Hi all, When I use SER in transaction stateful mode, I have the following problem: When A sends an "INVITE B" to SER, SER forwards the INVITE to B statefully. If B reply with "200 OK", everything goes fine as SER will delete the transaction from memory when it sees the 200 OK. However, if B send an "BUSY HERE" back to SER, SER will send an ACK to B right away and then forwards the "BUSY HERE" to A. A will then send an ACK to SER but SER won't realize that the ACK belong to the transaction and forward it to B. SER will then keep sending "BUSY HERE" to A until the transaction is timed out. I wonder if there is something to add in the configuration file to make SER understand that the ACK send from A should terminate the transaction. Any help will be highly appreciated! Minh