Re: [tcpm] draft-anumita-tcpm-stronger-checksum

Joe Touch <touch@isi.edu> Thu, 10 June 2010 21:21 UTC

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Date: Thu, 10 Jun 2010 14:19:46 -0700
From: Joe Touch <touch@isi.edu>
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To: "Biswas, Anumita" <Anumita.Biswas@netapp.com>
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Cc: tcpm@ietf.org, "Anantha Ramaiah \(ananth\)" <ananth@cisco.com>
Subject: Re: [tcpm] draft-anumita-tcpm-stronger-checksum
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Biswas, Anumita wrote:
...
>>> If keeping the standard TCP CRC intact (and covering TCP header & 
>>> data) and having an RFC1146 alternate checksum that works 
>> differently 
>>> than defined therein, perhaps it would be better to make it 
>> a new TCP 
>>> option then.
>>
>> Defined therein where? 
>
> http://datatracker.ietf.org/doc/draft-anumita-tcpm-stronger-checksum/
> 
> Section 3 - "Negotiating the use of CRC 32C"

There are two differences:

a) different processing rules
	computed over different portions of the segment
	and
	different rules for what happens to the original TCP checksum area
	and
	different rules for what to do when the option fails on SYNs

These are hard to fix without rewriting RFC-1146, which is feasible only if
there is a real need.

b) different algorithm
	this is easily fixed without modifying RFC-1146, by
	defining a new algorithm

	this assumes only the algorithm changes, though

Joe