OLSR
OLSR is short for Optimized Link-State Routing, a routing protocol designed especially for dynamically changing networks (wireless ad-hoc mesh networks for example), which overcomes network hiccups caused by the dynamic nature of networks for which it was designed. By measuring link quality, it tries to determine the "best" routes between any two nodes, so data streams get the lowest possible packet loss. On top of that, it has the possibility to announce additional routes. So, in a wireless mesh network, every node directly connected to an internet uplink would announce a default route. Nodes connected to some other network (say a university campus net) would announce routes to that specific network and so on.
In recent versions of OLSR, native IPv6 is also implemented, so network announcements as well as data transport can both happen in IPv4 and IPv6 simultaneously.
OLSR has proven itself to be highly scaleable, powering large mesh networks in various places (Athens: ~2000 nodes, Berlin: ~600 nodes, and more). By the way: OLSR isn't limited to wireless links, the InterCity-VPN of various Freifunk communities also sports OLSR as routing protocol.
So far, Hamburg is the first and only city sporting native IPv6 on their Freifunk mesh network, but that's bound to change quite soon, hopefully.
