Web & Internet Technology

1. What is servlet? What do you understand by servlet API? Describe the life cycle of a servlet.

Servlet is a technology used to create web applications. It works on the server side and is capable of handling complex requests obtained from the web server.

SERVLET API:

To create Java Servlets, we need to use Servlet API, which contains all the necessary interfaces and classes. Servlet API has 2 packages:

• javax.servlet
• javax.servlet.http

SERVLET LIFE CYCLE:

1. Servlet class is loaded: The classloader loads the servlet class when the first request for the servlet is received by the web container.
2. Servlet instance is created: The web container creates the instance of a servlet after loading the servlet class. The servlet instance is created only once in the servlet life cycle.
3. init(): The web container calls the init method only once after creating the servlet instance. The init method is used to initialize the servlet.
4. service(): The web container calls the service() method each time there is a new request to the servlet. This method checks the HTTP request type and calls the appropriate methods (doGet, doPost, etc).
5. destroy(): This method is called just once at the end of the Servlet's life cycle. It helps perform clean-up activities and removes the servlet from the container.

2. Give a comparison for Intranet, Extranet, and Internet.

3. State the difference between IPv4 and IPv6.

4. What is the meaning of the term 'Hypertext Transfer Protocol' in www environment? Why is HTTP stateless?

Hypertext transfer protocol or HTTP is a protocol that allows the transfer of information on the World Wide Web between clients and servers.

• Accessing Data on the Web: It serves as a protocol for accessing data on the World Wide Web (www), allowing users to retrieve web pages, images, videos, and other resources.
• Support for Various Data Formats: HTTP can transfer data in multiple formats, including plain text, hypertext, audio, video, etc.
• Efficiency in Hypertext Environment: The term "Hypertext Transfer Protocol" reflects its efficiency in managing hypertext environments.

HTTP is called a stateless protocol because in this each command is executed independently, without any knowledge of the commands that came before it.

• In this protocol, the communication generally takes place over a TCP/IP protocol.
• Request-Response Model: HTTP follows a request-response model. Clients send requests to servers, which respond with requested resources. After the response, the connection ends, not retaining any previous interaction data.
• Simplicity and Scalability: HTTP's statelessness simplifies communication. Each request is independent, easing management and scalability as servers don't store client session data.

5. What is URL? Explain different component of URL.

A Uniform Resource Locator (URL) is a set address for locating a unique resource on the internet, such as a file or an app.

• It is used to indicate the location of a web resource to access the web pages.
• Example: https://www.example.com/category-A/subcategory-A1/model-123.html

Components of a URL:

• Protocol: The protocol or scheme of a URL indicates the method that will be used for transmitting or exchanging data. In the example URL above, https:// is the URL's secure protocol.
• Domain: The domain or hostname of a URL is a user-friendly expression of the Internet Protocol (IP) address of a website. It points to the location of the website's host server. In the example above, the domain is www.example.com.
• Path: The path that follows the domain name inside a URL points to a specific file or other resource location. It can also include a query string. In our example URL, /category-A/subcategory-A1/model-123.html shows the path of the URL, which in this example, ends in a product page.
• Query: The query string, also known as a fragment identifier, is frequently used for internal searches and is commonly preceded by a question mark (?). In our example URL Model 123 is the query.

6. Why dynamic routing is preferred over static routing algorithm? Difference between static routing and dynamic routing

Static Routing: Static Routing is also known as non-adaptive routing which doesn’t change the routing table unless the network administrator changes or modifies them manually.

Dynamic Routing: Dynamic routing is also known as adaptive routing which changes the routing table according to the change in topology.

Dynamic routing provides key advantages over static routing, including scalability and adaptability. A dynamically routed network can grow larger more quickly and is able to adapt to changes in the network topology.

7. Distinguish between GET and POST method in HTTP.

The HTTP Get method is mainly used on the client (Browser) side to send a request to a specified server to get certain data or resources.

The HTTP Post method is mainly used at the client side to send data to a Specified server in order to create or rewrite a particular data.

