The Internet in Practice
The everyday operation of the network — how a device joins it, the applications and architectures built across it, how to see inside it, and how it is defended.
5 articles
- 1Networks & the Internet9 min
DHCP: How Your Device Joins a Network
How a device with no address at all joins a network: the DORA handshake that leases it an IP address, subnet mask, default gateway, and DNS server automatically — on a lease that quietly expires.
- 2Networks & the Internet10 min
Email: The Internet's Oldest Application
Email is a distinct application on the internet's plumbing, older than the web. It relays store-and-forward from mail server to mail server via a DNS MX lookup, and by original design never checked who the sender claimed to be — which is why SPF, DKIM, and DMARC exist.
- 3Networks & the Internet10 min
Peer-to-Peer: The Internet Without a Center
In a peer-to-peer network there is no central server — every node is both client and server. BitTorrent splits a file into pieces and a swarm trades them, so the more people want a file, the faster everyone gets it.
- 4Networks & the Internet9 min
Ping and Traceroute: Seeing the Network
Ping times an echo to tell you a host is alive and how far away it feels; traceroute lists every router in between by deliberately expiring packets one hop farther each time. Both ride on ICMP.
- 5Networks & the Internet9 min
Firewalls: Filtering the Traffic
A firewall decides which traffic may pass by matching packets against rules on address, port, and protocol. The real leap is memory: a stateful firewall welcomes the replies to connections you started while turning away strangers who arrive uninvited.