Dear all,

i'm experiencing issue using flow control when there is a speed change from 10G link to 2.5G.
The specific case is about GPON ONT (with line profile 2.5Gbps download an 1.0Gbps upload, both tested on SFP ONT or RJ45 external ONT), during an upload beacause the link is not symmetric, the ONT use pause frame to avoid congestion, so the switch should "cache" the packet and let the client to use full bandwidth.

Most of the time doing an upload test, the bandwidth is 1/3 of the total one (if the lantecy from client to server is more of 10ms) when using a CRS305 (just a switch) or RB5009 (PPPoE done by itsefl) with 10G uplink. Also counter are not increased on the TX\RX pause frame counter, so I think the problem is on the Marvell platform system.

Attach the ONT to a native 2.5G interface (Intel I225&226, Realtek R8125B or a Zyxel EX5601 with SFP cage) make it works as expected (full 1gbps bandwidth).

There is already a ticket opened for more thank 3 weeks (SUP-123458) but no one from Mikrotik Support has replied. May be some employee here can ping that ticket and start investigating this issue, i'm not the only one with this problem, as stated also in the ticket.

Thanks in advance!

This is a user support forum, users helping other users.
Mikrotik staff don't read everything here.
Your best bet is your ticket.

This is a user support forum, users helping other users.
Mikrotik staff don't read everything here.
Your best bet is your ticket.

I know but I’ve seen some employees there.. so it’s just an hope. I had opened other tickets to the support and always received at least a response, but this one (that is for my point of view a big issue) no one has replied, also with other people complaining..

RouterOS implements flow control with off as default; read: https://help.mikrotik.com/docs/display/ROS/Ethernet
Enable rx-flow-control & tx-flow-control on MikroTik ports to forward ONT pause frames is worth consideration.

RouterOS implements flow control with off as default; read: https://help.mikrotik.com/docs/display/ROS/Ethernet
Enable rx-flow-control & tx-flow-control on MikroTik ports to forward ONT pause frames is worth consideration.

I know, TX/RX FC enabled an all ports involved doesn’t make any impact. As I’ve also sai the counter of Tx/RX pause frame is still at zero.. so I don’t think it’s working as it should..

RouterOS implements flow control with off as default; read: https://help.mikrotik.com/docs/display/ROS/Ethernet
Enable rx-flow-control & tx-flow-control on MikroTik ports to forward ONT pause frames is worth consideration.

I know, TX/RX FC enabled an all ports involved doesn’t make any impact. As I’ve also sai the counter of Tx/RX pause frame is still at zero.. so I don’t think it’s working as it should..

I'm seeing the same issue on CRS310 viewtopic.php?p=1036138#p1036138 RouterOS is showing 0 RX Pause frames on the SFP interface even though the other end is generating 1000s of TX pause frames.

Dear all,

i'm experiencing issue using flow control when there is a speed change from 10G link to 2.5G.
The specific case is about GPON ONT (with line profile 2.5Gbps download an 1.0Gbps upload, both tested on SFP ONT or RJ45 external ONT), during an upload beacause the link is not symmetric, the ONT use pause frame to avoid congestion, so the switch should "cache" the packet and let the client to use full bandwidth.

Most of the time doing an upload test, the bandwidth is 1/3 of the total one (if the lantecy from client to server is more of 10ms) when using a CRS305 (just a switch) or RB5009 (PPPoE done by itsefl) with 10G uplink. Also counter are not increased on the TX\RX pause frame counter, so I think the problem is on the Marvell platform system.

Attach the ONT to a native 2.5G interface (Intel I225&226, Realtek R8125B or a Zyxel EX5601 with SFP cage) make it works as expected (full 1gbps bandwidth).

There is already a ticket opened for more thank 3 weeks (SUP-123458) but no one from Mikrotik Support has replied. May be some employee here can ping that ticket and start investigating this issue, i'm not the only one with this problem, as stated also in the ticket.

Thanks in advance!

Hiya.. just replied on another topic-related flow-control from my very very similar issue..

when using OLT 10G uplink port connected to CRS317 or direclty connected on mikrotik v7 hardware 10G sfp+ if i disable flow control on olt + sfp+ port on mikrotik... our speeds on wifi only 240mbps, if i enabled flow-control on both ends i get easy 700mbps down and upload on wifi6 phones ... doing the same test on olt uplink GE eletrica 1gbps port directly connected to mikrotik v7 etherne 1gbps port.. this issue does not happen with flow-control off.. working greak 800mbps download and upload on wifi6 phones... and also on cable... but on the SFP+ ports this issue happens only seems to fix it temporarily if you enable Flow-control on both ends.. OLT + Mikrotik SFP+ port.. this test was done with 3 different OLT manufacturers so we could exclude 1 manufacturer brand olt.. initially we tought this was OLT manufacturer problem, so we made testing on another OLT manufacturer with diferente cpu and chipset.. connected to mikrotik and same problems occured.. just to satisfy our testing we decided to borrow a spare OLT from another manufacturer from a nearby isp colleague.. and same results as described... SFP+ 10G uplink ports connected to 10G mikrotik devices only seem to work great on WIFI6 if we have flow-control enabled..but only works ok for a few days.. what makes us confused is why on electric 1Gbps ports ethernet this works great? with flow-control disabled.. but on SFP+ ports only works with flow-control enabled? i am starting to wonders if this is mikrotik software issue? or switch chip issue? we tested on CCR2116 device, tested also on x86_64 v7 mikrotik, also on CCR1036 v6.4xx long term.. and same exact problem occured on all models..


The more i think about it the more i get confused... is RJ45 eletric ports using different ethernet protocol from SFP ports on mikrotik? could it be related to code on interface queues? aldo all of the interfaces eletric and sfp have only-hardware-queues set.. nothing else..

I bought an RB5009 to link to internet with a Huawei MA5671A gpon. I put the gpon stick into the SFP+ port.
I tried to enable and disable Flow control on ethernet and SFP port but I've not noticed a difference in upload speed on Speedtest to a far server .

I experienced a poor UPLOAD speed (250/300 megabit )when used the ethernet 2.5 gigabit port. If I use a 1 gigabit port the upload speed is near to the maximum (850/950megabit)-

In my opinion there is some strange logic about the Flow control of RouterOs.

@stich86, any answer in SUP-123458 ?

@stich86, any answer in SUP-123458 ?

I see the counter to change when flow control is ON but I don't see any difference in upload or dowmload maximum speed under heavy load