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Link Access Procedure, Channel D (LAPD)

Link Access Procedures on the D channel (LAPD), specified in ITU-T Q.920 and ITU-T Q.921, is the second layer protocol on the ISDN protocol stack in the D channel.

It is heavily based on HDLC.


History of HDLC and LAP

Protocol dependencies

Example traffic



The LAPD dissector is fully functional.

Preference Settings

Example capture file

Display Filter

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

Capture Filter

You cannot directly filter LAPD protocols while capturing. XXX - is this true?