Re: iscsi : Async Message "target requests logout".

[Santosh Rao <santoshr@cup.hp.com>]

Julian,

The jist of my issue is that the draft must not mandate that the "close the
cxn" logout be used in response to an async msg of type "target requests
logout". In the case of initiators deploying session recovery, this flavor of
logout may not be used/supported at all !

Such initiators would always resort to a session logout (reason "close the
session") & re-login. [Whether they have to do this in 2 steps or 1, is the
subject of a seperate mail thread discussing logout optimization, also
currently under discussion.].

In general, initiators with different error recovery capabilites may respond
in different ways to these async messages and the draft must not mandate what
the initiator must do in response to these async messages.

Regards,
Santosh


Julian Satran wrote:

> Due to security reasons we adopted the rule of only one login / TCP
> connection. You can't relogin on the same TCP connection.
>
> iSCSI asynchronous messages are not SCSI AENs (although they carry those
> too). Support for iSCSI Async. Messages is not optional.
>
> The close connection flavor of the message is the handiest for recovery
> (initiator knows when he gets it
> that the target will close the target end of it).
>
> I think that the text saying perform a logout - implied also the "implicit"
> logout from a login with restart but I will check again.
>
> Julo
>
> Santosh Rao <santoshr@cup.hp.com>@ece.cmu.edu on 29-08-2001 23:08:36
>
> Please respond to Santosh Rao <santoshr@cup.hp.com>
>
> Sent by:  owner-ips@ece.cmu.edu
>
> To:   IPS Reflector <ips@ece.cmu.edu>
> cc:
> Subject:  iscsi : Async Message "target requests logout".
>
> All,
>
> I've some concerns on the new wording for async messages in rev 07. The
> new wording for the async message iscsi event "target requests logout"
> reads :
>
>  "2    Target requests Logout. This Async Message MUST be sent on the
> same connection as the one being  requested to be logged out.  Initiator
> MUST honor this request by issuing a Logout as early as possible, but no
> later than Parameter3 seconds.  Initiator MUST send a Logout with a
> reason code of "Close the   connection" to cleanly shutdown the
> connection.  If the initiator does not Logout in Parameter3 seconds, the
>
> target MAY send an Async PDU with iSCSI event code "Dropped the
> connection" if possible, or simply terminate the transport connection."
>
> In the following cases, the initiator may be unable to or may choose not
>
> to use "close the cxn" logout :
>
> 1) initiator is only implementing session recovery and is using single
> cxn sessions. In this case, it would just perform a session logout
> + re-login [or an implicit session
> logout and  re-login by sending another session login
> with the same ISID and NULL TSID.]
>
> 2) Initiator does not provide support for async messages and chooses to
> ignore async messgaes. Async messages are provided for diagnostic
> capabilities and differing classes of initiators may have differing
> level of diagnostic & recovery support. Simple initiators may just
> ignore the async messages as the message is bound to be followed by some
>
> action from the target end. Mandating the responses to async messages
> does not allow for this initiator behaviour.
>
> The "close the cxn" flavor of logout or the initiator responses to async
> messages must not be mandated, since differing levels of error recovery
> support in initiators can result in different behaviours.
>
> Regards,
> Santosh
>
>  - santoshr.vcf
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