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 193 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
ZyWALL USG 300 User's Guide
(Section 18.2 on page 302) to set up SIP, H.323, and FTP ALG settings.
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ALG

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