Subject: RE: [Sip] The Problem with PRACK

From: "Samir Srivastava" <[email-masked]>
Date: Thu, 9 Mar 2006 16:04:20 -0600

*why* should we do it? The UAs still need to be prepared for cases where
the path isn't e2e reliable, so they just get more complicated rather
than less. I guess maybe you sometimes save a couple of messages. Is
that what you are after?

	Paul

Yes. We have SIP over TLS e2e (SIPS) to avoid different SIP attacks
eavesdropping, MiTM etc. For the cases where calls are e2e secured we
don't get anything out of it, though it does make UA more complex. Going
forward we will have more secure deployments. With UDP, My SIP
credentials are learnt by SPAMMER, and I am bombarded with SPAMS. 

Apart from security use cases also, If messages become larger due to
different reason and TCP is used e2e, what we get there from this.

Thx
Samir

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From: "Brett Tate" <[email-masked]>
Date: Thu, 9 Mar 2006 18:03:01 -0500

> Yes. We have SIP over TLS e2e (SIPS) to avoid different SIP 
> attacks eavesdropping, MiTM etc. For the cases where calls 
> are e2e secured we don't get anything out of it, though it 
> does make UA more complex. Going forward we will have more 
> secure deployments. With UDP, My SIP credentials are learnt 
> by SPAMMER, and I am bombarded with SPAMS. 
> 
> Apart from security use cases also, If messages become larger 
> due to different reason and TCP is used e2e, what we get 
> there from this.

Currently offer/answer usage is one reason to support 100rel on TCP and TLS.

Another reason is for better interoperability concerning clipping with
devices unwilling to receive/present media until receive 18x with SDP.
PRACK allows the UAS to know when the 18x has been received.  Thus it can
delay sending media until it knows the UAC received the 18x.