Alg; Chapter 18 Alg; Alg Overview; What You Can Do In The Alg Screen - ZyXEL Communications ZyWALL USG 300 User Manual

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H A P T E R

18.1 ALG Overview

Application Layer Gateway (ALG) allows the following applications to operate
properly through the ZyWALL's NAT.
• FTP - File Transfer Protocol (FTP) is an Internet file transfer service.
• SIP - Session Initiation Protocol (SIP) is an application-layer protocol that can
be used to create voice and multimedia sessions over Internet.
• H.323 - This is a teleconferencing protocol suite that provides audio, data and
video conferencing.
The following example shows SIP signaling (1) and audio (2) sessions between
SIP clients A and B and the SIP server.
Figure 210 SIP ALG Example
The ZyWALL only needs to use the ALG feature for traffic that goes through the
ZyWALL's NAT.

18.1.1 What You Can Do in the ALG Screen

Use the ALG screen
ALG settings.
ZyWALL USG 300 User's Guide
(Section 18.2 on page 321) to set up SIP, H.323, and FTP
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ALG

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