ZyWALL ATP Series User’s Guide
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CHAPTER 15
UPnP
15.1 UPnP and NAT-PMP Overview
The Zyxel Device supports both UPnP and NAT-PMP to permit networking devices to discover each other
and connect seamlessly.
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. A gateway that
supports UPnP is called Internet Gateway Device (IGD). The standardized Device Control Protocol (DCP)
is defined by the UPnP Forum for IGDs to configure port mapping automatically.
NAT Port Mapping Protocol (NAT-PMP), introduced by Apple and implemented in current Apple
products, is used as an alternative NAT traversal solution to the UPnP IGD protocol. NAT-PMP runs over
UDP port 5351. NAT-PMP is much simpler than UPnP IGD and mainly designed for small home networks. It
allows a client behind a NAT router to retrieve the router’s public IP address and port number and make
them known to the peer device with which it wants to communicate. The client can automatically
configure the NAT router to create a port mapping to allow the peer to contact it.
15.2 What You Need to Know
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.
15.2.1 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.
See the NAT chapter for more information on NAT.
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