RE: iSCSI: definition of TSID (2.11.4 of draft 07)

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

Jim,

I see your point about the current wording possibly suggesting
an implementation option.

Can I suggest the following text:

  The TSID is a target-assigned tag which together with the InitiatorName
  uniquely identifies the session within the target.

It appears to me that it's all that's required for uniqueness, I 
don't think we need to mention ISID here.  If there are multiple
sessions with an initiator, each would anyway be assigned a different
TSID.  What am I missing?
--
Mallikarjun 


Mallikarjun Chadalapaka
Networked Storage Architecture
Network Storage Solutions Organization
MS 5668	Hewlett-Packard, Roseville.
cbm@rose.hp.com


>Marj,
>
>Comments in line (as usual...).  But for the person of few words, I'd agree
>with just this text (your first sentence only):
>
>"The TSID is the target assigned tag for a session with a specific named
>initiator
>that, together with the ISID uniquely identifies a session with that
>initiator."
>
>(I moved the word "name" around because the session is with the initiator
>not with the name.)
>
>Jim Hafner
>
>
>"KRUEGER,MARJORIE (HP-Roseville,ex1)" <marjorie_krueger@hp.com>@ece.cmu.edu
>on 08/28/2001 02:46:45 pm
>
>Sent by:  owner-ips@ece.cmu.edu
>
>
>To:   ips@ece.cmu.edu
>cc:
>Subject:  RE: iSCSI: definition of TSID (2.11.4 of draft 07)
>
>
>
>I'm curious why you've phrased it this way.  I think of it more like;
>
>"The TSID is the target assigned tag for a session with a specific
>initiator
>name that, together with the ISID uniquely identifies a session with that
>initiator.
><JLH>
>I don't really see the subtle difference between this text and mine, so I
>guess I don't have any problem with it.  At least it doesn't bind the
>definition to anything SCSI'ish.
></JLH>
>
>However, the target MUST enforce uniqueness of the SSID for a given I_T
>combination (in order for login and recovery rules to make sense).
><JLH>
>I think I see what you're getting at here, but I don't think the words
>capture it (it looks like an incorrect use of "I_T nexus" (a SCSI thing).
>Do you mean:
>
>  "However, the target MUST enforce the uniqueness of the SSID [aside:
>isn't this 'SID'?] for sessions with a given initiator."
>
>If so, I can go with this text, but I think this is stated in other places
>and need not be here.  But I won't argue if it is also here.
></JLH>
>
>The TSID MAY be a unique tag for a session with a specific initiator name."
><JLH>
>I don't think this belongs at all.  It is an implementation statement and
>so outside the scope.  It's a true statement, but I don't think it should
>be made explicit (especially in this part of the document -- I'd have less
>problem with this in the "Notes to Implementers" but even then it is
>suggesting a prefered(?) implementation).
></JLH>
>
>I know the last "rule" is more for convenience than to follow the "modeling
>rules" (but that's the most straight forward way to implement TSID
>assignment?).  From the target viewpoint, it must first set the context of
>the initiator name, secondly the ISID.
><JLH>
>First, it's not necessarily the most straightforward way. It could generate
>a unique TSID for every session regardless of initiator name.  That gives
>it a twobyte pointer to the session context.  That's a lot more efficient
>(perhaps) than having to also have an initiator name in that "pointer".
>So, if you go with your implementation, you have to index on the name+TSID,
>and that's too big, so you need an indirect pointer to the context and at
>that point it doesn't really matter what the TSID is relative to other
>TSIDs; you can use the name + joint SID=ISID||TSID as your index (it's only
>2 bytes more out of a possible 258!).
>
>So, I argue for no statement about implementation options, leave that to
>the clever programmers!
></JLH>
>
>Marjorie Krueger
>Networked Storage Architecture
>Networked Storage Solutions Org.
>Hewlett-Packard
>tel: +1 916 785 2656
>fax: +1 916 785 0391
>email: marjorie_krueger@hp.com
>
>> -----Original Message-----
>> From: Jim Hafner [mailto:hafner@almaden.ibm.com]
>> Sent: Tuesday, August 28, 2001 12:59 PM
>> To: ips@ece.cmu.edu
>> Subject: iSCSI: definition of TSID (2.11.4 of draft 07)
>>
>>
>> Folks,
>>
>> The following text defines TSID in referenced document (and with the
>> changes proposed by Mallikarjun):
>>
>> "The TSID is a tag that identifies the SCSI initiator port.
>> TSID is set by
>> the target.  It MUST be valid only in the final response."
>>
>> I'm trying to figure out what the TSID has to do with the
>> SCSI initiator
>> port.  As I understand it, they are completely unrelated (at an
>> architecture level).  In implementation may choose to use the
>> TSID as a
>> pointer to the session in a unique way across all sessions in
>> the target or
>> in a unique way across all sessions with a given named iSCSI
>> initiator or
>> it can do any number of other things.  It is, in my opinion,
>> unrelated to
>> the SCSI initiator port.
>>
>> I would propose the following alternative text:
>>
>> "The TSID is a tag set by the target that, together with the ISID,
>> identifies a unique session with the initiator."
>>
>> Comments?
>>
>> Jim Hafner
>>
>
>
>
>