TCP alone errors were strange : on the proxy node i couldn't register and got the following errors : 
Feb 25 12:15:28 server1 [Proxy-CSCF][31641]: ERROR: tm [ut.h:303]: uri2dst2(): no corresponding socket for "NET.SYRIATEL" af 2
Feb 25 12:15:28 server1 [Proxy-CSCF][31641]: ERROR: tm [t_fwd.c:469]: prepare_new_uac(): can't fwd to af 2, proto 1  (no corresponding listening socket)
Feb 25 12:15:28 server1 [Proxy-CSCF][31641]: ERROR: tm [t_fwd.c:1735]: t_forward_nonack(): failure to add branches
Feb 25 12:15:28 server1 [Proxy-CSCF][31641]: ERROR: siptrace [siptrace.c:1930]: trace_send_hep2_duplicate(): can't forward to af 2, proto 1 no corresponding listening socket
Feb 25 12:15:28 server1 [Proxy-CSCF][31641]: ERROR: sl [sl_funcs.c:362]: sl_reply_error(): stateless error reply used: I'm terribly sorry, server error occurred (7/SL)
=====================================================================================

These errors appearing when using two TCP and UDP, i could be able to register and make calls but still get errors
Feb 25 11:37:15 server1 [Proxy-CSCF][28999]: ERROR: ims_usrloc_pcscf [udomain.c:409]: update_pcontact(): Error updating record in DB
Feb 25 11:37:15 server1 [Proxy-CSCF][28999]: ERROR: ims_registrar_pcscf [notify.c:218]: process_contact(): failed to update pcscf contact
Feb 25 11:37:15 server1 [Proxy-CSCF][28999]: ERROR: tm [tm.c:1242]: w_t_reply(): cannot send a t_reply to a message for which no T-state has been established

In addition i cleaned all UDP SRV related records from DNS zone and tried to forced all instances in the TCP mode configuration

**Also, in the TCP mode all the  ip addresses that the registrations comes from are not the real ip's of the users, and also this is very strange
i got some random  IP's

On Fri, Feb 23, 2018 at 10:41 AM, Daniel-Constantin Mierla <miconda@gmail.com> wrote:

Hello,

have you look at syslog messages? Are there any errors? Between Kamailio instances, tcp for sip should work. Check also configs to be sure UDP is not enforced there.

Cheers,
Daniel


On 22.02.18 12:40, Amar Tinawi wrote:
Hello list 

For some reason i couldn't register on kamailio ims when i use only TCP protocols between nodes, the error was solved when i enabled UDP between I-CSCF and S-CSCF


is it mandatory for those two nodes to talk over UDP only ? or i'm missing something ? 
and in general for sip protocol which is better ? UDP or TCP ?


Regards,


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