Subject: RE: [SIP] new record-route text!

From: [email-masked]
Date: Tue, 2 Jan 2001 14:25:45 -0700

This would just encourage the use of B2BUAs by service providers who want to
retain control over the call (for applications, for billing, or other insane
and nefarious purposes). Nothing can prevent the administration of a proxy
in the chain of signaling (a chain ultimately initiated by the user) from
forcing all subsequent requests for a call to go through its systems - that
is their architectural perogative. B2BUAs may, however, break some
end-to-end mechanisms and introduce further latency to the signaling.

Jon Peterson
Level(3) Communications

-----Original Message-----
From: Christian Huitema [mailto:[email-masked]]
Sent: Tuesday, January 02, 2001 11:47 AM
To: Henning Schulzrinne; Jonathan Rosenberg
Cc: [email-masked]
Subject: RE: [SIP] new record-route text!

I am concerned with the mandatory aspect of the record-route parameter.
Part of the beauty of SIP is that it can operate in a strict end-to-end
mode; the record-route procedure allows intermediaries to arbitrarily
break that end-to-end property. I understand that this could be useful
sometimes, for some crazy network configurations, but if we make this
mandatory we should have at a minimum an escape hatch. More precisely,
the syntax of the contact header should allow us to distinguish between
two cases:
1) a contact address that can only be reached through the recorded
route,
2) a contact address that can be accessed directly.
I would contend that, if we don't want to recycle the SIP spec to the
proposed standard spec, the latter should be the default, as the strict
record route requirement breaks compatibility with the original
specification.

-- Christian Huitema

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From: Michael Thomas <[email-masked]>
Date: Thu, 4 Jan 2001 08:56:32 -0800 (PST)

> end-to-end mechanisms and introduce further latency to the signaling.

   I suspect that Jonathan is right in maintaining that
   the vast majority of rationale for RR is to deal with
   firewall/NAT's. Once you do the latter you've
   already broken e2e transparency, so thinking
   about it in terms of a B2BUA is probably
   actually the _right_ thing to do. In fact, I'd
   say that if the proxy needs to in some way
   control the session plane (ie, signal a
   firewall to open/close a hole), you've
   crossed the line: it's an UA. It doesn't
   matter whether the session actually traverses
   it because that's nothing more than a
   decomposed UA in disguise. And sure ALG's 
   cause lots of trouble -- but let's not
   pretend that we can change those issues by
   artfully maneuvering definitions to obscure
   the fact that it does, indeed, quack.

	    Mike