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Magnum 8000X Mixed-Media Fiber Hubs
With this large address table, SPM port modules can serve the needs of
medium-sized to large networks. The address tables are flushed periodically to update
the network status and to purge any inactive stations from the tables. See the figure and
table that follows:
Segment 1's packets are forwarded
when the destination addresses are
NOT in its address table.
Segment 1's packets are filtered
when the destination addresses are
in its address table.
Figure 2.5b: Forwarding vs. Filtering in SPM Modules
Packet
Source
Source
Address
Seg. 1
Not in table
Seg. 1
Not in table
Seg. 1
In table
Seg. 1
In table
Seg. 2
Not in table
Seg. 2
Not in table
Seg. 2
In table
Seg. 2
In table
Table 2.5: SPM Port Module Functionality
2.
Throughput Increase / Software Transparency
By selectively forwarding packets from the mixed-media hub's ports (or hub stack's
ports) to the rear-connector port based on its switching logic, an SPM increases the
available bandwidth for the users on both the hub side and the rear-segment side of the
network. As shown in Figure 2.5b, it keeps the local traffic on each side contained,
preventing unnecessary packets and bad packets from traveling to the other segment
and using up bandwidth needlessly. This results in more available network bandwidth
on both sides and a throughput increase for all users on both segments. An SPM needs
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Segment 1
(Bonus Port)
SPM Module
Destination
Address
Not in table
In table
Not in table
In table
Not in table
In table
Not in table
In table
11
Installation and User Guide (05/ 02)
Segment 2
(Inside of Hub)
Segment 2's packets are filtered
when the destination addresses are
in its address table.
Segment 2's packets are forwarded
when the destination addresses are
NOT in its address table.
Address Table
Maintenance
Add source to table
Add source to table
None
None
Add source to table
Add source to table
None
None
Filter/Forward
Action
Forward
Filter
Forward
Filter
Forward
Filter
Forward
Filter
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