02-214r1 SAS hash transport checking - minimum frame size checking

Bill Galloway BillG at breatech.com
Mon Jun 10 19:33:42 PDT 2002


* From the T10 Reflector (t10 at t10.org), posted by:
* "Bill Galloway" <BillG at breatech.com>
*
Rob,

I thought about it some more after we talked and I think the 28 should
stay. Part of the argument to relax the 28 size is that the link layer
should not be very aware of the protocol and we may define a new
protocol that does not have a 24 byte header.  It dawned on me later
that we do not have one link layer.  We have a link layer per protocol.
All frames in the SSP protocol have a 24 byte header and any new frames
we create will too. I see no reason for the SSP link layer to pass
frames that do not have a header.  All of the frames that we said are
ignored by the link layer actually need to be specified on a per
protocol basis.

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 4:54 PM
To: t10 at t10.org
Subject: 02-214r1 SAS hash transport checking - minimum frame size
checking


* From the T10 Reflector (t10 at t10.org), posted by:
* "Elliott, Robert (Server Storage)" <Elliott at hp.com>
*
In 02-214r1 SAS hash transport checking (approved by the SAS WG last
week), the SSP link layer state machine is given this rule:

    A frame shall be accepted if:
    ...
    b) the number of bytes between the SOF and EOF is greater than or 
    equal to 28 and less than or  equal to 1 052 bytes; 
    c) the CRC is valid.

Should the link layer enforce a minimum frame size of 28?

Options are:
1) require 0 bytes.  SOF followed by EOF would be valid at the link
layer but discarded by the transport layer.
2) require 4 bytes.  This ensures room for a CRC but no frame data. The
frame would be discarded by the transport layer.
3) require 8 bytes.  This ensures room for a dword of useful frame data
plus a CRC. The frame would be regarded by today's transport layer.
4) require 28 bytes.  This ensures room for a 24 byte SSP frame header
plus a CRC.  This is what 02-214r1 proposes.

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


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