8. What are the differences between TCP and UDP?

The transmission control protocol (TCP) is defined as a connection-oriented communication protocol that allows computing devices and applications to send data via a network and verify its delivery.

The User Datagram Protocol (UDP) is simplest Transport Layer communication protocol available of the TCP/IP protocol suite.

Transmission control protocol (TCP) and user datagram protocol (UDP) are foundational pillars of the internet, enabling different types of data transmission from a network source to the destination. TCP is more reliable, while UDP prioritizes speed and efficiency.

9. Explain different file transmission modes across FTP data connection.

The full form of FTP is File Transfer Protocol. It is a standard internet protocol provided by TCP/IP which is used for transmitting the files from one system to another system.

• The main purpose of FTP is for transferring the web page files from one system to the computer which acts as a server for other computers on the internet.
• It is also helpful for downloading the files to compute from other servers.

Advantages:

• Multiple transfers
• Efficiency
• Security
• Continuous transfer
• Simple
• Speed

Disadvantages:

• FTP is not compatible with every system.
• Attackers can quickly identify the FTP password.
• Does not allow running of simultaneous transfers to multiple receivers.

FTP transfer files using any of the following modes:

• Stream Mode: It is the default mode. In stream mode, the data is transferred from FTP to TCP in stream bytes.
• Block Mode: In block mode, the data is transferred from FTP to TCP in the form of blocks, and each block followed by a 3-byte header. The first byte of the block contains the information about the block so it is known as the description block and the other two bytes contain the size of the block.
• Compressed Mode: This mode is used to transfer big files. The compressed mode is used to decrease the size of the file into small and send it on the internet.

10. Write a short note on SMTP.

The Simple Mail Transfer Protocol (SMTP) is a set of rules for communication that enables applications to send electronic mail over the internet.

• It is a program used for sending messages to other computer users based on e-mail addresses.

Advantages of SMTP:

• It allows for bulk mailing.
• Low cost and wide coverage area.
• Offer choices for email tracking.

Disadvantages of SMTP:

• SMTP’s common port can be blocked by several firewalls.
• SMTP security is a bigger problem.
• If a message is longer than a certain length, SMTP servers may reject the entire message.

Working of SMTP:

• Composition of Mail: Users compose emails with a Mail User Agent (MUA), containing a body and a header.
• Submission of Mail: Completed emails are sent to the SMTP server on TCP port 25.
• Delivery of Mail: SMTP routes emails based on recipient domain; if different, it goes through Mail Transfer Agent (MTA) and MX record lookup.
• Receipt and Processing of Mail: Incoming emails are received by the exchange server, then stored by the Mail Delivery Agent (MDA).
• Access and Retrieval of Mail: Users retrieve stored emails from MDA using MUA and login credentials.

11. State the use of <pre> and <del> tags.

HTML <pre> tag:

The HTML <pre> tag is used to specify pre-formatted texts. Texts within <pre>....... tag is displayed in a fixed-width font.

• It maintains both space and line break.
• It is widely used to display language examples e.g. Java, C#, C, C++ etc because it displays the code as it is typed.
• The HTML <pre> tag also supports the width attribute.

HTML <del> tag:

HTML <del> tag is used to represent the range of text that has been deleted/removed from the document.

• It is used as a Markup for the deleted content.
• The browser generally renders it by strike a line through the deleted text, although this can be changed using the CSS property.
• To identify the deleted text and inserted text use <ins> tag with <del> which will display deleted and inserted text in a document.

12. Write down the features of the scripting language. How is the markup language different from the scripting language?

A Scripting Language is a series of commands within an executable file. The language is designed to integrate and communicate with other programming languages.

Features of scripting language:

• Interpreted: scripting languages are interpreted rather than compiled. This means that the source code is translated in real time once it has been executed, making it more flexible and easier to write.
• Objective: they are designed for very specific tasks e.g., web programming, artificial intelligence or task automation in operating systems.
• Variable declaration: scripting languages use what is known as dynamic typing. This means that data variables can be declared more flexibly throughout the code.
• Server-side vs client-side: scripts designed with these languages can run on both a web server and in a browser on the user's device.
• Memory: the memory employed in running a script is managed automatically by whichever interpreter is used.
• Cross-platform: Scripting languages integrate extremely well into all system types and even with other language types.

