Hi,
I've made another observation about my link recovery problem. The following
is the script that I used.
while :
do
time=$(iw dev wlan0 station dump | grep -A 1 '00:15:6d:ec:32:cd' |
grep 'inactive time' | cut -d ':' -f2 | awk '{print $1}' | head -2)
if [ $time -gt 1000 ]
then
echo "Link Lost"
prev_time=0
while :
do
time=$(iw dev wlan0 station dump | grep -A 1
'00:15:6d:ec:32:cd' | grep 'inactive time' | cut -d ':' -f2 | awk '{print
$1}' | head -2)
if [ $time -lt 500 ]
then
echo "Link Back"
echo $prev_time
break
else
prev_time=$time
fi
done
fi
done
Case1:
When the two nodes are connected in mesh mode. If I do "wifi restart" on a
node which is connected to another node. Then the two nodes will be
connected back again in less than 1 sec.
Case2:
When the nodes move away from each other so that the RSSi is over -102 dbm.
Then there is no longer a link until node comes back in the range. The link
recovery is really quick when it comes back in the range. This is when
there is no UDP packets being sent. That is, no traffic. I've tested this
by the above script. Where in, I monitor the "inactive time" continuously.
Case3:
I the presence of UDP traffic. When the nodes move away from each other so
that RSSi is over 102 dbm. There is no longer a link, like in above case,
until the node comes back in the range. But, the special problem here is
that, although the node2 (which moved out of range) comes back really quick
in less than 5 sec. The link is not recovered until 1 min.
The same tests when done with AP and STA mode in openwrt, the link recovery
happens pretty fast. Both in the presence and absence of UDP traffic. So,
the summary of above tests is that, when the nodes are configured in mesh
mode and when there is UDP traffic flowing through the nodes. The link
recover is slow when the nodes move out of range of each other and comes
back in range. Link recovery when there is no UDP traffic is fast. Also,
link recovery when then nodes are restarted is also fast.
Any suggestions would be really appreciated.
Regards,
Siva.
On Thu, Sep 20, 2012 at 1:08 PM, Sivateja Patibandla
<[email protected]>wrote:
> Javier,
>
> Thank you. That helps. I will run the script on my setup and try to
> figure out the problem.
>
> Regards,
> Siva.
>
> On Wed, Sep 19, 2012 at 8:00 AM, <[email protected]>
> wrote:
> > Send Devel mailing list submissions to
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> > Today's Topics:
> >
> > 1. long delay in link recovery after a link loss
> > (Sivateja Patibandla)
> > 2. Re: long delay in link recovery after a link loss (Javier Cardona)
> >
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Tue, 18 Sep 2012 17:39:50 -0400
> > From: Sivateja Patibandla <[email protected]>
> > To: [email protected]
> > Subject: long delay in link recovery after a link loss
> > Message-ID:
> > <CA+LeHHHx15FcyShMJ4b2-C9NJyg93f7ypp42LjO9aUJBO3=
> [email protected]>
> > Content-Type: text/plain; charset=ISO-8859-1
> >
> > Hi Guys,
> >
> > I'm working on setting up a mesh network with multiple unmanned aerial
> > vehicles. I'm working on Ubiquiti bullet 5 Ghz module. The hardware is
> > AR2313 with ath5k driver. I'm currently doing testing with just two
> > nodes (one is plane and one is ground station) being setup with . The
> > problem I've noticed today is as follows: If A (ground station) and B
> > (plane) are communicating and suddenly B goes out of range. Though, B
> > comes back immediately in the range. Both nodes can't communicate to
> > each other for at least a minute. The traffic is all UDP traffic. I
> > had this problem in the lab environment too. I could only get the
> > connection back by restarting the node B in lab environment. In the
> > tests that involved using proprietary firmware of Ubiquiti in access
> > point and station mode, there was no such delay in the link recovery
> > after failure at all. Any comments on this problem will be
> > appreciated.
