SAS-03rf, Expander Link Layer (XL)

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

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

> > Items (c) and (d) of the first lettered list of 
> > 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, 
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; does.  In
> the SL_CC state machine ( SL_CC1 to SL_CC2) this behavior 
> is described.
> In the XL's, c) and d) probably need to mention it as well.
> > 

Sorry if these seem like implementation-dependent issues.

Gil Romo 

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