Alg Service - Tenda W302R User Manual

Wireless-N Broadband Router
ALG Service Settings
ALG(Application Layer Gateway)
In the context of computer networking, an 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 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.
Usually allowing client applications to use
dynamic ephemeral TCP/ UDP ports to
communicate with the known ports used by the
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