[AG-TECH] packets dropped on the minute

Robert Olson olson at mcs.anl.gov
Tue Feb 18 12:29:44 CST 2003

the periodic packet loss is an indicator of misconfigured multicast routing 
somewhere along the line;  I don't know offhand specifically what may cause 
it but the network folks may (bill?)


At 01:03 PM 2/18/2003 -0500, Gurcharan S. Khanna wrote:
>we have had and continue to have similar problems. it seems
>related to how many bits we're pushing out--the more bits the
>greater the packet loss. seems like anytime we go over 2-2.5Mbps
>we start to see increasing packet loss. and increasing distortion
>in the audio especially.
>we have had some recent network hardware upgrades and don't
>notice this as much now, but it still seems an unknown cause.
>our networking people don't see this loss at all--but then maybe
>they wouldn't be expected to???
>all our traffic goes through a packetshaper, but they've played with
>that without any seeming improvement.
>our beacon seems to indicated a mixed picture--ok to some sites,
>bad to others, and in some cases it says we're not even seeing ourselves!
>i'd be very interested in possible causes and tools for diagnosing/
>confirming this behavior.
>Gurcharan S. Khanna, Associate Director
>Research Computing, Dartmouth College
>gkhanna at dartmouth.edu
>office: 603-646-1644
>--- Andrew Shewmaker` wrote:
>Now that we have used our AG node to attend a few events,
>we have most everything working well.  We did notice that
>every minute on the minute we lose packets on our display,
>audio, and video hosts.
>We are positive that we aren't seeing the packets at all
>because we can see with the MS Windows 2000 cpu monitor
>a huge drop in load, and then a resumption of the previous
>load.  Since there isn't a spike, that seems to indicate
>that the packets aren't suddenly coming through all at once.
>It almost makes the audio unusable...at the very least it
>seems to strike whenever someone says something interesting.
>Our networking people are trying to discover what is
>happening, but they don't have any likely suspects.
>Has anyone else seen something like this?  Can you help us
>fix this?  This is a significant quality issue for us.
>Andrew Shewmaker
>Associate Engineer
>Phone:  208.526.1415
>Fax:  208.526.4017
>Idaho National Engineering and Environmental Laboratory
>2525 Fremont Ave.
>Idaho Falls, ID 83415-3605
>--- end of quote ---

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