Hi Thomas,

[...]
> When I'm part of any kind of p2p "swarm", I can't upload reliably. It's so 
> bad 
> that I've rarely ever seen more than 20KBps per peer, and it's usually 
> between 
> 0 and 10KBps (5KBps is pretty average :o). 
> 
> I did some testing this weekend, and tried out the latest stable pfSense on 
> it 
> (I was running Debian Sid), and things improved a bit. Now I'm using an RT-
> AC66U
[....]

First of all, your network setup if not entirely clear. Is your p2p
client running on your Soekris net6501?

If so, is that wifi network with the Asus RT-AC66U between the Soekris
and the upstream network?

If not, why do you think the Soekris hardware is responsible for the
poor network performance?

My first two suspects of bad network performance would be:

1. Poor wifi. What is the packet loss and jitter (variation in latency)
between the wifi client and wifi AP? Ideally, this should be about 1 ms
RTT without much fluctuations, but 3 or 5 ms is usually acceptable too.
If you see latency over 10 ms, or over 5% packet loss, that is most
likely the culprit. Look into the location of the wifi, the channels
used by you and neighbours, etc. If you haven't done so, download a wifi
scanner to find out which channels are in use, and how strong they are.
Note that for 2.4 GHz (802.11g, 802.11n), an AP in e.g. channel 5 may
still interfere with channels 3 thru 7. 5 GHz (802.11n, 802.11ac) has
less users, but is more susceptible to interference by walls, floors and
doors.

2. Network saturation because of the use of UDP-based p2p traffic. TCP
has a fairly commanding congestion control algorithm, which
significantly backs-off in case of congestion. A fair portion of p2p
clients uses UDP, which lacks congestion control, and may continue to
send traffic. Unfortunately, this often results in higher latency,
collisions, and ultimately collapse of performance. It certainly pays of
to configure your p2p client to only use at max 50-75% of your upstream
bandwidth capacity.

Other sources might be poor TCP congestion control tuning, buffer bloat
or the opposite (too small buffers), poor Ethernet flow control, poor
upstream network. Insufficient TCP-offloading in your NIC, or -more
generally- not powerful enough CPU in your Soekris 6501 would be at the
bottom of list of suspects.

Hope this works.

Freek
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