Subject: RE: [AVT] Re: RTP/RTCP Port Sharing -> SCTP

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 18 Jul 2001 12:19:13 -0400

> -----Original Message-----
> From: Michael Thomas [mailto:[email-masked]]
> Sent: Wednesday, July 18, 2001 11:05 AM
> To: Fairlie-Cuninghame, Robert
> Cc: 'Leonid Rosenboim'; Ross Finlayson; [email-masked]
> Subject: RE: [AVT] Re: RTP/RTCP Port Sharing -> SCTP
> 
> 
> Fairlie-Cuninghame, Robert writes:
>  > 	c) only one endpoint needs to have a globally reachable 
> address for
>  > guaranteed bidirectional transport
> 
>    This seems like it defers the harder problem for about
>    10e-9s. If Valhala is gone and the ascendency NATs
>    asured, then double NAT's will be the norm.
> 
>    Then what?

Then you read draft-rosenberg-sip-entfw-02.txt, due out this week, which
explains how to handle this case.... :) The mechanism in there uses
bidirectional streams (which we call symmetric) whenever only one side its
natted, and otherwise uses a network intermediary outside of the firewall
when both are behind nats that don't support Christian's
http://search.ietf.org/internet-drafts/draft-huitema-natreq4udp-00.txt. When
contacting this network intermediary, its still useful to use symmetric RTP.

-Jonathan R.

---
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
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_______________________________________________
Audio/Video Transport Working Group
[email-masked]
http://www.ietf.org/mailman/listinfo/avt

---

From: Michael Thomas <[email-masked]>
Date: Sat, 21 Jul 2001 09:30:56 -0700 (PDT)

> contacting this network intermediary, its still useful to use symmetric RTP.

   Sigh. If the end result of most media sessions is a rendezvous
   to a intermediary, then our bragging rights over the IN will
   be nullified. I know that this is the implication of NAT's, but
   it still depresses me.

	    Mike

---

From: "Henning G. Schulzrinne" <[email-masked]>
Date: Sat, 21 Jul 2001 12:52:38 -0400

>    be nullified. I know that this is the implication of NAT's, but

It would be nice if all the effort expended on fixing the NAT stuff
would be matched by people deploying IPv6 applications (enabling IPv6 on
recent Solaris and Linux boxes, as well as routers, seems pretty
trivial, from our experience) or dispelling the notion that you can't
get addresses, which seems to often be perpetuated by people who have
other agendas (such as making it difficult to use more than one computer
on a home DSL/cable modem).

That said, I wonder if it wouldn't be easier to just have the client set
up one secure tunnel to this outside entity with a real IP address, for
all applications that are stymied by NATs, rather than inventing a new
mechanism for each application. This does mean two relaying points, but
avoids all the negotiation and myriad special cases. Can this be done
with the typical VPN setups in some of the more recent OSs?

-- 
Henning Schulzrinne   http://www.cs.columbia.edu/~hgs