On Mar 7, 2011, at 2:02 AM, David wrote: > Hi there, > > I've started using CTP+LPL in a project (thanks for the earlier > suggestion), and have a few questions about the network behavior when > the basestation mote is offline/unavailable. > > (in this mail, I assume a very basic setup, where the motes can > normally all reach the basestation directly over CTP). > > Also, I'm using the official TinyOS 2.1.1 release, installed from the deb > files. > > Basically I have these queries: > > 1. CTP send timeout length: > > If you send a packet over CTP, but the basestation is off, the "sent" > event never seems to fire (even with an error/timeout code). Or > rather, sometimes it does, but not other times. > > Will the "send" eventually timeout, or will the mote eternally be in a > "trying to send" state, without calling any event code in the app? > > If there is an eventual send timeout, then how long is it, and where > can it be configured?
There will be an eventual send timeout. But it might take a long, long time. With LPL, each packet transmission can take a while. And by default CTP can retransmit a packet up to 32 times. > > 2. Cancelling CTP send: > > If for instance you're trying to send data over CTP from sensors, but > your data is out of date (basestation off for a long time), or your > sensor changes it's mind about wanting to send - is there a way to > cancel an existing "in progress" send? > > I don't see an interface for this. Would stopping and starting the > radio, and the collect engines achieve the same thing? > > (at the moment: I'm assuming that if the mote has been offline for a > long time, that the first received packet's sensor data should be > ignored, due to likely being very out of date). Send has a cancel command. Take a look at the interface. > > 3. Updating the packet being sent. > > Alternately - if the CTP algorithm is taking a long time to send the > packet (basestation is off for a long time), is it safe to update the > not-yet-sent payload with newer details? (probably not safe, but just > checking). No. It's probably already loaded in the radio, so changing it in memory won't matter. > > 4. Time for CTP network to re-establish. > > If the motes are unable to contact the basestation for a long time > (eg: hours/days), but then later the basestation becomes available - > then how long typically would it take for the network to re-establish, > and for data to start coming through from the sensors? That is a great question: we've definitely tested starting a mote fresh, but if it was disconnected for a long time (the link was bad), it make take a while for the link estimate to come down to a point where the node might use it. It in part also depends on whether there are other nodes: the disconnected node might be creating routing loops, desperately searching for a route to the root. In that case it might take a while. This seems like a good test case to try sometime and make sure CTP handles well. Phil _______________________________________________ Tinyos-help mailing list Tinyos-help@millennium.berkeley.edu https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
