[BULK] - SAS Backoff Retry Priority

Greg Tabor greg at vitesse.com
Thu Aug 5 20:15:33 PDT 2004

* From the T10 Reflector (t10 at t10.org), posted by:
* Greg Tabor <greg at vitesse.com>

Is your concern that the Retry Priority Status rule contradicts the 
statement in 7.12.5:

"After an expander device transmits an AIP, it shall not transmit an 
OPEN address frame unless it has higher arbitration priority than the 
incoming connection request."


If so, here are two points to consider:

1. In the definition of "arbitration priority" is changed when 
IGNORE_AWT is set.

2. If, in your example, expander 2 phy Y transmitted an OPEN frame after 
AIP with a lower arbwait time than the one it received crossing on the 
same link, then the expander to the right of expander 2 would also wind 
up backing off and retrying the OPEN it originally forwarded to exp 2.Y 
and set IGNORE_AWT when it rearbitrates as well.  So, the decision 
settles into a consistent state in both expanders.

// Greg Tabor - Vitesse Semiconductor Corporation //
// voice: (719) 867-4414      fax: (719) 867-6203 //
//            email: greg at vitesse.com             //

Gil Romo wrote:
> An expander obeying backoff retry priority could violate rules stated in 
> subclause 7.12.5 "Expander rules and connection requests".
> The attached document describes a scenario where this may occur.
> ------------
> Gilbert Romo
> Circuits & Integration
> QLogic Corporation, Aliso Viejo, California
> Office: 949-389-6266
> E-mail: gil.romo at qlogic.com

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