Subject: [Simple] msrp-acm: Use Cases Comments

From: Ben Campbell <[email-masked]>
Date: Fri, 20 Feb 2009 14:36:13 -0600

Hi,

I've been working through draft-ietf-simple-msrp-acm-00, and have a  
few new thoughts about it. I am breaking these up into separate  
emails, to try to avoid discussion thread confusion.

I think the draft needs more analysis of the problems or use cases  
this draft sets out to solve. It may be this analysis exists in  
people's heads, but I think we should document it here.

In the case of the COMEDIA usage, there are some obvious use cases  
(the OMA media server use case mentioned in the draft, as well as  
situations were the network topology prevents the answering party from  
accepting TCP connections, while the offering party might could.

OTOH, the use cases for the c-line based addressing model are less  
clear to me. The draft states the use of more generic NAT traversal  
techniques as a motivation. We've done some internal white boarding,  
and I am not yet convinced this change is necessary for the use of  
TURN-TCP or ICE-TCP. In the case of TURN, an MSRP endpoint can simple  
construct it's session MSRP URL using the TURN allocation. ICE, on the  
other hand, defines it's own connection model. It seems like that if  
an MSRP endpoint wants to use ICE, it simply uses the ICE connection  
model rather than the base MSRP model, and things just work. (It gets  
more complicated if you want to use MSRP relays as ICE candidates--but  
my instinct tells me that is not a requirement.) For that matter, ICE- 
TCP has it's own mechanism for selecting the connection direction.

Thanks!

Ben.