[jloveless]

This is a nicely written article, however it's worth noting that the performance/reliability/availability differences across CDNs at a particular moment in time are pretty much non existent. These providers share the same backbone networks, same IX PoPs etc and thereby have little diversification benefit. See https://blog.edgemesh.com/understanding-diversification-netw... )

Where multi-CDN really shines is helping with regional specific solutions (e.g. China , India, Brazil, Argentina etc). It's probably worth nothing that the team at Streamroot helps do this client side and their p2p style option helps localize traffic as well. The former is certainly the way to go and the latter really helps add network level diversification. Of course - I'm biased as we offer similar lower level solutions.

[Jormundir]

This statement is not even close to true. At a particular point in time, different CDNs can have very different performance even for the same ISP in the same region.

[joshenders]

Absolutely. If you were a CDNs only customer this may be true but the reality is that you’re not and they are always going to be over-subscribed. Having worked at a CDN provider (Cloudflare), I can tell you that they are constantly battling resource contention via DDoS or other reliability issues.

Multi-CDN is the way to go for performance and availability, though as a customer it can be challenging because you’re forced to limit your configuration to the lowest common denominator of features and there’s not a great way to test consistency of your configurations across all vendors.

This article is essentially a high level sales pitch though; I didn’t find it all that useful. I implemented multi-CDN at Pinterest using Cedexis (DNS based), though with modern DNS providers like NSOne, Cloudflare, Dynect, a modern spark-based ETL pipeline, and the browser navigation timing API (RUM), it wouldn’t be too challenging to build something resembling Cedexis yourself.

[eldod]

Indeed the article is more an introduction to multi-CDN concepts, but take into account that it was written for the HTTP video streaming use-case, and not static content CDNs. A client-side implementation of switching would not be very useful for that kind of content.

For Cedexis, I think the strenght is not only in the configurable DNS routing system, but also because they set up a lot of probes for different CDNs & clouds, and share global aggregated data that anyone can access, which can be useful when you don't a Alexa top1000 traffic.

[eldod]

Have to disagree here, you can have very different performances from different CDNs for the same user at the same time. Some CDNs have their own backbone (or at least partially), a lot of them are using different routes, and a lot of the time, the issue is not with the backbone, but with peering inter-connections, which can be different between each ISP & CDN. And a CDN's capacity is shared between all its customers, so if you get a huge peak from one of them, it can impact the others too. Old but good example: Before Apple started building out its own CDN, it was using the leading commercial one, and when Apple was doing its iOS/MacOS updates, other broadcasters were having big troubles delivering their streams at the same time because the CDN was overloaded - but it doesn't mean that other CDNs were also all down. That's also why most video broadcasters are now doing multi-CDN for their biggest live events like Superbowl or the world cup - to be able to distribute the load on several networks.

[jloveless]

In this case - given this and the other comments - I stand corrected! I would love to see some data on examples of this occurring in the wild - and it 100% makes sense that a congested CDN provider would impact neighbors. It would be great if someone could do a writeup on examples and the detection/mitigation strategies. Perhaps issues like these (alongside cost) are driving the DIY CDN adoptions (Apple being the exemplar but also Tesla etc)? Also the Pinterest example is a great real world example - and they do an awesome job especially given the size of that cache - so there must be so real value from a performance standpoint! Out of curiosity does it seem like these dynamic switching decisions are better at the server level or client level?