How do I Google?

The Long complex answer of how I get to google.com Part 3

Quick Review

• Key is pressed on Keyboard
• Keyboard Polls through the Key matrix
• Keyboard Notices a Change and waits until the next USB packet can be sent
• Keyboard sends USB packet to Computer
• The OS gets packet and sends it to the correct Program

Quick Review

• The computer looks through its cache to turn google.com into an IP Address
• If not found then reaches out to DNS
• That goes through your local router, your IPs Routers until it gets to your DNS server
• The DNS info is queried recursively to get the correct IP address. Caching the responses to make it faster next time.

Whats Next?

• Keyboard
• Computer to Program
• URL Bar in Browser
• Finding the Web Server
• Sending Data to Web Server
• Retrieving Data from Web Server
• Browser getting other files from webpage
• Browser rendering the Data for the viewer

Assumptions

• Transmitting over Ethernet
  • No Ethernet Authentication (802.1X)
  • Not over Wifi or Cellular Data
• Not on a VLAN (Virtual Local Area Network)
• Using IPv4
  • Not using IPv6 or 6to4
• Has NAT (Network Address Translation)
  • Used to separate Local and Wide Networks
• TLS will not use Session Resumption
• Using HTTP 1.1 not HTTP2 or HTTP3

Protocols

Ethernet II Layer

• Uses Physical Addresses (MAC Address) to route data on the Local Network

IPv4 Layer

• Used as routing packets across networks

NAT

NAT Translation

• The source IP (192.168.88.4) is helpful when on the local network but not when google.com is sending its response

NAT Translation

• So the Router will change the Source IP to be your remote IP (100.35.134.67).
• NAT Table
  • 100.35.134.67:41186 from 142.251.35.164:443 will be translated to 192.168.88.4:41186 on response

What is TCP

Transmission Control Protocol is a way to deal with a couple of things

• Chunking large data
• Ensuring that the data can be reassembled in the correct order
• Ensuring all data is received
  • Re sending data that was lost or corrupted in transfer
• Managing Transfer speeds

Making a Connection

TCP Ports

What is TLS

• Transport Layer Security replaces the older Secure Socket Layer Protocol (SSL)
• Ensure that the server you are talking to matches the domain name.
• Tell each other what options they support
  • Encryption, Authentication, Integrity Algorithms
  • Support Renegotiation or Data Compression
  • Random value used to generate a temporary key for this session.
  • The server domain you want to reach

HTTP Request

HTTP Response

Putting It All Together

Todo: Part 4

• HTML Basics

• CSS, Images, and media

• JavaScript

• Rendering the Google Webpage