GarrettCom 8000X User Manual
Page 18
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
10
0
10
Segment 1
Segment 2
(Bonus Port)
(Inside of Hub)