I noted previously that the Microsoft CDN study, titled “Measuring and Evaluating Large-Scale CDNs”, had disappeared. Now its lead author, Microsoft researcher Cheng Huang, has updated his home page to note that the study has been withdrawn.

Also removed from his home page, but still available from one of his collaborators, is a study from earlier this year, “Understanding Hybrid CDN-P2P: Why Limelight Needs Its Own Red Swoosh“. I assume the link was removed because it extensively details the CDN discovery methodology also used in the more recent Microsoft CDN study, so if you missed reading the study while it was available, you might want to read this slightly older paper for the details.

I just read the P2P study, which reveals something that I conjectured in my earlier analysis of the study’s blind spots: the visibility into Verizon was almost non-existent. The P2P study asserts that Akamai is present in just four locations inside Verizon’s network. This seems improbable. Verizon is Akamai’s most significant carrier reseller and one of its largest enterprise-focused resellers. It is also one of the largest broadband networks in the United States, and is a significant global network service provider. It was also a close partner of Netli, who inked a deal making Verizon its primary source of bandwidth; I would expect that even though Akamai integrated Netli into its network after acquiring it, it would have kept any strategic points of presence in Verizon’s network. One would have expected that the researchers would have wondered what the chances were that a close partner wouldn’t have substantial Akamai footprint, especially when their chart of Limelight indicated 10 Verizon locations. (Remember that the charting methodology is much less accurate for a deep-footprint CDN.)

The researchers then go on to explore the effects of hybrid P2P using those Verizon nodes (along with AT&T, which also looks like an incomplete discovery). Unfortunately, they don’t tell us much of value about peer-assisted offload; the real world has made it amply clear that actual P2P effectiveness depends tremendously on the nature of your content and your audience.

The methodological flaws make the hybrid-P2P paper’s conclusions deeply and fundamentally flawed. But like the other study, it is an interesting read.