Hi, for those interested in MSRP protocol (instant message sessions and file transfer for SIP) there are bad news:
Even if there are already clients and servers (MSRP relays o IM conference servers) implementing the MSRP protocol (RFC 4975 and 4976) the SIMPLE WG will publish a new draft [*] that breaks these RFC's just to satisfy big vendors interested in deploying MSRP capable SBC/ALG boxes (so instead of solving NAT issues with MSRP relays as RFC 4976 states, they want it to be fixed in the router by doing ugly ALG, or in a SBC). This is terrible because all the MSRP devices should implement this new draft in order to interoperate (no backward compatibility at all). The draft also breaks the security defined in RFC 4975 (for example, TLS name based authentication cannot work anymore).
For further information I recommend reading these two posts:
http://blog.tekelec.com/blog/bid/29816/More-on-MSRP-Session-Match-Extension http://blog.tekelec.com/blog/bid/33138/MSRP-Session-Match-Backwards-Compatib...
and also these very *hot* mail threads in the SIMPLE maillist:
http://www.ietf.org/mail-archive/web/simple/current/msg09227.html http://www.ietf.org/mail-archive/web/simple/current/msg09229.html
[*] http://tools.ietf.org/html/draft-ietf-simple-msrp-sessmatch-11