User Datagram Protocol

User Datagram Protocol (UDP)

The UDP layer provides datagram based connectionless transport layer (layer 4) functionality in the InternetProtocolFamily.

UDP is only a thin layer and provides not much more than the described UDP port multiplexing.

Just like IP, UDP also doesn't provide any mechanism to detect PacketLoss, DuplicatePackets and alike.

There are a lot of protocols on top of UDP, including: BOOTP, DNS, NTP, SNMP, ...

UDP-Lite

Are you looking for Lightweight UDP? Then visit UDP-Lite.

History

XXX - add a brief description of UDP history

Protocol dependencies

IP: Typically, UDP uses IP as its underlying protocol. The assigned protocol number for UDP on IP is 17.

Example traffic

XXX - Add example traffic here (as plain text or Ethereal screenshot).

Ethereal

The UDP dissector is fully functional.

There are two statistical menu items for UDP available: Statistics/Endpoints which contains a tab showing all UDP endpoints (combination of IP address and UDP port) and Statistics/Conversations, which contains a tab showing all UDP conversations (combination of two endpoints).

Preference Settings

(XXX add links to preference settings affecting how UDP is dissected).

Example capture file

XXX - Add a simple example capture file. Keep it short, it's also a good idea to gzip it to make it even smaller, as Ethereal can open gzipped files automatically.

Display Filter

A complete list of UDP display filter fields can be found in the display filter reference

Show only the UDP based traffic:
```
 udp 
```

Capture Filter

Capture only the UDP based traffic:
```
 udp 
```

External links

RFC768 User Datagram Protocol

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