[AG-TECH] query re: delay

John I Quebedeaux Jr johnq at lsu.edu
Sun Oct 1 18:48:11 CDT 2006


The ISP could be employing some type of packet shaping that is  
queuing your various data streams. At least, i've had this happen at  
my university in the past and it manifested itself with my outgoing  
video and audio streams arriving at various times (generally intact,  
but sometimes slowed down or sped up as things caught up after being  
queued). My first stream had priority, but the rest did not.

You can see the ports associated with the audio and video when you  
pull down the properties command under... i think it's under the file  
menu on the venue client. That may help if you can then look at the  
traffic associated with that port/ip.

I'm also assuming you were bridging (unicast) as well. In general,  
the audio and video seem to be in sync simply due to network speeds  
and bandwidth on I2/etc. I believe. Also, your uplink bandwidth on  
your DSL is probably much lower than your downlink bandwidth causing  
some congestion on your outgoing. Were you exceeding your available  
bandwidth? Which way were you seeing the delays? Changing the  
location "room" wouldn't change anything except the ports you're  
sending/receiving on so I'd actually be surprised if it changed then.  
If you changed venue servers (went to NCSA instead) and saw a  
difference (like it went away) then that would be interesting to  
note.  If i use my ADSL connection I have to VPN to my campus first  
out of my ADSL in order to get the ports i need in/out and through  
the nat'ing etc. And then a session could easily blow away my  
available (even my 6Mb downlink) bandwidth on the incoming not to  
mention there is no QoS if i'm not VPN'd.

Just some thoughts from what little i know... John Q.
John I. Quebedeaux, Jr.; Louisiana State University
Computer Manager LBRN; 131 Life Sciences Bldg.
e-mail: johnq at lsu.edu; web: http://lbrn.lsu.edu
phone: 225-578-0062 / fax: 225-578-2597

On Sep 29, 2006, at 7:11 PM, Alan Sondheim wrote:

> I've been working on a PIG in Brooklyn, New York, through DSL,  
> connected through Argonne to an AG at West Virginia University,  
> Morgantown. We're using 2.4. My question - the sound delays  
> approximately 7.5 seconds (the video is about .5 which is  
> understandable). What could cause such a large delay? I don't think  
> it's congestion; we tried the Lobby as well as the Test Room; the  
> results were the same. One reason I'm curious - I work at times in  
> sound and it would help to understand the mechanism here.
> Thanks, Alan, sondheim at panix.com
> blog at http://nikuko.blogspot.com - for URLs, DVDs, CDs, books/ 
> etc. see
> http://www.asondheim.org/advert.txt - contact sondheim at panix.com, -
> general directory of work: http://www.asondheim.org
> Trace at: http://tracearchive.ntu.ac.uk - search "Alan Sondheim"
> http://clc.as.wvu.edu:8080/clc/Members/sondheim

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/ag-tech/attachments/20061001/aeee6a3d/attachment.htm>

More information about the ag-tech mailing list