Subject: [Sipping] Max-Breadth Draft

From: "Brian Stucker" <[email-masked]>
Date: Fri, 24 Mar 2006 09:51:19 -0600

Robert,

Finding this problem at SIPit is useful because it at least alerts implementors to the potential problem.

If the max-breadth header were used, aren't we relying on the attacker to not ask for a breadth of 2^32 or something equally silly? I know you define a 4xx response to this, but I didn't see any mention in the response as to giving the UAC a hint as to what the limit is (although it can certainly be titrated by the UAC with multiple probes).

Given that attackers are going to ask for the world, and legitimate applications won't know what the limit is, shouldn't the model be adjusted somewhat to having the proxy reject the request outright and tell the originator of the request that they get X forks (they asked for a max-breadth of X and got Y much like expires header operation for registrations and subscriptions), and that's it.

Basically, is it reasonable for applications to expect that a very large request will necessarily succeed due to administrator controls? If we're open to allowing QoS controls and the like to the media stream according to administrator bounds, why not the absolute tree size of a forked request.

Regards,
Brian
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