ISDN user-network interface layer 3 specification for basic call control (Q.931)
History
XXX - add a brief description of Q.931 history
Protocol dependencies
Q.931 was originally used as the call control protocol for ISDN. It is also used for VoIP; when used for VoIP, it's usually transported atop TPKT atop TCP.
Example traffic
XXX - Add example traffic here (as plain text or Wireshark screenshot).
Wireshark
The Q.931 dissector is fully functional.
Preference Settings
Make sure that preferences in TCP and TPKT are set to allow reassembly of packets.
- Whether to reassemble Q.931 messages spanning multiple TCP segments or not. (Default: yes)
- Reassemble segmented Q.931 messages or not. (Default: yes)
Example capture file
XXX - Add a simple example capture file to the SampleCaptures page and link from here. Keep it short, it's also a good idea to gzip it to make it even smaller, as Wireshark can open gzipped files automatically.
Display Filter
A complete list of Q.931 display filter fields can be found in the display filter reference
- Show only the Q.931 based traffic:
q931
Capture Filter
You cannot directly filter Q.931 protocols while capturing. However, if you know the TCP port used (see above), you can filter on that one.
External links
Q.931 is specified by ITU in Q.931.