Data synchronization: ALG synchronizes session data provided by two hosts exchanging data.

Full control over commands: The hardware recognizes the specific commands and requests and provides full control over them.

This aspect introduces the term “gateway” for ALG.

Conversion: ALG converts the network address information that is located between addresses acceptable on both sides of the NAT or firewall.

In this case, the network administrator will need to open a large number of ports in the firewall, which will make the network vulnerable to attacks. When there is no ALG used, the ports can become blocked.

Unlike ALG, firewall configuration supports only a limited number of known ports.

Usage of TCP/UDP port: Application Layer Gateway allows client apps to use dynamic ports to communicate with ports used by server apps.

When packets of this protocol pass through it, ALG modifies them in such a way that users behind the NAT can use the protocol What Are the Key Functions of Application Layer Gateway? Generally, the capacities of Application Gateways exceed those provided by firewalls. It manages such protocols as SIP and FTP using deep inspection packets to detect and block attacks before the traffic passes to the app. If a remote computer establishes a connection on this port according to the protocol, retransmission is automatically enabled.ĪLG is similar to a proxy server. Having identified the packet as belonging to this protocol, ALG substitutes its address and port instead of yours. Consequently, the remote side cannot establish a connection.

After passing the NAT, some parameters like port and address become incorrect. The NAT router relays packets coming from an external IP address inside the network. When packets of this protocol pass through it, it modifies them in such a way that users behind the NAT can use the protocol. The ALG deals with Telnet, FTP, SMTP, and HTTP ensuring a secure connection How Does Application Layer Gateway Work?īeing a component of a NAT router, Application Layer Gateway understands an app protocol.

Application level gateway