[e2e] How TCP might look with always there ESP

David P. Reed dpreed at reed.com
Wed Jul 18 00:50:38 PDT 2001

At 02:58 PM 7/17/01 -0400, Craig Partridge wrote:

>In message <NEBBJGDMMLHHCIKHGBEJAEKACJAA.dotis at sanlight.net>, "Douglas 
>Otis" wr
> >For which cases would ESP digests appear weaker than a 16 bit TCP checksum?
>If they had the same number of bits, then we'd have to evaluate the two
>over particular error models to determine which is stronger.

While this is true for one particular measure of effectiveness (average 
number of undetected erroneous packets from a distribution), I want to 
register the following observation:

if the model of the "corrupting" process is not stochastic, this measure is 
both meaningless and irrelevant.

2 examples:

1. deterministic corruption ( non probabilistic process explicitly 
dependent on data or externalities like timing or congestion).  In this 
case the measure is meaningless.

2. adversarial (conscious entities that may choose attack based on 
knowledge of the error detection method used).  Measure irrelevant and 

In other words there is no one measure for effectiveness of error detection 
that is appropriate over all situations.

- David
WWW Page: http://www.reed.com/dpr.html

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