A Core Competence Product Evaluation
What is Port Switching?
Basic managed Ethernet
repeater capabilities allow all Ethernet end stations
to share bandwidth over a single LAN segment.
The PS Hub 40 provides port switching across 4
internal LAN segments. Port switching refers
to the ability to assign end stations
connected to the hub to more than one LAN
segment. Each of the four internal LAN
segments of the PS Hub 40
provides a 10 Mbps shared Ethernet environment
for endstations assigned to that segment. (Note
that in an IP environment this has the effect of
creating multiple IP subnets). The four LAN segments can
be shared across as many as ten stacked port switching
hubs through cascade ports on the rear of the unit.
For our tests, we assigned ports to two internal segments (red
and blue), and connected these segments to a SuperStack II Switch
1000 using crossed Ethernet cables. As we had done with the
Switch
1000 for previous testing, we provided level 3 (IP) connectivity
between the two IP subnets using a dual-port Ethernet router (cisco 2514).
Port switching provides several attractive advantages
over the simpler repeater technology. First, moves,
adds and changes can be performed remotely using the
Transcend Quick Configuration Manager.
An endstation connected to any physical port termination
can be logically assigned to any of
four LAN segments. Each internal LAN segment in the port switching hub
operates as a separate repeater and provides an unique
collision domain, so only those end stations assigned to a given internal LAN
segment compete for bandwidth offered by that segment.
When cascade ports are used to connect or "stack" multiple
port switching hubs, shared Ethernet ports can be
assigned to any of the 4 LAN segments across the entire
set of interconnected hubs, so workgroups can be
extended across an enterprise network. This simplified
form of virtual LANs offers an inexpensive and unintimidating way
to migrate shared LAN segments to a microsegmented
or switched LAN environment, and complements the VLAN
capabilities of Ethernet switching products in the SuperStack II
series (see our evaluations of the SuperStack II
Switch 1000 and Desktop Switch).
The collision domains of the four internal LAN segments
persist across cascaded segments. Traffic flows across cascaded
ports are contained within cascaded segments so one busy segment does not interfere
with the performance of another. 