Markup languages are computer languages that are used to structure, format, or define relationships between different parts of text documents with the help of symbols or tags inserted in the document.

Benefits of Using Markup:

• They Improve SEO: This structuring helps search engines like Google understand the information on websites better.
• They Create Consistent Layouts
• They Enhance Accessibility.

13. Why is XML superior to HTML, What are the different types of parser used in XML?

HTML is used for displaying and formatting data on the web, while XML is designed to store and transport data.

The benefits of using XML compared to HTML include:

1. Data Structure: XML allows for more flexible and customizable data structuring, making it suitable for representing complex data.
2. Platform-Independent: XML is platform-independent, meaning it can be used on any operating system or device.
3. Extensibility: XML is extensible, allowing users to define their own tags and document structures, making it suitable for a wide range of applications.
4. Data Exchange: XML is often used for data interchange between different systems and applications due to its structured and standardized format.

Different Types of Parser Used In XML:

1. DOM (Document Object Model): A DOM document is an object which contains all the information of an XML document. It is composed like a tree structure.

   Features of DOM Parser

   • A DOM Parser creates an internal structure in memory which is a DOM document object and the client applications get information of the original XML document by invoking methods on this document object.
   • DOM Parser has a tree-based structure.

   Advantages

   • It supports both read and write operations and the API is very simple to use.
   • It is preferred when random access to widely separated parts of a document is required.

   Disadvantages

   • It is memory inefficient. (consumes more memory because the whole XML document needs to loaded into memory).
   • It is comparatively slower than other parsers.
2. SAX (Simple API for XML): A SAX Parser implements SAX API. This API is an event-based API and less intuitive.

   Features of SAX Parser

   • It does not create any internal structure.
   • Clients does not know what methods to call, they just overrides the methods of the API and place his own code inside method.
   • It is an event based parser, it works like an event handler in Java.

   Advantages

   • It is simple and memory efficient.
   • It is very fast and works for huge documents.

   Disadvantages

   • It is event-based so its API is less intuitive.
   • Clients never know the full information because the data is broken into pieces.

14. Write a short note on a) HTML Image Map b) XML Tree.

HTML Image Map:

• The <map> tag can be used to define the image map & the clickable area inside the image can be defined with the <area> tag.
• Purpose: HTML Image Maps are used to make certain areas of an image clickable, allowing users to interact with specific parts of the image rather than the image as a whole.

XML Tree:

• XML documents are formed as element trees.
• An XML tree starts at a root element and branches from the root to child elements.
• All elements can have sub elements (child elements)

                    
                        <root>
                              <child>
                                    <subchild>.....</subchild>
                            </child>
                        </root>
                    
                

• The terms parent, child, and sibling are used to describe the relationships between elements.
• All elements can have text content and attributes.

15. What are web browser cookies?

A cookie is a piece of data from a website that is stored within a web browser that the website can retrieve at a later time.

• Cookies are used to tell the server that users have returned to a particular website.
• Cookies help websites remember users and track their activities to provide a personalised experience.

Types & uses:

• Session cookies: Temporary cookies that exist as long as the browser session is active.
  • Deleted once the browser is closed or the user's session becomes inactive
  • Mainly used for maintaining user sessions, such as authentication
• Persistent cookies: Also called permanent or long-term cookies. Stored on the user's device for a specific period.
  • Used for long-term tracking and remembering user preferences
• First-party cookies: Set by the website currently being visited by the user.
  • Primarily used for enhancing user experience, collecting analytics data, and remembering settings like language preferences
• Third-party cookies: Collect data about browsing habits to serve targeted ads or analytics.
  • Often used for cross-site tracking and advertising purposes

Cookies can raise privacy concerns when they are used for tracking and profiling without user consent.

