Subject: RE: [MMUSIC] ICE feature - TCP alternates for a UDP stream

From: "Francois Audet" <[email-masked]>
Date: Fri, 4 Feb 2005 17:33:21 -0500

> I do not fully agree, about if it is circumvention or not. I do 
> understand the interest in developing a solution for this. The 
> proprietary solutions do handle these cases, and the standard will be 
> die if it doesn't work in the same scenarios. What I don't want is a 
> short term hack that will cause us twice the amount of 
> problems down the 
> road as the original problem.

Yeah, I'm also somewhat ambivalent on this. 

Is it really worthwile to have a back-off to TCP mechanism? Or should
we really instead take the stance that if the Firewall blocks UDP,
it is either because:

(1) They do NOT want to "real time media" going through. This may
    be the case for example on an Enterprise Firewall. In that
    particular case, then I think it is a circumvention.

(2) Always blocking UDP is essentially a feature deficiency of
    the Firewall, or a misconfiguration. Do we need to work around
    this or not is the question. 

I don't have a particularly strong opinion either way. 

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From: Jonathan Rosenberg <[email-masked]>
Date: Sat, 05 Feb 2005 08:21:42 -0500

inline.

>     this or not is the question.

Case (2) is the one I am worried about. In particular, it appears that 
there are numerous firewalls that do, in fact, allow outbound UDP, but 
they aren't capable of maintaining state to correlate in incoming UDP 
packet with the previous outgoing one. As a result, the incoming UDP 
packet is dropped.

Other enterprises block UDP not because of a desire to block multimedia 
traffic, but because UDP lacks the notion of a connection that can be 
tracked and terminated if needed.

I'll once again re-iterate that all of this is primarily around the 
issue of whether or not to run RTP over TCP. That is already a decision 
we have made. ICE is merely helping figure out if that option should be 
used or not.

-Jonathan R.
-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Director, Service Provider VoIP Architecture   Parsippany, NJ 07054-2711
Cisco Systems
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http://www.jdrosen.net                         PHONE: (973) 952-5000
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