RE: Response Code 2501

["Liu, Hong" <Hong.Liu@neustar.biz>]

Scott,

I know what it says in RFC959, and I also looked carefully at the tcpdump in
one of the most popular FTP implementations. Sometimes, we get too bolted
down to interpret the standard literally. Are you going to say that the
Linux implementation is not confirming to RFC959?

As I explained before, server initiated session termination is not a
"normal" operation that fits into the client-request server-response mode.
Having the server send the last message notifying the client that it is
closing down the session makes a lot of sense for the client to figure out
later on why the session is gone.

You got to have a sound technical argument why you are against it instead of
just saying that it does not fit into the client/server model, because
existing client/server implementation, i.e., FTP, does use the unsolicited
response before terminating a session.

If necessary, I will post the trace to the list for your reference.

--Hong


-----Original Message-----
From: Hollenbeck, Scott [mailto:shollenbeck@verisign.com]
Sent: Tuesday, August 13, 2002 7:51 PM
To: 'Liu, Hong'; 'ietf-provreg@cafax.se'
Subject: RE: Response Code 2501


[snip...]

> It is good that you brought up FTP as an example to shed 
> lights on how 421
> is being used. My colleague Ning Zhang collected an FTP trace 
> yesterday from
> an WFTP implementation on Linux. The trace clearly shows that 
> the FTP server
> sends 421 to the client before closing down the control 
> connection after
> timeout. 

Looking at RFC 959, I don't agree at all that the situation is similar.
Response code 421 is clearly identified as a _response_ sent for the various
ftp commands, not an unsolicited response to note connection closing as a
result of a timeout:

"421 Service not available, closing control connection.
This may be a reply to any command if the service knows it
must shut down."

> So, should result code 2501 be handled similarly in EPP in the case of
> server closing down the session?

Nope.  No unsolicited responses.

-Scott-