OK, seems like a bit of work for the generic case.
I have a simpler case, my A-interface is SCCP being carried
on a proprietary TCP protocol (I mentioned a long time ago).
I know that the SCCP carried on that proprietary protocol
is always ANSI. Can the SCCP protocol determine what dissector
was called just before it? i.e. MTP3, M3UA, or my proprietary protocol ?
If not, I was thinking of using the private_data member of packet_info.
Thanks for your help!
> -----Original Message-----
> From: ethereal-dev-bounces@xxxxxxxxxxxx
> [mailto:ethereal-dev-bounces@xxxxxxxxxxxx]On Behalf Of Jeff Morriss
> Sent: Wednesday, January 07, 2004 3:30 PM
> To: Ethereal Development List
> Subject: Re: [Ethereal-dev] Change how SCCP determines ANSI/ITU variant
>
>
>
>
> Guy Harris wrote:
>
> >
> > On Jan 7, 2004, at 2:45 PM, Michael Lum wrote:
> >
> >> I have ANSI MTP3/ANSI SCCP on one SS7 link for the A-interface
> >> (Base Station Controller to Mobile Switching Center) and
> >> ITU MTP3/ITU SCCP/ANSI TCAP on another SS7 link for the ANSI MAP
> >> interface
> >> (MSC to whatever, MC/HLR, etc.).
> >>
> >> Currently the SCCP dissector uses the extern 'mtp3_standard'
> provided by
> >> the MTP3 dissector. Obviously this causes a problem with the
> >> configuration
> >> above.
> >
> >
> > Because both links are in one capture? (If they're in separate
> > captures, you'd change the setting before or after reading in a file.)
> >
> > If so, then you'd need some way of making that a per-link property,
> > which would need
> >
> > 1) a mechanism for setting non-global properties through the UI, if
> > it can't be determined from the traffic;
> >
> > 2) a mechanism for specifying the link.
>
> I suppose it *might* be possible for the SS7 dissectors to determine the
> standard heuristically (on a message by message basis)? Sounds painful
> to me, but it might work.
>
> Of course, we could get then into issues like "what if MTP3 determines
> the standard is ITU but SCCP determines the standard should be ANSI"? I
> guess a global "I already decided the standard" flag could be used to
> clear that problem (while allowing the lowest-level protocol to be MTP3
> or M3UA or SCCP or...).
>
>
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