Intermittent S-CSCF → HSS Diameter Connection F ailure - CER Not Sent After TCP Connect

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

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