Re: iSCSI Some Thoughts on Digests

[Matt Wakeley <matt_wakeley@agilent.com>]

Bernard Aboba wrote:
> 
> >Could you explain how the requirement for a 32 bit end to end CRC
> >for TCP
> 
> Oh, so we're talking about *another* change to TCP?

I don't beleive that a "change" to TCP was implied (you are snipping part of
the sentence out of context).  The way I read the question is, why is a
cryptographic message integrity check (MIC) required if iSCSI embeds a CRC in
its PDUs and TCP provides the reliable delivery mechanism. [ David, your
statement was not very clear ]

If that was the question, then I beleive the answer is no, cryptography is not
needed.

iSCSI does need a CRC on the iSCSI PDUs because the TCP checksum is not
strong, plus it can be modified by infastructure products on the way. The only
way iSCSI can guarantee that the data sent is the data received is to include
a CRC as part of the iSCSI PDU.  [ Note this does *not* affect TCP at all, the
CRC is simply 4 bytes in the TCP stream that TCP is transporting ]

-Matt