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Skylin3
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Joined: Mon Jun 14, 2021 1:52 pm

Strange issue with UDP traffic

Sun Dec 25, 2022 8:53 pm

Hello. I am looking a way to diagnose strange bug, when ping indicating absolutely normal values like 20-50ms, but egress UDP is highly delayed (usually 200-500ms, up to 5s), like uplink ISP queuing traffic. This issue can be catched visually/audibly with voice/video streaming (twitch, google meet) or gaming and reproducible on 2 ISPs (cogent and one smaller local) with guaranteed channel (small office) with different routes, but winmtr, mikrotiks traceroute or pingplotter dont show abnormal behaviour.
Mikrotik hapac2, any firmwares from 6.4 to 7.6 now with defconf.
I have few VMs in different locations, including googles, so any advices appreciated.
 
DarkNate
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Posts: 999
Joined: Fri Jun 26, 2020 4:37 pm

Re: Strange issue with UDP traffic

Mon Dec 26, 2022 4:14 am

Sounds like a combination of bad configuration, bridge misconfig, using conn_track in the wrong place, bad MTU. Implement the guidelines here and see if it solves your issue:
viewtopic.php?t=176358
 
Skylin3
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Topic Author
Posts: 8
Joined: Mon Jun 14, 2021 1:52 pm

Re: Strange issue with UDP traffic

Mon Dec 26, 2022 2:05 pm

Sounds like a combination of bad configuration, bridge misconfig, using conn_track in the wrong place, bad MTU. Implement the guidelines here and see if it solves your issue:
viewtopic.php?t=176358
I asked for diag methods to clarify where is problem is located, not chaotically reconfiguring mikrotik in 999 time implementing fasttrack, queues, scripts ... $another_feature_without_any_effect. Its all done without any effect and router was reset to defconf. There is no overload on CPU or other resources and I can reproduce issue even with only one client connected to router and link usage of ~1 mbit.
However I read manual and have many questions - using MTU for edge router
which is usually 9000
(its not), using simple queues with only conclusion "bufferbloat is bad" (its not until you dont saturate link at port speed but simple queue cutting performance of router itself because intense use CPU and QoS on gigabit speeds is very big question) etc etc.
 
sindy
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Re: Strange issue with UDP traffic

Mon Dec 26, 2022 8:34 pm

a way to diagnose strange bug
...
winmtr, mikrotiks traceroute or pingplotter dont show abnormal behaviour
Do you specify protocol=udp and port=ppp when running Mikrotik's traceroute?

As for diagnosing, run /tool sniffer at Mikrotik to see whether the delay is caused by the Mikrotik itself (I suppose it isn't, but I admit that the same behavior with two unrelated ISPs is strange).

If traceroute in UDP mode shows nothing, do you have another Mikrotik on a public address so that you could send the UDP to it and sniff on it simultaneously? Traceroute is one possibility how to send a UDP packet from a command line, resolve a.b.c.d server=x.x.x.x port=ppp is another one.

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