Multi Connection Sessions and Active/Passive Targets

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

Hello,

I have a question regarding how the multi-connection session model would
work with Active/Passive target devices :

Consider the standard usage of multiple TCP connections within an 
iSCSI session, where the initiator and target setup each connection 
per available network interface port. THe intent here is to allow the SCSI
traffic to be spread across the available netowrk interface ports for the
purpose of load balancing, etc.

However, in the case of Active/Passive SCSI targets, traffic should be
sent only on the active port. Such multi connection sessions would not
distingush between the active and passive ports, causing traffic to be
sent to the passive port and active port. 

The use of multiple connections per session needs to be turned off when
speaking to such active/passive devices. (unless such devices dedicate a
group of network interface ports as active and passive). 
A couple of ways that come to mind to do this are :

a) Initiators maintain knowledge of active/passive device types and will
not initiate more than 1 TCP connection per session on such device types.
However, the recognition of the active/passive device would be based on the VID/PID fields in the response to an INQUIRY command, which makes this a
rather cumbersome approach.

b) Targets should indicate MaxConnections as 1 in their iSCSI LOGIN 
response for active/passive devices. This removes the need for initiators 
to detect Active/Passive devices and ensure the usage of the appropriate 
single or multiple tcp connections per session based on the device type.

Any thoughts on this ?

Thanks,
Santosh
correct usage of mul

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Santosh Rao
Software Design Engineer,
HP, Cupertino.
email : santoshr@cup.hp.com
Phone : 408-447-3751
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