Slow uploads when using explicit over TLS/SSL

I was comparing WinSCP 4.2.9 and FileZilla 3.3.4.1 upload transfers using an FTP over an explicit tls/ssl connection.
Of both clients, the settings are the same:
– Port 21
– Protocol: FTP + TLS Explicit Encryption (I also tried implicit and SSL)

I confirm that both clients switch to a secure channel via the AUTH TLS and PROT P commands.

However, WinSCP transfer rate to upload the same file is about 3 or 4 times slower than FileZilla. I did multiple tries, also tested implicit, explicit, passive, active... but same result. I also tried the winscp.com command-line version (which is what I really need), with same results.

Is there anything I'm missing?

Thank your very much!

Can you send me an email, so I can send you back a debug version of WinSCP to track the problem? Please include link back to this topic in your email. Also note in this topic that you have sent the email. Thanks.

Hello Martin,

I've just sent you the email.

Thanks!

Over long distance (WAN) on a tuned system, WinSCP caps around 500kbytes** both upload and download.

** somewhere between 450 and 600. I don't have the exact number as we stopped using winscp fairly quickly in our testing. If this becomes critical, I can ask for access to the remote PC again to get you that number.

We found that switching to FileZilla removed the download cap, reaching up to 4.4MB/s (40mbps - which was near the limit of the line). Upload was capped at 650kbytes, which has since been removed by the FileZilla devs if you use nightly build version (10-26 verified).

Why am I here? Because I have a client that wants to script downloads, and WinSCP does that. :D

To replicate the problem: Use WinSCP over long distance (our ping was 80ms) to a Unix SFTP server, ideally one with Openssh (and possibly HPN patches), and at least 100mb ethernet connection. You will see that WinSCP hits a cap and doesn't go beyond it. Both upload and download are affected.

Thank you.

Can you try it with WinSCP 4.3 beta?

Exactly, that's the same issue we were having. FileZilla works great, but it doesn't support scripting.
Martin, I just tried 4.3 beta, but it seems there's a bug, as it gives me the following error when trying to connect to our server over an explicit TLS connection:
I also tried all other SSL combinations, with the same result. I also got some "Invalid access to memory" errors...

Thanks

@roger.e: Can you send me an email, so I can send you back a debug version of WinSCP to track the problem? Please include link back to this topic in your email. Also note in this topic that you have sent the email. Thanks.

Just to let you know, I will test this once my customer gives me access to a test PC again. Right now they removed my access and have completely stifled my attempts to assist them with their problems... I did try to install WinSCP 4.3 on my local laptop but ran into that "Invalid access to memory" error but thought that was related to my lack of admin rights on my laptop.

Turns out the person I was working with has left, so that's why I've been stuck in limbo. I worked today with a non technical user to get WinSCP 4.3 beta installed on her PC. Cursory testing appeared that speeds are improved. She told me she was seeing 1100 kib/s. Still slow but better than before (We can reach up to 4.4mb/s on that network). Her system's completely untuned, so I can't tell if its WinSCP or her system.

I also got a peek at their prod downloads. 74.6 KiB/s ??!! no wonder they are complaining.

I can confirm this (WinSCP 4.2.9). Using scripting i get transfer speeds about 1/4 of what is normal. I checked against CuteFTPPRO and FileZilla. Connection is FTP with -explicitssl.

Tried the beta version 4.3 but still the same speeds (1/4 of other FTP clients)

Might be that the internal buffer WinSCP uses to read and transfer the files is too small??

Hello, any news on this? I'm also seeing this super-slow speed through FTPS compared with other FTP clients like FileZilla. I really like WinSCP, but this problem makes it unusable at the time of transferring big files. It's strange this bug can't be solved in an easy way. There must be some kind of buffer size limit set somewhere. Just guessing, but that's what it seems...

No wonder why I can only hit 90KB/s to my web host using WinSCP when I get 190KB/s using FileZilla. :(

Same here, doesn't make any sense...

Is this fixed on 4.3 beta2?

Fixed in 4.3.1 beta. :)

@war59312: Thanks for information!
Can others confirm this?