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I am trying to use FreePBX 13 (a GUI version of Asterisk) to create a mock VoLTE network with our cellphones (an iPhone 6S+ and an LG G3 VS985).

FreePBX has been set up as such: FreePBXForums: Using FreePBX 13 with a Mock Cellular Network

At the moment, we are able to register and make calls with computer clients, but the UEs (aka the cellphones) fail to register because of a "realm" mismatch among other things. Because of this I have a couple questions:

  1. If a client (even a UE) recieves a 401 Unauthorized message, is it allowed to stay static as what is happening with the UEs, or is it supposed to modify itself regardless?
  2. If it is allowed to stay static, is there any way to modify the in-congruent authentication parameters on either side?

If you would like to see the packets themselves, please see entries 23 and 16 (respectively for UE and Client registration) from the forum linked above.

Please let me know if you have any questions. I am somewhat new to SIP, so that is why I am asking this question.

C.Evenhuis
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Midimistro
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    Can't you set up FreePBX to have the realm the mobile UEs expect ? Or set up two SIP realms, one for your standard SIP clients (with whatever realm you choose) and one for the 3gppnetwork one for mobile UEs? – André Borie Jun 22 '17 at 14:00
  • That would be possible if I were just using Asterisk raw, but since I am using FreePBX, that is not possible as FreePBX automates that particular setup. However, this has been a recommendation for FreePBX so I am hoping that they consider this realm name change issue. In the meantime, I guess I could try using a raw copy of Asterisk on one of my other computers. – Midimistro Jun 22 '17 at 14:47
  • If anything, the question I am more so looking for an answer to is "does a UE have the right to keep its authentication values static even after a 401 message is recieved"? – Midimistro Jun 22 '17 at 14:52
  • You could potentially use a lightweight SIP proxy (siproxyd or OpenSIPs) as a "shim" to bypass the realm issue. UEs would use the SIP proxy which then completes calls between UEs registered on it and forwards all the other calls to upstream (in your case that would be FreePBX). – André Borie Jun 22 '17 at 15:06
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    I would say the UE is allowed to keep its auth values static as the auth is mandated by the SIM card and the realm is mandated by 3GPP standards. A standard SIP client would go back to the user to check the login/password/realm but in VoLTE it's supposed to be seamless so upon a 401 it just sits there and retries hoping that it'll eventually register. – André Borie Jun 22 '17 at 15:07
  • Although both of those ideas are quite helpful, the issue I am currently trying to get around is simply registering to FreePBX. Your explanation of VoLTE and the SIM cards makes sense, so it looks like I will have to make an adjustment somewhere on the network, or in FreePBX. Once the authentication issue is fixed, any issues such as realm congruence should be easy fixes. – Midimistro Jun 27 '17 at 20:20

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