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kadak avatar Ubuntu

How to fix network connection high instability

ky flag
kadak

I am facing a strange issue with my ubuntu computer. My Internet connection seams to work only a small instant every minute or so. Just enough to download POP3 emails but not enough to upgrade 100 MB packages.

I tried the following to assess the problem:

kadak@webcast:~$ ping 192.168.0.2
…
--- statistiques ping 192.168.0.2 ---
1382 paquets transmis, 219 reçus, +3 erreurs, 84,1534 % paquets perdus, temps 1410789 ms
rtt min/avg/max/mdev = 0.499/2.597/123.335/11.061 ms,  tuyau 3

84% packet lost, it is huge. 192.168.0.2 is our DHCP server.

I tried the same on another computer running Windows 10, connected to the same wifi point of access, no package loss. So I cast out a network issue.

I tried to connect to the point of access through Ethernet cable instead of Wifi… same problem. So I cast out a Wifi hardware problem.

Here are my system information :

kadak@webcast:~$ uname -a
Linux webcast 5.4.0-77-generic #86-Ubuntu SMP Thu Jun 17 02:35:03 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

Would anybody have some tip to further investigate the issue?

Cheers,

Kadak

EDIT: Here the result of syslog (interesting stuff I guess but too technical for me):

Jul  5 15:50:46 webcast systemd[1]: Started Network Manager Script Dispatcher Service.
Jul  5 15:50:56 webcast systemd[1]: NetworkManager-dispatcher.service: Succeeded.
Jul  5 15:51:07 webcast whoopsie[1555]: [15:51:07] Cannot reach: https://daisy.ubuntu.com
Jul  5 15:51:29 webcast wpa_supplicant[1217]: wlp2s0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-68 noise=-95 txrate=1000
Jul  5 15:52:33 webcast wpa_supplicant[1217]: wlp2s0: CTRL-EVENT-SIGNAL-CHANGE above=0 signal=-72 noise=-95 txrate=58500
Jul  5 15:53:17 webcast dbus-daemon[1925]: [session uid=1000 pid=1925] Activating via systemd: service name='org.freedesktop.Tracker1' unit='tracker-store.service' requested by ':1.2' (uid=1000 pid=1923 comm="/usr/libexec/tracker-miner-fs " label="unconfined")
Jul  5 15:53:17 webcast dbus-daemon[1925]: [session uid=1000 pid=1925] Successfully activated service 'org.freedesktop.Tracker1'
Jul  5 15:53:17 webcast systemd[1915]: Starting Tracker metadata database store and lookup manager...
Jul  5 15:53:17 webcast systemd[1915]: Started Tracker metadata database store and lookup manager.
Jul  5 15:53:20 webcast wpa_supplicant[1217]: wlp2s0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-70 noise=-95 txrate=65000
Jul  5 15:53:48 webcast tracker-store[14704]: OK
Jul  5 15:53:48 webcast systemd[1915]: tracker-store.service: Succeeded.
Jul  5 15:54:03 webcast wpa_supplicant[1217]: wlp2s0: CTRL-EVENT-SIGNAL-CHANGE above=0 signal=-72 noise=-95 txrate=65000
Jul  5 15:54:27 webcast wpa_supplicant[1217]: wlp2s0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-69 noise=-95 txrate=65000
Jul  5 15:54:46 webcast wpa_supplicant[1217]: wlp2s0: CTRL-EVENT-SIGNAL-CHANGE above=0 signal=-70 noise=-95 txrate=65000
Jul  5 15:55:26 webcast wpa_supplicant[1217]: wlp2s0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-66 noise=-95 txrate=65000
Jul  5 15:57:45 webcast wpa_supplicant[1217]: wlp2s0: CTRL-EVENT-SIGNAL-CHANGE above=0 signal=-72 noise=-95 txrate=65000
Jul  5 15:59:29 webcast NetworkManager[1197]: <info>  [1625493569.1809] manager: NetworkManager state is now CONNECTED_GLOBAL
Jul  5 15:59:29 webcast systemd[1]: Starting Network Manager Script Dispatcher Service...
Jul  5 15:59:29 webcast whoopsie[1555]: [15:59:29] The default IPv4 route is: /org/freedesktop/NetworkManager/ActiveConnection/5
Jul  5 15:59:29 webcast whoopsie[1555]: [15:59:29] Not a paid data plan: /org/freedesktop/NetworkManager/ActiveConnection/5
Jul  5 15:59:29 webcast whoopsie[1555]: [15:59:29] Found usable connection: /org/freedesktop/NetworkManager/ActiveConnection/5
Jul  5 15:59:29 webcast dbus-daemon[1196]: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' unit='dbus-org.freedesktop.nm-dispatcher.service' requested by ':1.12' (uid=0 pid=1197 comm="/usr/sbin/NetworkManager --no-daemon " label="unconfined")
Jul  5 15:59:29 webcast dbus-daemon[1196]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
Jul  5 15:59:29 webcast systemd[1]: Started Network Manager Script Dispatcher Service.
Jul  5 15:59:30 webcast whoopsie[1555]: [15:59:30] online
Jul  5 15:59:39 webcast systemd[1]: NetworkManager-dispatcher.service: Succeeded.
Jul  5 15:59:50 webcast wpa_supplicant[1217]: wlp2s0: CTRL-EVENT-SIGNAL-CHANGE above=1 signal=-69 noise=-95 txrate=58500
Jul  5 16:00:37 webcast wpa_supplicant[1217]: wlp2s0: CTRL-EVENT-SIGNAL-CHANGE above=0 signal=-72 noise=-95 txrate=58500
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FedKad avatar
cn flag
FedKad
Can you check syslog or journalctl for errors?
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kadak avatar
ky flag
kadak
I checked journalctl for errors. Quite a lot but which service should I particularly look at?
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FedKad avatar
cn flag
FedKad
I have no idea actually. But the "Network Manager Script Dispatcher Service" may be of interest. I would run the `journalctl -f` command on a terminal screen and leave it open. Then you may be able to correlate the messages displayed during the `ping` "timeout"s while a `ping` command is run on another terminal.
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kadak avatar
ky flag
kadak
Thanks. Apparently the problem is not there anymore. I just tried what you advised and 900 pings ran with 0% loss. Could it be an IP address conflict on the network and now the other user is down? How could I check that? Also today before writing this post I tried a few things among which I removed snapd. Anyway, I will check in the next few days if the problem is really solved or not and let you know. Thank you.
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waltinator avatar Ubuntu
it flag
waltinator

