Fwd: [AG-TECH] Delays in audio/video arriving

Bill Nickless 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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>>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 
>>a result.
>>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 
>>this happening.
>>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 Q.
>>John I. Quebedeaux, Jr.
>>LSU Biological Sciences
>>Computer Manager/LBRN
>>131 Life Sciences
>>e-mail: johnq at lsu.edu
>>web: http://lbrn.lsu.edu
>>phone: 225-578-0062
>>fax: 225-578-2597

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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