Wireshark-users: Re: [Wireshark-users] WIRESHARK Version 8.1.0 problems in DSCP coding
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From: "RUOFF LARS" <Lars.Ruoff@xxxxxxxxxxxxxxxxxx>
Date: Thu, 17 Dec 2009 18:39:11 +0100
Well, i think (i hope) there's some confusion here related to the indices used in RFCs:
That's how i see it, but correct me if i'm wrong:

The representation of a single octect in binary representation is usually given with the most significant bit (msb) to the left and the least significant bit (lsb) to right.
I.e. the binary representation of the value 0x80 would usually be written down as:
  7   6   5   4   3   2   1   0
+---+---+---+---+---+---+---+---+
| 1   0   0   0   0   0   0   0 |
+---+---+---+---+---+---+---+---+
where the indices on the top line represent the 2-exponent value that is to be associated with the bit at the given position.


However, in RFCs like RFC 2474, while still wrtitng down the fields in the left-to-right, msb-to-lsb order given above, the indices do NOT represent the 2-exponent but a running index for the only purpose of having a reference to a particular bit position.

i.e.
the specification of RFC2474's DiffServ field,
|        0   1   2   3   4   5   6   7
|      +---+---+---+---+---+---+---+---+
|      |         DSCP          |  CU   |
|      +---+---+---+---+---+---+---+---+

still means that DSCP is encoded in the 6 most significant bits of DiffServ.
And that's exactly the way Wireshark shows it, thus invalidating bug 3320.
I hope others can confirm this point of view. (or else i have a lot of bugged DiffServ implementations around here)

regards,
Lars
 


________________________________

	From: wireshark-users-bounces@xxxxxxxxxxxxx [mailto:wireshark-users-bounces@xxxxxxxxxxxxx] On Behalf Of Mion, Marcello (NSN - IT/Milan)
	Sent: jeudi 17 décembre 2009 14:11
	To: wireshark-users@xxxxxxxxxxxxx
	Subject: [Wireshark-users] WIRESHARK Version 8.1.0 problems in DSCP coding
	Importance: High
	
	
	Dear,
	With this Version of Wireshark I have problems in decoding correctly the DSCP value.
	 
	I got this link which is exactly what I'm facing. 
	https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=3320
	 
	Anyway  I'm not able to understand if the bug has been resolved and with what (Patch or Newer Version of Wireshark).
	 
	Can you be so kind to help me about?
	 
	Thanks a lot in advance.
	Best Regards.
	 
	Marcello Mion
	NSN-Italy