3Com ADSL Modem Ethernet - Manual (Page 19)

Advanced Bridging 3-3
The 3Com HomeConnect ADSL Modem Ethernet supports Unspecified Bit Rate
(UBR) traffic. The modem will normally attempt to use all of the available
upstream bandwidth when transmitting data. Optionally, on a bridge port basis,
the upstream traffic can be ’shaped’ to use only a portion of the available
bandwidth using the Peak Cell Rate parameter.
The Peak Cell Rate is specified in cell-per-second. Use the following formula to
determine the Peak Cell Rate to enter for a given throughput.
pcr_value = throughput / 3392
where:
throughput is the desired transmit rate in bits/second.
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To set the Peak Cell Rate use the command:
set port <port_number> pcr <pcr_value>
Advanced
Bridging
Remember to save your configuration using the save all command before
rebooting your 3Com HomeConnect ADSL Modem Ethernet so that your changes
will be written to permanent FLASH memory.
Advanced Bridging
Settings
Bridging is globally enabled by default, to disable bridging use the disable bridge
forwarding command.
The advanced bridging configuration options include Aging Time, Forward Delay,
Spanning Tree, and Spanning Tree Priority.
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To see the current settings for these options, use the command:
show bridge
Except for enabling Spanning Tree, most users do not need to change the
advanced parameters from their default settings.
The Aging Time is the time (in seconds) for aging out forwarding table
information.
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To change the Aging Time, use the command:
set bridge aging_time <seconds>
The Forward Delay is the time (in seconds) to wait while learning forwarding
information before starting to bridge packets.
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To change the Forwarding Delay, use the command:
set bridge forward_delay <seconds>
The Spanning Tree Protocol is used to eliminate network loops between bridges.
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To disable or enable Spanning Tree, use the commands:
disable bridge spanning_tree or
enable bridge spanning_tree