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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- UDP is unreliable. How can an application still get reliable delivery over it?
The application adds what it needs on top: sequence numbers to order and detect gaps, acknowledgements and retransmission for missing data, and timers. QUIC, used by HTTP/3, does exactly this over UDP, along with congestion control and encryption.
AdvancedQuick answer1 min read - What is head-of-line blocking, and how do HTTP/2 and HTTP/3 deal with it?
Head-of-line blocking is when one slow or lost item holds up everything queued behind it. HTTP/1.1 blocks at the request level, HTTP/2 fixes that with multiplexing but still blocks at the TCP level on packet loss, and HTTP/3 over QUIC removes even that.
AdvancedQuick answer1 min read - What is HTTP/3, and why does it run over QUIC instead of TCP?
HTTP/3 is HTTP carried over QUIC, a protocol built on UDP that has its own reliable streams, congestion control and built-in TLS 1.3. It avoids TCP head-of-line blocking, connects faster, and survives network changes such as moving from Wi-Fi to mobile data.
AdvancedQuick answer1 min read