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Magnum 8000X Mixed-Media Fiber Hubs Installation and User Guide (05/ 02)
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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:
Packet Source Destination Address Table Filter/Forward
Source Address Address Maintenance Action
Seg. 1 Not in table Not in table Add source to table Forward
Seg. 1 Not in table In table Add source to table Filter
Seg. 1 In table Not in table None Forward
Seg. 1 In table In table None Filter
Seg. 2 Not in table Not in table Add source to table Forward
Seg. 2 Not in table In table Add source to table Filter
Seg. 2 In table Not in table None Forward
Seg. 2 In table In table None Filter
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
Figure 2.5b: Forwarding vs. Filtering in SPM Modules
Segment 1’s packets are forwarded
when the destination addresses are
NOT
in its address table.
Segment 2’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.
Segment 2’s packets are filtered
when the destination addresses are
in its address table.
SPM Module
100
1
0
Segment 1 Segment 2
(Bonus Port)
(Inside of Hub)