User Datagram Protocol (UDP) ¶

User Datagram Protocol (UDP) is used for fast messaging, by applications that don't mind if a packet is lost/incorrect. It's

• connection-less 🦘: no prior connection is established
• stateless 🙉: no information about the session is kept

It's used when speed is more important than quality.

🐊️ Port: N/A

🗺️ Used by: dhcp, dig, dns...

✍️ UDP PDUs are called datagrams.

It's not trustworthy:

• 🚮 No warranty that the message will be received
• 🙅 No warranty that the message received is correct
• 🥏 No warranty that the message are received in the correct order

UDP Header

• 2 bytes for the "source port"
• 2 bytes for the "destination port"
• 2 bytes for the "size of the message"
• 2 bytes for the "checksum of the message"

• UDP Checksum Attack

👉 An attacker manipulates the checksum allowing tampered packets to by accepted. ➡️ Use encryption (IPSec, a VPN...).

• UDP Flood Attack

👉 An attacker send many UDP requests to slowdown or overwhelm the target. 💥 DoS ➡️ Setup filtering, rate-limiting...