Subject: iSCSI Markers

From: "John Hufferd" <[email-masked]>
Date: Thu, 10 Jan 2002 01:26:42 -0800

I stand corrected on the Name, of TUFs and not iWARP.  The draft that will
probably go experimental (TUFs) is a framing item that places PDUs at the
beginning of TCP Segments (hence TCP Mods).  We can not just take TUFs and
add that to our iSCSI protocol since our charter prevents us from doing
that.

I see no relationship to COWS, except both have an 8 byte header.   If you
have TUFs, you do not need to have Word Stuffing.  The problem with COWS is
not is header it is the Word Stuffing and the Replacement Pointers.

You have FIM or COWS, neither one is useful with TUFs, except that they
have a similar header with COWS, not is hardly a reason to put up with the
SCANNING and Stuffing of COWS Pointers in the Data.  This is especially
since depending on the development approach you may find the Pointers
pointing the wrong way for either sending or receiving in some HW
pipelining designs.  And it is always a poorer approach then FIM in
Software.

I think folks want TUFs but we do not have that option now.  And COWS does
NOT bring that any closer any quicker.

.
.
.
John L. Hufferd
Senior Technical Staff Member (STSM)
IBM/SSG San Jose Ca
Main Office (408) 256-0403, Tie: 276-0403,  eFax: (408) 904-4688
Home Office (408) 997-6136, Cell: (408) 499-9702
Internet address: [email-masked]

---

From: Paul Koning <[email-masked]>
Date: Thu, 10 Jan 2002 11:31:32 -0500 (EST)

>>>>> "John" == John Hufferd <[email-masked]> writes:
 John> You have FIM or COWS, neither one is useful with TUFs, except
 John> that they have a similar header with COWS, not is hardly a
 John> reason to put up with the SCANNING and Stuffing of COWS
 John> Pointers in the Data.  This is especially since depending on
 John> the development approach you may find the Pointers pointing the
 John> wrong way for either sending or receiving in some HW pipelining
 John> designs.  And it is always a poorer approach then FIM in
 John> Software.

Agreed. FIM is nasty, COWS is nastier.  Both may require a memory to
memory copy, but at least FIM doesn't require you to examine the data
you're moving.

Clearly, the real answer is a transport layer that isn't a byte stream
transport.  TP4 or SCTP, anyone?  :-)

       paul

---

From: "Douglas Otis" <[email-masked]>
Date: Thu, 10 Jan 2002 10:25:09 -0800

Paul,

I agree with you and John.  Maintaining conformity as well network layering
is important and advantages offered by the new transport easily outweigh
concerns balanced against modification of TCP.  No one needs to ask my
preference. : )

Doug