A checksum question

[Terry Raggett]

I'd like to know a little about the internals of RSYNC. I am a little 
confused as to why RSYNC is using both the simple 32 bit algorithm and 
the MD4 checksum function on the same files. From my testing this causes 
a vast overhead that is clearly not represented by RCP (fairly 
obvious!). Removing checksumming from a secure whole-file LAN transfer 
brings RSYNC in line with the general performance of RCP.

Can someone explain to me the rationale behind the checksum algoritm and 
use within the RSYNC protocol?

I'm asking this question as I am finding it rather difficult to convince 
some of our users that RSYNC is a viable replacement for RCP 
functionality, which is necessary to resolve some of the limitations we 
encounter with the standard RCP.

Many thanks in anticipation,

Terry Raggett