[Mesh] Ad-hoc mode and cjdns

[Marc Juul]

On Wed, Jun 17, 2015 at 11:16 PM, Cobin Bluth <cbluth at gmail.com> wrote:

> Hi All,
>
> I live in portland OR, and I am just recently getting interested in
> wireless meshnets.
> My current setup is two nodes, Raspberry Pi 2 Hardware, one with a tp-link
> TL-WN722N, and the other with some sort of "panda wireless-n" adapter.
> My problem is that I am getting around 30% dropped packets, and they are
> about a foot apart, which makes me wonder if using a ad-hoc is a good idea
> or not...
>
> I have them both running Ubuntu 14.04
> <https://wiki.ubuntu.com/ARM/RaspberryPi> and the most recent version of
> cjdns.
> My network configs are below:
>
>
> root at ubuntu:~# cat /etc/network/interfaces
> # interfaces(5) file used by ifup(8) and ifdown(8)
> # Include files from /etc/network/interfaces.d:
> source-directory /etc/network/interfaces.d
>
> # The loopback network interface
> auto lo
> iface lo inet loopback
>
> # The primary network interface
> auto eth0
> allow-hotplug eth0
> iface eth0 inet dhcp
>
> auto wlan0
> allow-hotplug wlan0
> iface wlan0 inet manual
>   wireless-channel 8
>   wireless-essid NeighborMesh
>   wireless-mode ad-hoc
>
>
> So then I decided to just remove the wireless usb adapters, and run cjdns
> over the eth0 interfaces, but I am still getting a consistent ~12% packet
> drop with that:
>
> --- fcfe:307d:38e5:5aa4:9bfc:a4ce:dd3d:969c ping statistics ---
> 76 packets transmitted, 67 received, 11% packet loss, time 75156ms
> rtt min/avg/max/mdev = 2.378/26.382/196.791/51.318 ms
>
>
>
> Pinging the IPv4 address outside of cjdns works great, always:
>
> --- 192.168.0.226 ping statistics ---
> 24 packets transmitted, 24 received, 0% packet loss, time 23002ms
> rtt min/avg/max/mdev = 0.640/0.675/0.783/0.036 ms
>
>
>
> What am I doing wrong?
>

Since you're getting packet loss on ethernet with what I assume is a fairly
default Ubuntu I have three theories of what's up

* Something running on the raspi is taxing it so much that it can't handle
the packets in a reasonable amount of time (kill all non-essential process,
check top and iotop output)
* Manufacturing problem (test each raspi ethernet with a known working
computer)
* The raspberry pi sucks

The Raspberry Pi has notoriously unreliable USB (it's using a mobile
chipset which probably wasn't really designed to run as a USB host). If I
remember correctly the ethernet adapter is attached over the USB bus.

I do not recommend using the raspberry pi for _anything_ with the two
exceptions of stuff that uses the raspberry pi camera or built-in H.264
hardware encoder (which is pretty unique). For everything else I recommend
using a Beagle Bone Black. Yes it's slightly more expensive but totally
worth it + it's actual Open Hardware unlike the Raspberry Pi.

For mesh stuff we exclusively use OpenWRT supported routers with ar71xx
chipsets. I can recommend the TP-Link N600 and N750 routers. If you really
want a full distro in a format similar to Raspberry Pi then go with the
Beagle Bone Black.

-- 
marc/juul
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