GarrettCom DS50 - Manual (Page 31)

Magnum DS50 / DS60s Dual Speed Hubs Installation and User Guide (06/02)
Packet Source Destination Address Table Filter/Forward
Source Address Address Maintenance Action
10 Mbps
Not in table Not in table Add source to table Forward
10Mbps Not in table In table Add source to table Filter
10Mbps In table Not in table None Forward
10Mbps In table In table None Filter
100Mbps Not in table Not in table Add source to table Forward
100Mbps Not in table In table Add source to table Filter
100Mbps In table Not in table None Forward
100Mbps In table In table None Filter
Table 4.1: DS50 / DS60 Dual-Speed Hub Functionality
2. Address Learning (Address Table Maintenance)
The Magnum DS50 / DS60 bridge logic is a state machine design which has a total
address table capacity of 2K addresses. With a large address table, a Magnum DS50 / DS60 can
serve the needs of medium-sized to large networks. Table 4.1 shows what filter / forward
action the Magnum DS50 / DS60 will take in each packet-processing situation and when a new
node address will be added to the internal Address Table. When a new node-address packet
comes into a port for the first time, then the new source address is “learned” at the same time
that the packet is forwarded. After learning, subsequent packets from the same node address
are routinely processed. The address tables are flushed periodically to update the network status
and to purge any inactive stations from the tables of both domains.
3. Throughput Increase
By selectively forwarding packets from each domain to the other domain based on
its switching (bridging) logic, the Magnum DS50 / DS60 increases the available bandwidth for
the users on both sides of the network. As shown in Figure 4.1, it keeps the local traffic on each
side contained, preventing unnecessary packets and bad packets from traveling to the other
domain and using up bandwidth needlessly. This results in more available network bandwidth
on both sides and a throughput increase for all users on both domains.
4. Software Transparency
The Magnum DS50 / DS60 Dual-speed Hub need no software set-up and is
transparent to system and application software, including network management software.
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