STP link layer

Day, Brian Brian.Day at lsi.com
Thu Jan 15 09:42:03 PST 2009


Formatted message: <a href="http://www.t10.org/cgi-bin/ac.pl?t=r&f=r0901152_f.htm">HTML-formatted message</a>

Hello Pooja...
No... the identification sequence does not occur once the OOB sequence has
determined that the link is a SATA link.
Since these are then SATA links, there are no SL_IR or SL_CC state machines
either.
So conceptually, as soon as the links exchange the COMWAKEs in your example,
they only contain the functionality as defined by the SATA specifications.
The STP protocol occurs when you have SATA devices connected to SAS
exapanders.  The links connected to the SATA devices only run SATA protocol.
The links connected to other SAS expanders or SAS end devices (i.e.
initiators) are SAS links, that may then establish STP connections.
Note that sections M.14 and M.15 of the SAS spec annex show examples of how
these SAS and SATA links work within the scope of the expander.
Hope this helps!
Brian Day
LSI Corporation
________________________________
From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf Of pooja gupta
Sent: Wednesday, January 14, 2009 10:15 PM
To: t10 at t10.org
Subject: STP link layer
Hi,
I am working on STP protocol in SAS and I have one doubt regarding STP link
layer.
After the SAS phy detects during phy reset sequence that it is connected to a
SATA device,
It issues COMWAKE and after the OOB sequence and speed negotiation are
completed,
Phy Layer Ready (SATA) message is sent to link layer.
Now my query is after this SATA_PHY_READY, does identification sequence
happens?
If yes, then it is said in the protocol that to transmit Identify Address
frame, Phy Layer
Ready (SAS) message is required and does SATA device will have addesses as
specified for
SAS devices?
If no, then how exactly does the state machine for Link Layer in case of STP
begin and interface with
SL_CC state machines as these state machines need Enable Disable SAS Link
(Enable) message from SL_IR
State machine which, I suppose do not execute in case of STP?
Please clarify my query.
Thanks
Pooja



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