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Wireshark-dev: Re: [Wireshark-dev] ASN.1 enumeration extension coding question

From: "Kukosa, Tomas" <tomas.kukosa@xxxxxxxxxxx>
Date: Tue, 18 Dec 2007 11:16:58 +0100
Hi,

it is fixed with revision 23916.

Tomas


 

> -----Original Message-----
> From: wireshark-dev-bounces@xxxxxxxxxxxxx 
> [mailto:wireshark-dev-bounces@xxxxxxxxxxxxx] On Behalf Of 
> Sergio Mayoral
> Sent: Tuesday, December 18, 2007 10:32 AM
> To: Developer support list for Wireshark
> Subject: Re: [Wireshark-dev] ASN.1 enumeration extension 
> coding question
> 
> Hi,
> 
> I am also having this problem. I found a book called
> "ASN.1 Communication between Heterogeneous Systems"
> written by Olivier Dubuisson, who looks to be an
> expert on ASN.1, where it is explicitly said:
> 
> - If the ENUMERATED type is extensible (or if the
> module includes the EXTENSIBILITY IMPLIED clause in
> its header), a preamble of one bit is appended to the
> bit-field (without being octet-aligned).
> 
> "Normally small non-negative whole number encoding"
> 
> - if 0 <= n <= 63, a 0-bit is appended to the
> bit-field (without being octet-aligned), followed by
> the binary encoding of n on 6 bits.
> 
> Regards
> 
> --- "Nichols, Roger" <Roger.Nichols@xxxxxxxxxxxx>
> wrote:
> 
> > 
> > Hi,
> > 
> > Is this the proper forum to ask a question about
> > 'why' something is
> > coded the way it is?
> > 
> > We are developing a V.34 enabled T.38 end point, and
> > are confused by the
> > Wireshark decoding.  It seems the Wireshark decoder
> > is aligning fields
> > which are extension values.  For example, the 2002
> > T.38 ASN.1 notation
> > for V.34 Data Field values.  We are not aligning
> > these enumeration
> > values, but Wireshark does.  See line 1211 of
> > packet-per.c, a comment
> > which says to align without giving a reference, and
> > 1214 which does the
> > alignment.  Reading ITU X.691 section 13, I would
> > not expect this
> > beahvior.  As Wireshark community is the only place
> > I know of an
> > existing product which handles the V.34 additions to
> > T.38, it seems a
> > good place to ask.  Why are these values aligned? 
> > We could not find an
> > ITU reference giving us reason to do so.
> > 
> > Thanks,
> > 
> > Roger Nichols
> > Firmware Engineer
> > 
> > Cantata Technology, Inc. (a Dialogic company) 
> > 15 Crawford Street
> > Needham, MA 02494
> > USA
> > 
> > Tel:    781 292 9399 
> > Fax:    781 453 3521
> > Email:  roger.nichols@xxxxxxxxxxxx
> > Web:    www.dialogic.com
> > 
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> 
> 
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