YF Consulting - Cyber Security

Step 1: The Initial Request

It all begins with a simple action: you type https://yrume.com into your browser and press Enter. Your computer now has a destination domain but doesn't know the server's actual address (its IP address). The first task is to translate the human-readable domain into a machine-readable IP address.

Step 2: Domain Name System (DNS) Lookup

Your computer initiates a DNS query to find the IP address for yrume.com. The lookup process follows a specific hierarchy to resolve the name as efficiently as possible:

[Your PC] --> [Browser Cache?] --> [OS Cache?] --> [Router Cache?] --> [ISP DNS Server] --> [Root Servers] --> [.com TLD Servers] --> [yrume.com Authoritative DNS]

The authoritative DNS server for yrume.com responds with the IP address (e.g., 104.21.23.123). Your computer now has the destination IP address.

Step 3: Layer 2 Determination (ARP)

Your computer needs to send the data packet. But to whom? It performs a crucial check:

1. Is the destination IP on my local network? Your PC compares the destination IP with its own IP and subnet mask. In this case, the server is on the internet, not the local network.

2. Find the gateway's MAC Address. Since the destination is remote, the packet must be sent to the local network's gateway (your router). To do this, your PC uses the Address Resolution Protocol (ARP). It sends a broadcast on the local network asking, "Who has the IP address of the gateway (e.g., 192.168.1.1)? Tell me."

3. The Gateway Responds. The router responds with its physical (MAC) address. Your PC now wraps the data packet in an Ethernet frame with the router's MAC address as the destination.

Packet Destination IP: 104.21.23.123 (yrume.com) Ethernet Frame Destination MAC: [Your Router's MAC Address]

Step 4: The Journey Through Gateways and Firewalls

The packet is sent to your router. The router strips off the Ethernet frame, inspects the packet's destination IP, and forwards it to your Internet Service Provider (ISP). The packet then hops across multiple routers on the internet, each one bringing it closer to the destination server.

Along the way, the packet must pass through firewalls. Corporate firewalls, ISP-level firewalls, and finally the server's own firewall will inspect the packet to ensure it meets security rules (e.g., allowing traffic on port 443 for HTTPS).

[Your PC] --> [Router] --> [ISP Network] --> [Internet Backbone] --> [Server's ISP] --> [Server Firewall] --> [yrume.com Server]

Step 5: Reaching the Destination Server

Once the packet successfully passes the server's firewall, it is received by the server's operating system. The OS network stack unwraps the packet, sees it's destined for the web server process (listening on port 443), and hands it off. The web server then processes the request and begins formulating a response, which will follow a similar journey back to your computer.