Subject: [Simple] MSRP-ACM Discussion Summary

From: Ben Campbell <[email-masked]>
Date: Mon, 18 May 2009 16:11:55 -0500

(As individual)

The discussion thread on MSRP-ACM seems to be dying out, and I don't  
think we've reached closure on most of it. In order to jump start it,  
I am going to attempt to summarize the issues that I think are still  
open. I will start separate threads for each issue. Please reply to  
_this_ message to comment on whether I have offered a fair summary, or  
mischaracterized or omitted anything material. Please reply to the  
specific issue threads to discuss the issues themselves.

1)  We have consensus that the transport address connection parts  
(section 4.2 of draft-ietf-simple-msrp-acm-00) must allow backwards  
compatibility with a peer that uses an RFC4976 MSRP relay. We have had  
one proposal on how to accomplish this, which involved updating 4975  
to allow a middlebox to modify the authority part of an MSRP(S) URI in  
the SDP "a=path" property.

We further determined that this proposal may interfere with the use of  
MSRPS URIs (i.e. TLS) in the case where said middlebox is transparent  
to TLS. It modified an MSRPS URI to point to itself, but transparently  
relays the TLS handshake to a relay (or other MSRP device that uses a  
TLS server cert.). The modified URI no longer matches the server cert,  
so things break.

We've had some discussion about using the comedia-TLS fingerprint  
mechanism for certificate matching rather than SubjectAltName matching  
to get around this issue. This discussion is far from "baked". We've  
also had some objection (primarily from Jon) to doing work around a  
new class of MSRP TLS intermediary without better describing that  
intermediary, as well as concerns (primarily from Ben ) about  
standardizing MSRP mechanisms to work with non-standardized  
middleboxes without a better understanding of them.

2) We have little or no objection to the usage of the comedia "setup"  
attribute   (section 4.1 of draft-ietf-simple-msrp-acm-00. )

Is this a fair summary? Have I mischaracterized or missed anything?

---

From: Ben Campbell <[email-masked]>
Date: Tue, 19 May 2009 16:39:42 -0500

(as individual)

On May 18, 2009, at 4:11 PM, Ben Campbell wrote:

> think we've reached closure on most of it. In order to jump start  
> it, I am going to attempt to summarize the issues that I think are  
> still open. I will start separate threads for each issue. Please  
> reply to _this_ message to comment on whether I have offered a fair  
> summary, or mischaracterized or omitted anything material. Please  
> reply to the specific issue threads to discuss the issues themselves.

Since Christer split the ongoing thread along pretty much the same  
lines that I intended, I will not start redundant threads as I  
threatened to do above :-)

Thanks!

Ben.

---

From: "Christer Holmberg" <[email-masked]>
Date: Wed, 20 May 2009 07:07:51 +0200

Hi, 

>Since Christer split the ongoing thread along pretty much the 
>same lines that I intended, I will not start redundant 
>threads as I threatened to do above :-)

I did the split before I realized that you intented to do the same.
Sorry for that :)

Regards,

Christer