[zwang97]

If I want to use multiple ATAs with the same account (for instance, Broadvoice) at home and at office, does it create conflict? I am a newbie so I don't know if anyone actually did this and what is the result? When someone tries to call, will the two devices ring the same time and if two persons pick up the call the same time, what will that be? Three persons hear from eath orther? Just like an extension of your home phone?

thanks.

[rizsher]

Any service provider that offers unlimited calling plans will definitely NOT let you use multiple adaptors. For most Pay As you Go type service providers it shouldnt really make any difference, though its always better to read their terms n conditions.

[mberlant]

Beyond the Terms and Conditions, most SIP servers are not configured to support multiple simultaneous registrations. Speaking only technically, if your service provider is single threaded you will find that your two (or more) ATAs will fight with each other for the attention of the SIP server (and, with it the ability to make and take calls).

In order to know the current status of your ATA (alive/dead, IP address, listening port, DND status, etc.) your ATA registers with the SIP server once every so often. This interval varies by provider, and is usually between 30 and 1800 seconds. Let's say that your service provider wants registration refreshing every 60 seconds, which is pretty typical.

For the sake of this example, let's take the case of two ATAs. You set up your home ATA (on public IP address 1.2.3.4) and it's busy refreshing once every minute. So far, so good. You set up a second ATA in the office and start it up. It sends a Register packet to the SIP server, saying, "I'm at 24.24.24.19. Please send calls my way." The SIP server says, "OK. Check back in in 60 seconds." Ten seconds later, though, your home ATA's 60 second timer expires and it sends a Register packet saying, "I'm at 1.2.3.4. Please send calls my way." Now the SIP server is listening to your home ATA. 50 seconds after that your office ATA times out and reregisters, stealing the connection back from the home ATA. And, so on.

Some SIP servers will eventually flag this behavior as fraudulent, but the vast majority will simply naively allow the tug of war to continue forever.

The bottom line is that you need to confirm with your service provider whether they permit multiple appearances (simultaneous SIP registrations) on one account and if so, how.

[zwang97]

According to your description, only one of the ATAs will ring when receiving a call. Maybe it's different from softphones. I did a test on stanaphone. I run stanaphone's softphone on multiple locations (IPs) and call the number. Then both of the softphones ring at the same time and when either one pick up the call, the other simply releases a missed call message.

[rizsher]

I've got a SPA3000. Tried setting it together with Xlite behind THE router, with the same account from Voiptalk.org. Sure enough, if I call the incoming PSTN number, both Xlite and the SPA3000 ring, picking one up stops the other ringing. Though, this MAY be because both the client are using the SAME public IP, if I were to set them up in two separate locations,the behaiviour may change.

[zwang97]

[quote="rizsher"]II observe the same thing on different IPs. I suppose the two softphones fight each other but actually they don't.

[mberlant]

As I said above, most service providers do not support multiple simultaneous registrations (including BroadVoice, the one you first mentioned). The ones that do support multiple simultaneous registrations are usually ones that do not offer unlimited calling plans.

By the way, it is just coincidence that you succeeded with softphones and failed with hardware devices.

[ctylor]

Learning the truth of this meant that I had to make a choice between an IP phone and an ATA device, because running both at the same time with my voipp resulted in a tug of war that made one of them useless. Had I known that, I would have held off on my purchase of the second piece of equipment. Sigh.

Thanks for the very clear explanation by mberlant for this behaviour.