DNS Caching and TTL Explained
Why DNS changes take time. The TTL value, where caches live, and how to plan a DNS migration without downtime.
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DNS Record Types: A, AAAA, MX, TXT, CNAME, NS
A points to an IPv4 address. CNAME aliases one name to another. MX routes email. TXT holds anything. The handful of records that run the internet.
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How DNS Resolves Names to IP Addresses
You type example.com and your browser gets back 93.184.216.34. The full journey: stub resolver, recursive resolver, root servers, TLD servers, authoritative servers.
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Ports and Sockets Explained
An IP address gets you to the machine. A port gets you to the right program. The (IP, port) tuple is called a socket and it is the foundation of every network connection.
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The TCP 3-Way Handshake Explained
SYN, SYN-ACK, ACK — three packets that establish every TCP connection. The mechanism, the costs, and why HTTP/2 and QUIC try to avoid it.
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UDP — Fast and Stateless
UDP is the opposite of TCP. No handshake, no acknowledgments, no retransmissions. Just send and hope. Why DNS, video calls, and games rely on it.
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TCP — The Reliable Connection Protocol Explained
TCP is what makes HTTP, SSH, and email work. Streams, ordering, retransmission, congestion control — all hidden behind a simple read/write API.
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NAT and PAT Explained
How one public IP serves a whole house, office, or country. Source NAT, destination NAT, port translation, and why CGNAT exists.
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Private vs Public IPs (RFC 1918 Explained)
Why your laptop has a 192.168.x.x address but websites don’t. How private IP ranges work and when to use which.
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IPv6 Addresses Explained
Why we needed IPv6, how 128-bit addresses work, dual-stack, and how to read those long colons.