16. What is the difference between an Applet and a Java Application?

Java applications are just like a Java program that can be executed independently without using the web browser.

• A Java application does not necessarily require a graphical user interface for executing a Java application.

Java Applets are small Java programs that are designed to be included with the HTML web document. They require a Java-enabled web browser for execution.

17. What is an Applet? Discuss the life cycle of an Applet. Give one example of passing parameters in Applet.

An applet is a Java program that runs in a Web browser. An applet can be a fully functional Java application because it has the entire Java API at its disposal.

• It cannot run independently but requires APIs for its.
• A Java applet does not require any prior installation.

Applet Life Cycle:

1. init − This method is intended for whatever initialization is needed for your applet.
2. start − This method is automatically called after the browser calls the init method.
3. stop − This method is automatically called when the user moves off the page on which the applet sits.
4. destroy − This method is only called when the browser shuts down normally.
5. paint − Invoked immediately after the start() method, and also any time the applet needs to repaint itself in the browser.

Parameter in Applet: We can get any information from the HTML file as a parameter. For this purpose, Applet class provides a method named getParameter().

Syntax: public String getParameter(String parameterName).

18. Write a short note on Java Socket.

Java Socket is an endpoint for communication between two machines over a network. It enables bidirectional data flow between a client program and a server program.

• Java Socket programming is used for communication between the applications running on different JRE.
• Java Socket programming can be connection-oriented or connection-less.

Socket Classes:

1. Socket: Represents a client-side endpoint of a connection.
2. ServerSocket: Represents a server-side endpoint that listens for incoming connections from client sockets.

Communication Protocol:

Sockets in Java support various communication protocols, TCP provides reliable, connection-oriented communication, while UDP offers faster, connectionless communication.

Usage:

Java sockets are used to implement various network applications, such as client-server applications, web servers, chat applications, and distributed systems.

Socket Operations:

1. Establishing Connection: Client sockets connect to a server socket by specifying the server's IP address and port number.
2. Sending and Receiving Data: Sockets facilitate the exchange of data between client and server using input and output streams (InputStream and OutputStream).
3. Closing Connection: Sockets should be properly closed using the close() method to release network resources after communication is complete.

19. Explain about JSP architecture.

JavaServer Pages (JSP) is a technology used to develop dynamic web pages in Java.

JSP architecture is a 3-tier architecture that separates a web application's presentation, logic, and data layers.

Layers of JSP Architecture:

• The presentation layer, or client side, is responsible for displaying the user interface and handling user interaction.
• The logic layer, or server-side, is responsible for processing user requests and handling business logic.
• The data layer is responsible for storing and retrieving data from a database or other storage system.

Components of JSP Architecture:

• JSP pages: These are the main building blocks of a JSP application. They contain a combination of HTML, XML, and JSP elements that generate dynamic content.
• Servlets: JSP pages are converted into servlets by the JSP engine. Servlets are Java classes that handle HTTP requests and generate dynamic content.
• JSP engine (web container): This web server component is responsible for processing JSP pages. It converts JSP pages into servlets, compiles them, and runs them in the Java Virtual Machine (JVM).

20. What is a web container? What is a servlet engine?

Web Container is a java application that controls servlet. Servlet does not have a main() method, So they require a container to load them.

• Container is a place where servlet gets deployed.

Functionality:

• Servlet Management: Web containers handle servlet lifecycle, loading, initializing, and invoking servlet methods for client requests.
• Request Handling: They receive HTTP requests and forward them to appropriate servlets, managing the response sent back.
• Thread Management: Web containers manage multiple threads efficiently.
• Security: Web containers enforce security measures like authentication, authorization, and secure communication.
• Resource Management: They manage server resources to ensure optimal performance and scalability.

An example of a web container is Tomcat.

Servlet Engine: [Same as Web container]

21. Explain active attack and passive attack.

Active Attacks:

Active attacks involve some modification of the data stream or the creation of a false stream.

