In Application and Content Networking Software (ACNS) 5.x.x, the root Content Engine (CE) can be configured to fetch with HTTP or FTP from the origin server. This document discusses some caveats regarding the FTP server software.
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Q. Can the CE fetch content via FTP from any FTP server?
A. No. The FTP server software must support either:
The reason for this is that the ACNS acquirer needs to know the last-modify time and file size before it can download the file. Currently, ACNS uses MDTM if the FTP server supports it; if not supported, ACNS uses the LIST command on the file. If both are not supported, fetching via FTP fails.
Q. Which FTP servers have been tested and work with ACNS?
A. These have been tested with ACNS 5.x.x software:
Note: Within ACNS, the acquirer tries PASV first. If the server responds with an error or not-implement, ACNS uses PORT mode. The acquirer does support active mode (PORT) if the PASV command is not supported by the server. If the server hangs on the PASV command however, FTP fails and never attempts PORT mode.