Introducing a New Network Protocol

The AREDN team is introducing a new networking technology into the nightly builds with the ultimate long term goal of replacing OLSR.

OLSR has many faults which AREDN has lived with for a long time. For the last couple of years we’ve been looking at alternatives and making incremental steps in the codebase to allow us to introduce something new. We can finally do that by adding Babel (https://www.irif.fr/~jch/software/babel/) to AREDN.

Babel has a number of qualities which make it good for AREDN. First, it’s a loop free protocol so, regardless of how the network is changing, routing loops will never form in the network. Second, it’s primarily a reactive protocol which sends changes to neighbors when needed rather than broadcasting its state continually. Third, the protocol understands the difference between wired, wireless, and tunneled links –  the three link types AREDN utilizes. Fourth, it’s a layer-3 routing protocol, which integrates easily with how AREDN already operates. Fifth, it’s highly configurable which will allow an optimal setup for our use case. Finally, it’s simple.

We considered a number of options, and another contender was B.A.T.M.A.N. Advanced. Unfortunately this protocol is not a good fit for AREDN as it primarily focuses on level-2 wireless networking. AREDN needs a protocol which can do more. We evaluated how we could use BATMAN and it wasn’t simple, efficient or pretty.

If you’re interested in more comparisons between Babel and other options there are many good presentations on YouTube. This is a great primer on Babel itself: https://www.youtube.com/watch?v=1zMDLVln3XM

Babel will roll out into the nightly builds alongside OLSR and the two will operate in parallel. If there is a Babel-only path between two nodes in the network, then Babel routes will be used to send traffic. If not, then OLSR routes will be used. This will let us deploy Babel and examine its performance in our networks without disturbing nodes which are not running Babel.

Important: Be aware that older radios with limited memory – the ones using the tiny firmware images – will not be able to support both protocols and should be eventually replaced.

 Evaluating success will depend on a few things, and the more feedback from the community the better. Our goals are to provide a more stable network, better routing decisions, and lower network overhead. Assuming success, the time scale to replace OLSR will be measured in years. Once OLSR is gone, any node not running Babel will disconnect, and we don’t want to leave our users behind so we are giving this as much time as needed for the transition to the newer protocol.

AREDN nightly build 20250217, which includes the Babel protocol,  is now available.  

The only other thing that's changed in this build compared to the 3.25.2.0 production release is the addition of an icon that shows if a link is running the Babel protocol.  It looks like this:

Go forth and test (cautiously)!

The AREDN development team