Check your WiFi MTU, using

ip link

also notice your WiFi interface's name.

The MTU (Maximum Transmission Unit) is the size of the largest packet that can be sent in a single network transmission. If a packet exceeds the MTU of a link, the data must be split into multiple packets (fragmented). These multiple packets must be sent over the link, received, acknowledged, and reassembled at the far end. If your link is misconfigured, and you have to fragment every packet you send, your actual data transfer rate drops.

Ethernet (wired) networks use an MTU of 1500 bytes.

Due to additional per packet overhead for WiFi (8 bytes PPPoE header), WiFi uses an MTU of 1492.

Your MTU should be set by your DHCP server, check your router's config.

You can set your own MTU (setting does not persist over restarts) with

sudo ip link set dev name mtu 1492

where "name" is the interface name from above.

Here's an example:

walt@squid:~(0)$ ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp63s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:24:21:7f:e5:1c brd ff:ff:ff:ff:ff:ff
3: wlxf46d04b1790f: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DORMANT group default qlen 1000
    link/ether f4:6d:04:b1:79:0f brd ff:ff:ff:ff:ff:ff
walt@squid:~(0)$   sudo ip link set dev wlxf46d04b1790f mtu 1492
[sudo] password for walt: 
walt@squid:~(0)$ ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp63s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DEFAULT group default qlen 1000
    link/ether 00:24:21:7f:e5:1c brd ff:ff:ff:ff:ff:ff
3: wlxf46d04b1790f: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1492 qdisc mq state UP mode DORMANT group default qlen 1000
    link/ether f4:6d:04:b1:79:0f brd ff:ff:ff:ff:ff:ff

My WiFi "interface name" is "wlxf46d04b1790f".

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