RE: Bit numbering I-D nit

["Julian Satran" <Julian_Satran@il.ibm.com>]

Pat,

The "nits" document requires a certain numbering from the MSB to the LSB but not necesarily 0 to 31 (that is an example).
I did already the changes in the iSCSI document to fulfill this requirement. Now our "presentation" and SCSI are similar.
Obviously when sent on an Ethernet (but that is 1000 layers away :-)) bit 7 gets out first and the same holds for the CRC calculation (somewhat arbitrary).


Julo

pat_thaler@agilent.com Sent by: owner-ips@ece.cmu.edu 23-03-02 01:25 Please respond to pat_thaler

To:        John Hufferd/San Jose/IBM@IBMUS, roweber@acm.org         cc:        ips@ece.cmu.edu         Subject:        RE: Bit numbering I-D nit

John,

The bits would be on the wire the same way we present the bit numbering.
Both specs use the same position in a word as the most significant, but they
name the bits differently. This can lead to human confusion and
interoperabillity problems. It is important to let the reader know that
there are two different naming schemes applied to the bits by the different
standards they are dealing with. We have had to handle a very similar
problem in mapping Ethernet payloads into a Sonet frame for the 10 Gig
Ethernet work. 

We should let the reader know about the bit labeling with a brief
description before the header diagrams. For instance, in the iSCSI draft, we
could add something like the following to the text of clause 9:

"Note that SCSI and IETF documents use different conventions for labeling
bits and bytes. SCSI documents label the bits of each byte from 0 to 7 with
7 being the most significant bit. SCSI documents label the bytes with byte 0
being the first byte. IETF documents label the bits of each word from 0 to
31 with 0 being the most significant bit. Therefore, SCSI would label the
first bit of the first word as bit 7 of byte 0 and IETF would label the same
bit as bit 0. This document labels bits following the IETF conventions. This
is a difference in labeling convention and does not represent a difference
in placement of bits or fields."

For the Fibre Channel related documents, the paragraph could be: 

"Note that Fibre Channel and IETF documents use different conventions for
labeling bits. Fibre channel documents label the bits of each word from 0 to
31 with 31 being the most significant bit. IETF documents label the bits of
each word from 0 to 31 with 0 being the most significant bit. Therefore,
Fibre Channel would label the most significant bit of a word as bit 31 and
IETF would label the same bit as bit 0. This document labels bits following
the IETF conventions. This is a difference in labeling convention and does
not represent a difference in placement of bits or fields."

An alternative place for this would be under Conventions used in this
document, but I think it is better to put the information in the section
with the headers. This could be in addition to an Annex if people feel an
Annex necessary.

Pat


-----Original Message-----
From: John Hufferd [mailto:hufferd@us.ibm.com]
Sent: Thursday, March 21, 2002 8:04 AM
To: roweber@acm.org
Cc: IPS Reflector
Subject: Re: Bit numbering I-D nit



Ralph,
I may have looked at this wrong, but though we have to change the way we
present (print) the bit numbering, the bits on the link are the same way it
was, or at least that is the way I read the RFC requirement.  What do you
think is the issue?

.
.
.
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: hufferd@us.ibm.com


Ralph Weber <ralphoweber@compuserve.com>@ece.cmu.edu on 03/20/2002 08:34:57
PM

Please respond to roweber@acm.org

Sent by:    owner-ips@ece.cmu.edu


To:    IPS Reflector <ips@ece.cmu.edu>
cc:
Subject:    Bit numbering I-D nit



I am getting serious flack from the Fibre Channel
community over the bit numbering requirement
in http://www.ietf.org/ID-nits.html.

The problem is that Fibre Channel uses the
other bit numbering scheme and interoperability
woes seem certain unless something gets
documented in the IETF RFCs.

Everybody agrees that the body of the FC
Frame Encapsulation and FCIP drafts can
have the IETF bit numbering in the figures.

What they all want is an appendix, or some
such thing in the drafts/RFCs that translates
it all back to the Fibre Channel view of
reality.

Such a thing seems destined to make waves
in the IETF review process, and possibly
even be a target for the RFC Editor's ax.

Should I just jump of the top of the Hilton
now, or is there a way out of this mess?

Thanks.

Ralph...