Learning series · 6 episodes · Senior / Staff
The Connection Is More Than an IP
Six networking investigations covering DNS, safe address cutovers, HTTPS identity, TLS setup, HTTP transport blocking and QUIC mobility.
Start series →Follow the decisions in order
- Part 1 of 6
Senior
The API is healthy. Why does the first request wait on DNS?Trace stub, recursive and authoritative lookups, including TTLs, CNAME chains and negative caching.
- Part 2 of 6
Staff
We changed the DNS record. Why are 20% of users still on the old IP?Design a safe DNS-based migration despite existing resolver caches, HTTP connections, stale answers and rollback limitations.
- Part 3 of 6
Senior
The server has a valid certificate. Why does the browser refuse HTTPS?Explain SAN hostname validation, intermediate and root trust chains, SNI and client-specific certificate policy.
- Part 4 of 6
Staff
TLS 1.3 is faster. Should a payment API accept 0-RTT?Compare full TLS 1.2 and TLS 1.3 setup, PSK resumption, early-data replay and safe application policy.
- Part 5 of 6
Staff
HTTP/2 multiplexes requests. Why can one lost packet stall them all?Distinguish HTTP application serialization, TCP stream-level head-of-line blocking and independent QUIC stream delivery.
- Part 6 of 6
Staff
The phone switched from Wi-Fi to 5G. Why did the request survive?Explain address-independent QUIC connection IDs, path validation, anti-amplification and backend affinity across network changes.