WSFTP on W2K to Solaris 8 FTP server timeout on large files

Posted on 2003-02-20
Medium Priority
Last Modified: 2013-12-21
An ftp transfer of a large file (circa 800k) from the WSFTP client on W2K to a standard Solaris 8 ftp server fails while a small file (circa 5k) is successfull.

The FTP connection is established on port 21 and a small file tarnsfered OK (port 20 - active). When a large file is transfered the file is created on the Solaris system as 0 blocks and never increases. After a couple of minutes the WSFTP client times out and the transfer fails leaving the target file at 0 blocks.

'netstat -an' shows connections are left in the 'LISTEN' state on ports 20 & 21 on the Solaris server.

The Twist: if a standard 'ping' is run in paralell from the W2K system the large file transfers OK!!!
Question by:brains
LVL 18

Accepted Solution

liddler earned 160 total points
ID: 7986748
I have seen something like this before, it was due to block or packet size being congiured too small on (I think)a checkpoint firewall (or maybe it was a switch).  The small ftps worked because they were within the packet / block size.
Sorry I can't remember the details

Author Comment

ID: 8260050
thanks liddler, traced the problem down to a cisco router which is configures to use a small packet size when routing out over ISDN cards! Switched the ftp client to a Solaris box and the problem vanished. Looks like W2K could not negotiate the packet size correctly!

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