Internet Basics Lecture Series

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Questions and Answers

What is the main semantic difference between PUT and POST requests in HTTP?

PUT requests identify the entity being sent, while POST requests identify the resource that will handle the enclosed entity.

Describe the function of a forward proxy and how it differs from a reverse proxy.

A forward proxy acts as an external-facing stand-in for origin servers, whereas a reverse proxy is an internal-facing proxy that balances load among multiple origin servers.

List two benefits of caching mechanisms in web services.

Caching improves response times for repeated requests and reduces network bandwidth usage.

Define hypertext and hypermedia.

Hypertext is text that contains links to other texts, while hypermedia extends this concept to include graphics, video, and sound. Signup and view all the answers

What is meant by 'Semantic Transparency' in the context of HTTP?

Semantic Transparency means that the use of caches must not affect the responses as if they were served directly by the origin server. Signup and view all the answers

What are the initial steps in W3C's standardization process?

The process begins with an expression of interest by members or the public, which, when sufficiently raised, leads to the formation of a Working Group. Signup and view all the answers

How can a server prevent the caching of its responses?

A server can prevent caching by specifying a past expiration date or using a Cache-Control header set to 'must-revalidate'. Signup and view all the answers

What do the acronyms ISP, POP, and IXP stand for?

ISP stands for Internet Service Provider, POP stands for Points of Presence, and IXP stands for Internet eXchange Points. Signup and view all the answers

What should a cache rely on to determine if it is fresh when there is no Expires header?

A cache can use the Last-Modified header to heuristically determine freshness by checking for recent changes. Signup and view all the answers

Explain the purpose of a web accelerator proxy.

A web accelerator proxy improves web performance through techniques such as prefetching, compression, and image manipulation. Signup and view all the answers

What is the relationship between URI, URL, and URN?

URI is a global identifier that can be a URL (which locates a resource) or a URN (which names a resource independent of its location). Signup and view all the answers

Differentiate between a proxy, a gateway, and a tunnel server.

A proxy acts on behalf of an origin server, a gateway serves as an intermediary for another server, and a tunnel server relays messages without inspecting them. Signup and view all the answers

What happens when a resource on the origin server changes but the cached version is still being used?

The cached version becomes outdated and can violate the principle of Semantic Transparency. Signup and view all the answers

How does the Basic authentication scheme for HTTP transmit credentials and what is its main security concern?

It transmits credentials as user ID/password pairs in base64 encoding, which is not encrypted, making it insecure as the credentials are in plain text. Signup and view all the answers

Under what conditions are HTTP requests considered safe and idempotent?

Safe requests do not alter state, while idempotent requests have no additional effects if executed multiple times. Signup and view all the answers

What is a potential security risk associated with embedding credentials in the URL?

Embedding credentials in the URL is insecure as it can easily be exposed in server logs and browser history. Signup and view all the answers

What role does the Advisory Committee play in W3C’s standardization process?

The Advisory Committee decides if and when the specifications produced by the Working Group can be published as Recommendations. Signup and view all the answers

What is the significance of Project Xanadu in relation to the web?

Project Xanadu is considered a precursor of the web as it aimed to create a hypertext system that could connect documents extensively. Signup and view all the answers

How do Content Delivery Networks (CDNs) work to enhance performance?

CDNs work by replicating a resource on multiple local nodes, directing client requests to the nearest node to reduce latency. Signup and view all the answers

What are the five constraints that define the REST architectural style?

The five constraints are Resource Identification, Uniform Interface, Self-describing Messages, Hypermedia as the Engine of Application State (HATEOAS), and Stateless Interactions. Signup and view all the answers

How does the caching mechanism in REST improve performance and scalability?

Caching allows responses to be served without accessing the origin server, thereby reducing response times and scaling to handle more requests. Signup and view all the answers

In Richardson’s model, what is Level 3 and which REST principles is it related to?

Level 3 is Hypermedia Controls, which relates to the principles of HATEOAS and Stateless Interactions. Signup and view all the answers

What does the Uniform Interface constraint provide for RESTful APIs?

It provides a standardized way to interact with all resources, simplifying interaction design. Signup and view all the answers

What are the principles that should govern the design of RESTful APIs?

The design should prioritize statelessness, resource identification, supported representations, and hypermedia control. Signup and view all the answers

What steps should be followed in designing a RESTful API according to Masse's book?

Define the data model, split data into resources, name resources with URIs, define the supported uniform interface subset, design accepted and served representations, link between resources, model typical sequences of events, and define error conditions. Signup and view all the answers

What are the main functions of the Presentation Layer in the application layers pattern by Fowler?

