Netflix 的 Open Connect 架構

在「研究人员绘制Netflix CDN服务器位置图」這邊看到在討論 NetflixOpen Connect 架構,也就是 Netflix 自己的 CDN 架構。引用的論文是「Open Connect Everywhere: A Glimpse at the Internet Ecosystem through the Lens of the Netflix CDN」這篇。

翻了一下論文,看起來還是頗傳統的方法,從一堆伺服器去 query 找出來:

Indeed, Netflix server domain names are too specific, i.e., including details on the physical location of the server. This makes it unlikely that redirection takes place based on these domain names. Additionally, we ran a distributed DNS lookup campaign from Planetlab nodes to verify our assumption that Netflix DNS names always resolve to a single IP address, independently of the client location.

另外也有用窮舉法去查:

We implemented a crawler, which generated DNS names following the pattern outlined above and attempted to resolve those generated domains names to IP addresses. The crawler was fed with lists of known countries, airport codes and ISPs. We curated these lists manually, consulting publicly available lists of countries and airport codes. For the ISPs, we conducted an extensive search on the Internet, including but not limited to the Netflix ISP Speed Index, Wikipedia, various ISP rankings or recommendation lists and discussions in web forums.

所以總共列了 243 個國家地區,3468 個機場編號 (IATA) 與 1728 個 ISP 去搜尋:

In total, our curated lists contained 243 countries, 3,468 airport codes and 1,728 ISP names. In total we tested 16 different network connection types.

不過也有發現到錯字:

The DNS names actually include a typo, the Carrasco International Airport in Uruguay is abbreviated MDV instead of MVD. We used the ISP names found to verify that what was really meant is the airport in Uruguay.

然後找出了:

不過事實上因為 Netflix 已經規劃全面走 HTTPS:「Netflix 對 sendfile() 在 TLS 情況下的加速」、「Protecting Netflix Viewing Privacy at Scale」,所以在 Certificate Transparency%.nflxvideo.net 會有完整的列表,看起來遠超過這篇論文所給的數字:

gslin@home [~/tmp] [14:55/W5] grep isp.nflxvideo nflxvideo.html | sort | uniq | wc
   1311    1311   65827
gslin@home [~/tmp] [14:55/W5] grep ix.nflxvideo nflxvideo.html | sort | uniq | wc
     77      77    3230

來寫信給論文作者提看看好了...

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