Ethereal-dev: Re: [Ethereal-dev] dealing with 2 dissectors on the same port

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From: Jeff Morriss <jeff.morriss@xxxxxxxxxxx>
Date: Thu, 20 Jun 2002 15:20:55 -0400
Michael,


SCTP tries first to find the ULP by looking at the Payload
Protocol Identifier. Only if that does not work the port is
used.

M2UA uses PPI = 2 and M2PA uses PPI = 5.

This means if you use the correct PPI in your M2UA, M2PA
implementation ethereal will find always the correct ULP.
Yo do not need to disable a protocol. By using this you
can also transport M2UA and M2PA over the same assoc and
ethereal will dissect it correctly.
Oops, I forgot to mention that these captures are from an older M2PA implementation which didn't set the PPI... (In fact I also have to use version 1.1 of "packet-m2pa.c".) SCTP has code to look at the ports if the PPI doesn't find a sub-dissector, but then we run into the problem that M2UA and M2PA have the same port... 

Regards,
-Jeff

--
Jeff Morriss
Senior Support Engineer
Ulticom, Inc.
Helpdesk: +1-856-787-2765
Fax: +1-856-222-9947