why does the PIX firewall send an [RST,ACK] pocket?

[lfejslfejs]

the customer often encounts an ftp error during data transferring.

there are a PIX 525 firewall and a Netscreen firewall between the FTP client and FTP server.

the following the captured data in the networks

I want to know what cause the PIX firewall sent an [RST,ACK] packect

Please refer the detail captured data in the attachment.

[amritpatek]

Start the logging on the PIX and look for build and teardown messages when the problem happens. Check that teardown of the connection happens because of the RST packet, then you will need to use sniffer to figure out what device is sending RST packets. One reason could be one side or another is timing out the connection or sending a rst forcing the pix to teardown the connection.