[AG-TECH] packets dropped on the minute

[Gregory Bell]

Andrew,

The predictable, one-minute cycle should make your problem easier to
debug. You might want to ask your network folks to run multicast debug
commands on the relevant routers, as a start.  Also I would consider
disabling CGMP / IGMP-snooping on the affected subnet, if appropriate -
just to rule out one failure mode.  Good luck!

- Greg Bell, LBNL

Robert Olson wrote:
> 
> 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?)
> 
> --bob
> 
> At 01:03 PM 2/18/2003 -0500, Gurcharan S. Khanna wrote:
> >hi,
> >
> >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.
> >
> >thanks,
> >===========================
> >Gurcharan S. Khanna, Associate Director
> >Research Computing, Dartmouth College
> >gkhanna at dartmouth.edu
> >office: 603-646-1644
> >http://research.dartmouth.edu/
> >http://www.dartmouth.edu/~gkhanna
> >
> >-gurcharan
> >--- Andrew Shewmaker` wrote:
> >Hi,
> >
> >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.
> >
> >Thanks,
> >
> >Andrew
> >
> >--
> >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 ---