Question on FTP 1

[welshguy]

Guys,

I have a query with FTP access from IE so hoping someone might have hit this.

Basically it's regarding how FTP access works from within IE.

There is a setting within IE/Advanced options called enable folder view for FTP - now according to MS In q309816

http://support.microsoft.com/directory/article.asp?ID=KB;EN-US;Q309816&

this merely changes the FTP mode from active to passive FTP which is fine but what I don't understand is this.

From my tests with Folder view enabled - the client when accessing say ftp://ftp.microsoft.com goes directly out to port 21 on the ftp server (fair enough).

Yet with the setting disabled the same client will go through the proxy server out on port 80 then connect through the firewall to the FTP server.

I can find no MS info on this behaviour - has anyone got any idea or come across this.

Cheers

 

[Tels]

Active mode and passive mode all have to do with the way the ftp protocols on the client and server sides interact.
Passive mode exists to prevent problems connecting through firewalls.

In active mode, the client initiates a connection to prt 21 of the server, and the server initiates a connection back. If the firewall doesn't expect this connection, it will not be established, ftp will not work as a result.

In Passive (PASV) mode, the client opens a connection to the server, signalling that it is in Passive mode. The server opens a port, and then signals the client to make a second connection. hence both connections originate on the client, and the firewall is happy.

The active/passive option is an FTP protocol norm, not specific to microsoft, and there mainly for compliance with firewall technology. try this link.

http://www.slacksite.com/other/ftp.html

That should totally fix your infothirst

Tels Win2000 Network Administrator

 

[welshguy]

Thanks for the reply

But this is the confusing part - I realise how passive and active mode work as you say.

But it's in passive mode that the client is making the direct connaction out on port 21 - under active mode the request goes out through the proxy under http.

It's this behaviour under http that bothers me - why does the passive mode client(with option enabled) make a direct connection out on port 21 and the active mode client go straight out via the proxy.

I can adapt the ruleset on the firewall to enable passive mode ftp in fact it's probably safer from a security side but can't follow the behaviour I'm seeing under these settings that's confusing me.

Cheers for any help/inspiration.

 

[ShackDaddy]

Could it be that as a proxy-SOCKS client, the system has an FTP helper dll that guides an active mode client through the proxy?

One clue might be that IE 5 supports WEBDAV access, and I think WebDAV might take active-mode connections on port 80.

ShackDaddy

 

[welshguy]

Shackdaddy,

Haha !!!

Thanks - this sounds very possible - I'll check it out !

Cheers
welshguy