Performance Measures — Part 1 MCQs with Explanations

Threads are sequential units of controlled execution for applications.

The browser negotiates a TCP three-way handshake with the remote web server to set up a TCP/ IP connection.

The handshake consists of a Synchronize, Synchronize-Acknowledge, and Acknowledge message to be passed between the browser and the remote server.

The handshake allows the server to acknowledge and accept the attempt.

The Transport layer is where our TCP (or UDP) communication takes place.

The status code 200 indicates a successful response from the server.

The status code 500 means that there was an error when trying to fulfill the request.

The Application layer handles the top-level communication that the client and servers use, like HTTP and SMTP for email clients.

The status code 404 means that the server could not find the resource requested.

The maximum size of an IP packet for IPv4 or IPv6 is 65535.

Performance refers to the speed at which an application functions. It is a multifaceted aspect of quality.

When we’re talking about web applications, the time it takes your application to be presented to your users is what we will call web performance.

The speed at which your application responds to your users’ interactions is what we’ll call runtime performance.

The span of time that you are waiting for the page to be usable depends on web performance.

In addition to starting and stopping sound and video, you can skip (or “seek”) to a desired location within the media by setting the currentTime property.

When we compare the runtime performance for coalescing functionality, using functions, and using objects, the Firefox UsingFunct shows a better performance.

When we compare the runtime performance for coalescing functionality, using functions, and using objects, the Firefox UsingFunct shows a poorer performance.

Closure Compiler can be run in either of two modes: 1. In Simple mode it mostly performs like most other minifiers, removing whitespace, line breaks, and comments 2. In Advanced mode it rewrites the JavaScript by renaming variables and functions from longer descriptive names to single letters to save file size, and it inlines functions, coalescing them into single functions wherever it determines that it can

In Advanced mode, the Closure Compiler rewrites the JavaScript by renaming variables and functions from longer descriptive names to single letters to save file size, and it inlines functions, coalescing them into single functions wherever it determines that it can.

Firebug is an extension of Mozilla.

Firebug is an extension for the Mozilla Firefox browser that allows you to debug and inspect HTML, CSS, the Document Object Model (DOM) and JavaScript.

Web developers use Firebug for the following reasons : 1. Inspect the behavior of HTML/CSS, and modify style & layout with true WYSIWYG 2. Debug JavaScript 3. Detect performance of website 4. Track Cookies & Sessions

The goals for using Firebug is : 1. Performance 2. Modularity 3. Shared code 4. Compatibility

The features present in the User Interface are : 1. Port of Firebug’s Visual Object Representation (aka Reps) 2. Recreation of Firebug 1.3 User Interface with pixel precision 3. Menu options 4. Resizable Side Panel 5. Skinnable Interface

The default value of the property overrideConsole is true.

Only disableXHRListener property has a default value false. The properties disableWhenFirebugActive and showIconWhenHidden has a default value of true.

When Firebug is used as a JavaScript Debugger and Profiler, it can be used to find scripts easily and also pause the execution in any desired line.

Slow for PhantomJS is a command line script that allows page performance analysis from live URLs, unlike YSlow for Command Line (HAR) where a pre-generated HAR file is needed in order to analyze page performance.

YSlow for PhantomJS introduces new output formats for automated test frameworks: TAP (Test Anything Protocol) and JUnit.

Intially, YSlow was an extension of Firefox.

For a deeper analysis of a page’s web performance you can use YSlow.

There are totally 23 rules in the ruleset of YSlow (V2) namely : 1. Minimize HTTP Requests 2. Use a Content Delivery Network 3. Avoid empty src or href 4. Add an Expires or a Cache-Control Header 5. Gzip Components 6. Put StyleSheets at the Top 7. Put Scripts at the Bottom 8. Avoid CSS Expressions 9. Make JavaScript and CSS External 10. Reduce DNS Lookups 11. Minify JavaScript and CSS 12. Avoid Redirects 13. Remove Duplicate Scripts 14. Configure ETags 15. Make AJAX Cacheable 16. Use GET for AJAX Requests 17. Reduce the Number of DOM Elements 18. No 404s 19. Reduce Cookie Size 20. Use Cookie-Free Domains for Components 21. Avoid Filters 22. Do Not Scale Images in HTML 23. Make favicon.ico Small and Cacheable

It is mandatory to run FireBug before running YSlow.

The YSlow for Mobile works as bookmaklet.

A content delivery network (CDN) allows you to distribute your static assets like images, JavaScript files and stylesheets to geographically distributed servers. This gets the content of your page to your user’s browser faster.

If you want to run tests on web sites that are not publicly available—like a QA or development environment, or if you can only have your test results stored on your own servers because of legal or other reasons, then installing your own private instance of WebPagetest is the way to go.

In the Auth tab you can specify credentials to use if the web site uses HTTP authentication for access.

The Script tab can be used to run more complex tests that involve multiple steps including navigate to multiple URLs, etc.

The setUserAgent spoofs the client user agent.

The Block tab allows us to block content coming in our request.