Re: new to VPN

[Joe Touch <touch@ISI.EDU>]

Paul Koning wrote:
>>>>>>"Joe" == Joe Touch <touch@ISI.EDU> writes:
>>>>>
> 
>  Joe> 1) For some algorithms, such as DES, hardware can be 10-100x
>  Joe> faster than software. For others, e.g., MD5, software and
>  Joe> hardware have similar speeds.
> 
> If you have a software implementation of MD5 that runs at several
> gigabits per second, I'd love to see it...

Well, for grins I dug up the scripts I used to measure MD5 for Sigcomm 
back in 1995. I ran them on the following:

	Dell Precisin 530 PC
	dual XEON 2.4Ghz processors (only 1 of which is used)
	1GB RAMBUS RAM

The Sigcomm paper predicted, on a processor with at least 2-way 
parallelism (e.g., the XEON), that the limit would be:

My measurements of optimized code (as postted at ?? in 1995) are:

	unoptimized (RFC code):		1.03  Gbps +/-0.06
	optimized, main memory:		1.604 Gbps +/-0.008
	optimized, cache memory:	1.627 Gbps +/-0.001

The 3.06 Ghz processors should achieve over 2 Gbps easily (see below). 
That would indeed be multigigabit; this is, IMO, reasonably close. Sure, 
you can have custom hardware do better, but vs. riding the PC CPU curve, 
there isn't much of a win.

FWIW:

In RFC1810 I approximated 2/(3N) bits/second, where N=ns/instruction. 
Ten turns of Moore's law later (7.5 years), it appears that:

	2.4 Ghz XEON = 0.4 ns/inst

	2 / (3 x 0.4) = 1.666 Gbps predicted

	1.627 measured

or roughly 2.4% off... ;-)

Joe