Web Applications Overview
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Questions and Answers

What is the main function of the web application server?

  • To serve static content to clients
  • To provide user authentication services
  • To generate and send results back to the web server (correct)
  • To manage the database directly

    • Which layer of the web application architecture is responsible for user interface components?

  • Presentation Layer (correct)
  • Business Layer
  • Database Layer
  • Persistence Layer

    • How can the layers of a web application architecture be modified?

  • Changes are reflected only during server upgrades
  • Each layer can be upgraded independently (correct)
  • Only all layers can be changed at once
  • Layers must be rewritten to accommodate changes

    • What does the Business Layer primarily do?

    <p>Manages the interactions between user requests and the data accessed</p> Signup and view all the answers

    Which of the following describes the Persistence Layer?

    <p>It provides access to persistent storage of data</p> Signup and view all the answers

    What common technology is used to build user interface components in the Presentation Layer?

    <p>HTML, CSS, and JavaScript</p> Signup and view all the answers

    What type of logic is encoded in the Business Layer?

    <p>Workflow logic for data processing</p> Signup and view all the answers

    What is a crucial benefit of using a three-tier architecture for web applications?

    <p>Isolation of presentation, logic, and data handling</p> Signup and view all the answers

    What does the Same-Origin Policy (SOP) restrict?

    <p>Communication between different origins</p> Signup and view all the answers

    Which components must be identical for two URLs to share the same origin?

    <p>Protocol, domain, and port number</p> Signup and view all the answers

    Which of the following best explains why SOP is important?

    <p>It prevents access to sensitive data on other websites.</p> Signup and view all the answers

    What is the primary function of Cross-Origin Resource Sharing (CORS)?

    <p>To specify which origins can access server resources</p> Signup and view all the answers

    What does the Access-Control-Allow-Origin header do?

    <p>Specifies which origins are allowed to access the resource</p> Signup and view all the answers

    Which situation would require a preflight request in CORS?

    <p>Requests with custom headers or methods</p> Signup and view all the answers

    What aspect of web application security does SOP primarily enhance?

    <p>User privacy and data isolation</p> Signup and view all the answers

    How does CORS maintain security while allowing cross-origin communication?

    <p>By specifying allowed origins and methods through headers</p> Signup and view all the answers

    What is the primary function of the Domain Name System (DNS)?

    <p>To convert domain names into IP addresses.</p> Signup and view all the answers

    Which component of the DNS process acts as a librarian, searching across various servers?

    <p>DNS Recursor</p> Signup and view all the answers

    What is the role of the Root Nameserver in the DNS process?

    <p>To direct the DNS Recursor to TLD nameservers.</p> Signup and view all the answers

    What type of IP address is typically represented as 192.168.1.1?

    <p>IPv4</p> Signup and view all the answers

    In the DNS hierarchy, what is the purpose of the Authoritative Nameserver?

    <p>To deliver the exact IP address for a requested hostname.</p> Signup and view all the answers

    What is a primary characteristic of the client-server model?

    <p>Tasks are divided between clients and servers with no resource sharing.</p> Signup and view all the answers

    What occurs first when a user enters a URL in their web browser?

    <p>The request is sent to a DNS resolver.</p> Signup and view all the answers

    Which of the following best describes a client in the digital world?

    <p>A program running on a local machine requesting services.</p> Signup and view all the answers

    What best describes a TLD Nameserver's function in the DNS resolution process?

    <p>To narrow down the search to a specific top-level domain.</p> Signup and view all the answers

    What role does a server play in the client-server architecture?

    <p>Processes and delivers service requests from clients.</p> Signup and view all the answers

    Which of the following IP address formats is newer and more complex than IPv4?

    <p>IPv6</p> Signup and view all the answers

    How does centralized security benefit web applications?

    <p>Simplifies the implementation of enhanced security measures.</p> Signup and view all the answers

    What is one advantage of automated monitoring in web applications?

    <p>Decreases the need for manual user tracking.</p> Signup and view all the answers

    What defines a client program's operation?

    <p>It starts upon user request and terminates after service completion.</p> Signup and view all the answers

    What is one key distinction between clients and servers in this model?

    <p>Clients initiate requests, while servers respond to those requests.</p> Signup and view all the answers

    Which of the following is NOT a benefit of using web applications?

    <p>More complexity in managing access permissions.</p> Signup and view all the answers

    What is the primary function of a session in web applications?

