Cooper Bussmann Wireless Ethernet & Device Server BU-945U-E 802.11 DSSS User Manual
3.6 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
A bridge connects several Ethernet networks together, and makes them appear as a single Ethernet network to higher protocol layers.
By default, the BU-945U-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 BU-945U-E can be unnecessarily overburdened. Use filtering to reduce broadcast traffic sent over the radio. Refer Section 3.13 “Wireless Message Filtering” for how to configure a filter.
By default, 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 enabling the bridge Spanning Tree Protocol (see section 3.10 “Spanning Tree Algorithm / Redundancy” for more details).
Router Operation
A router joins separate IP sub-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 of the devices in these 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. For details on configuring routing rules, see section 3.12 “Routing Rules.”
3.7 Radio Configuration
The BU-945U-E can be configured for different radio transmission rates. A reduction in rate increases the reliable range (transmission distance). The factory-default data rate settings are suitable for the majority of applications and should only be modified by experienced users.
The BU-945U-E allows for a configurable fixed rate or an Auto radio transmission rate. When a fixed rate is configured the radio transmission rate is never altered, even under extremely poor conditions. The Auto rate will automatically change the radio data rate to give the best throughput. When a radio transmission is unsuccessful the BU-945U-E will automatically drop to the next lowest data rate and if subsequent transmissions are successful at the lower rate, the BU-945U-E will attempt to increase to the next highest rate. When a station connects to an access point the two devices negotiate a data rate based which is within configured range of radio data rates for both devices.
