Re: [Discuss-gnuradio] Gigabit Ethernet cards

[Josh Blum]

On 07/05/2010 07:33 AM, Manuel Fuhr wrote:
> On Fri, Jul 2, 2010 at 22:40, Marcus D. Leech<address@hidden>  wrote:
> > I suspect that my GiGE NIC may be dropping packets.  It's an
> > RTL8168d-type chip, according to "dmesg".
> >
> > Are there known-to-be-good-with-GnuRadio NICs for PCI with low-profile
> > brackets out there?  This is for
> >   a 2U server platform.
> I have the same problem that some packets from the USRP2 are getting dropped.

In general you will want to avoid the realtek chipsets. Though many are 
fine, you are more likely to have performance and driver issues.

> Test was made using "rx_timed_samples --rxrate 25000000 --nsamps
> 1000000" and "rx_timed_samples --rxrate 62500000 --nsamps 1000000" (on
> Windows built as release target) but it often indicates dropped
> packets (SX) on both platforms. Capturing with wireshark (or ulogd
> with pcap target) and decoding the VRT packets afterwards (using some
> python scripts) shows the same result. I tried using the benchmark_rx
> example but it fails because even after sending
> "STREAM_MODE_STOP_CONTINUOUS".

The default buffer size is way too small. You are bound to see dropping 
even when the average processing rate can keep up with no problem.

I just pushed code up to the master that requests a sizable buffer (half 
a second a full rate) by default, prints a warning when the resized 
buffer is too small, and added to the application notes about this: 
http://www.ettus.com/uhd_docs/manual/html/usrp2.html#resize-the-send-and-receive-buffers

-Josh