Subject: RE: [MMUSIC] RTSP connections question.

From: "Jae-Hwan Kim" <[email-masked]>
Date: Thu, 17 Feb 2005 10:24:18 +0900

> Section 9.3 of rtsp-bis08 indicates the following:
> > A server SHOULD NOT initiate a close of a connection directly after
> > responding to a TEARDOWN request for the whole session. A server
> > SHOULD NOT close the connection as a result of responding to a
request
> > with an error code. Doing this would prevent or result in extra
> > overhead for the client when testing advanced or special types of
> > requests.
> 
> But this seems like a DoS security risk.  If a malicious user decided
to
> send gibberish request or request that are almost correct and but not
> quite, the server may respond with an error code because it can't
parse
> the request.  But if it cannot close its connection to the client,
then
> the client may overload the server with many gibberish requests and
> eventually cause the server to not accept valid connections.
> 
> [tz] My understanding is that the server has the freedom to include
the
> "Connection: close" header if it suspects that the client is launching
a DoS
> attack and wants to close the connection after the current
request/response is
> complete. See Section 12.10 of RFC2326.
[Jae-Hwan Kim] "Connection: close" seems to be used, even when the
server waits RTSP timeout after the completion of TEARDOWN response; it
seems not to mean direct disconnection. In case of DoS, IMO, this is
good point-out and the above context of rtsp-bis08 is a recommendation
so that server may behave bravely.
> 
> What is the purpose of saying that the server SHOULD NOT close the
> connection as a result of responding to a request with an error code?
> It seems like it would be the right thing to do, no?
[Jae-Hwan Kim] I think "460 Only aggregate operation allowed" is a good
example. There is no way for client to know whether server supports
non-aggregate control except negotiation.
> Aravind

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From: Aravind Narasimhan <[email-masked]>
Date: Thu, 17 Feb 2005 16:35:47 -0500

>so that server may behave bravely.
I will point this out in the spec.

>non-aggregate control except negotiation.
I do agree that some error messages may require a server to keep the 
connection open, so that the users may try again, but I think we need to 
be more specific about them, so that mainstream servers can protect 
themselves from DoS.