SAS Expander Routing Resources

Elliott, Robert (Server Storage) elliott at
Mon Dec 8 14:31:51 PST 2003

* From the T10 Reflector (t10 at, posted by:
* "Elliott, Robert (Server Storage)" <elliott at>
> * From the T10 Reflector (t10 at, posted by:
> * Gil Romo <gil.romo at>
> *
> In 4.6.4, the standard states that "The ECR routes messages 
> ...  Enough routing 
> resources shall be provided to support at least one connection."
> What should be the expander's response when it is has no more 
> routing resources
>  (ie, the expander finds a matching destination port that 
> supports the requested 
> connection rate and none of those phys are returning Phy 
> Status (Connection))?
> I don't believe the standard defines the expected behavior.
> Thanks,
> Gil
> ------------
> Gilbert Romo
> Circuits & Integration
> QLogic Corporation, Aliso Viejo, California
> Office: 949-389-6266
> E-mail: gil.romo at

One approach is to assume the ECM knows and does not offer any 
pathway resolution (no Arb Won, Arb Lost, or Arb Reject) in
that situation.  The request remains in limbo until it can
be serviced.

Another is to let the ECM treat it as a Waiting On Connection
situation (the fact that it is waiting on a connection between
two unrelated phys, not a connection occupying a destination
phy, doesn't matter much).

If you think the standard needs to describe one or both of
these (or some other approach), please suggest the text and 
where it should go.

Rob Elliott, elliott at
Hewlett-Packard Industry Standard Server Storage Advanced Technology

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