On Tue, 2008-10-28 at 11:48 -0400, Damian Krzeminski wrote:
> > With the new NAT compensation feature, no SBC is needed for it.
> >
>
> Are you saying that when NAT traversal is enabled I do not have to
> configure and enable Internet Calling?
> Or are you saying that Internet Calling (as in: "routing SIP urls calls
> through specific SBCs") is not needed at all?
>
> BTW: I asked Bob about it and I think he said Internet Calling might still
> be needed (I might have misunderstood something but I think he mentioned
> other capabilities of SIP aware firewalls that our NAT compensation does
> not handle).
>
> I'd like to know what would be the typical usage patterns here so that we
> can design UI that matches it.
Unfortunately, there is no way to provide any answer other than: It
Depends
If what you have at the edge of your network (the thing between your
private net and The Internet) is a simple NAT (like most of us have at
home and many small businesses use), it may be that calling an arbitrary
SIP URL will "just work" without an SBC. Some mapping at that NAT will
be needed to allow the same thing to work inbound (from the Internet to
your PBX) to send the initial INVITE to the proxy.
However... in many cases, the thing at the edge of the network will be
some much more aggressive Firewall, or perhaps something that is "SIP
Aware" (shudder) and will be more difficult to get through. In those
cases, the expedient configuration may be to explicitly route to some
SBC that does the "right thing".
There is no "general case" here, and no (obvious) way for us to
automatically test for what will work best in a given situation.
Part of the confusion in this discussion has come from the fact that in
the past we have recommended the use of an SBC for two overlapping jobs:
* Compensating for NATs and avoiding Firewalls so that SIP can be
used across the public/private network barrier and with clients
behind NATs
* Dealing with the idiosyncrasies required by ITSPs (like
requiring that the entire PBX register with one or more
numbers).
These are distinct jobs. In 4.0 we're introducing the NAT compensation
capability to the proxy to attack the former, and sipXbridge to attack
the latter. There is some overlap (if you've got a NAT between you and
your ITSP then you need to get through it, for example).
How will it work in any given situation? We should have pretty stable,
nearly feature-complete 3.11 builds soon, and then we hope that our
amazing community will tell us....
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