Hello Kamailio Community,

We're experiencing a critical issue in Kamailio where S-CSCF randomly stops sending CER to HSS in some cases after establishing TCP connections, causing complete authentication failures.

Please find the attached (IMS containers + HSS )logs  and the current configuration.

Environment

• Kamailio Version: kamailio 6.0.2 (x86_64/linux) d4dc5d
• Deployment: SCSCF and HSS as a container on same physical machine using macvlan networking

Components:

• SCSCF: 172.22.1.20
• HSS: 172.22.1.3
• ICSCF: 172.22.1.19

Problem Description

The issue occurs randomly - the system works normally for periods of time, then suddenly the Diameter connection between SCSCF and HSS fails and enters a reconnection seems loop.

Here's the cycle we're observing:

1. SCSCF: WARNING: cdp [peermanager.c:337]: peer_timer(): Inactivity on peer [hss.epc.mnc092.mcc418.3gppnetwork.org] and no DWA, Closing peer...

2. State Timeout (~40 seconds later): S-CSCF: ERROR: cdp [peerstatemachine.c:164]: sm_process(): in state Closed timeout event Timeout

3. Reconnection Attempt (~30 seconds later):

SCSCF: INFO: cdp [peerstatemachine.c:551]: I_Snd_Conn_Req():  Peer hss.epc.mnc092.mcc418.3gppnetwork.org

SCSCF: INFO: cdp [receiver.c:991]: peer_connect(): Trying to connect to 172.22.1.3 port 3870

SCSCF: INFO: cdp [receiver.c:1090]: peer_connect(): Peer hss.epc.mnc092.mcc418.3gppnetwork.org:3870 connected

4. HSS Side (waiting indefinitely):HSS: [hss:0.19.37] 2025/12/25 04:46:39.060208 [INF]  [scscf>hss:0][waiting for CER from 172.22.1.20:33284]

Cascading Effects:

ICSCF accumulates branches:

ICSCF: ERROR: tm [t_fwd.c:792]: add_uac(): maximum number of branches exceeded

ICSCF: ERROR: tm [t_fwd.c:1771]: t_forward_nonack(): failure to add branches

Result: each UE cannot be able to register to IMS and VoLTE service outage for all UEs

Best regards,

Qasim Loay