[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>
*
Gil,

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 7.12.4.1 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.

Regards,
-- 
////////////////////////////////////////////////////
// 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


*
* For T10 Reflector information, send a message with
* 'info t10' (no quotes) in the message body to majordomo at t10.org




More information about the T10 mailing list