| Configuring the Security Features | 205Parameter Description Configuration MethodH.235 Encryption Configure the H.235 encryption.The supported types are asfollows:• Disabled—the encryptedcalls are not supported.• Optional—both theencrypted and theunencrypted calls aresupported. The secure callsare supported only if the farend supports encryption.• Compulsory—unencryptedcalls are not supported.Default: Off.Web user interfaceWhen H.235 is enabled on both sites, RTP streams will be encrypted, and a lock icon appears on the monitorof each system after successful negotiation.Defending against AttacksVCS sometimes may receive calls from unknown caller, and the calls may be unable to answer. For thecommunication security, VCS supports the features of defending against attacks. You can configure the abnormalcall answering feature to handle the abnormal SIP incoming call or configure the safe mode call feature to verify theH.323 incoming call.• Configuring Abnormal Call Answering• Configuring the Safe Mode CallConfiguring Abnormal Call AnsweringWhen the destination address of the incoming SIP call does not match the local address, the call is considered tobe an abnormal call. You can deal with them by setting them as the abnormal SIP incoming call. You can reject theabnormal SIP incoming call, or answer it by using IP address or SIP account randomly. This feature is not applicableto VP59.Procedure1. On your web user interface, go to Setting > Call Features > Abnormal Call Answering.2. Configure and save the following settings:
