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Bug 164 – Slow file transfers

: Core
: Unspecified
: Enhancement
: Medium
: 0
: 5.8
Many users report WinSCP not to utilize all available bandwidth.

This topic is discussed in FAQ:
Releated: Bug #1, Bug #17.
Also WinSCP 4.1 will support (less secure) Arcfour cipher, which should be fast.
WinSCP (FAR plugin 1.5.1 base on WinSCP 3.8.2) is as fast as PSCP (8 MB/s) and SFTP (3 MB/s) (PuTTY 0.60):

WinSCP 3.8.2 is as fast on upload as SSH Secure Shell 3.2.9, but much slower on download on WinXP. On Win2K it is as fast:

Transfer rate is capped at 100KBps:

SCP significantly faster than SFTP:

PuTTY 0.59 much faster than 0.58:
4.2.1 almost twice as fast as 4.1.8 on Windows Vista:
Suggestion for fixing network speed after installing SP2 for Vista:
It has been suggested by ultramage that increasing SSH socket buffer size may instead transfer speed. See Bug 615.
Bug 615 has been rolled back by Bug 677 as some users were having problems with it.
The fix was reintroduced by Bug 690, with option to disable it, in 5.0.3.
Bug 787: 5.0.6: When Optimize connection buffer size is enabled, also FTP socket internal buffer size is increased.
Bug 1141: 5.2.2: Increase local SSH send buffer to improve performance
Bug 1273: 5.7: Size of connection receiving buffer increased.
5.8: Improved transfer speed:
- with SFTP and SCP protocols when CPU is limiting factor.
- with SFTP on high latency connections Bug 1295
5.8.3: Dynamically increase TCP send buffer on fast connections.
S3 specific entry: Bug 1732
Bug 1769: Hardware accelerated AES (AES-NI)