How to see what your users see
Live broadcast TV is one of the most popular services in fibre networks. You can get high quality pictures because there is enough bandwidth to send video uncompressed. But the nature of broadcast media is that it is very sensitive to packet loss or jitter. There is no retransmission of packets because it is live – you can’t hold the stream to get a lost packet back. And buffering is also a problem, keeping too large a video buffer to mitigate jitter will make your neighbour scream “GOAL!” long before you see it on your own screen – so it’s not really 100% “live” anymore.
Multicast based TV is also difficult to troubleshoot. It takes so little – a single packet lost – for the problem to be immediately visible to the viewer as picture freeze or pixilation. Plus, as most viewers watch TV, its during evening time peak hours that the most problems are reported and that’s when you that work with the network are at home as well. On top of that, to actually track down where packets are getting lost can be a very tedious task. You will most likely have to go from port to port, from switch to switch to figure out where the packet loss happens in the network. If the problem is only seen during peak viewing hours in the evening and if you only have one or a few probes to work with, finding the root cause can take days to track down. Meanwhile your users are suffering and complaining and their resentment towards your service and network grows out of the frustration of not having the perfect picture they expect.
Enter real-time protocol monitoring of MPEG over multicast. This powerful feature available in Waystream MS and ASR series of switches uses the network processor in these systems to monitor the multicast traffic passing through. Going deep into the TV-streams the feature allows the switch to detect packet loss and jitter (variation in delay) which are typical issues that gives a poor TV experience. Since the feature can monitor multiple channels at the same time, and since each error can be individually tracked per channel it gives you a powerful insight into the quality of the multicast TV running through the switches.
This built in multicast probe turns every switch in your network into a monitoring station. Some customers use this to proactively monitor the network by collecting data and graphing it. Others mainly use it as a troubleshooting tool, activate when there is a problem in order to quickly pinpoint where in the network the cause is.
Having this function in the switches complements similar features in many setopboxes. When combined you have a powerful tool built into your network that lets you see what your users sees.
