URL to Rendering -- Full Flow Analysis

Framing

This synthesis traces the complete path from pressing a key to seeing pixels on screen. It integrates hardware, OS, network, and browser concepts into one coherent flow.

The Complete Flow

Key Press → OS Interrupt → Browser Input
    ↓
URL Parsing → HSTS Check
    ↓
DNS Lookup (Browser → OS → Router → ISP → Root → TLD → Auth)
    ↓
ARP (IP → MAC)
    ↓
TCP Handshake (SYN → SYN-ACK → ACK)
    ↓
TLS Handshake (ClientHello → ServerHello → Key Exchange)
    ↓
HTTP Request (GET / HTTP/1.1 + Headers)
    ↓
HTTP Response (200 OK + HTML)
    ↓
Browser Rendering:
  HTML Parsing → DOM Tree
  CSS Parsing → CSSOM
  DOM + CSSOM → Render Tree
  Layout (position/size)
  Painting (pixels)
  Compositing (layers)
  GPU Rendering (screen)

Layer-by-Layer Analysis

Layer 1: Hardware (Keyboard)

Keyboard Interrupt: Physical key press → scan code
OS Interrupt Handler: Converts scan code to character
Browser Autocomplete: Local suggestions (no network)

Layer 2: Browser (URL Processing)

URL Parsing: Break into protocol, domain, path
HSTS: Security check—force HTTPS if required

Layer 3: Network (DNS + Connection)

DNS Lookup: Domain → IP resolution
- DNS Cache: Browser → OS → Router → ISP caches
- Recursive DNS: Full hierarchy traversal
- DNS Hierarchy: Root → TLD → Authoritative
ARP Protocol: IP → MAC for local delivery
TCP Handshake: Reliable connection (3-way)
TLS Handshake: Encrypted tunnel (for HTTPS)

Layer 4: Application (HTTP)

HTTP Request: GET/POST + headers + body
HTTP Response: Status + headers + body (HTML)

Layer 5: Rendering (Browser Engine)

HTML Parsing → DOM Tree
CSS Parsing → CSSOM
Render Tree: DOM + CSSOM (visible only)
Layout: Calculate positions and sizes
Painting: Rasterize to pixels
Compositing: Combine layers
GPU Rendering: Hardware acceleration

Key Insights

Each layer is independent: Keyboard works without network; DNS works without HTTP; Rendering works without network
Caching everywhere: DNS caches at 4+ levels; browser caches HTML/CSS/JS
Security is layered: HSTS (app) + TLS (transport) + HTTPS (protocol)
Rendering is parallel: HTML parsing + CSS parsing happen somewhat independently
GPU acceleration: Only the final stages (compositing, paint) use GPU

Contrasts

Aspect	HTTP	HTTPS
Encryption	None	TLS (all data encrypted)
Port	80	443
Security	Vulnerable to MITM	Protects against eavesdropping
Performance	Faster (no handshake)	Slower (TLS handshake overhead)

Visual Explanation

Semantic Network

Connections

This synthesis connects to ALL 29 concept pages in this ingestion, plus existing pages:

DNS (existing, updated)
TLS Handshake (existing, updated)
TCP Handshake (existing, updated)
Socket (existing, updated)
HTTPS (new concept page)

Edge Cases

Packet loss: TCP Packet Drop triggers retransmission
DNS failure: Browser shows error page (DNS_PROBE_FINISHED_NXDOMAIN)
TLS error: Certificate warnings, HSTS blocks override
HTML errors: Parser auto-corrects malformed HTML
CSS errors: Silently ignored (lenient parsing)