[Linux-aus] SIP

Russell Stuart russell-linuxaus at stuart.id.au
Thu Jul 4 07:43:05 EST 2013

On Wed, 2013-07-03 at 08:57 -0400, David Lyon wrote:
> Where you see their point is on the receiving side of telephone calls. 
> If 'anybody' can make free voip calls, then anybody will call. I'm 
> meaning telephone canvassors/telemarketers here.

Yes, an open SIP system would end up as heavily SPAM'ed as email.  But
it in practice hasn't worked out that way.  People who opt to have a
VOIP (SIP) home phone don't get any more marketing phone calls that
someone who doesn't.  Why?  Because the system isn't open.

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.

After all, they have to do something to earn the right to charge you for
a service that you could otherwise supply yourself.  Actually behind the
scenes they do several things.  Phone numbers are a finite resource, and
they have to be routed.  Being finite you will still have to pay for
them.  It doesn't matter they are artificial, any more than it matters
water rights, copyright or carbon credits are artificial.  More
importantly if the service is going to be reliable, they have to
implement end to end QOS.  If you don't do they you end up with
something like Skype - working wonderfully one second, and dropping out
the next.  It turns out QOS is pretty hard to do well.

The bottom line is although a SIP could in principle be entirely open
are "free", it currently isn't and likely will never be so.  So your
Business friends have nothing to fear from moving from the PSTN to SIP.

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