A method, system and computer program product are described for managing network communications to a Session Initiation Protocol (SIP) server capable of SIP processing using a SIP stack. A data packet is received from a network device. It is determined, from the data packet, whether the network device is a device recognized by the SIP server. Responsive to this determination, and before SIP processing using the SIP stack, it is determined whether the data packet conforms to a permitted configuration. The permitted configuration includes that data of the data packet indicates an unfragmented User Datagram Protocol (UDP) packet and that data indicative of SIP data in the received data packet matches a parsing rule. If the data packet conforms to the permitted configuration, it is passed to the SIP stack, if not it is discarded.