Count me in for second pony :D

Regards,

Grzegorz

From: Petr Špaček <petr.spacek@nic.cz>
Organization: CZ.NIC
Date: Wednesday 2019-07-10 at 09:14
To: "ripe-atlas@ripe.net" <ripe-atlas@ripe.net>
Subject: Re: [atlas] DNS RTT over TCP: twice as long than UDP?

On 09. 07. 19 13:51, Ponikierski, Grzegorz wrote:

From this traffic looks like dig measures time between packets 4 (DNS

query) and 6 (DNS response) which is precisely 8.5ms and matches what

dig shows. Including TCP handshake it takes 23.7ms, 2.8x longer which is

expected .

RTT can be measured on different layers for the same communication

stream. In case of DNS over UDP we just ignores UDP overhead because it

doesn't add any packets. With TCP additional packets are added which

significantly increase time that end-user have to wait from first packet

to get information that he/she needs. IMO RTT should always be measured

from 1^st packet to packet which has information that you have actual

data. If we want to measure raw DNS performance without overhead then it

must be explicitly market it measurement description.

If I could get a ponny, I would like to get both numbers:

a) Time measured from moment of sending the very first packet (TCP SYN

or UDP query) to arrival of DNS answer (not counting TCP FIN etc.).

b) Time measured from moment of sending the DNS query (also think of TCP

fast open!) to arrival of DNS answer (not counting TCP FIN etc.).

Having both numbers would allow to calculate latency of connection vs.

DNS query separately, which gets even more important when we consider

DNS-over-TLS etc.

--

Petr Špaček  @  CZ.NIC