Subject: [MMUSIC] RTSP & NAT discussion on wednesday and thursday.

From: Magnus Westerlund <[email-masked]>
Date: Mon, 14 Jul 2003 19:14:19 +0200

Hi,

On wednesday at dinner time there will be a as proposed in the MMUSIC 
agenda an RTSP discussion meeting. The preliminary meeting place is in 
the main foyer near the registration counter at 17.30-17.40. We will try 
to put together an agenda for this meeting during tomorrow.

However this mail is about something else, namely the RTSP and NAT 
traversal document. This is a preparation for what will be further 
discussed during wednesday and thursday and concerns open issues.

Issue number one: What is the goal of the RTSP & NAT document. This has 
previous been communicated as documenting solutions that do not require 
further standardization and to give guidelines for RTSP ALGs and how to 
handle firewalls.

However it is evident that we need a solution for traversal of symmetric 
NATs for RTSP. As all known possible solutions requires server side 
extensions to work, further requirements for this work should be 
considered.

Possible other considerations for this work is:

- Enable RTSP servers to be placed behind a NAT. Will allow for 
implementing RTSP server for other purposes than on-demand content and 
provide a richer usage of RTSP.

- Provide mitigation of the RTP DoS attack threat. It can't be 
completely solved, however it can be severely limited to only be 
possible to perform by attackers that can hijack traffic inside a 
network. And as a an attacker having this possibilities can do many 
other really bad stuff, this is probably enough.

- Do not worsen security. We should do anything to avoid worsening 
security for RTSP.

- Have only a single solution to provide interoperability and incentive 
to implement this solution.

- Consider complexity of operations and implementation for any proposal.

- Time to availability of solution.

So please consider if you have any further requirements that should be 
consider for this work. We should in the next weeks have some consensus 
on what work we should perform regarding the solution for symmetric NATs 
and RTSP. The result of this discussion will be used to decide on what 
solution to select.

The current proposals to a solution for the symmetric NAT traversal are:

- Symmetric RTP
- Co-located STUN
- ICE for RTSP

They are documented in the draft-ietf-mmusic-rtsp-nat-01.txt. Please 
read and comment so that we can start putting an analysis together.

Best Regards

Magnus

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From: Tom Marshall <[email-masked]>
Date: Mon, 14 Jul 2003 11:14:29 -0700

> and RTSP. The result of this discussion will be used to decide on what 

Perhaps I misread this, but it sounds like you are saying that we should
agree on one traversal solution.  I thought the RTSP NAT document was
intended (and does) present the various NAT traversal solutions along with
their strengths and weaknesses, and let the implemetors decide which to use?

-- 
...if the church put in half the time on covetousness that it does on lust,
 this would be a better world.
        -- Garrison Keillor, "Lake Wobegon Days"

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From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 14 Jul 2003 19:50:48 -0400

> their strengths and weaknesses, and let the implemetors decide which to 

You need to be really careful with approaches like that. The problem 
is interoperability. Unless you agree on a mandatory to implement 
mechanism, you will have problems. Furthermore, it makes it hard to 
use the same client in deployments where one solution vs. another 
would be the optimal one. We have suffered alot on both these points 
in sip, where sip clients work in specific cases dependenting on which 
nat solution they have used. It has been a real barrier to deployment.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                600 Lanidex Plaza
Chief Technology Officer                    Parsippany, NJ 07054-2711
dynamicsoft
[email-masked]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com

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From: Magnus Westerlund <[email-masked]>
Date: Tue, 15 Jul 2003 10:00:02 +0200

Hi Tom and Jonathan,

My goal is in regards to the symmetric NAT solution which requires 
server modifications to only have one solution. However when it comes to 
solution that can be implemented at the client side without server 
modifications or simply servers running the updated RTSP they will all 
be documented.

Best Regards

Magnus