hi Richard, i thank you for your fast answer.
> On 5 Dec 2018, at 16:04, Richard Sharpe <realrichardsharpe@xxxxxxxxx> wrote:
>
> On Wed, Dec 5, 2018 at 6:47 AM francisco javier sanchez-roselly
> <franciscojavier.sanchezroselly@xxxxxxxx> wrote:
>>
>> hi All, i am checking some 802.11 frames and i have two doubts taking into account 802.11-2016 standard.
>>
>> the first one has to do with To DS and From DS bits. the dissector groups these bits as a ‘DS status’ field not defined in the standard. the meaning is clear, but in my opinion, this association breaks the endianness criterion for the rest of the frame fields.
>
> The code dealing with those two fields was likely written well before
> IEEE80211-2016 or even IEEE80211-2012 were written. The standard may
> have changed in that area.
>
>> my other suggestion refers to FCS field, as standard says the general convention is not followed for this field, and the highest order term is transmited first.
>
> I think you have misunderstood and perhaps you are looking at the way
> we write the fields in a frame from left to right. The lowest order
> bit of each field is first on the wire, and the frames will generally
> be laid out in memory with the left most fields in the lowest
> addresses. On little endian systems the lowest order bytes will be in
> the lower addresses as well.
my understanding after reading the standard and checking same capture frames is, little endian -first bit sent is the most significant- is used inside fields. the standard is clear when field size is greater than 8 bits -first octet sent the one containing the less significant bit-, but for fields smaller than 8 bits nothing is clearly stated and Wireshark presentation seems reasonable -first field sent is the one containing the less significant bit-.
the point is that for FCS is literally says: 'Any field containinga CRC is an exception to this convention and is trasmitted commencing with the coefficient of the higest-order term.’ in my opinion this means the FCS is transmiitted a whole, not considering byte boundaries. in Wireshark CRC in wire is 0x3fca42e0 and the dissection is 0xe042ca3f, i guess the dissection should be 0x3fca42e0
i ask for the clarification because as professor these facts sometimes are relevant.
i appreciate your help and patience, regards.
francisco javier sanchez-roselly
>> please ask you to guide me if i am missing something. otherwise, i will be glad to contribute with any change in the code.
>>
>> thanks, regards.
>>
>> francisco javier sanchez-roselly
>>
>>
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>
>
>
> --
> Regards,
> Richard Sharpe
> (何以解憂？唯有杜康。--曹操)(传说杜康是酒的发明者)
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