[Linux-aus] SIP

Jeremy Visser jeremy at visser.name
Thu Jul 4 12:04:35 EST 2013

On 04/07/13 09:50, David Newall wrote:
> On 04/07/13 07:13, Russell Stuart wrote:
>> > If you have a VOIP home phone, you don't just expose a SIP handset to
>> > the internet.  You deal with a SIP provider, who in effect only accepts
>> > phone calls from other providers who don't accept generate huge numbers
>> > of marketing calls.  Think of it as a GMail service for SIP.  If your
>> > provider starts letting through a whole pile of unwanted calls, you
>> > would move to another provider.
> Never heard of such a service.  Sounds potentially valuable.  Who does it?

Practically everybody.

However, it must be said if you take up a SIP-based VoIP service with
one of the many ISPs in Australia, it is basically a PSTN service
delivered over IP.

VoIP providers *rarely* talk to other VoIP providers (there are
exceptions, but usually they only occur when there are clear business
incentives -- c.f. the merger of iiNet and Internode). If you are on
VoIP provider A, and call someone on VoIP provider B, the connection in
the middle will typically be based on PSTN switching, usually with a big
telco such as Telstra, Optus, or maybe Symbio in between.

What I think David is visualising is a more peer-to-peer based SIP
setup, which is *far* harder to implement (and certainly darn near
impossible to monetise, which is why you don't see any traction for P2P
SIP from businesses developing VoIP solutions).

There are sites like http://www.sipbroker.com/ which attempt to index
all VoIP providers out there, giving some quasi-P2P solution. In
practice, though, most VoIP providers firewall SIP traffic to their own
customers (due to spam and abuse), so trying to use that service doesn't
work anyway. It's not a practical and scalable solution anyway, even if
it was working.

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