[ltp] VOIP

[morpheus]

> What I'd like is to just use a hand set to appear as
> if I am a US local caller when I have to deal with
> my US clients. I beginning to think this won't work.
> When at home I'd need this:
You should be able to do this easily with Vonage.  I think they now
offer boxes that sit behind a router/firewall and are adapters only,
with no built-in router.  You'd have to ask them.

> handset -> box -> my firewall -> over the Atlantic -> Vonage
> and on to the phone system -> client
I believe Vonage uses SIP or MGCP.  The signaling should not have any
problems even on a slow or unreliable link.  As for the voice, with
compression I think you only need about 48Kbps, which should be no
problem across the Atlantic. Remember, most cheap long distance
companies use VoIP for trunking anyway, so you shouldn't notice a
difference.

If you want details, what happens is the "box" sends a request to the
Vonage signaling server saying that a phone at IP address
xxx.xxx.xxx.xxx wants to make a call to a telephone number yyyyyyyy.
The Vonage server finds it's closest PSTN gateway to that number (they
probably have them in most big markets, including the UK) and then it
sets up an IP voice link between your phone and that PSTN gateway.  The
gateway places a normal PSTN call to the destination number and connects
you.  Remember, the IP voice link is routed via IP, so your voice is not
going to Vonage, it goes direct to the gateway.

So, it doesn't really matter where your phone is located, in fact,
Vonage has no idea since they only see an IP address.

You may experience quality degradation calling "minor" markets where
there is no PSTN gateway...for example when I call New Zealand, the
closest gateway is Taiwan, and the call is then passed on to a cheap
Taiwanese LD company who probably compresses the hell out of it and
sends it to NZ...so I get up to a three second delay.

> And how would it work when I am travelling in the US?
> 
> handset -> T22 -> box -> hotel firewall -> over the Atlantic the other
> direction -> my firewall -> switch box -> my firewall -> again over
> the Atlantic -> Vonage and on to the phone system -> client?
In the US it will work the same, perhaps better since there are more GWs here.

> My home Linux firewall is not something I'd think I
> could replicate with someone else's idea of a home
> user's router... I've got FreeSwan tunnels, local DNS,
> snort, etc, etc...
> 
It shouldn't make a difference.  I believe Vonage uses a Session Border
Controller which means it can pass SIP to you even if you're NATted.



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