RE: New Technical Issues RE: WG last call in progress on VLAN/Priority Draft

["Nelson, David" <dnelson@enterasys.com>]

Emile van Bergen writes...

> And in the case of the VLAN attribute, it
> *does* contain an unsigned integer value, one that's calculated as
> follows:
> 
> value = vlanflag * 16777216 + vlanid
> 
> The reverse goes as follows:
> 
> vlanflag = value / 16777216
> vlanid = value % 16777216
> 
> (where
>  * denotes unsigned integer multiplication,
>  + denotes unsigned integer addition,
>  / denotes unsigned integer division and
>  % denotes taking the reminder of an unsigned integer division,
>  all to be carried out on unsigned integers in the range 0 .. 2**32-1)

Well, that would be one method of defining the VLANID attribute that
would clearly an integer data type.

> I'm not believing that people on this list would have to be explained
> that shifting and masking bits are *not* magic operations that you can
> only perform if you program in assembly (or its portable flavour, C),
> but that those are normal mathematical operations on normal integers:
> multiply and take remainder (by powers of 2).

No.  My point was that packing multiple, separate fields into an opaque
data container is representing a complex data type, whether you perform
the packing using bit or octet offsets in a string type or arithmetic
manipulations on an integer type.  Packing is packing.  :-)


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