#Using filezilla on mac for scp download

There have been some improvements in the recent releases, which allow WinSCP to utilize high-latency connections as efficiently as FileZilla.Д¬PU вЂ“ The SFTP, being encrypted, is CPU intensive. I do not think this is your trouble either, at least if you have used the latest version of WinSCP for the tests. See also Bandwidth-delay product on Wikipedia. So it's not only how the actual SFTP client is efficient, but also how an underlying TCP layer is efficient. But if there's a big discrepancy between the bandwidth and the network delay, even that 1 MB can be too small to saturate the bandwidth.ДЄn underlying TCP protocol can suffer a similar problem. For example WinSCP can request up to 32 chunks for 32 KB each at once, totaling 1 MB (these are defaults). Most SFTP clients (including FileZilla and WinSCP) overcome the problem by both requesting a large chunk of the file in each single 'read' request and by sending (queuing) multiple 'read' requests without waiting for a response to previous.

If the client spends this time uselessly waiting, your transfer speed will be low. When downloading, the SFTP client sends a 'read' request to the SFTP server, waits for a response, appends returned data to a local file and repeats, until the end of the file.Д®ven if your connection is fast, if the server is far away (or slow), it takes a time for the data to arrive back. Network delay/latency вЂ“ The SFTP is packet oriented-protocol. There are three common factors that affect a transfer speed:Д«andwidth вЂ“ An obvious factor that's apparently not your trouble.

So could the 180ms delay to the server be a mathematically limiting factor as Martin and Michael touched on a bit? Or could there still be something else to blame such that I can improve the throughput? If not, I'd appreciate if anyone knows any other (like lftp but runs well on Windows) open source downloader that is secure and supports segmented downloading. Whereas if I start a secondary concurrent transfer in Filezilla I get constant 1.3MiB/s for it also. I tried with latest version winscp 5.73 and with sftp mode I got 555kb/s and about 805kb/s max with scp mode.

Also cpu usage is very low, 2% to 8% max. UPDATE: In response to Martin's information (see his answer below) I am adding that ping is 180ms to 190ms pretty constant between server and client that is downloading. Server is running OpenSSH 6.7p1 (Debian) client is FileZilla on Windows. If someone has a good explanation of why transfers peak at 1.3MB/s I'd really like to know, and if its possible to increase this without resorting to using segmented downloading. So at 1.3MB/s constant transfer FileZilla is pretty good compared to the other methods of transfer. I also tried WinSCP and it was the slowest regardless of method SCP/SFTP. I know that I can use some other SFTP client that supports segmented downloads such as lftp, know of other good ones that are open source?Д«ut I still want to know what is it that limits downloading one file to just 1.3MB/s, is it some technical limitation with TCP and buffers etc or some configuration issue? I checked and for sure there's no traffic throttling enabled at all for FileZilla.ДЄlso I tried rsync and it was worse than FileZilla/SFTP.

#Using filezilla on mac for scp download

So why can't I download just one file at faster than 1.3MB/s and get closer to saturate available bandwidth (~6+MB/s)?

I'm downloading from a server and downloads are maxing out at 1.3MiB/second with FileZilla but I can start concurrent downloads and they will download at 1.3MiB/second also.