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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: Bit numbering I-D nitJohn, 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...
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