely based on the I.P. addresses in the packet headers. For this purpose, I.P. defines packet structures that encapsulate the data to be delivered. It also defines addressing methods that are used to label the datagram with source and destination information.

Transmission Control Protocol (TCP)

TCP is a connection-oriented protocol and offers end-to-end packet delivery. It acts as the backbone for connection. It exhibits the following key features:

  • Transmission Control Protocol (TCP) corresponds to the Transport Layer of OSI Model.
  • TCP is a reliable and connection oriented protocol.
  • TCP offers:
    • Stream Data Transfer.
    • Reliability.
    • Efficient Flow Control
    • Full-duplex operation.
    • Multiplexing.
  • TCP offers connection oriented end-to-end packet delivery.
  • TCP ensures reliability by sequencing bytes with a forwarding acknowledgement number that indicates to the destination the next byte the source expect to receive.
  • It retransmits the bytes not acknowledged with in specified time period.

TCP Services

TCP offers the following services to the processes at the application layer:

  • Stream Delivery Service
  • Sending and Receiving Buffers
  • Bytes and Segments
  • Full Duplex Service
  • Connection Oriented Service
  • Reliable Service

Stream Deliver Service

The TCP protocol is stream-oriented because it allows the sending process to send data as a stream of bytes and the receiving process to obtain data as a stream of bytes.

Sending and Receiving Buffers

It may not be possible for sending and receiving process to produce and obtain data at the same speed. Therefore, TCP needs buffers for storage at sending and receiving ends.

Bytes and Segments

The Transmission Control Protocol (TCP), at the transport layer, groups the bytes into a packet. This packet is called a segment. Before transmission of these packets, these segments are encapsulated into an I.P. datagram.

Full Duplex Service

Transmitting the data in duplex mode means the flow of data in both directions at the same time.

Connection Oriented Service

TCP offers connection-oriented service in the following manner:

  1. TCP of process-1 informs TCP of process – 2 and gets its approval.
  2. TCP of process – 1 and TCP of process – 2 and exchange data in both the two directions.
  3. After completing the data exchange, when buffers on both sides are empty, the two TCP’s destroy their buffers.

Reliable Service

For the sake of reliability, TCP uses an acknowledgment mechanism.

Internet Protocol (IP)

Internet Protocol is a connectionless and unreliable protocol. It ensures no guarantee of successful transmission of data.

To make it reliable, it must be paired with a reliable protocol such as TCP at the transport layer.

Internet protocol transmits the data in the form of a datagram, as shown in the following diagram:

Internet Protocol (IP)
Internet Protocol (I.P.)

Points to remember:

  • The length of datagram is variable.
  • The Datagram is divided into two parts: header and data.
  • The length of header is 20 to 60 bytes.
  • The header contains information for routing and delivery of the packet.

User Datagram Protocol (UDP)

Like I.P., UDP is a connectionless and unreliable protocol. It doesn’t require making a connection with the host to exchange data. Since UDP is an unreliable protocol, there is no mechanism for ensuring that data sent is received.

UDP transmits the data in the form of a datagram. The UDP datagram consists of five parts, as shown in the following diagram:

User Datagram Protocol (UDP)
User Datagram Protocol (UDP)

Points to remember:

  • UDP is used by the application that typically transmit small amount of data at one time.
  • UDP provides protocol port used i.e. UDP message contains both source and destination port number, that makes it possible for UDP software at the destination to deliver the message to correct application program.

File Transfer Protocol (FTP)

FTP is used to copy files from one host to another. FTP offers the mechanism for the same in the following manner:

  • FTP creates two processes such as Control Process and Data Transfer Process at both ends i.e. at client as well as at server.
  • FTP establishes two different connections: one is for data transfer and other is for control information.
  • Control connection is made between control processes while Data Connection is made between
  • FTP uses port 21 for the control connection and Port 20 for the data connection.
File Transfer Protocol (FTP)

Trivial File Transfer Protocol (TFTP)

Trivial File Transfer Protocol is also used to transfer the files, but it moves the files without authentication. Unlike FTP, TFTP does not separate control and data information. Since there is no authentication exists, TFTP lacks security features. Therefore, it is not recommended to use TFTP.

Key points

  • TFTP makes use of UDP for data transport. Each TFTP message is carried in separate UDP datagram.
  • The first two bytes of a TFTP message specify the type of message.
  • The TFTP session is initiated when a TFTP client sends a request to upload or download a file.
  • The request is sent from an ephemeral UDP port to the UDP port 69 of an TFTP server.

Difference between FTP and TFTP

1OperationTransferring FilesTransferring Files
4Ports21 – Control, 20 – DataPort 3214, 69, 4012
5Control and DataSeparatedSeparated
6Data TransferReliableUnreliable
Difference between FTP and TFTP


Telnet is a protocol used to log in to a remote computer on the Internet. Several Telnet clients have a user-friendly user interface. The following diagram shows a person is logged in to computer A, and from there, he remote logged into computer B.


Hyper Text Transfer Protocol (HTTP)

HTTP is a communication protocol. It defines a mechanism for communication between the browser and the webserver. It is also called request and response protocol because the communication between browser and Server occurs in request and response pairs.

HTTP Request

HTTP request comprises of lines which contain:

  • Request line
  • Header Fields
  • Message body

Key Points

  • The first line i.e. the Request line specifies the request method i.e. Get or Post.
  • The second line specifies the header which indicates the domain name of the server from where index.htm is retrieved.

HTTP Response

Like HTTP requests, HTTP response also has a specific structure. The HTTP response contains:

  • Status line
  • Headers
  • Message body

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