SAS SSP link layer - which NAK for frame size errors

Elliott, Robert (Server Storage) Elliott at hp.com
Tue Jun 11 12:58:23 PDT 2002


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
*
I will reword the SSP link layer SSP_RF1:Frame_Rcv state to follow these
rules:

a) frame 28 to 1052 bytes with good CRC => ACK  (goto SSP_RF2)(frame
sent to transport layer)
b) frame 28 to 1052 bytes with bad CRC => NAK (goto SSP_RF2)(frame not
sent to transport layer)
c) frame <28 or >1052 bytes => ignored by link layer (no CRC check) (no
state change)(frame not sent to transport layer)

Should I remove NAK(GENERAL_ERROR) from the primitive list since there
is no stated reason to generate it?

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



> -----Original Message-----
> From: Bill Galloway [mailto:BillG at breatech.com] 
> Sent: Tuesday, June 11, 2002 9:44 AM
> To: Mark_Evans at maxtor.com; t10 at t10.org
> Subject: RE: SAS SSP link layer - which NAK for frame size errors
> 
> 
> * From the T10 Reflector (t10 at t10.org), posted by:
> * "Bill Galloway" <BillG at breatech.com>
> *
> That is what I remembered too.
> 
> Bill Galloway
> BREA Technologies, Inc.
> P: (281) 530-3063
> F: (281) 988-0358
> BillG at breatech.com 
> 
> -----Original Message-----
> From: Evans, Mark [mailto:Mark_Evans at maxtor.com] 
> Sent: Tuesday, June 11, 2002 9:31 AM
> To: 'BillG at breatech.com'; t10 at t10.org
> Subject: RE: SAS SSP link layer - which NAK for frame size errors
> 
> 
> HI Bill,
> 
> I thought we came to the conclusions in Minneapolis that the 
> only thing that should cause a NAK on an SSP frame was a CRC 
> error, and that all other checking of the frame would be done 
> at the transport layer.  Did I miss something?
> 
> Regards,
> 
> Mark Evans
> Maxtor Corporation
> 
>  -----Original Message-----
> From: 	Bill Galloway [mailto:BillG at breatech.com] 
> Sent:	Tuesday, June 11, 2002 6:52 AM
> To:	t10 at t10.org
> Subject:	RE: SAS SSP link layer - which NAK for frame size errors
> 
> * From the T10 Reflector (t10 at t10.org), posted by:
> * "Bill Galloway" <BillG at breatech.com>
> *
> I do not believe that the SSP link layer should NAK an illegal
> (malformed) frame.  It should only be responsible for ACK/NAK 
> on something that looks like a real frame (i.e. SOF 
> reasonable byte count EOF).
> 
> Bill Galloway
> BREA Technologies, Inc.
> P: (281) 530-3063
> F: (281) 988-0358
> BillG at breatech.com 
> 
> -----Original Message-----
> From: owner-t10 at t10.org [mailto:owner-t10 at t10.org] On Behalf 
> Of Elliott, Robert (Server Storage)
> Sent: Monday, June 10, 2002 5:18 PM
> To: t10 at t10.org
> Subject: SAS SSP link layer - which NAK for frame size errors
> 
> 
> * From the T10 Reflector (t10 at t10.org), posted by:
> * "Elliott, Robert (Server Storage)" <Elliott at hp.com>
> *
> Which NAK should the link layer return if it detects a frame 
> size that is out of bounds?
> 
> There are currently two NAK primitives:
> NAK(GENERAL ERROR)
> NAK(CRC ERROR)
> 
> Options:
> 1. Use NAK(GENERAL ERROR) to report both too-small and 
> too-large frames 2. Add NAK(FRAME SIZE ERROR) and use it for 
> both cases 3. Add NAK(FRAME SIZE TOO SMALL) and NAK(FRAME 
> SIZE TOO LARGE) 4. Rename NAK(GENERAL
> ERROR) to NAK(FRAME SIZE ERROR) and use it for both cases 5. 
> Add NAK(FRAME SIZE TOO SMALL) and NAK(FRAME SIZE TOO LARGE) 
> and remove NAK(GENERAL ERROR)
> 
> [if the link layer doesn't enforce any minimum frame size, 
> only the too-large case need be handled]
> 
> The group's conclusion will need to be included in the SSP 
> link layer's SSP_TAN and SSP_RF state machines.
> 
> --
> Rob Elliott, elliott at hp.com
> Industry Standard Server Storage Advanced Technology Hewlett-Packard
> 
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