Flow control (rwnd) vs congestion control (cwnd, slow start)

TCP has two different reasons to limit how much data can be in flight. Flow control protects the receiver from being overwhelmed; congestion control protects the network from overload. The receiver advertises a receive window (rwnd), while the sender also maintains a congestion window (cwnd). The amount of outstanding data is constrained by both.

StackShade deck

Predict → explain → retrieve

COURSE CONTENTS

01How the Internet Works + OSI ModelWeek 1 · 4 topics0/4

OSI Model Explained — interactive deep dive15 min OSI Layer Explorer + Encapsulation Simulator15 min What happens when you type google.com12 min TCP handshake + OSI vs TCP/IP + practice quiz15 min

02Physical & Data Link LayersWeek 1–2 · 5 topics0/5

Signals, bandwidth, latency, copper vs fiber vs radio12 min Ethernet frames, MAC addresses, ARP in action14 min Interactive: ARP resolution walkthrough10 min Switches, VLANs, and why hubs died12 min Trace a frame across 2 switches (worksheet)20 min

03Network Layer: IP & RoutingWeek 2–3 · 6 topics0/6

IPv4 anatomy: network vs host bits, CIDR15 min Interactive: subnet calculator playground15 min Routing tables, default gateway, longest-prefix match12 min NAT, private ranges, and why IPv6 exists12 min How routers learn: static, RIP, OSPF, BGP (bird's-eye)14 min Subnet 3 networks + design a small topology30 min

04Transport Layer: TCP & UDPWeek 3–4 · 5 topics0/5

TCP deep dive: handshake, sequence numbers, ACKs, retransmission16 min Animated 3-way handshake + teardown10 min Flow control (rwnd) vs congestion control (cwnd, slow start)14 min UDP & QUIC: why HTTP/3 ditched TCP12 min Analyze a TCP stream in a packet capture25 min

05Application Layer: HTTP, DNS & FriendsWeek 4–5 · 6 topics0/6

DNS end-to-end: resolver → root → TLD → authoritative14 min Interactive: DNS lookup journey10 min HTTP/1.1 vs 2 vs 3: multiplexing, streams, QUIC14 min TLS handshake, certificates & the chain of trust14 min WebSockets, SMTP/IMAP, DHCP essentials12 min Inspect real requests in browser DevTools20 min

06Security & Troubleshooting ToolkitWeek 5 · 5 topics0/5

Firewalls, VPNs, proxies: what each one really filters12 min Common attacks: SYN flood, DNS spoofing, MITM (defense view)14 min Interactive: layer-by-layer troubleshooting scenarios15 min Hands-on: ping, traceroute, dig, curl, netstat30 min Wireshark: follow one full HTTP conversation30 min