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qbic
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RB4011iGS+ TX Pauses.

Sat Jan 30, 2021 2:09 pm

Hi,

I'm on 6.48 stable, RB4011/revision2. This router is excellent and fast. Previously I had gr3/hex that was maxing out with latest firmware @870mbps (a lot of txpauses or drops) ... so I''ve upgraded (there should be info on benchmark page with latest firmware and/or factory one... as performance is dropping between FW releases - which is understandable).

The only one interesting issue I've found is that even if its maxed out at 20% cpu usage... I've found that in Tx stats of the eth1/wan portI get Tx Pauses - and interesting correlation is that it happens almost at same rate as Tx&Rx 64 size frames.

Yesterday it was 64 vs 63 TxPause

today its

81 vs 80...


Its almost nothing.. i know but it might be indicative of some bug.
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Cha0s
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Re: RB4011iGS+ TX Pauses.

Sat Jan 30, 2021 2:52 pm

Pause frames are part of Flow Control.
https://en.wikipedia.org/wiki/Ethernet_flow_control
https://wiki.mikrotik.com/wiki/Manual:I ... e/Ethernet

If anything, high CPU usage could cause to miss transmitting a pause frame, not increase them.
 
biomesh
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Re: RB4011iGS+ TX Pauses.

Sat Jan 30, 2021 2:59 pm

The correlation between the small frame sizes and counts is probably correct as pause frames are generally small.

Cha0s mentored this is how flow control works. The numbers are not that high, but if you don't like it, just disable it on your devices (routers and switches).
 
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qbic
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Re: RB4011iGS+ TX Pauses.

Sat Jan 30, 2021 4:38 pm

But then any TxPause frame will be dropped one. Load on RB is never higher than 20% (1gbps fiber).

Tx Flow control is enabled on purpose, I'm only surprised that such fast RB and still with pause frames.
 
mkx
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Re: RB4011iGS+ TX Pauses.

Sat Jan 30, 2021 5:36 pm

I'm only surprised that such fast RB and still with pause frames.

In the stats window it is shown that your router passed somewhere around 550M packets, of those 220M were pretty small packets (64-127 bytes). If you look at test results, you'll see that routing speed with small packets is around 300Mbps ... which is quite much less than wire speed. Even if all pause frames were because of small frames, it's still only 81 pauses out of 220M frames (or 0.36 PPM). Not something I'd loose sleep over. But then it could be that pause frames were due to upstream congestion ...
BR,
Metod
 
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Cha0s
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Re: RB4011iGS+ TX Pauses.

Sun Jan 31, 2021 5:28 pm

But then any TxPause frame will be dropped one. Load on RB is never higher than 20% (1gbps fiber).

Tx Flow control is enabled on purpose, I'm only surprised that such fast RB and still with pause frames.
Flow control does not know or care about your router load.
It only cares about congestion on the interface that its enabled.

https://en.wikipedia.org/wiki/Ethernet_flow_control
Ethernet flow control is a mechanism for temporarily stopping the transmission of data on Ethernet family computer networks. The goal of this mechanism is to avoid packet loss in the presence of network congestion.
A sending station (computer or network switch) may be transmitting data faster than the other end of the link can accept it. Using flow control, the receiving station can signal the sender requesting suspension of transmissions until the receiver catches up. Flow control on Ethernet can be implemented at the data link layer.
In other words, if you don't like it, then disable it.
It baffles me how can someone enable a feature that they don't understand, and then proceed to say it's a bug.
More like B(ug)EBKAC...
 
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qbic
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Re: RB4011iGS+ TX Pauses.

Sun Jan 31, 2021 9:37 pm

Sure it might be the case with congestion on other interfaces but that was not the case :-) (at least not on my side). Sadly I cant access counters on the ONT terminal.
 
mkx
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Re: RB4011iGS+ TX Pauses.

Mon Feb 01, 2021 12:23 am

Sure it might be the case with congestion on other interfaces but that was not the case :-)

How did you determine this? Just because router can route at speeds averaging above 1Gbps (that's what tests are telling) it doesn't mean it can do it at all times. And if ROS' IP stack can not ingest packets from interface's Rx buffers, these won't get emptied ... and then interface can only drop arriving frames. Or, if flow control is enabled, interface can send a pause frame.
BR,
Metod
 
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qbic
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Re: RB4011iGS+ TX Pauses.

Mon Feb 01, 2021 11:34 am

The only thing I was able to confirm is TxPauses on other interfaces (enabled on all), they only shows on Eth1 (my "Wan") that is connected to Huawei ONT.

And another question to illuminated members - how can i know if router (eth driver) is supporting multi-queue-ethernet-default (mq pfifo).
 
mkx
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Re: RB4011iGS+ TX Pauses.

Mon Feb 01, 2021 3:20 pm

And another question to illuminated members - how can i know if router (eth driver) is supporting multi-queue-ethernet-default (mq pfifo).

I guess only support@mikrotik.com can tell you that. If you get any feedback, please share it with us.
BR,
Metod

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