Alg - TRENDnet TEW-692GR User Manual

ALG

ALG (Application level gateway): It allows customized NAT traversal filters to be plugged into the
gateway to support address and port translation for certain application layer "control/data" protocols
such as FTP, SIP, RTSP, file transfer in IM applications etc. In order for these protocols to work through
NAT or a firewall, either the application has to know about an address/port number combination that
allows incoming packets, or the NAT has to monitor the control traffic and open up port mappings
(firewall pinhole) dynamically as required. Legitimate application data can thus be passed through the
security checks of the firewall or NAT that would have otherwise restricted the traffic for not meeting its
limited filter criteria.
42