Fast MAC algorithms?

Peter Gutmann pgut001 at
Fri Jul 24 01:30:24 EDT 2009

[I realise this isn't crypto, but it's arguably security-relevant and arguably
 interesting :-)].

James Hughes <hughejp at> writes:

>TOEs that are implemented in a slow processor in a NIC card have been shown
>many times to be ineffective compared to keeping TCP in the fastest CPU
>(where it is now).

The problem with statements like this is that they smack of the Linux
religious zealotry against TCP offload support in the kernel, "TOE's are bad
because we say they are, and we'll keep asserting this until you go away".  A
decade ago, during the Win2K development, Microsoft were measuring a 1/3
reduction in CPU usage just from TCP checksum offload.  Given the time frame
this was probably on 300MHz PII's, but then again it'd be with late-90s
vintage NICs.  On the other hand I've seen even more impressive figures with
their more recent TCP chimney offload (which just moves more of the NDIS stack
onto the NIC, I think it came out around Server 2003).

Does this mean that MS have figured out (a decade or so ago) how to make TOE
work while the OSS community has been too occupied telling everyone it doesn't
to do anything about it?  There must be some reason for the difference between
the two camps.


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