On Fri, Mar 20, 2020 at 9:10 AM Ted Hardie <[email protected]> wrote:
> On Fri, Mar 20, 2020 at 7:16 AM Ralf Weber <[email protected]> wrote: > >> Moin! >> >> If the hardware and the location of the client and server are >> identical it is impossible to get more throughput, better latency using >> DoT or DoH, then DNS over UDP/53 given two similar written servers. >> > > Hi Ralf, > > A trivial example in which this is not true is in the case where one or > more routers in the network path maintain different queues for UDP and TCP > traffic. When this is the case, a robust queue for TCP and a meager one > for UDP can easily mean that the end-to-end performance for the client is > better for DoT (or DNS over TCP/53), simply because the loss on the UDP > path is high. This is especially true if you measure over a flight of > queries (say, all the DNS queries a web page needs to resolve) and DoT > keeps an open session for the whole flight. To put this another way, > if what you are measuring is the DNS component of page load time, DNS > timeouts for the lost UDP packets in a queue-starved path can kill the > performance. > > As Eric points out, we have to be careful to describe what we're measuring > here, and there are definitely different views of what we're optimizing > for. > What may have been overlooked and/or erroneously given too much weight, is the single report being used to compare performance. (I don't have the original report URI handy, but I'm sure many participants here do.) IIRC, the measurements were done exclusively from AWS locations, and further cherry-picked by AWS location. So yes, we need to be careful not only on what we are measuring, but how we are performing that measurement. IMNSHO, that report would be better characterized as anecdotal rather than statistically representative of the real world. I'm definitely not against productive discussions, but we should get good data first. An example of good data, are the experiments conducted by Geoff Huston and George Michaelson from APNIC. I'd encourage those asserting performance claims to work with them to get reliable data that can be analyzed in this forum. Brian
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