RE: iSCSI PDU Formats

["Robert D. Russell" <rdr@mars.iol.unh.edu>]

Julian:

I would like to request 2 further changes to PDU formats:

1. In the SCSI Response PDU, the field starting at byte 20
   used to be called "Basic Residual Count", but is now called
   "Residual Count".  It is valid only when either the "U" or "O"
   bit is set.

   In the Data-in PDU, the field starting at byte 20 is reserved,
   but the field starting at byte 44 is called "Residual Count"
   and is valid only when either the "U" or "O" bit is set.

   I propose moving the "Residual Count" field in the Data-in PDU
   from byte 44 to byte 20, so that it is consistent with the
   SCSI Response PDU.  (The field in byte 44 of the Data-in PDU
   would then become reserved.)


2. The Login Request and Login Response PDUs now have a new 4-bit
   field labelled CNxSG.  This field consists of 2 2-bit parts.

   I propose labeling each part separately -- bits 0-1 to be
   labeled "CS" for Current Stage, bits 2-3 "NS" for Next Stage.

   I believe this makes understanding and coding much simpler,
   because in all cases these fields are interpreted separately,
   and when the T bit is 0 the Next Stage has to be ignored.
   It is a lot easier to ignore it if it is a separate field.


Thank you.

Bob Russell
InterOperability Lab
University of New Hampshire
rdr@iol.unh.edu
603-862-3774