Published on Tue, Dec 9, 2014 by Aaron
About two weeks ago, CloudFront had a major global outage lasting ~ 90 minutes. That was a exceptionally widespread outage and those don't happen too often, but regional CDN performance degradations are by no means exceptional. In the spotlight today: France.
France is a country where CDNs struggle to deliver solid performance consistently to everybody. The performance problems vary from an occasional hiccup to frequent slowdowns and elevated failratio. Let's look at a recent timeframe of 5 days, Nov 29 - Dec 03 2014.
The chart shows the Failratio in France for CDNetworks, Akamai, Limelight, Tata Communications (formerly: Bitgravity) and Fastly, based on a sample of our RUM data. Our RUM sends a Fail beacon if the browser could not completely fetch a highly cacheable 15 KB static object from CDN within 5 seconds.
The data shows elevations in the Failratio for Akamai, CDNetworks, Limelight and Tata Communications on multiple days for part(s) of the day. Fastly is a difference case: Failratio was elevated all day, every day. Let's zoom in on Akamai, CDNetworks and Fastly, to show the problems occur not in all of France, but on one or a few networks only.
Akamai's performance on two networks of SFR is much worse than on the other networks in France. The charts below give a clear picture. A vertical blue line was drawn for every test that passed (browser fetched 15 KB object CDN within 5000 ms) and a vertical red line was drawn for every test that failed to finish within 5000 ms. The top chart is for all of France, with the two SFR networks excluded. There is a lot more blue than red and this is what you expect from a CDN. For AS8228 and AS15557 however, the charts look very different. Our RUM took more measurements on AS15557 than on AS8228, so the 'shades' of red and blue are different, but we see about the same on both networks: between ~18:15 and 21:15, there is more red than blue.
Orange is a large ISP in France and on Dec 3 2014, we received the highest number of beacons per ASN from clients on their AS3215 network. The first chart below shows CDNetworks' Failratio for France, excluding AS3215. That looks normal. On AS3215, the CDN's performance is normal for the biggest part of the day, but between~ 19:45 and 21:00 there is a lot more red. Not good.
And then there is Fastly. Fastly's Failratio is fine on all the major networks in France, except on AS12322 of ISP Free. Two charts again, the top showing France excl. AS12322 and below that is a chart for AS12322 only. The Failratio on that network is a stunning 50% throughout the day. What is most striking: Fastly's performance on that network has been that bad for a long time. The chart below - for all of France, not just AS12322 - shows Fastly's Failratio having been about the same at least since Nov 9.
As the last chart shows, it's not just Fastly, Akamai and CDNetworks. We already mentioned Limelight and Tata Communications earlier in this article, and you can see EdgeCast is not fully in the clear either, with Failratio elevations on Nov 10 and Nov 13. Let's conclude with this statement: "no CDN delivers excellent performance everywhere all the time". Also true: "All CDNs suffer from significant performance degradations every now and then".
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