Types of Active Attacks:

1. Masquerade: Takes place when one entity pretends to be different.
2. Replay: Passive capture of the data unit and its subsequent retransmission to produce an unauthorized effect.
3. Modification of messages: Some portion of a legitimate message is altered or the messages are delayed or reordered to produce an unauthorized effect.
4. Denial of Service (DoS): Prevents or inhibits the normal use or management of communications facilities. This attack may have a specific target.

Passive Attacks:

Passive attacks are in the nature of eavesdropping on, or monitoring of, transmissions. The goal of the opponent is to obtain information that is being transmitted.

Types of Passive Attacks:

• Release of Message Content (Snooping): Obtaining sensitive or confidential information from intercepted messages or files.
• Traffic Analysis: Analyzing patterns of communication to derive information, even if message contents are encrypted.

Prevention Measures:

For active attacks: Implement strong authentication, integrity checks, and robust access controls.

For passive attacks: Use encryption to protect message content and randomize traffic patterns to thwart analysis attempts.

22. Explain Denial of Service (DoS) attacks. Discuss Real-time Transport Protocol (RTP).

Denial of Service (DoS) Attacks:

A Denial-of-Service (DoS) attack is an attack meant to shut down a machine or network, making it inaccessible to its intended users.

DoS attacks accomplish this by flooding the target with traffic, or sending it information that triggers a crash.

Methods of DoS Attacks:

• Flood attacks: Occur when the system receives too much traffic for the server to buffer, causing them to slow down and eventually stop. Popular flood attacks include:
  • Buffer overflow attacks: The concept is to send more traffic to a network address than the programmers have built the system to handle.
  • ICMP flood: Leverages misconfigured network devices by sending spoofed packets that ping every computer on the targeted network.
  • SYN flood: Sends a request to connect to a server, but never completes the handshake. Continues until all open ports are saturated with requests.
• Exploiting vulnerabilities: Some DoS attacks exploit vulnerabilities that cause the target system or service to crash. In these attacks, input is sent that takes advantage of bugs in the target that subsequently crash or severely destabilize the system.

Real-time Transport Protocol (RTP):

Real-time Transport Protocol (RTP) is a network protocol for the delivery of audio and video over the internet.

RTP is designed to provide end-to-end network transport functions suitable for applications transmitting real-time data, such as audio and video.

Use of Real-time Transport Protocol:

• Voice over IP (VoIP): RTP is commonly used in VoIP systems to transmit audio over the internet. It allows for the real-time delivery of voice calls with low latency.
• Video conferencing: RTP is often used in video conferencing systems to transmit audio and video in real time.
• Streaming media: RTP is used in many streaming media applications to deliver audio and video over the internet.
• Telephony: RTP is used in many telephony systems to transmit audio and video between devices. It allows for the real-time communication of multiple parties in a call.
• Broadcast television: RTP is used in some broadcast television systems to transmit audio and video over the internet.

23. What is the purpose of proxy?

A proxy is like a middleman in computer networks.

The purpose of a proxy is to act as an intermediary between a client and a server, serving several key functions:

• Boosting privacy: A correctly configured proxy server can shore up your digital security by masking your original IP address and replacing it with its own.
• Bypassing blocks: You can regain access to blocked websites by connecting to a proxy server—so long as the proxy itself isn't blocked.
• Igniting firewalls: Proxy servers sit between web browsers and the internet, meaning they can block certain web domains.
• Improving performance: Proxies can store local copies of sites so that they load faster the next time you access them. Plus, if multiple people try to access one site all at once, the proxy can send one request and forward it to them all.
• Digital convenience: A proxy server is a much more convenient way to allow or deny certain domains.

24. Write short note on a. Packet Filtering

Packet filtering is a firewall feature that allows or drops data packets based on simple, pre-defined rules regarding IP addresses, ports, or protocols.

Types of packet filtering:

• Static packet filtering firewalls: Static packet filters are so-called because users set firewall rules and these rules remain the same until they are changed.
• Dynamic packet filtering firewalls: Dynamic packet filtering is named because dynamic firewalls adjust the way they operate according to pre-set parameters.

