FTP download very slow behind Mikrotik

RouterOS General
1

Hi,

I write here because I can’t., for the love of God, understand why is this happening. We are a local ISP and own serveral Routerboard (all of them CCR) as PPPoE server + border router. Some weeks ago one I received a ticket regarding new deploy for a private customer who had a dedicated link + CCR1009. They complained about low FTP download throughput from their FTP server located on the cloud. So the scenario was FTP client, behind CCR and FTP server on the Internet side.

I verified and that was true. We set apart first the pppoe tunnel and still got slow FTP throughput. I checked the FTP Server from my own home and the download speed was acceptable and higher than behind the Mikrotik.

So I set up a lab.

  1. I took a brand new CCR1009-7G-1C-1S+ (same model than the one on the customer location) and connected it to the Internet using a neutral broadband ISP. Routerboard had basic config: DHCP client on WAN, DHCP Server on LAN, Masquerade NAT, no queees whatsoever and nothing else . I placed a notebook behind the Mikrotik and tested with Filezilla FTP client. FTP download was somewhat slow = 15Mbps

  2. Then I removed the Mikrotik and connected the same notebook, with the same FTP client to the same cloud FTP server directly to the broadband ISP router. Download speed was about double = 30Mbps.

  3. I repeated the tests many times and always download speed behind the Mikrotik was slower than w/o the Mikrotik on the middle.

  4. Upgraded Mikrotik to latest LTS version (6.49.10 (long-term)) and rates were the same.
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    Has anyone experienced something like this with this model or any other?? Any default setting must be changed to increase FTP speed?

Thanks!

2

If it is only this one ftp site that is running slowly, my GUESS would be that it might be due to out of order packets.
You could try turning fast path off
(I think but am not sure that because some packets still have to go the slow way, you will get some out of order packets.
If fast path is off, presumably they will all follow each other nicely over the slow way)
(If this is the issue, maybe some older tcp stack on ftp server??)

If it also applies to other sites and websites, you can perhaps play with the rx/tx flow control on the ethernet ports.