Brian, [ sorry for coming back to this thread so late ]
On Wed, 6 Nov 2013 17:02:50 -0800 Brian Somers <[email protected]> wrote: > Using a sample of our US traffic over a 7 minute period, I see > 112,044 lookups of www.facebook.com out of a total of 4,081,834 > queries (2.74%). That's 266 www.facebook.com queries per second. > > Doing a lookup where our resolver is only missing > star.c10r.facebook.com (which the www.facebook.com CNAME points at; > the record with a 60 second TTL) takes 1.6ms. Doing a lookup where > everything's cached, our resolver takes 0.7ms. > > Given that our prefetch implementation actually charges the client > that first queries the record in the last 3 seconds of its TTL, and > given that we now cap our resolvers at 6 threads, this means that in > the 7 minute period, we had 7 clients waiting for the upstream rather > than 265 times 7 cilents. > > This is a relatively big win, but is also a drop in the ocean -- not > much more than a second of latency shared among these clients. > > The real win for us is that we don't ask facebook the same question 6 > times per minute (one per thread). Instead, we ask once every 57 > seconds. This is bigger in the grand scheme of things because it > makes the facebook auth servers happier :) First, thank you for providing actual data! Much appreciated. :) But... while the Facebook case is interesting, I am thinking you'll get a lot more win from sites with long latencies. So, looking at #5 on the top 1 million web sites list: baidu.com. From here I see latencies between 300 and 500 msec. The TTL for the A record of baidu.com is 600 seconds. It's not just China. Going to #16 on the list is wordpress.com, which gives me times of 100 to 200 msec from all of its 6 (!!!) name servers. At #29 ask.com has times between 90 and 200 msec. At #37 apple.com also has times between 100 and 200 msec. (I didn't check all of the names in between, since I expect that yahoo.co.jp and yandex.ru and so on probably only care about "local" traffic in the same way that Baidu seems to. I took special care to single out Apple because I'm mean that way.) The busy server + long latency is where we'll see the most win, IMHO. Cheers, -- Shane p.s. What's the point of having a ton of name servers if they're all in California/Beijing/wherever? People, if you're going to have a lot of NS for your domain, please peer the network of at least one server in AMS-IX so I can get fast DNS resolution from here in Holland. Thanks! ;) _______________________________________________ DNSOP mailing list [email protected] https://www.ietf.org/mailman/listinfo/dnsop
