Re: iSCSI : Digest Error recovery causes data corruption

[julian_satran@il.ibm.com]

Pierre,

Please don't put salt on my wounds...  (and explicitly for the reasons you
mentioned) I suggested that back in San Diego.  There where 2 reason for
abandoning it:

1- it can be practically done without TCP modification if CRCs are put in
the IPsec Authentication Header but the IPsec people won't have anything
weaker that any of the cryptographic digests and without IPsec we are out
of options (no change to TCP!)

2-more important Storage Proxies would like to have their separate data
digest (or equivalent)

Regards,
Julo




Pierre Labat <pierre_labat@hp.com> on 31/01/2001 20:19:17

Please respond to Pierre Labat <pierre_labat@hp.com>

To:   ips@ece.cmu.edu
cc:
Subject:  iSCSI : Digest Error recovery causes data corruption




Hello,


I would invite you to revisit the Mike Krause mail about
"iSCSI Data Integrity - Digests".

If Alternative 1 or 2 is adopted, when a digest error (CRC)
occurs, the segment could be discarded, and TCP will
retransmit. For software implementation with an hardware
assist to calculate the CRC, (same kind of the one that exists
now to calculate the checksum now), if a CRC error is detected
it could be assimilated as a checksum error.
Hence there is no need to overload the iSCSI protocol
to deal with digest errors, because the iSCSI layer could not
see them.

Why to do complicate when simple an efficient can be achieved?

Regards,

Pierre