G cluster_village_b Village B cluster_village_c Village C ms_bob Bob (from village B) pbx_b SIP B ms_bob->pbx_b call Alice hlr_c HLR C pbx_b->hlr_c mslookup by MSISDN sip_c SIP C pbx_b->sip_c call ms_alice Alice (from village A) msc_c MSC C ms_alice->msc_c msc_c->ms_alice call msc_c->hlr_c attached sip_c->msc_c call