If you’ve been following AREDN development, 2025 brought the most significant architectural change in the project’s history: a move from OLSR (Optimized Link State Routing) to Babel as the underlying mesh routing protocol. For anyone building out or relying on the five-county mesh, it’s worth understanding what changed and why.
Why OLSR had to go
OLSR served AREDN well for years, but it was never designed for networks the size and complexity that AREDN meshes have grown into. As node counts increased and RF topologies got more varied — mixing 2.4 GHz, 5.8 GHz, and 3.4 GHz links across different terrain — OLSR started showing its limits. Routing storms (situations where the network floods itself with route recalculations) became a real problem on larger meshes, and the protocol’s convergence time after a node goes down or comes up was slow enough to matter during actual EmComm activations.
What Babel brings
Babel is a modern distance-vector protocol designed specifically for diverse, unstable mesh topologies. Key improvements for real-world AREDN deployments:
- Faster convergence after a node change — the network stabilizes more quickly after a reboot, a power failure, or a new node joining
- Better behavior on large networks — Babel scales more gracefully as the mesh grows
- Improved handling of mixed-band links — relevant as the five-county mesh connects 2.4 GHz near-range links to longer 5.8 GHz backbone shots
The transition issue to know about
The first production release with Babel (3.25.x) shipped with a known intermittent bug: after a reboot or firmware upgrade, Babel connectivity between two nodes could fail in one direction, evidenced by a Babel Metric value of -1 in the node panel. The AREDN team identified it quickly and a fix followed. If you upgraded nodes during the initial release window and saw one-way connectivity issues, that was likely the cause — check that all nodes in the mesh are on the same current production firmware.
What this means for JFMDNA
The JFMDNA buildout across Montgomery County and the surrounding area is at a stage where this transition matters. Nodes that are still on older AREDN firmware (pre-3.25.x) won’t participate fully in Babel routing and will fall back to tunnel or legacy behavior. Getting all nodes — especially the anchor sites — onto current firmware is the priority right now. If you have a node in the mesh and haven’t upgraded recently, now is the time.
More at arednmesh.org and the live mesh map at worldmap.arednmesh.org.