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Wireshark-bugs: [Wireshark-bugs] [Bug 6542] Wireshark needs an option to dissect ISDN D channel

Date: Sat, 5 Nov 2011 13:06:39 -0700 (PDT)
https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=6542

Guy Harris <guy@xxxxxxxxxxxx> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Wireshark's failing to      |Wireshark needs an option
                   |dissect the LAPD payload as |to dissect ISDN D channel
                   |DPNSS                       |traffic as DPNSS

--- Comment #3 from Guy Harris <guy@xxxxxxxxxxxx> 2011-11-05 13:06:38 PDT ---
I just checked it:

    http://www.niccstandards.org.uk/files/current/nd1301_2001_03.pdf

It looks as if it does *not* run LAPD on the D channel; the layer 2 protocol is
Yet Another HDLC-Derived Protocol, and has a 2-octet address field just as LAPD
does, but the bits that are the SAPI in LAPD are the "FRAME GROUP" in DPNSS and
the bits that are the TEI in LAPD are a reserved bit and the "DLC
INDENTIFICATION[sic] NUMBER" in DPNSS.

As such, that's probably best done by

    1) having a dissector for DPNSS's layer-2 protocol

and

    2) having a preference setting for ISDN to select whether the D channel
traffic is LAPD or DPNSS (and perhaps other protocols as needed).

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