Local Network - Upnp; Local Network - Igmp Snooping - NetComm NB6 User Manual

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Local Network – UPnP
The UPnP is only available for Windows XP/Vista/7. If you are not a Windows XP/Vista/7 user, you may
ignore this page.
Enabling the UPnP IGD and NAT traversal function allows the users to perform more applications
behind NAT without additional configuration settings or ALG support on your ADSL Router.
You can enable the UPnP function through this web page by checking Enable UPnP and press Apply.
Local Network – IGMP Snooping
Traditionally, IP packets are transmitted in one of either two ways - Unicast (1 sender to 1 recipient) or
Broadcast (1 sender to everyone on the network). Multicast delivers IP packets to just a group of hosts
on the network.
Without IGMP snooping, multicast traffic is treated in the same manner as broadcast traffic, that is, it
is forwarded to all ports. With IGMP snooping, multicast traffic of a group is only forwarded to ports
that have members of that group. IGMP snooping generates no additional network traffic, allowing you
to significantly reduce multicast traffic passing through your switch.
The figure below shows a simple network connected via this ADSL router. There are four Ethernet
clients, one using USB, and two wireless clients.
Now suppose the video server is the multicast transmitter and host A and D are multicast receivers. If
we do not turn on the IGMP snooping function, the router will forward the multicast traffic to all hosts
on all interfaces and consequently block and interrupt the traffic of USB and wireless users, shown as
the following figure.