Subject: iscsi: sequence timeout

From: "Gwendal Grignou" <[email-masked]>
Date: Tue, 27 Aug 2002 13:03:01 -0700

Hello,

First of all, I have a little editing comment: for coherency,
"Sequence timeout" should be renamed "Sequence reception timeout". (2
occurrences)

I have a question about what to do when the Sequence reception timeout
occurs. According to the document, in 5.14.1.b), a sequence timeout is
considered as an implicit sequence errors documented in 5.8 which is
considered as an implicit digest errors documented in 5.7. Target can
either send a recovery R2T or complete the command with sense data,
indicating a "protocol service CRC error". But it is also mentioned in
5.7 that the target should wait for all the data, signaled with a Data
PDU with an F bit) before finishing that command...

To solve this chicken&egg thing, could it be mentioned the target can
terminate the command when the Sequence reception timeout pops up? But
then it has to handle the case the final DataOut PDU arrives after the
"Sequence reception timeout" interval. Should the target take more
drastic action to prevent this situation?

Gwendal.

---

From: "Mallikarjun C." <[email-masked]>
Date: Tue, 27 Aug 2002 15:19:02 -0700

Gwendal,

Yes, "sequence timeout" should be changed to "sequence reception 
timeout" for consistency.  Thanks.

> occurs. According to the document, in 5.14.1.b), a sequence timeout is

Only the option of a recovery R2T is allowed in this case, given that
it's the description of "recovery within-command" (and 5.14.1.b makes it
clear).

>could it be mentioned the target can
> terminate the command when the Sequence reception timeout pops up

Only if it's certain that there are no more PDUs relating to the same 
ITT in the pipe *and* the initiator won't issue any further.  The only way 
to ascertain this to ensure that the task is terminated on either end.

>Should the target take more
 
Yes, one of the means to force a termination by the target is to drop the 
session.  And I don't recommend it on a sequence reception timeout for 
one I/O.....
--
Mallikarjun

Mallikarjun Chadalapaka
Networked Storage Architecture
Network Storage Solutions
Hewlett-Packard MS 5668 
Roseville CA 95747
[email-masked]