ZyXEL Communications MAX318M2W, User Manual

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Chapter 7 Network Settings
MAX318M2W User’s Guide
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the computer that sent the request. After that computer’s connection for that
service closes, another computer on the LAN can use the service in the same
manner. This way you do not need to configure a new IP address each time you
want a different LAN computer to use the application.
ALG
Some applications, such as SIP, cannot operate through NAT (are NAT un-friendly)
because they embed IP addresses and port numbers in their packets’ data
payload. Some NAT routers may include a SIP Application Layer Gateway (ALG).
An Application Layer Gateway (ALG) manages a specific protocol (such as SIP,
H.323 or FTP) at the application layer.
A SIP ALG allows SIP calls to pass through NAT by examining and translating IP
addresses embedded in the data stream.
UPnP
Universal Plug and Play (UPnP) is a distributed, open networking standard that
uses TCP/IP for simple peer-to-peer network connectivity between devices. A
UPnP device can dynamically join a network, obtain an IP address, convey its
capabilities and learn about other devices on the network. In turn, a device can
leave a network smoothly and automatically when it is no longer in use.
How do I know if I'm using UPnP?
UPnP hardware is identified as an icon in the Network Connections folder
(Windows XP). Each UPnP compatible device installed on your network will appear
as a separate icon. Selecting the icon of a UPnP device will allow you to access the
information and properties of that device.
NAT Traversal
UPnP NAT traversal automates the process of allowing an application to operate
through NAT. UPnP network devices can automatically configure network
addressing, announce their presence in the network to other UPnP devices and
enable exchange of simple product and service descriptions. NAT traversal allows
the following:
• Dynamic port mapping
• Learning public IP addresses
• Assigning lease times to mappings
Windows Messenger is an example of an application that supports NAT traversal
and UPnP.
Cautions with UPnP