So we have been working diligently to resolve an issue in relation to a vendor deployed Cisco Telepresence Show and Share setup. We ended up with through the troubleshooting process with two requirements. Basically what we were seeing was if the access port attached to the receiver was configured or negotiated at 100Mbps as opposed to Gigabit that the video stream would not play with any measure of predictability.

When everyone would go home or be out for lunch, the stream would play okay, but when the switch became even slightly busy, the video would most of the time not even provide a single key-frame and hence no video. Keep in mind that this was a 768kbps stream, so it was insane to think this could actually be the switch causing the issue.

With Auto-QoS defaults, we were dropping around 500 packets in 10 seconds. We actually forced this work by modifying marking the multicast traffic generated at the server on the server’s access switch and by modifying the output buffers for QoS on the client attached 2960S Access Switch. This required giving 70% of the buffer to the priority Queue, making sure CS5 marked traffic was getting inserted into the Priority Queue, and setting the thresholds for the priority queue to allow oversubsciption at 3200%.

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