iSCSI: questions on tags, unsolicited data

["Mallikarjun C." <cbm@rose.hp.com>]

Julian,

Comments on iSCSI-02b draft.  Please comment on the first 
section (non-editorial).  Thanks!

o The discussion of target tags in the draft is inconsistent. 
  Section 2.6.3 states that it must not be 0xffffffff.  The payload
  diagram in 2.6 for WRITE Data PDU shows that the value of 0 (zero)
  is reserved since zero is used for unsolicited data.  Seems like
  both are reserved for unsolicited data.  Why? 

  Sections 2.15.2, 1.2.2.1, 2.6.3 must be fixed to reflect this 
  reserved value. (some sections state that there's no reserved value...)

o Section 2.1.5 allows target suggesting a tag width.  Why is this
  allowed?  Is the intention to support targets with 16-bit processors?
  I would argue that this provides an undue design burden on initiator
  implementations to cater to both 32 and <32 cases.  My recommendation
  is to drop this support.

o More clarifications on unsolicited data are in order - 
	- Are multiple unsolicited Data PDUs legal (total data size
          below the limit)?
	- Can unsolicited data be in the Command PDU (immediate)
          AND continue into a separate unsolicited Data PDU?

  If either of this is true, it appears that the "F - Final" bit 
  of the SCSI Write PDU should also be supported in the SCSI Command
  PDU.

EDITORIAL:

o Suggest adding a statement to the discussion of CmdRNs in 
  section 1.2.2.1 to the effect of: "There should only be one
  outstanding task with a given CmdRN (including 0) in a given
  session."

o Section 1.2.2.1, para 7 has a sentence "Incoming data is always 
  implicitly solicited.".  Suggest adding the phrase to the sentence
  "by virtue of the SCSI READ command issued earlier".

o Since urgent pointer usage is out of consideration now, seems like
  we can relax the requirement about MSb's in bytes 0 & 1 of every 
  payload - thus using the bits for other purposes like retry.

o Section 2.11, para 1: "still active and all it's components" 
  should be "still active and all its components".

o Section 2.6, there is no discussion of bits "O" and "U" in the
  SCSI READ Data PDU.  I assume they are overflow and underflow,
  this needs to be added.

o The last para in section 2.11.4 is a repetition of last para in 
  section 2.11.  Suggest dropping the second.

o NOP-In payload diagram has no "P-bit" (bit 6, byte 1).  A typo
  of "0" needs to changed to "P".

o Fix section 2.12.1 title from "Target Task Tag" to "Target Tag".

o Section 2.14, first sentence: Change "The logout is used.." to
  "The logout response is used...".

o Section 2.17, para 3 refers to map commands.  This is an obsolete
  reference, and should be removed.

o Section 7, first sentence: Change "There will be a well-known port..."
  to "There will be a well-known TCP port...".

--
Mallikarjun 


Mallikarjun Chadalapaka
M/S 5601			
Networked Storage Architecture
Network Storage Solutions Organization
Hewlett-Packard, Roseville.
cbm@rose.hp.com