Hi! I admit I have still not read the whole Babel's draft but I am skipping from sections to sections as I find them interesting.
Does Babel require bidirectional reachability? In draft I read that Babel tries to determine bidirectional reachability, but I was not sure if this means only such links are taken into consideration for routing? In "Cost Computation" section it is written that "if the txcost is infinite, then the cost is infinite" so probably this means such links are seen as non-existent (worst cost). This is of course reasonable, as all packets require ACKs on link-level so at least something should be coming back. But does bidirectional reachability than imply also symmetric routing? Or can Babel decide on an asymmetric route? As I understand it can. But then why this "artificial" (?) requirement of bidirectional reachability? Shouldn't this be just left out and if packets get to the other side (probably with ACKs on link-level) then this is it, this is all we want to know for routing? There is probably a spelling error here: "How a the txcost and rxcost are combined" I must say that I have problems understanding the symbols in explanation of the Bellman-Ford algorithm, but probably this is because I am expecting something else. If I understand now the description correctly (and my test implementation of it in Haskell works correctly), then all nodes are computing shortest paths how they are reachable from other nodes. Not what can they reach? How/when do then nodes exchange this information? (I am not reimplementing Babel, just trying to port shortest path algorithm into my framework so that I can maybe play with other approaches than shortest path later on.) So what I am doing is that each node (name one B) sends packets to all its neighboring nodes about all its known shortest paths to know nodes. After each node (name one A) receives such packet it checks if the path over this node (B) is better than currently known path (taking into the account the cost of the edge from B to A). So what I am getting at the end is that each node (like A) has information about how is best for other nodes to send it packets. But this is not really useful. I would need information in other direction. Mitar _______________________________________________ Babel-users mailing list [email protected] http://lists.alioth.debian.org/mailman/listinfo/babel-users
