[AG-TECH] Bridge Traffic/Router Issues

Christoph Willing c.willing at uq.edu.au
Sat Jul 18 22:43:22 CDT 2009

On 18/07/2009, at 9:23 PM, Mike Weaver wrote:

> OK, here's a weird one.  AG 3.2b1 on Fedora 11.  Started the venue  
> client w/
> default settings (in particular, unicast mode).  Went to the ANL venue
> server lobby.  Had some issues w/ RAT & D-Bus.  Did some  
> investigation and
> then got side-tracked with other tasks.  Sometime later I got bumped  
> from
> the venue server, but the client was still running.  Sometime later  
> still
> (sorry about the uncertainty of the timing) we started noticing  
> timeout
> issues on our LAN.  Web browsing would hang at various stages (DNS,
> connecting..., transferring...) for 20-30 seconds, every 10-15  
> minutes.
> Sometimes long enough to timeout the connection.  Clicking refresh  
> would
> bring the page up fine.  One other possibly relevant detail; I was  
> running
> the venue client as root.
> Users also started complaining about getting disconnected when  
> remoted in
> (RDP & Citrix).  Long story-short, we tracked it down to CPU  
> utilization
> spikes on our router (Cisco 7206, FastEthernet PIC).  The CPU  
> utilization
> (sometimes as high as 100%) was almost entirely from interrupts, no  
> process
> or memory issues.  While investigating NetFlow data, I notice a  
> large number
> of flows to the Auckland University bridge server in New Zealand.  I  
> found &
> exited the running venue client and the network problems stopped.  No
> guarantee that the venue client was to blame, but the problem  
> persisted
> steadily for almost a week, and hasn't reoccurred in over 2 days  
> coincident
> with exiting the venue client.  Pretty strong circumstantial  
> evidence IMHO.
> Looking at the venue client logs, the start of the network issues
> corresponded almost exactly with entering the lobby.  There are a  
> number of
> errors related to contacting bridges, but most are due to DNS issues  
> as we
> block a lot of central & southeast Asian networks  
> (.ru, .kr, .cn, .tw, .hk,
> etc...).  If someone is interested (hint hint Tom), I can provide  
> the logs,
> but their pretty big due the length of time the client was running  
> so I
> didn't want to post them to the list.
> Any idea what kind of traffic might be flowing between the venue  
> client and
> a bridge in these circumstances?  Anything periodic on the order of  
> every
> 10-15 minutes?  We're trying to characterize the data and determine  
> why the
> router was having issues with it.


I wonder if it had anything to do with someone testing a high  
bandwidth video format e.g. HD without using a separate multicast  
address for it in venue you were in? In that case you probably  
wouldn't see the HD video in vic, yet the associated traffic would  
still flow into your network (whether by multicast or via a unicast  


Christoph Willing                       +61 7 3365 8316
QCIF Access Grid Manager
University of Queensland

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