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  2. MIDRANGE-L
  3. August 2006

Re: FTP problem

Steve,


"The problem is that the FTP control data is encrypted as it comes through
the firewalls, so it cannot be read to do the IP "natting" at the firewall." 

Yep.  This is one of the big problems with the way SSL FTP works.
"Most third-party clients handle this by storing the original control address and using it during the transmission. Native FTP programs such as MSDOS and IBM's FTP do not allow for this and uses each control block as it is sent."
Sounds like a reference to the EPSV and EPRT (extended FTP) commands. Unfortunately, that's not available on i5/OS -- too bad, since it solves most of the common problems people have with FTP. But... that's IBM for you, something has to be available for 15 years before the iSeries finally gets it.
"There is also a feature called Clear Control Channel that allows the userid and password to be sent encrypted, then all other data exchanged over the control channel to be sent as clear text. In our case, this would allow the firewall to see the IP address and correctly "nat" it to the proper IP. All data sent over the data channel will remain encrypted. According to our vendor, this is a feature normally found only in third-party FTP software, and they are fairly certain this feature would not be available on the default AS/400 operating system FTP software." 

This response seems highly incorrect in light of the fact that we are
already FTPing from another bank using Sterling Software.

Is their response correct?
Is your other FTP that uses Sterling Software also SSL encrypted? The issues raised by your technical contact are only related to SSL FTP, and won't have any impact on standard FTP.
But the description makes sense, and the guy sounds like he knows what he's talking about.

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