networking

Two things reliably surprise teams new to AWS: the network they must build before anything can talk, and an invoice driven by charges nobody chose deliberately. The two are connected, because moving data is where much of the cost hides. This lesson covers the virtual network primitives, the traffic charges that follow from them, and how to read a bill.

The object types look like an arbitrary vocabulary until you notice they are layers of controllers, each reconciling the one below. This lesson works up from the pod, explains why a Service can point at something whose address changes constantly, and shows that the whole system is joined by one mechanism: a label match.

Isolation is the point, and a container that can reach nothing and keep nothing is useless. This lesson covers how a network namespace is wired to the outside, why published ports and container-to-container traffic work completely differently, and where data has to live given that the writable layer disappears.

Before a byte of HTTP moves, a name has to become an address. Follow the full resolution path from stub resolver to authoritative server, see how TTLs govern change, then trace head-of-line blocking from HTTP/1.1 through HTTP/2's TCP problem to HTTP/3 running on QUIC over UDP.

TCP turns a lossy packet service into an ordered byte stream, and almost every performance surprise on the internet comes from how it does that. Work through the handshake, cumulative ACKs, retransmission timers, the two windows, slow start and AIMD, CUBIC versus BBR, bufferbloat, and when to reach for UDP instead.

IP is the only layer the whole internet agrees on. Work through IPv4 and IPv6 addressing, CIDR subnet math by hand, what a routing table really holds, longest-prefix match, why NAT ended end-to-end addressing, and how one BGP announcement can pull a network off the internet.

A packet is a stack of nested envelopes, and the bottom layer has rules of its own. Work through encapsulation, Ethernet frames, MAC learning inside a switch, ARP, and MTU, then diagnose the classic failure where small requests succeed and large ones hang forever.

How load balancers spread traffic across servers, what L4 and L7 actually mean, the routing algorithms in real use, and the failure modes you need to design around.

HTTP status codes are essential for effective communication between clients and servers on the web. This lesson breaks down each class of status codes (1xx, 2xx, 3xx, 4xx, 5xx), explains their meaning, and provides practical guidance on when to use them in your applications.