How the Web Works

Quiz: Trace the Request

intermediate8 min read

Trace the Request: End-to-End

You type https://app.example.com/dashboard into your browser and hit Enter. What follows is a chain of events involving DNS, TCP, TLS, HTTP, caching, and browser rendering.

These 10 questions walk you through that chain, step by step. Each question tests a concept from this module. Don't guess — trace through the system mentally, the way a packet traces through the network.

Question 1: DNS Resolution

Quiz
You type https://app.example.com/dashboard and press Enter. The browser has never visited this domain. What is the FIRST network-level action the browser takes?

Question 2: TCP Handshake

Quiz
DNS returns the IP 93.184.216.34. Now the browser needs to establish a connection. How many round trips does the TCP three-way handshake require?

Question 3: TLS 1.3 Handshake

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The server supports TLS 1.3. After TCP is established, how many additional round trips does the TLS 1.3 handshake add?

Question 4: HTTP/2 vs HTTP/1.1

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The connection is established. The browser requests /dashboard (HTML) which references 3 CSS files, 5 JS files, and 12 images. With HTTP/2, how does the browser fetch all 20 resources?

Question 5: Cache-Control Headers

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One of the CSS files was cached from a previous visit with headers: Cache-Control: public, max-age=31536000, immutable. The file is named style.a8f3e2.css. What does the browser do?

Question 6: CDN Edge Caching

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The HTML for /dashboard is not cached in the browser. The site uses a CDN. The CDN edge server in the user's city has a cached copy (s-maxage has not expired). What happens?

Question 7: Head-of-Line Blocking

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During the page load, a TCP packet carrying stream 3 data (a JavaScript file) is lost in transit. The connection uses HTTP/2 over TCP. What happens to stream 7 (an image) whose data has arrived at the TCP layer?

Question 8: Browser Architecture

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The HTML is parsed and the browser encounters an inline script that runs a heavy computation for 300ms. During those 300ms, what CAN still happen smoothly?

Question 9: Latency vs Bandwidth

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A user on a 200 Mbps connection has 150ms RTT to your origin (no CDN). Loading the page requires 5 sequential round trips. The total critical resources are 100KB compressed. What dominates the load time?

Question 10: Full Picture

Quiz
A returning user (has cached TLS session, DNS cached, static assets cached) navigates to a new page on your HTTP/3-enabled site with a CDN. What is the minimum number of round trips before the first byte of HTML arrives?
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