SIP ALG - Computer Definition
(SIP Application-Level Gateway) A function in a router that allows SIP-based VoIP packets to traverse the network's firewall. Because Internet-based telephony is so widely used, the SIP ALG function is often enabled by default in many routers, including consumer-based wireless routers. However, SIP ALG implementations are not the same and are known to cause problems, including failing to handle incoming calls. In such cases, the function must be disabled, and either a SIP proxy is deployed or ports are opened in the router to allow VoIP traffic to reach the telephone switch (PBX). See SIP proxy and SIP.