In the terminology you defined, "node ETX" is what white bit indicates. I.e., Set white bit indicates that "node ETX" of the new link is smaller (kind of ETX=1). As "node ETX" of the evicted node can not be less than 1 and its "ETX" (to the Root) is greater than that of the new node, it is OK to evict the node.
Regards, Manjunath D ################################################################################################################ *************************************************************************************************************** On Wed, 11 Aug 2010, Xiaohui Liu wrote: > Hi, > > Thanks for your reply. > > I guess there is some misunderstanding here. When I say ETX, I mean ETX from > the neighbor to the root, not the ETX of the local link to the neighbor. > Let's call this ETX the node ETX for ease of exposition. If the network > layer can find some existing neighbor in neighbor table with worse node ETX > than the new neighbor and recommends insertion, why the underlying estimator > simply evicts a random neighbor regardless of its node ETX? This can evict a > neighbor with smaller node ETX. Look forward to your further explanation. > > On Wed, Aug 11, 2010 at 12:39 PM, Philip Levis <[email protected]> wrote: > >> >> On Aug 10, 2010, at 10:50 PM, Manjunath Doddavenkatappa wrote: >> >>> >>> Just a guess, >>> >>> Before asking the routing layer whether a new route to a neighbor is >>> promising, the estimator >>> asks physical layer whether the white bit of the incoming packet (from >> the >>> sender of the new link) is set. Only if the white bit is set then >>> estimator proceeds. Since the set white bit already indicates that local >>> link is good (may be interpreted as ETX=1), it may not be required to >> verify >>> the local ETX values of the existing neighbors. >>> >>> Please correct me if I am wrong. >>> >>> Manjunath D >> >> Sort of -- please refer to the 4-bit link estimation paper. >> >> Normally, when the estimator first learns about a neighbor, it waits before >> making communication with that neighbor available (actually putting it into >> the link table as an active link). The reason is simple: after receiving >> only one packet, the estimator can't provide a good estimate, and so making >> the link active might cause a protocol to choose a very very poor link. >> >> The white bit circumvents this initial estimation phase. The white bit >> indicates that there's a high probability that the underlying link is high >> quality; this allows the link estimator to skip the initial estimation and >> make the link immediately available for the routing layer to use. >> >> Phil > > > > > -- > -Xiaohui Liu > _______________________________________________ Tinyos-help mailing list [email protected] https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
