Is using Outgoing SIP Registration the only way to allow incoming calls if you do not allow port forwarding or any new incoming connections?

JMain

1/21/24, 1:49 AM

If I use a SIP provider that uses SIP REGISTER for connections (instead of using an IP address), the outgoing registration originating from my side opens a connection to the SIP provider, and they use that same connection to send calls to me. I don't have to do any port forwarding, and I don't have to allow any incoming connections through the firewall.

I'm not asking if that is recommended. I am specifically asking if that (Outgoing SIP REGISTER) is the ONLY method that allows incoming calls to work without any port forwarding or without allowing any incoming connections (other than established connections).

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Peter Zhabin

1/21/24, 2:32 AM

Well, unless REGISTER has been received over (NAT, STUN, whatever) the only other way left for the PBX to reach you is via INVITE to a static translation. However I'm a little lost to what's a difference between REGISTER from a private IP that does some hole punching and "established connections"

JMain

1/21/24, 2:37 AM

"However I'm a little lost to what's a difference" ... The difference is that with the register option, the PBX can basically work in any environment without involving the firewall. It basically just works. The outgoing registration (outgoing from the pbx point of view, as the pbx initiates the register, it's actually registar for incoming calls) it creates a persistent connection that is used for incoming calls and therefore doesn't require a new incoming connection from the outside at all.

Peter Zhabin

1/21/24, 2:43 AM

The REGISTER is initiated by the client, hence the question. If the client has initiated REGISTER, it has already done it's side of hole punching in a properly configured NAT. The PBX on the contrary signals a call to the client with INVITE on a last known IP ita has registered to or a static allocation. I'm not entirely sure what you're trying to achieve and/or avoid..

JMain

1/21/24, 3:53 AM

I'm not asking about register, I'm asking if there any other methods (other than register) that does the hole punching like register does? For example, Twilio doesn't support register at all so using register to hole punch isn't an option with Twilio.

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EN: Is using Outgoing SIP Registration the only way to allow incoming calls if you do not allow port forwarding or any new incoming connections?

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