Putty PSCP & PSFTP Poor Performance

[Nick Venidis]

I have the following ssh2 connection working successfully:

Windows 2000 (putty Release 0.52 ssh client)---> PIX Firewall--->IBM
Firewall--->OpenSSH 2.9.9p2 Server (on AIX 4.3.3)

Can anyone explain why file transfer performance is so slow when using
pscp or psftp especially when trying to retrieve files from the openssh
server to the windows 2000 client? I cannot achieve anything faster
than 16kb/sec. If I use non-freeware client software such as SecureFX,
my transfer rates over the same connection improve dramatically to
anywhere from 300 to 700 KB/sec of the same 100 MB file without changing
any configuration parameters on the server. My transfer time of this
same file with SecureFX is only 2-3 minutes, while the transfer with the
putty ftp clients takes close to 2 hours. Standard FTP is also much
faster and slightly better than the numbers generated by SecureFX. Are
there configuration settings either within Putty or the OpenSSH server
that I need to manipulate to improve these transfer rates? Would
upgrading the OpenSSH server to 3.4 offer configuration setting
enhancements that would improve the performance? NAT is running on the
IBM Firewall.

Thanks for any assistance.

Nick Venidis
IBM PSeries Benchmark Center
ni...@us.ibm.com