Calling from external VoIP/SIP client

[CapnOdin]

I would like to be able to call UEs from a VoIP/SIP client like MicroSIP or alternatives.
Having read that the P-CSCF is the entry point of the ims, I have tried exposing the ports it uses in 4g-volte-deploy.yaml.
However when trying to register from MicroSIP I get these errors and warnings.

[pcrf] WARNING: Cannot find Gx Sesson for IPv4:192.168.1.122 (../src/pcrf/pcrf-rx-path.c:181)
[pcrf] ERROR: No Gx Session (../src/pcrf/pcrf-rx-path.c:207)
ERROR: <script>: Diameter: AAR failed on subscription to signalling

I am not familiar with Diameter, do I need to authenticate to the Diameter instance running on the P-CSCF or should I be running a Diameter instance together with the VoIP/SIP client to handle the authentication?

I have added the VoIP/SIP client user to the pyHSS but not to the HSS nor to OsmoHLR as they do not seem to support the type of data such a user would have e.g. text usernames and not having an opc.

I am not confident that my approach is correct at all so for this reason I have neglected to attach a pcap file, as I would like to hear how one would go about connecting a VoIP/SIP client, rather than focus on my misguided attempt at doing it.

About my setup, everything is run on a single rpi 5 host using 4g-volte-deploy.yaml and srsenb.yaml and with a LimeSDR Mini 2.0. This is working great with our Quectel RG255C UEs.

If anything is unclear I will be happy to clarify it.

[herlesupreeth]

If you are using only SIP clients to call, then you would need to disable Rx diameter interface on P-CSCF as follows

#!define WITH_RX ====> ##!define WITH_RX

This way it wont need authorization from PCRF.

[herlesupreeth]

NOTE: If you are attempting to call a COTS UE from SIP client (another UE), it may not work depending on UE. Because most UEs need QoS for VoLTE call to be successful and disabling Rx interface on P-CSCF results in no QoS maintained/signaled for the call

[CapnOdin]

Thank you for your reply. If I understand you correctly then in order to call into the network with a VoIP client, I would essentially need to make my own client, akin to one of the simulated UEs. except without the radio interface, integrated with a VoIP client gui or see if I can find one pre-made.
Off the top of your head do you know of any such software?

Our intention is to only cover a single event site with the network, but we have some people offside we need to provide the ability to call the UEs at the site, for this purpose we would prefer to use the existing internet infrastructure to facilitate the external calls.
Maybe some other solution might be more appropriate then trying to access the network the same way a local UE would. What about accessing the IMS as an external mobile network would, when routing calls to an UE in the IMS?

[herlesupreeth]

Off the top of your head do you know of any such software?

I havent used any but I remember some in community trying out IMSDroid but I dont know how is the support for that

Maybe some other solution might be more appropriate then trying to access the network the same way a local UE would. What about accessing the IMS as an external mobile network would, when routing calls to an UE in the IMS?

One of the community member has contributed to this quite recently but its for 5G only currently. But, you can take a look at ibcf folder for the configuration used to achieve calling from IMS to outside world and vice versa. Note that for this to work you need to get a SIP trunk head number. I am not sure how to get this either