[AG-TECH] Multicast beacon questions

[Bill Nickless]

The beacons emit packets at 10 packets per second when operating 
correctly.  As mentioned earlier on this thread, some combinations of 
beacon code and java runtimes "run away" and blast more than 10 packets per 
second--up to the hundreds or low thousands mentioned earlier.  When that 
happens the beacon in question needs to be killed and restarted.  (If 
anyone can find the bug and fix it everyone would be grateful!)

The Access Grid video and audio groups routinely generate more traffic than 
the beacon group, even with O(100) beacons.  There is value in having the 
beacon group generating O(1000) packets per second, because it smokes out 
network configurations that are unable to handle Access Grid traffic 
levels.  Problems like multicast rate limits, dense-mode forwarding 
regions, and software forwarding will show themselves earlier rather than 
later when the beacon group is running at O(1000) packets per second.

In other words, we want the beacon group operating at the 
packets-per-second level of an Access Grid session so as to find problems 
before people are sitting at Access Grid nodes ready to get work done.

Each beacon is generating approximately 6 kilobits/sec of data.  At O(100) 
beacons, that's 600 kilobits/sec of data.  Given that even intercontinental 
network links are operating at OC-3 (155 megabits/sec) minimum these days, 
a 600 kilobits/sec traffic load should not be seen as unreasonable.

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Bill Nickless    http://www.mcs.anl.gov/people/nickless      +1 630 252 7390
PGP:0E 0F 16 80 C5 B1 69 52 E1 44 1A A5 0E 1B 74 F7     nickless at mcs.anl.gov