Subject: RE: [SIP] symmetric RTP as a solution for NAT traversal

From: "Christian Huitema" <[email-masked]>
Date: Fri, 16 Mar 2001 07:57:18 -0800

> How does symmetric RTP create a risk of hijacking?

You discard the SDP information and instead reply to whatever address
the first RTP packet came from. If this first packet comes from a third
party, you end up with a session to the third party instead of a session
to the original target. As I said, this is a mild risk: the third party
has to be able to find out which port you listen to, and it has to have
good timing. Also, the third party has to find a way to shut down the
original target of the call.

-- Christian Huitema

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From: Michael Thomas <[email-masked]>
Date: Fri, 16 Mar 2001 08:04:46 -0800 (PST)

> original target of the call.

   And this has a fairly straightforward solution in any
   case: use SRTP to place a keyed integrity check
   on the packet.

		Mike