Betweenness estimation in OLSR-based multi-hop networks for distributed filtering

• Traditional firewalling on multi-hop networks has a critical impact on network resources.
• Centrality metrics can be used to identify a core of nodes able to enforce filtering/monitoring.
• OLSR routing information can be used to efficiently identify this core of nodes without overhead.
• We propose a method that scales on realistic network dimension and topologies.
• Enforcing firewalling only on this core reduces the impact and stops most unwanted traffic.

In traditional networks special efforts are put to secure the perimeter with firewalls: particular routers that analyze and filter the traffic to separate zones with different levels of trust. In wireless multi-hop networks the perimeter is a concept extremely hard to identify, thus, it is much more effective to enforce control on the nodes that will route more traffic. But traffic filtering and traffic analysis are costly activities for the limited resources of mesh nodes, so a trade-off must be reached limiting the number of nodes that enforce them. This work shows how, using the OLSR protocol, the centrality of groups of nodes with reference to traffic can be estimated with high accuracy independently of the network topology or size. We also show how this approach greatly limits the impact of an attack to the network using a number of firewalls that is only a fraction of the available nodes.