User manual

ALG Switch
In the context of computer networking, an application-level gateway (also known as ALG or
application layer gateway) consists of a security component that augments a firewall or NAT
employed in a computer network. 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, BitTorrent, SIP, RTSP, file transfer in IM applications
etc. In order for these protocols to work through NAT or a T 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.
SIP-ALG: select Enabled to activate SIP ALG feature or Disabled to disable this feature.
The Session Initiation Protocol (SIP) is an IETF-defined signaling protocol, widely used for
controlling multimedia communication sessions such voice and video calls over Internet
protocol (IP). The protocol can be used for creating, modifying and terminating two-party
(
unicast) or multiparty (multicast) sessions consisting of one or several media streams. It is a
text-based Application Layer protocol.
But as many use NAT to communicate with the public networks, and the IP address and port
combination in SIP packets are needed for addressing, we must come up with an effective
way to deal with SIP NAT traversal. SIP ALG is an easy solution with which you are only
required to enable SIP ALG on NAT application in this router to easily experience the smooth
SIP connection between private networks and public networks or even in two private
networks with your VoIP devices.
Press SAVE button to apply your settings.
51