Application Gateway - Planet GRT-504 User Manual

3.2.3 Application Gateway

The Application Level Gateway acts as a proxy for applications, performing all data exchanges
with the remote system in their behalf. This can render a computer behind the firewall invisible to
the remote system. It can allow or disallow traffic according to very specific rules, for instance
permitting some commands to a server but not others, limiting file access to certain types, varying
rules according to authenticated users and so forth. This type of firewall may also perform very
detailed logging of traffic and monitoring of events on the host system; furthermore can often be
instructed to sound alarms or notify an operator under defined conditions. Application-level
gateways are generally regarded as the most secure type of firewall. They certainly have the most
sophisticated capabilities.
Level 5: Application
Level 4: TCP
Level 3: IP
Level 2: Data Link
Level 1: Physical
Host PC
Proxy Application
Internal
Interface
Proxy Server
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Check URL
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GRT-504 4-Wire G.SHDSL.bis Firewall Router User's Manual
Telnet
FTP
Http
SMTP
External
Interface
Public Server
Request Page
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