Jeff Finkelstein, director of network architecture at US cableco Cox Communications, on how to calculate the savings provided by a Content Delivery Network (CDN), and the possibility of moving all video delivery to unicast.
When designing a CDN for optimal delivery of video in live environments, what are the key bandwidth drivers and trends to consider?
The first question to ask is – why are we putting in a Content Delivery Network?
The sum of the network costs based on growth due to cacheable traffic must be greater than the cost of the CDN and the the network traffic that will terminate southbound in the CDN (total cacheable traffic minus the total non-cacheable traffic). In other words, how much are we going to save with a CDN?
The second question is – how large does the cache in each location need to be? The larger the cache, the higher the hits, but also the higher the dispersion of unique titles.
And thirdly – where in the network do we place the caches? The lower in the network the more devices but less cache is needed, but the total cost must be offset by network savings.
What network delivery methodologies might you use?
We are looking at using a Content Delivery Network for network DVR (nDVR) and IP video delivery.
What challenges or concerns are commonly encountered?
The unknown of the return on investment (ROI) on CDN deployments is a big concern. The best mathematical models are just that – models. The actual deployments will show how correct our theories were, based on a real-world analysis of numbers.
Looking ahead, how might this all differ from the networks of the future?
One view of the future networks is that everything is unicast, but the ability to scale the network as large as may be necessary in the core and metropolitan rings is under discussion.
We are also looking at ways to provide a more switched digital video (SDV)-like method of delivering IP video, but some of the glue holding it together is still under discussion by operators and vendors. We will have to see how this plays out in the future.