[e2e] FTP data port

[David P. Reed]

Bob - respectfully disagree.  If you read RFC 385, one TIP problem was 
related to email - and was solved by MLFL.

Bhushan's RFC354 is the first FTP document to describe the "data connection".
Though it does mention the idea of sending a file to the "local printer" on 
a TIP,this is not a *problem* but a feature.

Though I am not aware of any document that describes the reason for a 
change from earlier FTP specs that use the same connection for data and 
control, the rationale I recall discussing with Abhay was almost certainly 
to simplify by not requiring multiplexing, esp. when data types varied.

Why the connection was opened by the server is probably because both ends 
needed socket numbers to be chosen and verified, for "security" reasons, 
and the logical end for the SOCK command to be originated from was the client.

Since I was only a spectator at the time (I got involved in the Internet 
project, and only kibitzed on ARPANET stuff), I may be wrong.


Note that it
At 07:03 PM 2/26/01 +0000, Bob Braden wrote:

>   *> From end2end-interest-admin at postel.org Mon Feb 26 10:52:07 2001
>   *> From: "Oleg Vishnepolsky" <oleg at inforocket.com>
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>   *> Subject: [e2e] FTP data port
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>   *> Date: Mon, 26 Feb 2001 13:42:33 -0500
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>   *> Why does FTP protocol has FTP server to connect out to a data port 
> specified to a client, as opposed to the client connecting to a
>   *> port specified by the server ? Is there a historical reason for 
> doing that ?
>   *> Oleg Vishnepolsky
>   *> -
>   *>
>Yes.  It had to do with supporting ARPANET TIPs (Terminal Interface
>Processors, essentially a terminal multiplexor glued onto an ARPANET
>IMP.)
>
>I think you will find this history recorded in the early RFCs about
>FTP.  Try going to http://www.rfc-editor.org/rfcsearch.html and
>search for "FTP".  Of the 69 document hits,, you would probably find
>a discussion of the TIP problem and user/server issues around
>1973.
>
>Bob Braden