[VOIPSEC] P2Pnat Media - A H.323 alternative to ICE

[Dan Wing]

Simon Horne wrote:
> I guess the big design differentiator between P2Pnat Media and ICE is that 
> its smarts are in the network and not the client. The network (local 
> gatekeeper) decides, as part of existing call routing and before the call 
> setup message is sent, how any relevant NATs are to be transversed for the 
> call, removing all the complexity from the client and avoiding the need for 
> the long list of "candidates" 

What does it do in a situation like this:

                           [h.323 gateway]
                                |
                   +---------[router]-------------+
                   |                              |
                 [NAT]                            |
                   |                              |
   [endpoint]--[router]----------------------[endpoint]

With ICE in this situation, ICE would cause the media to take the 
southern route.  If I understand your new approach correctly, this 
situation would cause the media to be relayed through the H.323 gateway 
or routed up through the NAT (I'm not sure which), but never just along 
that southern route.

(It's a separate argument for how often network topologies such as this 
appear in the wild, and how important it is to optimize the media path 
for such topologies).

 > and associated media establishment delays
> generally associated with ICE.

ICE hides those delays by only ringing the phone after a connectivity 
check has completed -- sortof a "poor-man's connectivity precondition".
http://tools.ietf.org/html/draft-ietf-mmusic-ice-15#section-12.1.1

-d