SAS-03rf, Expander Link Layer (XL)

Gil Romo gil.romo at qlogic.com
Wed Apr 16 14:46:47 PDT 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* Gil Romo <gil.romo at qlogic.com>
*
Rob, please see my comments on crossing OPENs below.

> > Items (c) and (d) of the first lettered list of 7.15.9.1 
> > State description, 
> > define the conditions that generate Backoff Retry and Backoff 
> > Reverse Path 
> > responses, respectively.  Does the  XL6:Open_Response_Wait 
> > state manage these 
> > arbitration issues or is it done by the expander connection manager?
> 
> The XL state machine manages both "OPENs crossing on the wire" and 
> an inbound OPEN arriving after an AIP.  

So, the ECM does not manage these situations?
 
> 
> XL only reaches XL6 when it has sent an outbound OPEN.  If an inbound 
> OPEN arrives and they cross on the wire,  7.12.3 has the rules for 
> picking the winner.  If an inbound OPEN arrives after an AIP arrives, 
> then it should always win.
> 

In an expander, 7.12.3 Arbitration fairness is done by the ECM, but in 7.15.9.1, 
there is no request sent to the ECM and no confirmation received from the ECM.

> However, 7.12.3 doesn't include the latter rule; 7.12.2.2 does.  In
> the SL_CC state machine (7.14.4.3.3 SL_CC1 to SL_CC2) this behavior 
> is described.
> 
> In the XL's 7.15.9.1, c) and d) probably need to mention it as well.
> 
> > 

Sorry if these seem like implementation-dependent issues.

Gil Romo 

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