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I have been studying the pricing for a few CDN systems (namely, GCP, AWS and Azure), and need help clarifying my understanding for price dynamics for a VOD vs Live on CDN.

Assumptions for the comparison are -

  1. Both the streams (VOD and Live) are of same quality.
  2. VOD content is hosted on an external CMS and is transfered to the CDN origin server on a push basis everytime a new video is hosted.
  3. Live Content is being HLS streamed from a suitable streaming server (say wowza) to the CDN origin server.

From what I see in the pricing details for AWS and Azure, I dont see any difference in pricing for cacheable content(VOD) vs non cacheable(Live) content. My intuition tells me that VOD should be cheaper because the cache hit rates would be higher on the edge server. While for Live, the cache hits would be almost 0. Hence I expected significant difference in CDN pricing for the two but I am not seeing it in the pricing model for AWS and Azure, except for GCP.

Can you help me understand if my understanding is going wrong here or if there is actually no difference in the pricing for Live and VOD over a CDN?

Thanks.

user2244221
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1 Answers1

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Forgetting for the moment that you might use CDN storage for VOD assets. You are not likely to see different pricing for Live vs VOD with most CDN's. Which gets the best cache hit rates also depends a lot on how popular your live streams are, and how wide you VOD catalog is.

Typically, Live hit rates are going to be higher, because you have a bunch of clients asking for the same segments at approximately the same time. This mean, that the CDN doesn't need to keep a lot of data in the cache. For VOD, if you have a catalog of say 100's of assets, thats a lot of data to keep in the caching layer, which means you are likely to see misses, as the less popular data is purged from cache, and needs to be fetched from the origin. CDN's typically have limited storage capacity in their edge CDN nodes, and some CDN's may have "mid tier" nodes that have increased storage capacity, but is further from the users.

If you have few assets, and a not very popular live stream, the pattern may of course be the exact reverse, but that makes it really hard to price these things different, because it really depends a lot.

Now, if you are using CDN storage for the origination of your VOD content, of course that will have an extra cost, for almost all CDNs, including AWS and Azure. For AWS it would likely be S3 as the origin storage (you won't necessarily find "storage" pricing under CDN pricing, as they are seperate products for both AWS and Azure).

colde
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  • Thats insightful. Thanks for pointing out that cache hits would be actually better for Live than VOD in most cases with decent number of viewers. As a followup, I am not seeing any cache miss penalties on AWS and azure while I do see them in GCP. Does AWS/azure not charge for it or is it hidden in some manner? – user2244221 Nov 08 '18 at 10:50
  • @user2244221 to my knowledge they don't charge for it. And for AWS, it might actually be useful to route traffic through Cloudfront even though it's all cache misses, because the traffic is cheaper that way. It's rare that i find CDN's that handle it that way. – colde Nov 08 '18 at 16:47