What Causes (Lost Carrier)session count
Posted 19 March 2012 - 07:03 AM
I moved to a new thread, because it is no longer about the new rules, but a (related) technical question.
Checking my session report better, I find it is mostly one device that causes all the session counts. That one device often looses the session after as little as 10 minutes. Other infrastructure devices keep the session all day.
Can you explain to me what sort of event could cause a "(Lost carrier)" session end?
Its a fixed device. In fact, its a cheap TP-WR941ND router that is used as a switch (all routing functions disabled) to connect two more outdoor access points, as well as serves a small enclosed space with its own access point. When I look with chilli_query, indeed the session disappears after 10 minutes, even though sessions for the AP's behind it stay active all day.
Something that the device does causes this (Lost Carrier), I need to figure out what. It would help me if I knew a bit better what the (Lost Carrier) meant in a technical sense.
Posted 19 March 2012 - 08:32 PM
It cannot be the first case if the device is a fixed router of course.
Posted 19 March 2012 - 10:47 PM
Skimming the Coova source, I see that carrier lost is given either if the DHCP lease times out without renewal request. (known reason) and also for any unknown reason (the source has a "if known cause send cause else send carrier_lost" phrase)
Because the infrastructure devices are hardcoded IP, they do not (need to) do any DHCP. However, if I sniff the network, I see that the UBNT devices send an gratuitous DHCP anyway (even though they have hardcoded IP) but the TP-Link - OpenWRT does not. So for the UBNT indeed, the session remains, but for the TP-LINK the session is lost after 10 minutes. Until it needs to do something again, at which point Coova sees it again.
Running Coova in debug mode give messages that confirm this, I see DHCP requests from UBNT, and I see a DHCP release for the TP-Link.
I could of course increase the lease and leaseplus parameters in Coova. That would probably also reduce other sessions renewals, especially from smartphones in sleepmode or walking in and out of range. I suspect increasing leaseplus (the grace period) is best, as it probably starts using that if the DHCP pool runs out. Or I could find out how to make OpenWRT also give a gratuitous DHCP.
Posted 20 March 2012 - 09:38 AM
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