[Babel-users] Should I use wifi mesh routing in crisis situations?

[Valent Turkovic]

On Thu, Jun 22, 2017 at 4:37 PM, Benjamin Henrion <zoobab at gmail.com> wrote:
> On Thu, Jun 22, 2017 at 4:21 PM, Valent Turkovic
> <valent at otvorenamreza.org> wrote:
>> Hi,
>> my name is Valent and I'm founder of www.otvorenamreza.org which is a
>> partner project with Wlan Slovenia (we are neighbours) and also
>> www.meshpoint.me
>>
>> We have used Babel for almost a year and it has show to be excellent,
>> recently we had tested it in real worlds situation with on extreme
>> sport event in which over 19,000 people have been online on 4 nodes
>> (each node with two 2.4 ghz radios)... in peak we had over 500 users
>> at the same time!
>>
>> All nodes were wired, we didn't use wireless mesh, only wired mesh so
>> to say in star + hub and spoke topology.
>>
>> I would like to ask this group what kind of setup do you use for
>> wireless mesh and which hardware?
>>
>> We currently have mostly single radio nodes (tplink wr841nd and
>> ubiquiti nanostation Loco m2) in our network and by default all of our
>> nodes also run mesh on same radio but via adhoc interface.
>>
>> In my short experimentation this showed to work quite poorly, even
>> with two nodes separated by only 10 meters on top of two building this
>> mostly failed to work and we had lots of connectivity issues. Once I
>> switched these two nodes to ap and sta modes link was rock solid.
>>
>> We have few nodes that are connected to the network only via wifi
>> adhoc mesh interface but these are only border nodes, and they are not
>> so important if then don't work perfectly.
>>
>> Did anyone experiment with running wireless point to point and point
>> to multipoint backone links with babel? Can you share what kind of
>> bandwidth speeds did you reach? Did you have any issues? Can you share
>
> Speed is not dependent on the routing, protocols like babel don't try
> to assess the speed of the link. Babel relies on the ETX metric, which
> is packet loss based, and would prefer a 56kbps link over a gigabit
> one if the first one has less packet loss.

Maybe my choice of "speed" was not correct, but I would like to hear
from real worlds tests what works and what are some best practices for
setting up 4-5 hop mesh network.

For example I see two setups.

First setup:
- a grid with four nodes separated 300m making it 300x300m (let's say
this is as big as having a grid of 3x3 football (soccer) fields)
- on each corner of this field two single radio devices or one dual radio device
- one radio would be used for mesh other for clients

second setup:
- four nodes spread in a line, each node separated by 500 meters
- first and last node would have client and mesh radios, nodes in
between would only have mesh radios
- there are two different variants in this setup
   * variant a) middle mesh nodes have two radios and sector antennas,
one for upstream one for downstream traffic
  * variant b) middle nodes have single radio and omni antenna which
is used for both upstream and downstream traffic

Has anyone done real worlds tests like these and what kind of devices
were used and what kind of speeds were reached?

> Doing mesh over a single frequency is a throughput suicide, as radios
> are half-duplex.

Yeah, I know.