RE: Bit numbering I-D nit

[pat_thaler@agilent.com]

Julian,

 

The nits document specifically says that bit zero is the most significant bit in a word or field. SCSI labels the most significant bit of the byte as 7 so I don't see how we can comply with the nits document and be similar to SCSI labeling. When you say you already did the changes, do you mean you have already renumbered tables for the next draft or are you referring to Draft 11?  Draft 11 shows bit 7 as the MSB of each byte which is consistant with SCSI and not with the nit.

 

Or do you mean that our next draft is similar to SCSI in that you number bits within a byte rather than within a word though the bits are numbered in opposite order? If so, I think it would be useful to the reader to point out the difference.

 

Regards,

Pat

 

-----Original Message-----
From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
Sent: Friday, March 22, 2002 4:37 PM
To: pat_thaler@agilent.com
Cc: ips@ece.cmu.edu; John Hufferd; owner-ips@ece.cmu.edu; roweber@acm.org
Subject: RE: Bit numbering I-D nit

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...