Interview Q&A / Computer Networks
Computer Networks interview questions
What happens when you open a website, TCP vs UDP, DNS and HTTP.
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- How does DNS resolution work, step by step?
Your device asks a recursive resolver, which checks its cache and, if needed, asks a root server, then the TLD server (like .com), then the domain's authoritative server, which returns the IP address. Every answer carries a TTL, so resolvers and devices cache it and skip most of these steps next time.
IntermediateIn-depth4 min read - What is DNS TTL, and why do DNS changes seem to take time to "propagate"?
TTL is how many seconds resolvers may cache a record. When you change a record, resolvers that cached the old one keep serving it until its TTL expires, so different users see the change at different times.
BeginnerQuick answer1 min read - How do Cache-Control and ETag let a browser reuse a response?
Cache-Control: max-age tells the browser how long it may reuse a response without asking. After that, the browser can revalidate with If-None-Match and the ETag; if nothing changed, the server replies 304 Not Modified with no body.
IntermediateQuick answer1 min read