Mostly following rules are used:

• Source and Destination IP address: Packets from certain IP addresses are only allowed to pass blocking other addresses.
• Source and destination ports: Packets from defined ports are accepted.
• Direction of traffic: Allows traffic only in defined direction. That is allows only either inbound packets or outbound packets.

Advantages of Packet Filtering

• Easy setup: Utilizes understandable options that decrease installation time.
• Fast defense: Enables simple, efficient, and quick allow and drop decisions.
• Inexpensive deployment: The least expensive firewall options.
• Light resources: Uses minimal compute resources (memory, CPU processing, etc.) which frees up resources for more computationally intensive features and capabilities.

b. Proxy Firewall

A proxy firewall is a network security system that protects network resources by filtering messages at the application layer.

• Proxy Firewalls are the most secure types of firewalls, because they work at the application level.
• Firewall proxy servers centralize all activity for an application into a single server.

Advantages:

• Enhanced Security: Proxy firewalls inspect and filter traffic at the application layer, allowing them to detect and block various types of threats, including viruses, malware, and unauthorized access attempts.
• Access Control: This enables organizations to restrict access to certain websites, services, or protocols, thus minimizing the risk of data breaches and unauthorized access.
• Content Filtering: Proxy firewalls can also be configured to filter content based on predefined criteria, such as URL categories, keywords, or file types.

Drawbacks:

• The proxy-based firewalls are not compatible with all protocols.
• Another major drawback of proxy firewalls is latency, especially during heavy traffic.

c. Three-way Handshaking TCP Connection Establishment

A TCP connection is a connection-oriented protocol used to establish and maintain communication between two computers. A network connection is established between a client and server in three steps.

1. Step 1 (SYN): In the first step, the client wants to establish a connection with a server, so it sends a segment with SYN (Synchronize Sequence Number) which informs the server that the client is likely to start communication and with what sequence number it starts segments with.
2. Step 2 (SYN + ACK): The server responds to the client request with SYN-ACK signal bits set. Acknowledgement (ACK) signifies the response of the segment it received and SYN signifies with what sequence number it is likely to start the segments with.
3. Step 3 (ACK): In the final step, the client acknowledges the response of the server, and they both establish a reliable connection with which they will start the actual data transfer.

Advantages:

• The three-way handshake ensures a reliable connection establishment process.
• Three-way handshake helps prevent unauthorized access or data interception.
• The three-way handshake allows each party to confirm the successful receipt of synchronization information from the other party.

Disadvantage:

In situations where resources are limited or network traffic is heavy, the overhead associated with the handshake process can impact overall system performance.

d. VPN

VPN stands for Virtual Private Network. It refers to a safe and encrypted network that allows you to use network resources in a remote manner.

• Using VPN, you can create a safe connection over a less secure network.

VPN Work Process:

• VPN works by creating a secure tunnel using powerful VPN protocols.
• It hides your IP address behind its own IP address that encrypts all your communication.
• Thus, your communication passes through a secure tunnel that allows you to use network resources freely and secretly.

VPN Protocols:

There are several different VPN protocols that are used to create secure networks:

• IP security (IPsec)
• Point to Point Tunneling Protocol (PPTP)
• Secure Sockets Layer (SSL) and Transport Layer Security (TLS)

25. What is the responsibility of the Mail Transfer Agent?

MTAs transfer electronic mail messages between sender and recipient computers using the SMTP protocol, ensuring efficient message transmission.

MTA is responsible for many tasks in the email delivery process:

• Queuing: Storing emails in a queue for sequential dispatch to the recipient's server.
• Optimal Scheduling: Determining the best timing for email dispatch considering recipient time zones and other relevant factors.
• Connection Oversight: MTAs manage the initiation, maintenance, and termination of network connections crucial for email transmission.
• Data Transmission: They facilitate the transfer of email content, attachments, and other relevant data between network points.
• Generating bounces: Generating and transmitting bounce messages to the sender for undelivered emails.
• Tracking delivery status: Monitoring and logging the delivery progress of each email—whether delivered, bounced, or deferred.