[AG-TECH] Packet Loss

[Chris Kendrick]

Hi Andrew

On Thu, 2006-08-24 at 09:00 +0100, Andrew A Rowley wrote:
> Hi,
> 
> Can I ask which bridges / VV servers you were using?  I am guessing it was the AGSC ones (roberts/virgo/ag2server), but if this is not the case, it is worth trying this out; as all our bridges are in Manchester (although the inSORS and AG2/3 servers are on different VLANS, they are in the same building), there are rarely multicast difficulties between the bridges.  If the Australian site was using a bridge in Australia, and you were using one in the UK, this would have been the same as both of you using multicast, as the bridges would have to talk in multicast.

Our bridge is on the same subnet as our AG Nodes.  So if the AG node
can't to multicast to the Bristol VV neither can our bridge.  We are not
on AARNET.  We are on Grangenet.  I don't know if Grangenet peers to
JANET.  But when I go to the Bristol VV I don't get any audio/video
feeds if I don't switch to unicast.

The VV servers I was using were University of Bristol and University of
Leeds.  The Bridge I was using was AGSC/Manchester for both VV's

The Bristol Physical Venue was using inSors

> The fact that the packet loss followed a pattern could suggest that there was either something that periodically used the CPU at one of the sites (if you were getting bad audio from them, this would suggest their site), or something that was periodically flooding the network with packets or using packets with a high priority somewhere in the network.
> 
> I have seen something like this at one point when I tried to run a beacon on one of the inSORS servers.  Every time the beacon fired packets, the users on the bridge would see high packet losses.  This could be what is happening in your case - are you or the other site running a beacon on any of the machines in use for AG?  If so, try disabling this and see if it happens again.
> 

I wasn't running a Beacon, but the other site possibly was.

> Andrew :)

Thanks for your feedback Andrew, its given more for me to go on if the
loss repeats its self next time.

Chris Kendrick
VPAC

> 
> ============================================
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> 
> > -----Original Message-----
> > From: owner-ag-tech at mcs.anl.gov [mailto:owner-ag-tech at mcs.anl.gov] On
> > Behalf Of Chris Kendrick
> > Sent: 24 August 2006 01:53
> > To: ag-tech at mcs.anl.gov
> > Subject: [AG-TECH] Packet Loss
> > 
> > Hi All
> > 
> > I was running an AG session between, VPAC (Melbourne, Victoria,
> > Australia) and The University of Bristol in the UK Yesterday.
> > 
> > For some reason I was getting ~5sec patches of huge packet loss (as
> > shown in the RAT reception quality matrix) roughly every 3 minutes from
> > them (voice went extremely choppy), but they were always receiving good
> > audio from me.
> > 
> > I was running AG2.4 compat they were running inSors. and we had met in
> > the University of Bristol VV
> > 
> > I also Started a desktop AG2.4 compat at VPAC and joined the session, I
> > received packet loss from Bristol and from the original VPAC node, (due
> > to the VPAC nodes both connecting to the Bristol unicast bridge, the
> > traffic from the other VPAC node was obviously traveling to Bristol and
> > Back and getting packet loss on the return trip)
> > 
> > also we tried switching the Bristol inSors node between unicast and
> > multicast, and we also tried going to the University of Leeds VV and
> > having the Bristol node switch between unicast and multicast again.
> > Still got exactly the same packet loss pattern only coming from Bristol
> > 
> > My question is what tools tecniques can I use to further diagnose what
> > is going wrong if it happens next time?
> > 
> > Any advice gratefully received.
> > 
> > Chris Kendrick
> > VPAC
> > 
>