Posts tagged “Networking”
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12 posts
Why small TCP writes stall: Nagle's algorithm, delayed ACKs and TCP_NODELAY
Split a request into two small writes and the second piece can wait for the peer's ACK. What RFC 896, 1122 and 9293 say about Nagle's algorithm and delayed ACKs, and what TCP_NODELAY changes.
The Retry-After header: what it means on 429, 503, 413 and 3xx, and how clients should read it
Retry-After per RFC 9110 and RFC 6585: its two value formats, what it means with each status code, turning an HTTP-date or a seconds value into a wait, and handling invalid or huge values.
Happy Eyeballs v2: how dual-stack clients race IPv6 and IPv4
How RFC 8305 clients query AAAA and A, sort addresses and stagger connection attempts to use whichever connects first when DNS returns IPv6 and IPv4, and what its recommended defaults mean.
Added a DNS record but it still says the name doesn't exist? NXDOMAIN, NODATA and negative caching
Why resolvers can keep saying "no such name" after you add a record: NXDOMAIN vs NODATA, the negative TTL from the SOA, the NXDOMAIN cut, and the 5-minute cap on failure caching.
Safe and idempotent HTTP methods: why retrying POST is risky and PUT isn't
What RFC 9110 means by safe and idempotent methods, which ones a client may resend after a dropped connection, why POST and PATCH need care, and how If-Match makes an update conditional.
Why TIME-WAIT sockets pile up: TCP's 2×MSL, Linux's 60 seconds, and what tcp_fin_timeout doesn't change
Why the side that closes a TCP connection first sits in TIME-WAIT, RFC 9293's 2×MSL versus Linux's fixed 60 seconds, what tcp_fin_timeout actually controls, and tcp_tw_reuse's default.
HTTP Range requests, 206 and 416: how resuming a download works
How Range, Content-Range and If-Range work with 206 Partial Content and 416 Range Not Satisfiable, per RFC 9110, and why a server may ignore Range and send 200.
no-cache vs no-store: which Cache-Control directive stops storage
no-cache doesn't mean "don't cache". Using RFC 9111, this post compares no-cache, no-store, max-age=0 and Pragma, and shows where behavior varies across CDNs and browsers.
301, 302, 307 or 308? Permanent vs temporary redirects, and why POST turns into GET
The differences between HTTP redirects 301, 302, 303, 307 and 308, from RFC 9110 and the WHATWG Fetch standard: when POST becomes GET, and how caches and search engines treat each code.
What does the /24 in 192.168.0.0/24 mean? CIDR and subnets
What the /24 after an IP address means, how it relates to the subnet mask, how to work out the network and broadcast addresses and usable hosts, and the private IPv4 ranges.
From domain name to IP address: how a DNS lookup works
What happens between typing a name and getting an IP address: stub and recursive resolvers, authoritative servers, caches, A and AAAA records and TTL, explained from the RFCs.
Why bücher.example turns into xn--bcher-kva: IDNs and Punycode
Why a domain with accents or non-Latin script shows up as xn--… in DNS settings and certificates, how Punycode spells it in ASCII, the mapping rules before it, and homograph phishing.
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