An IPsec tunnel connecting the subnets behind the gateways moon and sun is set up. The authentication is based on Preshared Keys (PSK). Unfortunately the secret keys of moon and sun do not match, so that the responder cannot decrypt ISAKMP message MI3. The resulting encrypted notification message cannot in turn be read by the initiator moon. In order to avoid a notify-war, any further generation of PAYLOAD_MALFORMED messages is suppressed.