User manual

WI-MOD-9-E Wireless Ethernet User Manual
WI-MOD-9-E Manual V1.9 Page 32
3.7 Normal Operation
After addresses are configured, the units are ready for operation.
Refer to Section 1 for an explanation on the operation of a Bridge and Router.
Transparent Bridge Operation
Bridges are typically used to connect sections of the same IP network together.
By default, the WI-MOD-9-E is configured as a transparent bridge. When a transparent bridge is
started, it learns the location of other devices by monitoring the source address of all incoming
traffic. Initially it forwards all traffic between the wired Ethernet port and the wireless port,
however by keeping a list of devices heard on each port, the transparent bridge can decide which
traffic must be forwarded between ports - it will only transfer a message from the wired port to
the wireless port if it is required.
A bridge will forward all Broadcast traffic between the wired and wireless ports. If the wired
network is busy with broadcast traffic, the radio network on the WI-MOD-9-E can be
unnecessarily overburdened. Filtering may be used to reduce broadcast traffic sent over the radio.
Refer Section 3.10 for how to configure a filter.
A transparent bridge does not handle loops within the network. There must be a single path to
each device on the network. Loops in the network will cause the same data to be continually
passed around that loop. Redundant wireless links may be set up by using the Spanning Tree
Algorithm function - refer to section 3.9.
Router Operation
A router joins separate Ethernet networks together. The router has different IP addresses on its
wired and wireless ports, reflecting the different IP addresses of the separate Ethernet networks.
All the devices in the separate networks identify the router by IP address as their gateway to the
other network. When devices on one network wish to communicate with devices on the other
network, they direct their packets at the router for forwarding.
As the router has an IP address on each of the networks it joins, it inherently knows the packet
identity. If the traffic directed at the router can not be identified for any of the networks to which
it is connected, the router must consult its routing rules as to where to direct the traffic to.
The WI-MOD-9-E has one routing rule which may be configured. This routing rule is the
gateway address. The WI-MOD-9-E will direct all unknown IP network traffic to this gateway IP
address.
3.8 Spread-Spectrum Operation
The WI-MOD-9-E operates on the 902-928MHz license-free radio band using a frequency-
hopping spread-spectrum technique. Devices on this radio band must use a spread spectrum
technique to allow multiple users to share the band with minimal interference. The Access Point
changes frequency (hops) in a specific sequence, and the Clients linked to it hop with it.