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romeor
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bufferbloat.. again. Help please

Tue Nov 08, 2022 9:48 pm

Hello,

Am running the topology attached. In short: two ISP-s, 5G is in separate VRF. So my TV-sets are using routing rule to go out via 5G connection. All other using Fibre connection. I have every port in every MT device Bridge configuration HW offload off and on 100 mbps ports have Flow control on. This is quite stable atm, but still i see a lot of RX pause on TV 100mbps ports (main router has 5x1gbps and 5x100mbps ports).

As I watch HQ VOD and IPTV (HLS streams, every single chung download speed according to MT graph and port stats is 75-90Mbps one time burst), i think I'm being caught by bufferbloat coming from Services providers. Sometimes my TVs start to buffer the picture. I tried another configuration when TV-s were connected to MT WiFi devices in bedrooms, but it was the same situation.

When i first met this issue, i googled for buffering 1g-100mbps and learned that i have to turn on flow control on 100mbps ports on MT devices, but it didn't help. For some reason really helps combo: FC on and HW offload off. But even nows or thens buffering visits me. I tried to run on WiFi (tvs have only 100mbps card on board, but they run also wifi, which is way faster), still the same issue. I would say it is VOD and IPTV services issue, but no. The issue goes away only and only when I connect my TV-s directly to another router (zyxel) which comes with another zyxexl 5G external router . I also tired to run without dual isp stack keeping only 5G or optics. Still the same issue. And i tried to replace hap ac3 with main router, still no luck. Am having also FastTrack on atm. Also friend of mine are running same ISP and same IPTV and VOD services without any issues, but they have no MT devices. So i'm stuck.

If i understand right, FC means, that port gets command to stop forward or slow down. I can even see it on MT port traffic graph. It looks like pause, but when there are much these pausese occur in a row, i'm getting picture buffering, cuz tv doesn't get any bit of data and depletes its player buffered stream.

So the question is - how to solve this issue? CAKE? Where should I add the queue? As an interface queue for 100 mbps ports or simple queue ? If simple, what should it look like? Target?
Anybody knows, what are those switching chips buffer sizes? Why this happens only with mikrotik?

Or may be i should stop raping these cheap boxes and buy a decent switch with like 4 MB buffer and install it right after main router and connect everything else to it instead of main router now?
Am also waiting for RB5009UPr+S+IN to be in stock to replace the main router, which is pretty oldie now and can't handle even 300 mbps speed without FT disabled. But still can't find any information on buffer sizes within the chipsets.. We can't loose the situation, when we connect a 100mbps device to 1gbps port.. Its life. These TV-s are all 2021 and 2022 m/y. Still vendors install this piece of crap.

I just can't believe, that there is no solution for this situation. I really enjoy MT devices and have lots of them in other place, but this stupid situation at my homeplace drives me crazy and am now thinking to replace all the MT-s with zyxels just to stop that buffering issue. Any helps please.
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smyers119
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Re: bufferbloat.. again. Help please

Wed Nov 09, 2022 4:46 pm

Are you running any qos? have you tried turning on the basic queueing for the 100mbps interfaces / bridges?
 
romeor
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Re: bufferbloat.. again. Help please

Wed Nov 09, 2022 5:19 pm

Hello,

I've tried to set up simple queue that will limit speed to TV-s IP-s around 85-90 mbps, but situation was the same.

A this moment, as I have fasttrack on, i don't have any qos.
 
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smyers119
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Re: bufferbloat.. again. Help please

Wed Nov 09, 2022 5:41 pm

the hardware queues's aka ring buffers work with fastrack. and holds about a 100packets.
 
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smyers119
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Re: bufferbloat.. again. Help please

Wed Nov 09, 2022 5:45 pm

any of the interface queue's should not effect fastrack to anything but that interface
 
romeor
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Re: bufferbloat.. again. Help please

Wed Nov 09, 2022 5:49 pm

well, yes i've tried some. but mby i was doing something wrong. any advice on interface queue i could apply? and which one? 100mbps ports?
 
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smyers119
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Re: bufferbloat.. again. Help please

Wed Nov 09, 2022 5:53 pm

are you seeing drops/errors on the 100mbps interfaces??
 
romeor
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Re: bufferbloat.. again. Help please

Wed Nov 09, 2022 6:18 pm

i see RX pauses only. If i turn off the FC and turn on the HWO, i see RX overflows on uplink
 
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smyers119
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Re: bufferbloat.. again. Help please

Wed Nov 09, 2022 6:31 pm

I would try and use the pfifo queue and keep upping the bucket size until you get rid of the pause frames.
 
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smyers119
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Re: bufferbloat.. again. Help please

Wed Nov 09, 2022 6:32 pm

i see RX pauses only. If i turn off the FC and turn on the HWO, i see RX overflows on uplink
rx pauses on which interface?
 
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Re: bufferbloat.. again. Help please

Wed Nov 09, 2022 6:55 pm

rx pauses on both interfaces watching to tv-s.
pfifo should be configured on these interfaces? how big the value should be for start?
 
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Re: bufferbloat.. again. Help please

Wed Nov 09, 2022 7:08 pm

rx pauses on both interfaces watching to tv-s.
pfifo should be configured on these interfaces? how big the value should be for start?
pfifo starts off at 50.

I would double it until there is no pause frames, then drop it by a quarter until there is pause frames. Then you'll have your ideal bucket size.
 
romeor
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Re: bufferbloat.. again. Help please

Wed Nov 09, 2022 10:14 pm

Well, my IPTV uses HLS ans it is pretty bursty as what i see from Mtik interface graph. Those bursts are like 4000 up to 8000 pps and up to 87 mbps. I don't think kind of 100 or even 1000 packets queue size could help somehow. so i've created new queue with size 4000 packets and it doesn't seem to be working too. See those empty sports on graph? during them TV starts to buffer.
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romeor
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Re: bufferbloat.. again. Help please

Thu Nov 10, 2022 3:47 am

well, i have to apologize . this issue has nothing to do with Mtik devices. Tonight I've made a longer test run on pure 5G connection and it turned out that it is the issue. It seems like these kind of burst just kill it in some way. When I'm on fibert it is ok both with Mtik and without. When I'm on 5G both no Mtik and with Mtik situations buffer occurs from time to time. I proceeded information to ISP.

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