RE: iscsi : DataPDULength can differ in each direction.

[Paul Koning <pkoning@jlc.net>]

Excerpt of message (sent 3 October 2001) by Robert Snively:
> I would have thought that it was indicating the DataPDULength it
> was capable of accepting, committing the other port to not
> exceeding that value.

Clearly that is what it has to be.  If a PDU length limit is per
direction, the only interpretation that works is that you indicate the
max length you're willing to have coming IN.  There is no reason to
indicate the max you're willing to send -- all that is required is
that you never send more than the limit indicated by the other side
(but you may never send something as big as that limit, if your own
transmitter has a limit smaller than that).

So the notion of two numbers, one per direction, is fine, but the word
"use" is ambiguous.  A clearer wording is "... specify in
DataPDULength the maximum PDU length it is willing to receive".  Then
the sender can send PDUs smaller than the DataPDULength requested by
the destination, or the same, but not larger.  (This is how MTU works.) 

    paul

> > -----Original Message-----
> > From: Santosh Rao [mailto:santoshr@cup.hp.com]
> > Sent: Wednesday, October 03, 2001 10:32 AM
> > To: Dev - Platys; Julian Satran
> > Cc: Sandeep Joshi; ips@ece.cmu.edu
> > Subject: iscsi : DataPDULength can differ in each direction.
> > 
> > 
> > Deva, Julian & All,
> > 
> > I think we have a more fundamental problem here, that spans beyond the
> > issue of which negotiation model should be used for numerical & binary
> > key negotiation. This problem needs to be addressed seperately.
> > 
> > The DataPDULength can and should be allowed to be different in each
> > direction. I -> T direction PDUs should be allowed to use a different
> > PDU Length than T -> I direction PDUs. 
> > 
> > Each side should be allowed to specify the DataPDULength it will be
> > using and there should be no attempt to negotiate this value. 
> >