[SIPForum-techwg] IP PBX / SP Interop Draft Version 5 proposededits

[Hadriel Kaplan]

Hi again,
	
> -----Original Message-----
> From: Rohan Mahy [mailto:rohan at ekabal.com]
> 
> The current version of the spec already requires public IP addresses on
> each side.

Of course - and an SBC provides such an address to the enterprise (as I
assume an enterprise one would to the service provider).  It's just not
necessarily the PSTN gateway's physical IP address, which may or may not be
public.

 
> Can you publicly provide an in-scope example that breaks with public IP
> addresses?

It is very frustrating not being able to express the other problem sets
without giving away information about some providers.  I guess I can safely
at least say one of the specific cases which may break it, although for the
opposite flow direction but still due to following your rules, is that
either what you define as "public addresses" is not always knowable to be
public - that is to say, the address is a non-reserved, assigned address
space and looks "public" but is not routable between domains (it is not
advertised) - or simply that the far-end receiver is in a restricted space
which cannot reach the public originator directly through routed paths.
Unless the SBC knows that the far-end has reachability to those routes, it
has no way to a priori know the far end receiver can actually reach the
originator without the SBC's help.  If the SBC were to give the far-end the
originator's address it would lead to one-way or no-way media, whereas the
SBC itself could provide the far-end with its local address which can
bridge/relay the domains.  In some ways I assume SBCs built for the
enterprise side must face similar issues in order to support large complex
Enterprise networks.

-hadriel