Hi guys, Thanks for the replies. I agree with you on the fact that the routing tables are correct, i.e. * the end-to-end link quality embeds the concept of distance * routes have a cost that monotonically decreases as the packet moves towards the base station.
Nevertheless, the implementation of RouteSelect.selectRoute(..) still doesn't fully convince me: shouldn't we check that the packet is actually decreasing the cost while it is being forwarded? Both MintRoute and the old routing algorithm (tos/lib/Route) included this check. We know that routes have a cost that decreases when the packet gets closer to the sink, but routes can change while a packet is already being forwarded, and there is no relation (I guess) between the cost of different routes for different time instants. For example, consider the following: * suppose that node n0 sends a packet through the path p0 = n1.n2...nx... with minimum cost * suppose that there is a route update while the packet is being forwarded, and that node nx decides to change parent and selects a new route with minimum cost px = ny.nz.... Although we know that px has a decreasing cost, we are missing the relation with the previous path p0, and the new path px may include some nodes of path p0, as well. What do you think about this? Thanks, Paolo 2007/9/10, Philip Levis <[EMAIL PROTECTED]>: > On Sep 10, 2007, at 5:40 AM, Paolo Masci wrote: > > > Hi, > > > > I was giving a look to the multihop routing > > algorithm implemented in tos/lib/MultiHopLQI. > > I have noticed that nodes select their parent > > evaluating the end-to-end link quality > > of the path to the base station. > > > > In order to avoid cycles, shouldn't they select > > their parent evaluating also the distance from > > the base station? Without the check on the distance, > > there is no guarantee that the packet gets closer > > to the base station: isn't there the risk of cycles? > > (for example, I guess it may happen in scenarios > > with long paths and with link quality that frequently > > changes) > > No. It expects route cost to monotonically decrease. Take a look at > the logic which checks if a received packet is from a node with a > lower cost. That implies there might be a cycle. > > Phil > > _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
