FW: Backoff and Reverse
john.lohmeyer at lsil.com
Mon Mar 1 09:28:21 PST 2004
* From the T10 Reflector (t10 at t10.org), posted by:
* John Lohmeyer <john.lohmeyer at lsil.com>
>----- Original Message -----
>From: "Hugh Curley" <hcurley at indra.com>
>To: <t10 at t10.org>
>Sent: Friday, February 27, 2004 7:21 AM
>Subject: Backoff and Reverse
>> > Is there any legitimate reason for the Backoff and Reverse Expander
>> > operation as shown in figures H7 and H1 of SAS 1 Rev3?
>> > My thinking is:
>> > If a SSP connection is open, regardless of who opened it, both
>> > send any SSP frames they may have. Therefore, if Device A opened
>> > connection, and Device B has frames, it would respond with Open
>> > Device B would not refuse A's offer of connection because of
>> > rate. If A's rate is too fast for B, the connection will be refused
>> > Y (Open Reject(Connection Rate not Supported)). If A's rate is
>> > B wants, B will just accept what is offered because B is a target.
>> > I was told that the only reason for Backoff and Reverse is if the
>> > device (B in this case) desired a different protocol. But here, B
>> > single protocol device, it cannot talk any other protocol.
>> > I could understand the operation if there was another expander in
>> > and both A and B made open requests for the other at approximately
>> > time. The connection request gets through A's expander (the one
>> > now in B's expander both requests are vying for the same resources.
>> > request wins, then that will be forwarded to A's expander and the
>> > and Reverse operation will be as shown.
>> > My reason for this question is:
>> > On previous occassions when I have noted this type of inconsistency
>> > standard, further understanding showed that the standard was correct
>> > was wrong. Now, I am concerned that there is something that I do
>> > understand. Is it possible to have a Backoff and Reverse with a SAS
>> > delivery subsystem and the "to" device is an SSP only target?
>> > Thank you,
>> > Hugh Curley
>> > hcurley at Indra.com
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