SORT BY:

LIST ORDER
THREAD
AUTHOR
SUBJECT


SEARCH

IPS HOME


    [Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

    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...
    
    
    
    
    


Home

Last updated: Fri Mar 22 20:18:18 2002
9282 messages in chronological order