IP Routing Explained
Every router holds a forwarding table and every packet carries a destination. The router finds the longest matching prefix, resolves the next hop, and forwards — we follow one packet across several hops and show what changes at each step: MAC addresses rewritten, TTL decremented, the routing decision repeated.
Topics covered:
- The forwarding table: prefixes, next hops, and interfaces
- Longest-prefix match: why a /32 beats a /24
- Next-hop resolution: ARP and NDP between direct neighbors
- What changes per hop: MAC rewrite, TTL decrement, checksum
- Default routes and how they keep tables small
- How BGP and OSPF populate the tables that forward packets
Related articles
TCP Nagle and Delayed ACK: Why Small Writes Stall for 40ms
The Nagle algorithm and delayed ACK interaction that adds a 40ms stall to small writes, how to see it in tcpdump, and when TCP_NODELAY actually helps.
HTTP Keep-Alive and Connection Reuse: What the Machine Actually Does
Why HTTP/1.1 needs Connection: keep-alive, what the server timeout does, and how curl and ss reveal whether your connections are being reused or rebuilt.
DNS Resolution End to End: From resolv.conf to Recursive Lookup
What really happens when you resolve a hostname — resolvers, cache TTLs, CNAME chains, EDNS, TCP fallback on truncation, and how DoH changes the path.
More in Networking
HTTP/3 and QUIC Explained
The transport protocol that replaces TCP — multiplexing without head-of-line blocking, connection migration, and 0-RTT.
WatchThe Full Lifecycle of an HTTP Request
Watch a single request travel from a browser through DNS, TCP, TLS, HTTP, a load balancer, a server, and a database — with live packet-level tracing.
WatchLoad Balancing Protocols
Layer 4 vs. layer 7 balancing, NAT rewrites, and health checks — the actual packet and request flows that distribute traffic across a backend pool.
DetailsSockets and the Network Stack
The path a byte takes from a syscall to the wire — sockets, kernel buffers, queues, and protocol layers, and where sendto and recvfrom actually do their work.
DetailsCongestion Control Visualized
How TCP probes for available bandwidth — slow start, congestion avoidance, and packet loss as the signal that tells senders when to back off.
DetailsHTTP/2 and HTTP/3
Streams, frames, and the transports underneath — what HTTP/2 multiplexing changes at the application layer and what moving to QUIC changes at the transport layer.
DetailsTLS Handshake Explained
The cryptographic negotiation inside TLS 1.3 — key exchange, certificate validation, and the single round trip that encrypts everything after it.
DetailsDNS Resolution Visualized
Follow a query from stub resolver to authoritative server — cache hits, recursive walking, TTL expiry, and the exact packet flow that turns a hostname into an IP.
DetailsTCP Three-Way Handshake Explained
SYN, SYN-ACK, ACK — the exact packets that open a TCP connection, the sequence numbers that synchronize both directions, and what each side actually stores.
DetailsDepth, delivered weekly
One technical dispatch a week — articles and episode notes before they go public.
One technical dispatch per week. No noise.