> >
> > Regards,
> > Siva.
> >
> >
> > ------------------------------
> >
> > Message: 2
> > Date: Tue, 18 Sep 2012 15:41:06 -0700
> > From: Javier Cardona <[email protected]>
> > To: [email protected]
> > Subject: Re: long delay in link recovery after a link loss
> > Message-ID:
> > <
> capjqad_ows9ess1u-xe1gnggfk0wfxupgxcxbn6b7ncpayr...@mail.gmail.com>
> > Content-Type: text/plain; charset=ISO-8859-1
> >
> > Hi Sivateja,
> >
> > On Tue, Sep 18, 2012 at 2:39 PM, Sivateja Patibandla
> > <[email protected]> wrote:
> >> Hi Guys,
> >>
> >> I'm working on setting up a mesh network with multiple unmanned aerial
> >> vehicles. I'm working on Ubiquiti bullet 5 Ghz module. The hardware is
> >> AR2313 with ath5k driver. I'm currently doing testing with just two
> >> nodes (one is plane and one is ground station) being setup with . The
> >> problem I've noticed today is as follows: If A (ground station) and B
> >> (plane) are communicating and suddenly B goes out of range. Though, B
> >> comes back immediately in the range. Both nodes can't communicate to
> >> each other for at least a minute. The traffic is all UDP traffic. I
> >> had this problem in the lab environment too. I could only get the
> >> connection back by restarting the node B in lab environment. In the
> >> tests that involved using proprietary firmware of Ubiquiti in access
> >> point and station mode, there was no such delay in the link recovery
> >> after failure at all. Any comments on this problem will be
> >> appreciated.
> >
> > I have no explanation for your observations. All I can say is that
> > the protocol should be able to handle the scenario you describe. If
> > you are willing to investigate this, you could start by simulating
> > link losses with hwsim and you should observe that flows are
> > reestablished as soon as the link is recovered.
> >
> > What follows is an excerpt of one of our tests:
> >
> > for i in `seq 1 5`
> > do
> > echo -n `date +%s` Breaking link:
> > echo 0 > /sys/kernel/debug/ieee80211/${PHY0}/hwsim/group
> > ping -q -I mesh0 192.168.77.11 -c 20 -i 0.1 -w 1 | grep loss |
> > cut -d, -f 3
> > sleep 1
> > echo -n `date +%s` Restoring link:
> > echo 3 > /sys/kernel/debug/ieee80211/${PHY0}/hwsim/group
> > ping -q -I mesh0 192.168.77.11 -c 20 -i 0.1 -w 1 | grep loss
> > | cut -d, -f 3
> > done
> >
> > And this is the output we observe:
> >
> > (...)
> > 10 packets transmitted, 10 received, 0% packet loss, time 905ms
> > rtt min/avg/max/mdev = 0.123/0.274/1.235/0.324 ms
> > 1348007532 Breaking link: 100% packet loss
> > 1348007534 Restoring link: 0% packet loss
> > 1348007535 Breaking link: 100% packet loss
> > 1348007537 Restoring link: 0% packet loss
> > 1348007538 Breaking link: 100% packet loss
> > 1348007540 Restoring link: 0% packet loss
> > 1348007541 Breaking link: 100% packet loss
> > 1348007543 Restoring link: 0% packet loss
> > 1348007544 Breaking link: 100% packet loss
> > 1348007546 Restoring link: 0% packet loss
> > PASS
> >
> > Hope that it helps.
> >
> > Javier
> >
> > --
> > Javier Cardona
> > cozybit Inc.
> > http://www.cozybit.com
> >
> >
> > ------------------------------
> >
> > _______________________________________________
> > Devel mailing list
> > [email protected]
> > http://lists.open80211s.org/cgi-bin/mailman/listinfo/devel
> >
> >
> > End of Devel Digest, Vol 7, Issue 17
> > ************************************
>
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