is restarted if necessary fig2 illustrates a typical tcap message flow originating from a private node 231 to a public node 131 though pce stp mate 1 100 m 1 of the system 1 m which is in a mated pair configuration with the system 1 m u2032 a tcap begin message is originated from private node 231 pc value is 1 1 1 bearing opc value of 1 1 1 dpc value of 3 3 3 and tid value of 000001 in the direction 51 pce 100 intercepts the tcap begin message and stores tid and opc in the hash table pce 100 then replaces opc value with 5 5 5 which is the pc of the system 1 for public network 10 and replaces tid value with an available unique tid value i e 100001 in this example pce 100 forwards the message to public node 131 once public node 131 receives the message then public node 131 generates a tcap response message bearing opc value of 3 3 3 dpc value of 5 5 5 and tid value of 100001 and forwards the message in the direction 52 pce 100 intercepts the tcap response message and look up dpc and tid in the hash table and finds that private node 231 and tid value of 000001 corresponds.