S-CSCF replies “Forbidden - Domain not served” - sr-users

13 Jun 2019

We have configured Kamailio IMS (P, I, S-CSCF) to use a single realm with the same
NETWORKNAME and trying to make a call between bob and alice.

We are getting S-CSCF replies “Forbidden – Domain not served” in two scenarios:

  1.  When bob calls alice, the INVITE went from P->S->I->S and the destination
S-CSCF responded this error
  2.  During SIP registration in responding to SUBSCRIBE (endpoint still can register even
with this reply, so we proceeded with making call)

In quick search we found that in scscf/kamailio.cfg route{ } implementation there is a
case when this error is generated:

                # Terminating
                if (uri == myself || uri =~ "tel:.*") {
                        if (!term_impu_registered("location")) {
                                xlog("L_DBG", "We need to do an UNREG
server SAR assignemnt");
                                assign_server_unreg("UNREG_SAR_REPLY",
"location", "term");
                                exit;
                        }
                } else {
                        sl_send_reply("403","Forbidden - Domain not
served");
                        exit();
                }
                route(term);
                break;

What is this error designed for? Also in general are we supposed to rework the routing
code in Kamailio.cfg (P, S, I-CSCF)?

Thanks for any suggestions in advance.

Yin