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Re: [Discuss-gnuradio] gmsk in light of fpga modifications

From: Daniel O'Connor
Subject: Re: [Discuss-gnuradio] gmsk in light of fpga modifications
Date: Fri, 19 Jan 2007 08:09:05 +1030
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On Friday 19 January 2007 01:19, Brett L. Trotter wrote:
> > Also you might be running out of entropy..
> Saw the entropy problem when using /dev/random, but /dev/urandom seems
> happier- in either case, at some point, ctrl+c's quit working and the
> session basically locks up (with scp, it eventually stalls out- the most
> I transferred was a MiB)- but typing causes packets to traverse the
> tunnel even though the typed text does not render, nor seem to reach the
> other end. I ran a ping -A and lost '0%':

Hmm, at least in FreeBSD urandom will give you randomness even when the 
entropy pool is empty, whereas random will not.

I believe that reading from urandom will consume entropy if it is available - 
this could cause a problem if SSH later needs randomness as it will block 
reading from urandom.

> So bottom line is, the ssh dies off. I'm going to try out the tcpdump
> suggestion from Greg Troxel and see what things look like.

Good idea :)

> It's possible that the interface is seeing so many errors that the
> checksums occasionally work out despite the errors- I'm going to also try
> increasing the symbols/sample.

Hmm, but TCP will correct for these errors - it only uses 32 bit CRC but it's 
not that likely to give a false positive.

Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C

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