Networking Basics

A simplified overview of networking

What happens behind the scene when you ask ChatGPT a question?

From the networking perspective, several steps occur to process your request and provide a response. Here's a simplified overview of the process, using the real-world devices and the TCP/IP model as a reference:

  1. Device to Local Network (MacBook Pro -> Router)

  • Device: MacBook Pro, IP: 192.168.1.10, MAC: AA:BB:CC:DD:EE:FF

  • Router: Netgear Nighthawk, IP: 192.168.1.1, MAC: 11:22:33:44:55:66

  • Step 1: You open the OpenAI ChatGPT app on the MacBook Pro. The app sends an HTTPS request to api.openai.com. The request is encrypted and compressed (Application Layer).

  • Step 2: The request is split into TCP segments with a source port (random) and destination port 443 (HTTPS) (Transport Layer).

  • Step 3: The segments are encapsulated into IP packets. The source IP is 192.168.1.10, and the destination IP is the IP address of api.openai.com (e.g., 104.21.90.123).

  • Step 4: The packets are encapsulated into Ethernet frames with the source MAC (AA:BB:CC:DD:EE:FF) and destination MAC (11:22:33:44:55:66) of the router. The frames are sent via Wi-Fi to the Netgear Nighthawk (Network Access Layer).

  1. Router to ISP (Nighthawk -> AT&T Fiber Network)

  • Step 5: The router de-encapsulates the frame, extracts the IP packet, and re-encapsulates it for forwarding over the fiber connection to the AT&T network. The source IP changes to the public IP address assigned by AT&T (e.g., 70.123.45.67).

  • Step 6: The router forwards the IP packet through AT&T’s fiber network (Physical/Network Access Layer).

  1. ISP to OpenAI Servers (AT&T -> Internet -> Cloudflare -> OpenAI)

  • Step 7: AT&T routes the packet across its network, using BGP to reach Cloudflare (which fronts OpenAI’s servers). Routers along the way use the destination IP (104.21.90.123) to forward the packet across the internet (Internet Layer).

  • Step 8: The packet arrives at Cloudflare’s data center, which handles load balancing and routing the packet to OpenAI’s servers.

  1. Response from OpenAI (api.openai.com -> MacBook Pro)

  • Step 9: OpenAI processes the request and sends a response back to 70.123.45.67 (your public IP).

  • Step 10: The response traverses the internet back through AT&T and reaches your Netgear Nighthawk router.

  • Step 11: The router sends the response via Wi-Fi back to your MacBook Pro, re-encapsulating the data in Ethernet frames with your device’s MAC address.

  • Step 12: The MacBook Pro de-encapsulates the frames, processes the TCP segments, and decrypts the HTTPS response to display the ChatGPT result.