Tag
ttl
- Feb 27, 2026 The IPv4 Header Fields That Forwarding Rewrites Which of the twenty header bytes a router must read, which it decrements or recomputes in place, and where the header checksum stops protecting anything. networking
- Oct 17, 2025 DNS TTL, Resolver Caches, and the Real Duration of a Cutover How negative caching, recursive resolvers, and connection reuse stretch a five-minute TTL into hours of split traffic, and what actually bounds the redirect window. cloud infrastructure
- Aug 22, 2025 Negative Caching: NXDOMAIN, NODATA, and the SOA Minimum How a resolver distinguishes a name that does not exist from a name with no records of the requested type, and how the SOA fields set the lifetime of both. internet protocols
- Jul 17, 2025 TTL Expiry and the Two Ways an Entry Dies How deadline-based caching separates logical expiry from physical reclamation, why lazy and active expiry put the cost in different places, and how clocks and replicas make a TTL a bound rather than a promise. backend systems
- Dec 25, 2023 What ICMP Echo and TTL Probing Actually Measure The difference between the forward and return paths a traceroute samples, why hop times are often wrong, and what rate limiting on the control plane does to the numbers. networking
- Oct 10, 2022 Record Semantics: CNAME Exclusivity and RRset Atomicity Why a CNAME cannot coexist with other data at the same name, how RRsets are ordered and cached as units, and what an alias does to the query type. internet protocols