* The bandwidth required to meet the quality metric for IPV conferencing
Continuing our discussion about IP Video (IPV) as a carrier’s managed VPN feature, we heard back from Neil Davies, Chief Scientist at Predictable Network Solutions. His company is a consultancy that provides tools and technology to help service provides better manage their networks.
Neil initially wrote us saying, “We’ve been running [IPV] for ourselves for the last 2.5 years…[with] Video Telephony…[making up] about 80% of VPN tunnel capacity between our sites. We run multiple services each with their own assured bounds on quality degradation [including] VoIP, distributed filestore, remote terminal services, collaboration tools, etc.
Davies continued by saying, “The key issue is to understand the VPN’s properties – what loss/delay/jitter it introduces and how close to its rated value you can drive the VPN and still get a predictable data transport (take it from me it is not 100%!). Then it is a matter of differentially sharing out the loss and delay that managing the traffic load creates. With the right analysis and the appropriate tools in end-point network elements (don’t need the cooperation of your carrier – we do it over standard products) this is not difficult.”
We followed up by phone with Davies and asked him about the quality and the bandwidth needed. On the quality issue, he said their video conferences were set up to offer sufficient video quality so that conference participants could communicate clearly using only sign language. (While Davies and his colleagues do use the audio channel, the sign language metric provides a measure of how clear and latency-free the picture quality must be.)
But what intrigued us was the bandwidth required to meet the quality metric: Davies suggested that a 512Mbps upload and 2Mbps download connection could support an office of 10 people with 3 to 4 VoIP lines (or a video call + 1 concurrent VoIP call) while concurrently supporting typical business data applications. Davies presented his approach to Ofcom (the U.K. telecommunications regulatory agency) last month, discussing quality in data networks and its properties.
Our observations: Neither enterprises or carriers should automatically throw bandwidth at IPV without first understanding that techniques like enhanced traffic management and (we hasten to add) better video compression can be used to offer acceptable IPV picture quality. And while telepresence picture quality that approximates a Blu-ray disk player on a 1080p TV screen may be nice to use, maybe a somewhat lesser picture quality will suffice. We will watch with interest to see how enterprise trades off the cost of capacity with the need for good video—and hopefully proper traffic management within the VPN can help IT managers balance the cost vs. the quality.
