Simulators
TCP/IP Stack Simulator
1 / 15
Your Device (Client)
Application
HTTP · SMTP · DNS · FTP
Transport
TCP · UDP
Internet
IP (v4 / v6) · Routing
Link Layer
Ethernet · Wi-Fi · MAC
📡
Active
→
DNS
Web Server
Application
HTTP · SMTP · DNS · FTP
Transport
TCP · UDP
Internet
IP (v4 / v6) · Routing
Link Layer
Ethernet · Wi-Fi · MAC
Packet / Data Structure
◀Outermost header (Link Layer)Innermost data (Application)▶
DNS
www.example.com → 93.184.216.34
DNS
DNS Lookup: Finding the Server
Before connecting, the browser must translate www.example.com into an IP address using DNS.
- •Query sent to DNS server: 'What IP is www.example.com?'
- •DNS responds: 93.184.216.34
- •DNS uses UDP port 53: fast, no connection needed
DNS is the internet's phone book; it translates human-readable names into machine-readable IP addresses.
TCP/IP Layer Reference
4
Application
What the data means
HTTP, HTTPS, SMTP, FTP, DNS
3
Transport
Reliable delivery between ports
TCP (reliable) · UDP (fast)
2
Internet
Routing across networks
IP (IPv4 / IPv6) · ICMP
1
Link Layer
Physical delivery on one link
Ethernet · Wi-Fi · 802.11