Alg; Chapter 16 Alg; Alg Overview; What You Can Do In The Alg Screen - ZyXEL Communications ZyWall USG 50-H Series User Manual

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H A P T E R

16.1 ALG Overview

The Application Layer Gateway (ALG) allows the following applications to operate properly
through the ZyWALL's NAT.
• SIP - Session Initiation Protocol (SIP) - An application-layer protocol that can be used to
create voice and multimedia sessions over Internet.
• H.323 - A teleconferencing protocol suite that provides audio, data and video
conferencing.
• FTP - File Transfer Protocol - an Internet file transfer service.
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.

16.1.1 What You Can Do in the ALG Screen

Use the ALG screen
ZyWALL USG 50-H User's Guide
(Section 16.2 on page 276) to set up SIP, H.323, and FTP ALG settings.
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ALG

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