    <p>To remember user actions during their session.</p> Signup and view all the answers

    How is a session ID typically stored on the user's device?

    <p>As a cookie.</p> Signup and view all the answers

    What occurs when a session expires?

    <p>The user is logged out and session data can be deleted.</p> Signup and view all the answers

    What distinguishes tokens from sessions in web applications?

    <p>Tokens can be used in stateless communication.</p> Signup and view all the answers

    Which type of token is commonly used in OAuth frameworks?

    <p>OAuth Tokens</p> Signup and view all the answers

    What is the main purpose of token generation upon successful authentication?

    <p>To produce a token containing user information and permissions.</p> Signup and view all the answers

    What does a JSON Web Token (JWT) contain?

    <p>Encoded information about the user and their permissions.</p> Signup and view all the answers

    What role do tokens play in authentication systems?

    <p>They verify user identity and define access rights.</p> Signup and view all the answers

    Study Notes

    How Web Applications Work

    • Web application servers process tasks and generate results based on data requests.
    • Information is sent from the web server back to the client’s device (laptop, desktop, mobile).
    • The requested information is displayed on the user’s screen.

    Web Application Three-Tier Architecture

    • Multi-Tier Architecture allows independent upgrades and replacements of different layers.

    Presentation Layer

    • Interface layer accessible via browsers, includes UI components built with HTML, CSS, and JavaScript.
    • Responsible for presenting data to users and interacting with them.

    Business Layer

    • Also known as Business Logic or Domain Logic; processes user requests and manages data flow.
    • Contains workflow rules such as booking hotel rooms on related websites.

    Persistence Layer

    • Storage or data access layer; handles data calls and manages access to application’s persistent storage.
    • Optimizes data retrieval by integrating with the business layer.

    Same-Origin Policy (SOP)

    • A browser security feature that restricts documents/scripts from different origins from interacting.
    • An origin consists of the protocol, domain, and port number; two URLs are considered the same origin if these match.
    • Prevents malicious scripts from accessing sensitive data across different sites.

    Purpose of SOP

    • Enhances security and user privacy by isolating data from different origins.

    Cross-Origin Resource Sharing (CORS)

    • A mechanism that allows web servers to specify which origins can access their resources.
    • Involves CORS headers that permit or deny access based on specified conditions.

    CORS Details

    • Access-Control-Allow-Origin is a key header that identifies permitted origins.
    • Preflight requests (OPTIONS) check server permissions for specific requests.

    Benefits of Web Applications

    • Centralized Security Protocols streamline security management.
    • Controlled Access simplifies user permission handling.
    • Analytics and Monitoring provide insights into user behavior and system performance.

    Client-Server Model

    • A distributed application structure separating providers of services (servers) from requesters (clients).
    • Clients make requests, while servers respond with data; clients do not share resources.
    • Examples include email systems and the World Wide Web.

    DNS (Domain Name System)

    • Functions as the Internet's phonebook, translating domain names into IP addresses for browser access.
    • Allows users to navigate using familiar domain names instead of numeric IPs.

    DNS Resolution Process

    • Converts hostnames like www.example.com into IP addresses.
    • Involves multiple DNS servers: Recursor, Root Nameserver, TLD Nameserver, and Authoritative Nameserver.

    Traffic Routing Using DNS

    • When requesting a website, the user's input is processed by a DNS resolver managed by their ISP.
    • Ensures efficient and correct traffic routing to the desired web resources.

    Sessions

    • Initiated when a user logs in; generates a unique session ID for tracking.
    • Session ID is stored as a cookie, while session data resides on the server.
    • Sessions typically expire after inactivity or upon user logout.

    Tokens

    • Secure strings used for user identification and authentication in web applications.
    • Facilitate stateless authentication, minimizing server resource usage.

    Types of Tokens

    • JSON Web Tokens (JWT) include encoded user details and permissions, digitally signed for integrity.
    • OAuth Tokens enable limited resource access without exposing user passwords.

    Token Functionality

    • Generated upon successful authentication; contains necessary user information.
    • Transmitted to clients and stored in local storage or cookies for subsequent requests.

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    Quiz Team

    Description

    Explore the fundamental concepts of how web applications function, including the three-tier architecture that separates Presentation, Business, and Persistence layers. This quiz will enhance your understanding of each layer's role in processing user requests and managing data flow.

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