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Module 6: Application Layer

The Application Layer is where users interact with the network.

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6.1 HTTP / HTTPS

HyperText Transfer Protocol is the foundation of the web.
  • Request/Response Model: Client sends request, Server sends response.
  • Methods: GET, POST, PUT, DELETE.
  • Status Codes: 200 OK, 404 Not Found, 500 Server Error.
  • HTTPS: HTTP over TLS (Encrypted).

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6.2 DNS (Domain Name System)

DNS is the phonebook of the internet. It translates human-readable domain names (google.com) into IP addresses (142.250.190.46).

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Resolution Process

  1. Browser Cache: Check local cache.
  2. Resolver: Ask ISP’s DNS resolver.
  3. Root Server: Ask Root server (returns TLD server IP).
  4. TLD Server: Ask TLD server (returns Authoritative server IP).
  5. Authoritative Server: Returns the actual IP.
DNS Resolution

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6.3 DHCP (Dynamic Host Configuration Protocol)

DHCP automatically assigns IP addresses to devices on a network.
  • DORA Process: Discover, Offer, Request, Acknowledge.

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Next Module

Module 7: Network Security

Protecting the network.