Fwd: [AG-TECH] Delays in audio/video arriving
nickless at mcs.anl.gov
Tue Apr 29 11:05:52 CDT 2003
Good morning John,
This sounds like you might be running into a packeteer or some such.
Many campuses have these devices to limit the amount of peer-to-peer
traffic (think Kazaa and other media "sharing" programs). Among other
things, devices like the packeteer have very long queues in them and a
strict rate limit.
We ran into a similar problem recently with the MOO text chat channel. A
packeteer was delaying outbound TCP packets for many seconds, making the
chat session unusable.
>>Date: Mon, 28 Apr 2003 12:55:55 -0500
>>Subject: [AG-TECH] Delays in audio/video arriving
>>From: John I Quebedeaux Jr <johnq at lsu.edu>
>>To: ag-tech at mcs.anl.gov
>>X-Mailer: Apple Mail (2.552)
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>>Sender: owner-ag-tech at mcs.anl.gov
>>I've got one for anyone who might understand/know/guess what causes this:
>>Our AG 1.x node has been up since December but only since two weeks ago
>>have our multicast streams been visible outside of our state network via
>>I2 (i.e. we've been receiving all along but not sending properly).
>>My problem is that my outgoing streams are delayed - incoming fine.
>>Outgoing are delayed... at different rates and as bad as 1-10 seconds
>>later. Typically 2-5 seconds and it varies.
>>When I test (with anybody outside our campus network) - I am receiving
>>video and audio pretty well. I get the occasional studder/drop in audio
>>but generally it's very clear and the RAT shows maybe 1-2% loss at times
>>with my receiving.
>>Outgoing is another issue. I'll get as much as 50-60% loss at times that
>>the RAT tells me and other times it is just 1-10%. Sometimes it clears up
>>and then degrades again. What is really interesting - and I'm not much of
>>a network guy - but my audio and video streams are delayed... in that
>>they arrive anywhere from instantly to 10 seconds later to the other
>>site. Not much loss actually... although the audio will end up choppy as
>>What's even more interesting is that one camera video will be less
>>delayed (or even not delayed) while the others are delayed at different
>>rates. The audio is delayed (or not at times) as well. I've seen delays
>>as high as 10 seconds. It happens from both my node and my pig node.
>>Between my two buildings (i.e. between my node and my pig) I don't see
>>I'm trying to get my network support on campus to look into this but they
>>don't respond well unless I can tell them what and where I think the
>>problem is. Multicast was enabled just for this application - so they are
>>new to this.
>>So... any suggestions on how I might troubleshoot this or if someone
>>might have an idea of what might be happening (someone has seen this
>>before) I'd appreciate if you dropped me a note to give me a direction to
>>head me in.
>>I do know our on campus equipment is Cisco... I'm supposedly on a gigabit
>>8 port switch to our campus fibre and then out to I2 (via LaNET here in
>>the state) onto the Abiliene network. My AG node has Linux 7.3 for the
>>audio and video capture and windows xp for the display.
>>Anywhere to point me is appreciated.
>>John I. Quebedeaux, Jr.
>>LSU Biological Sciences
>>131 Life Sciences
>>e-mail: johnq at lsu.edu
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
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