HSS Cx Server-Name chicken or the egg

[lyatanski]

For the IMS case, on HSS Cx interface 3GPP TS 29.229 we have User-Authorization-Request (UAR) Command (6.1.1) from ICSCF to HSS and by no suprise User-Authorization-Answer (UAA) Command (6.1.2) response. The UAA should include Server-Name AVP in order the ICSCF to know where to forward the SIP REGISTER message. Unfortunately, as far as I could see, impu->server_name is only assigned in hss_ogs_diam_cx_mar_cb and hss_ogs_diam_cx_sar_cb using hss_cx_set_server_name. This is all fine and dandy, but these messages are sent from the SCSCF, which could not be reached as the ICSCF do not receive its URI.

Checking with Dockerized VoLTE Setup is not much help, as they are using additional HSS by the name FHoSS.

How I stumbled upon this? I'm trying to create IMS setup from scratch. For reproduction, the commands should be:

• docker compose up -d
• docker compose run test

The empty Server-Name AVP could be confirmed either by checking trace from the test

or from ICSCF logs:

icscf-1  |  6(11) INFO: ims_icscf [cxdx_avp.c:138]: cxdx_get_avp(): cxdx_get_server_name: Failed finding avp
icscf-1  |  6(11) INFO: ims_icscf [cxdx_avp.c:138]: cxdx_get_avp(): cxdx_get_capabilities: Failed finding avp
icscf-1  |  6(11) INFO: ims_icscf [cxdx_avp.c:138]: cxdx_get_avp(): cxdx_get_result_code: Failed finding avp
icscf-1  |  6(11) DEBUG: ims_icscf [cxdx_uar.c:226]: async_cdp_uar_callback(): successful UAA response
icscf-1  |  6(11) ERROR: ims_icscf [cxdx_uar.c:231]: async_cdp_uar_callback(): Empty capability list returning 600
icscf-1  |  6(11) DEBUG: <core> [core/msg_translator.c:162]: check_via_address(): (192.168.69.3, 192.168.69.3, 0)
icscf-1  |  6(11) DEBUG: tm [t_reply.c:1782]: cleanup_uac_timers(): RETR/FR timers reset
icscf-1  |  6(11) DEBUG: tm [t_reply.c:634]: _reply_light(): reply sent out - buf=0x7fe1505cc0e0: SIP/2.0 600 Busy eve... shmem=0x7fe14bbc4100: SIP/2.0 600 Busy eve

Am I missing some way to provision the SCSCF URI in the HSS in Mongo for example or is there another way this is supposed to work?

[acetcom]

@lyatanski

Thank you for sharing your detailed question regarding the IMS setup and the behavior of the Server-Name AVP in the HSS Cx interface.

Based on the nature of your inquiry, it seems more suitable for the Discussions forum rather than the Issues section, as it involves exploring configurations and behavior rather than reporting a confirmed bug. To keep the repository well-organized and ensure appropriate usage of the Issues and Discussions sections, I have moved your question to the Open5GS Discussions forum.

I encourage you to follow up there with additional context or any further observations you may have. The Discussions forum is a great place to collaborate with the community and receive advice on complex scenarios like this one.

Thank you for understanding, and I hope this helps facilitate productive troubleshooting!
Sukchan Lee