G cluster_village_b Village B cluster_village_a Village A ms_alice Alice (from village A) msc_b MSC B ms_alice->msc_b Location Updating hlr_b HLR B msc_b->hlr_b Location Updating hlr_alice Alice's home HLR hlr_b->hlr_alice mslookup by IMSI hlr_b->hlr_alice GSUP proxy forwarding