ZyXEL Communications ZyWall 110 User Manual page 454

FTP ALG
The FTP ALG allows TCP packets with a specified port destination to pass through. If the FTP server is
located on the LAN, you must also configure NAT (port forwarding) and security policies if you want to
allow access to the server from the WAN. Bandwidth management can be applied to FTP ALG traffic.
H.323 ALG
• The H.323 ALG supports peer-to-peer H.323 calls.
• The H.323 ALG handles H.323 calls that go through NAT or that the Zyxel Device routes. You can also
make other H.323 calls that do not go through NAT or routing. Examples would be calls between LAN
IP addresses that are on the same subnet.
• The H.323 ALG allows calls to go out through NAT. For example, you could make a call from a private
IP address on the LAN to a peer device on the WAN.
• The H.323 ALG operates on TCP packets with a specified port destination.
• Bandwidth management can be applied to H.323 ALG traffic.
• The Zyxel Device allows H.323 audio connections.
• The Zyxel Device can also apply bandwidth management to traffic that goes through the H.323 ALG.
The following example shows H.323 signaling (1) and audio (2) sessions between H.323 devices A and B.
Figure 315 H.323 ALG Example
SIP ALG
• SIP phones can be in any zone (including LAN, DMZ, WAN), and the SIP server and SIP clients can be in
the same network or different networks. The SIP server cannot be on the LAN. It must be on the WAN
or the DMZ.
• There should be only one SIP server (total) on the Zyxel Device's private networks. Any other SIP servers
must be on the WAN. So for example you could have a Back-to-Back User Agent such as the IPPBX
x6004 or an asterisk PBX on the DMZ or on the LAN but not on both.
• Using the SIP ALG allows you to use bandwidth management on SIP traffic. Bandwidth management
can be applied to FTP ALG traffic. Use the option in the Configuration > BWM screen to configure the
highest bandwidth available for SIP traffic.
• The SIP ALG handles SIP calls that go through NAT or that the Zyxel Device routes. You can also make
other SIP calls that do not go through NAT or routing. Examples would be calls between LAN IP
addresses that are on the same subnet.
• The SIP ALG supports peer-to-peer SIP calls. The security policy (by default) allows peer to peer calls
from the LAN zone to go to the WAN zone and blocks peer to peer calls from the WAN zone to the
LAN zone.
• The SIP ALG allows UDP packets with a specified port destination to pass through.
• The Zyxel Device allows SIP audio connections.
Chapter 15 ALG
ZyWALL USG Series User's Guide
454