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The IP probing is an interesting methodology, although it would not work for GCE as VM IPs are entirely virtualized[0]. That said, the methodology's biggest fla
by jsolson 11y ago
The IP probing is an interesting methodology, although it would not work for GCE as VM IPs are entirely virtualized[0]. That said, the methodology's biggest flaws (even with AWS as I see it) are that they don't know the machine-count of individual racks (and this number can vary more than you might expect) and, more importantly, they don't know the sizing on individual hosts.
Putting my original point differently: DigitalOcean may be big or small, but counting physical hosts is a terrible way to estimate its size. Better would be to count available cores and RAM, but of course those are much harder numbers to pin down as cloud providers tend to go to some lengths to abstract away the details of physical hosts.
[0]: Supporting live migration for individual VMs mostly necessitates that the IPs within a virtual network be meaningless w.r.t. the physical host locations -- also GCE advertises a /32 subnet via DHCP and requests the guest route all packets to their 'gateway'. Handling actual routing (to avoid a needless extra hop) is done via the Andromeda SDN.
- tim333 11y agoNetcraft have a somewhat vague article on their methodology on their site eg. >By arranging for a number of IP addresses to send packets to us near simultaneously, low level TCP/IP characteristics can be used to work out, within an error margin, if those packets originate from the same computer, by checking for similarities in a number of TCP/IP protocol header fields. To build up sufficient certainty that IP addresses on the same computer have been identified, many visits to the sites in the Web Server Survey are necessary, which takes place during a period of over a month. >Informal checking with two of the largest dedicated server companies suggests that the survey counts about 2⁄3 – 3⁄4 of the machines in their datacenters. http://www.netcraft.com/internet-data-mining/hosting-provider-server-count/ http://www.netcraft.com/internet-data-mining/hosting-provide...
- boulos 11y agoAnd because DigitalOcean doesn't have load balancing as a service, people generally just expose their Droplet to the internet as their website. Netcraft's methodology works fine here, likely misses or undercounts Droplets behind nginx/HAproxy and is wildly off for people behind load balancers like Google's Load Balancer Or AWS's ELB. Disclaimer: I work on Compute Engine, but I also knew plenty of people at DigitalOcean.