Planet AND-4102, Руководство пользователя

Страница: 50 / 92

802.11n Wireless ADSL 2/2+ Router
ADN ‐ 4102
50
User Datagram Protocol (UDP) ports on which the applications open data connections. Such applications
include the File Transfer Protocol (FTP) and various IP telephony protocols.
ALG 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, 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.