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Re: [Discuss-gnuradio] Timestamps, data rates

From: Juha Vierinen
Subject: Re: [Discuss-gnuradio] Timestamps, data rates
Date: Thu, 16 Apr 2009 21:05:50 +0000

>> Similar issues exist on the transmit side.


> Actually they are quite different.  When we assert flow control, we flow
> control _everything_ upstream between the USRP2 and the host.  Unless
> you want your network to die, die, die, don't put a switch between
> the USRP2 and the host if you are transmitting, and for sure, don't
> plug anything else into the switch.

Mental note to self: unplug USRP from campus-wide LAN first thing
tomorrow. I just checked and I could find_usrps my USRP2 from home,
and I'm on a 100 Mbit hub, 1 km away from work, on the same _large_

I guess I'll then go for a PCI Express card with many independent
ethernet interfaces. I just would've been so practical to just plug
USRP2s into a switch.

How about overflows. What is the probability that a USRP2 will drop
samples guring 24 h of 10 MHz receiving when connected directly to a
computer? I guess there is no mechanism that guarantees that the data
is delivered, but there has to be a mechanism that guarantees that you
know if samples have been lost?

> For all the gory details on this, see a good reference on Gigabit
> ethernet flow control.  I found Rich Seifert's, "Gigabit Ethernet:
> Technology and Applications for High-Speed LANS" useful.  You could
> also read the GigE ethernet spec.

I'll try to look this up. but I think I'm mentally about six-seven
layers above or below this stuff in the OSI model ;)


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