ping and rtt calculation/display

paziulek · 07-24-2020, 06:04 PM

hi all!

does anybody know why ping sometimes displays two decimal places for xx.10 only, sometimes - it does xx.1 ?
I cant see any logic here - it does that for .10 only.. no other hundredths of a ms...

ping utility, iputils-s20180629
Linux deb10 4.19.0-9-amd64 #1 SMP Debian 4.19.118-2+deb10u1 (2020-06-07) x86_64 GNU/Linux

berndbausch · 07-24-2020, 06:54 PM

I get double digits, and triple digits for the summary:

Code:

$ ping -c3 1.1.1.1
PING 1.1.1.1 (1.1.1.1) 56(84) bytes of data.
64 bytes from 1.1.1.1: icmp_seq=1 ttl=58 time=3.67 ms
64 bytes from 1.1.1.1: icmp_seq=2 ttl=58 time=3.46 ms
64 bytes from 1.1.1.1: icmp_seq=3 ttl=58 time=3.47 ms

--- 1.1.1.1 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 3.462/3.537/3.679/0.111 ms
$ uname -a
Linux odroid 3.10.107-190 #1 SMP PREEMPT Mon Sep 4 20:41:37 UTC 2017 armv7l armv7l armv7l GNU/Linux
$ cat /etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=16.04
DISTRIB_CODENAME=xenial
DISTRIB_DESCRIPTION="Ubuntu 16.04.6 LTS"
$ ping -V
ping utility, iputils-s20121221

michaelk · 07-24-2020, 07:17 PM

If I understand the question, of the different versions I have tested only 3 significant digits are displayed but never xx.10.

Code:

pinging localhost
64 bytes from localhost (127.0.0.1): icmp_seq=1 ttl=64 time=0.057 ms

Pinging a wifi device on my network
64 bytes from sprinkler.localnet (192.168.0.212): icmp_seq=1 ttl=100 time=4.94 ms

Pinging google.com
64 bytes from atl14s08-in-f142.1e100.net (216.58.193.142): icmp_seq=1 ttl=119 time=31.6 ms

paziulek · 07-24-2020, 08:21 PM

I am sorry! - forgot about the attachment

I watched the rrt for a few minutes, then re-tried and it did come back with just 1 decimal for all ms - the only exception was the .10 - so no difference between now and the original post

attaching again

berndbausch · 07-24-2020, 08:39 PM

I had not seen your attachment, sorry. Well your ping is six years younger than mine; perhaps they gradually develop the capability of displaying decimal digits.

Seriously, I tend to consider this a (very) minor bug. I may have a Debian 10 VM lying around to check this.

paziulek · 07-24-2020, 09:08 PM

well, what's minor and not depends where and how the results are being used. If rounding up the values is not doing what it what was planned, than the results are wrong.
for you or me, this is a 'minor' one but i guess when you try to eg. sort the results it might give you a misleading outcome. Not even looking at the byte count... I guess things are either right, or wrong.

michaelk · 07-24-2020, 09:10 PM

I finally saw the same thing as in your attachment. I assume it is due to some rounding error in the calculation on how the utility creates the output that produces the "anomaly". It would take a bit to examine the source code but since it is a minor bug not worth the effort.

paziulek · 07-24-2020, 09:33 PM

shared what i planned to share - someone will examine the source code...

BTW
"Logic will take you from A to B"
in this case:
"Logic will take you from A to around the corner of B"
But that's not Albert anymore...