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

[Emile van Bergen <openradius-radextwg@e-advies.nl>]

Hi,

On Tue, Mar 14, 2006 at 04:47:50PM -0500, Nelson, David wrote:

> 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.

*roffle* Surprise! It's the same definition as the one in the draft.
Calloo, callay, and joy abounds.

Cheers,


Emile.

> > 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.  :-)

Agreed about that last sentence. But to come to your point: some things
are so closely associated that closely packing them together is *good*.

Eg. the number of hours, minutes and seconds that a session lasted are
so closely related that we decided to do all kinds of bad, bad magic to
those 3 values and pack them together into one attribute:
Acct-Session-Time. 

If all packing is bad, I suppose you also consider /that/ attribute a
candidate for a complex data type as well? No? Why not?

Cheers,


Emile.

-- 
E-Advies - Emile van Bergen           emile@e-advies.nl      
tel. +31 (0)78 6136282           http://www.e-advies.nl    


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