Download of large files over native FTP may fail when ICAP Response Modification is enabled on the ProxySG.
ProxySG will need to download the whole file before sending it to the ICAP server for scanning. If the file is large, it will take a while before the download completes and the client may time out unless the proxy sends some keep-alive traffic.
When there is no ICAP configured, the ProxySG will serve the file to the FTP client instantly.
The following policy will enable the ProxySG to send an FTP Patience Page to the FTP client and prevent it from timing out. For information on how to install CPL into the local policy file, please see 000010101.
; CPL used to send patience page to FTP client when using ICAP
condition=ftp_sites response.icap_feedback(patience_page, 5)
define condition ftp_sites
; enter your list of FTP servers here