iSCSI: multiple sessions b/n a pair of WWUIs.

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

> To: ips@ece.cmu.edu 
> Subject: Re: iSCSI: session login and ISID 
> From: julian_satran@il.ibm.com 
> Date: Tue, 10 Apr 2001 14:21:49 +0300 
          

> WWUI can be presented during login phase (2.10.9 is correct and in-line with 1.2.7) Two > sesions can have the same ISID but will have different TSID. The question of whether 
> more than one session should be allowed between a pair of wuis is under debate.

> Julo


Julian,

There seems to be some disconnect between your comments above and the
name-disc draft. As per the name-disc draft Section 2(d) :

"There can be only one iSCSI  session with a given ISID between an iSCSI
Intiator Node and an iSCSI Target Node."

The iSCSI [&name-disc] drafts should explicitly state that ISID is
uniquely assigned for a given initiator. Similarly, the TSID is uniquely
assigned for a given target. 

On the subject of multiple sessions for a given pair of WWUIs, this MUST
be a requirement. iSCSI must allow multiple sessions for a given pair of
WWUIs.

This is required because single-connection session models would like to
setup multiple sessions b/n initiator hosts and multi-ported targets and
export the multiple paths to LUs to upper layer wedge drivers like EMC
Powerpath, Veritas VxVm, etc.

Inability to establish multiple sessions b/n a pair of WWUIs implies
iSCSI layer will only export one path to the upper layer wedge drivers,
thereby, breaking such applications. 

This also implies iSCSI would then take on all the responsibilities of
providing load balancing and fail-over capabilities and would require
the use of multi-connection sessions for that purpose.

By allowing multiple sessions for a given WWUI pair, iSCSI layer could
achieve equivalent functionality using single connection sessions and
would also not break existing wedge drivers.

Regards,
Santosh
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