The Presentation Layer is responsible for rendering data, reacting to events, and handling communication or conversation logic such as sessions. Signup and view all the answers

How do layers and tiers differ in an architectural context?

Layers are functional organization units, while tiers are physical organization units that can host these layers, such as client-server structures. Signup and view all the answers

What architectural decision is crucial for determining how functionality is distributed between client and server?

The key decision is how much functionality is 'shipped' to the client, distinguishing between thin and thick client models. Signup and view all the answers

Provide examples of Remote-Presentation Applications as defined in the content.

Examples of Remote-Presentation Applications include thick client models, Single Page Applications (SPAs), and multi-device web applications. Signup and view all the answers

Describe the Resource Layer's role in the application layers pattern.

The Resource Layer provides logic to access the data required by the application logic, including interactions with databases, files, and other support functions. Signup and view all the answers

What is the role of intermediaries in RESTful architecture?

The presence of intermediaries is promoted to enhance communication, caching, and overall efficiency of interactions between clients and servers. Signup and view all the answers

What characteristics define Distributed Applications according to the content?

Distributed Applications often use a thick client model and feature Single Page Applications (SPAs) where the client handles presentation and some application logic while delegating processing to the server. Signup and view all the answers

What is the main advantage of using semantic HTML elements over non-semantic ones?

Semantic HTML elements improve accessibility and SEO by providing meaning to the content, enhancing how browsers and search engines interpret it. Signup and view all the answers

How did HTML5 change the way embedded video and audio are handled compared to previous versions?

HTML5 introduced native mechanisms for embedding video and audio, replacing reliance on non-native technologies like Flash. Signup and view all the answers

What are the two main types of form validation in HTML and when should they be used?

The two main types are client-side validation, which should be used for immediate feedback to users, and server-side validation for ensuring data integrity before processing. Signup and view all the answers

What factors does the CSS cascade mechanism consider to resolve conflicts between styles?

The cascade mechanism considers importance (using the !important directive), specificity (how many selectors match), and source order (later rules winning). Signup and view all the answers

In the context of CSS specificity, which selector has the highest priority?

The highest priority is given to the Element ID selector. Signup and view all the answers

When would you recommend using a Single Page Application (SPA)?

SPAs are recommended for applications requiring rich, complex user interfaces and aiming for a seamless user experience. Signup and view all the answers

What are some options available for creating dynamic server-side web pages?

Options include using Content Management Systems like WordPress and static site generators like Jekyll. Signup and view all the answers

How is the MVX pattern defined for JavaScript web applications, particularly when X is C, P, or VM?

In this pattern, C represents Controller, P is for Presenter, and VM is for ViewModel, each serving distinct roles in managing application logic and UI. Signup and view all the answers

Study Notes

Lecture 1

Hypertext contains links to other texts. Hypermedia is hypertext including graphics, video, and sound.
Project Xanadu led by Ted Nelson was a precursor to the web.
W3C standardization involves expressing interest, forming working groups, defining activities, and producing specifications and guidelines.
Advisory Committee decides when recommendations can be published.

Lecture 2

ISP is Internet Service Provider, providing internet access.
POP is Point of Presence, where customer data enters the ISP network.
IXP is Internet eXchange Point, where ISP networks connect.
URI is a global identifier for resources. A URL is a URI that locates a resource and URN names a resource independent of its location.

Lecture 3

Proxy acts on behalf of an origin server.
Gateway acts as intermediary, and clients interact as if it was the origin server.
Tunnel server only routes messages without looking at them.
HTTP requests are safe if they don't change state and idempotent if they have the same effect no matter how often performed.
Safe methods are GET, HEAD, OPTIONS, and TRACE. Idempotent methods are GET, HEAD, OPTIONS, PUT, DELETE.
PUT requests identify the enclosed entity while POST requests identify the handling service.
Proxy types include forward (N:1), reverse (1:N), and web accelerators.

Lecture 4

Application layers include presentation, application logic, and resource layers.
Layers are functional units whereas tiers are physical units.
Architectural decisions determine which layer handles functionality.
Remote/distributed application split can be a thick or thin client handling presentation and other layers.

Lecture 5

Semantic elements in HTML, like and , have predefined meaning.

HTML5 uses native mechanisms for handling video and audio.

HTML form validation can use client-side (JavaScript) or server-side mechanisms.

CSS rules are resolved through importance, specificity, and source order.

Single-page applications are well-suited for applications with complex requirements.

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