networks — Learning Book

Bandwidth vs Throughput vs Latency vs Jitter

The four performance words precisely: rates vs times, the highway model, bandwidth≠speed, latency-bound vs bandwidth-bound, BDP, and jitter/QoS.

Intermediate fundamentals performance bandwidth throughput latency jitter rtt bandwidth-delay-product cdn qos 2026-07-12

Ethernet — Frame Format, MAC Addresses & EtherType

The L2 reality: 48-bit MACs (OUI + device, broadcast/unicast/multicast), the frame format, EtherType demux, FCS best-effort error detection, and the 1500-byte MTU.

Intermediate layer-2 ethernet mac-address frame ethertype fcs mtu csma-cd broadcast oui 2026-07-12

How Switches Work — MAC Learning, CAM Table, Forward/Flood/Filter

Self-teaching frame forwarding: learn from SOURCE, decide by DESTINATION; forward/flood/filter, the CAM table, one-switch-one-broadcast-domain, and CAM overflow.

Intermediate layer-2 switch cam-table mac-address-table mac-learning flooding broadcast-domain collision-domain port-security cam-overflow 2026-07-12

VLANs — Segmentation, Access vs Trunk Ports, 802.1Q Tagging

Slicing one switch into many virtual switches: access vs trunk, the 4-byte 802.1Q tag, tag add/strip journey, native-VLAN hopping, and VLAN-scoped flooding.

Intermediate layer-2 vlan 802.1q tagging access-port trunk-port native-vlan broadcast-domain segmentation vlan-hopping inter-vlan-routing 2026-07-12

Spanning Tree Protocol (STP/RSTP) — Loop Prevention & Root Bridge Election

Why L2 loops are fatal (no TTL → broadcast storm) and how STP blocks them: root-bridge election, root/designated/blocking ports, path cost, and RSTP's fast convergence.

Intermediate layer-2 stp rstp spanning-tree loop-prevention root-bridge bpdu broadcast-storm bridge-id portfast bpdu-guard 802.1d 802.1w 2026-07-12

ARP — Resolving IP → MAC, ARP Cache, Gratuitous ARP

The glue between IP and MAC: broadcast request / unicast reply, next-hop-only resolution, caching, gratuitous ARP for failover, and why ARP spoofing enables MITM.

Intermediate layer-2 arp address-resolution arp-cache gratuitous-arp arp-spoofing mitm broadcast ndp next-hop default-gateway 2026-07-12

How the Internet Works End-to-End — A Packet's Journey

A packet's full journey from browser to server and back: DNS, ARP, encapsulation, TCP/TLS handshakes, hop-by-hop routing, and why the network is best-effort.

Intermediate fundamentals dns tcp udp ip routing arp encapsulation 2026-07-07

OSI 7-Layer Model — What Each Layer Does and Why the Split Exists

The seven layers and why layering exists; PDUs, the L2-vs-L3 (switch-vs-router) distinction, OSI-vs-TCP/IP reality check, and the L2/L3/L4/L7 vocabulary.

Intermediate fundamentals osi-model layering switch router layer-2 layer-3 encapsulation mac ip 2026-07-07

TCP/IP Model — How the 4/5-Layer Model Maps to Reality vs OSI

The real stack the internet runs on: 4- vs 5-layer, the OSI→TCP/IP mapping, where TLS/sockets sit, and the hourglass/narrow-waist model.

Intermediate fundamentals tcp-ip-model osi-model layering hourglass narrow-waist ip sockets tls 2026-07-07

Encapsulation & Decapsulation — Segments → Packets → Frames → Bits

Dolls-in-dolls header wrapping/unwrapping: PDU names, load-bearing header fields, demultiplexing pointers, router re-encap per hop, and header overhead.

Intermediate fundamentals encapsulation decapsulation pdu headers demultiplexing mtu ethertype ttl mac ip 2026-07-07