VCS Media Issues - Troubleshooting Bandwidth

[solomonstrength]

My Topology: Dual-NIC VCS-E between two Firewalls

Even with my 50 Mb of reserved BW to WWW using ISP QoS Priority Queue, I cannot run a clean large conference call made up of mostly H323 participants.   There seems to be a ceiling of about 18Mbs where the video for all participants becomes extremely pixilated and with accompanying audio that’s very glitchy/choppy.  

The VCS-E media stats for most, if not all participants, showed A/V packet loss, as well out-of-order pkts (I guess chnl 4 is receive):

All of my path interfaces are clean with no duplex mismatches. So my question is this:   Could the root cause of this BW issue still be on the internal network (including Codian, VCS-c, VCS-e) or is this looking like an www provider network issue (including QoS)?  

Thanks for any insights.

[Wayne DeNardi]

QoS only comes in to play when the link is 100% congested, so unless you're filling your WAN link with other traffic as well as video, the QoS probably isn't even kicking in to action.

Do you have any packet inspection happening for H.323 on the firewalls?  If so, turn that off for a start - that's known to cause issues such as this.

Wayne

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[Nick Halbert-Lillyman]

Just to confirm - you have a 50Mbps shared internet conneciton, with a priority queue assigned for voice/video traffic?

Remember that a QoS priority queue will generally only allocate 30 - 35% of availible bandwidth, so if your WAN link is congested, 18Mbps sounds right for how much bandwidth you can expect to be prioritized for voice and video before all excess traffic just becomes first in, firt out.

It would be worth checking the stats at around 12Mbps - if everything is working correctly, there should be very mimimal loss.  Likewise, see if you can generate 20Mbps+ of traffic over the same link after hours (I am assuming the link won't be congested at this time).  If it works fine at 12Mbps during business hours and fine at 20Mbps+ after hours, you can bet your bottom dollar that you are exceeding the allocated bandwidth on your QoS priority queue.

As for a solution, it's not reccomended to go above around 35% for your priority queue or other traffic can become slow and unusable.  You would need to have a seperate, dedicated link for video conferencing or enough bandwidth so that your video traffic requirements didn't exceed 35% of the total availible bandwidth.