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Magnum P62-Series Hardened Switches Installation and User Guide (11/03)
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On Magnum P62-Series units, there are three
LED’s for each of the RJ-45 switched ports. The F/H
indicates full-duplex when ON or half-duplex when OFF.
The (LK/ACT) LED is steady ON to indicate LINK, and
blinking to indicate transmitting / receiving. The 10/100
LED is ON for 100Mbps and OFF for 10 Mbps (when LINK
is made). For fiber ports, the LEDs are the same except there
is no F/H LED because 10Mb is not possible.
There must be a device connected to the Magnum
P62-Series unit via a cable. A proper link (LK light) must be made between both devices at each
end of the cable in order for each LINK LED to provide a valid indication of operating
conditions.
2.4 Frame Buffering and Latency
The Magnum P62-Series Hardened Switch is a store-and-forward switch. Each frame
(or packet) is loaded into the Switch’s memory and inspected before forwarding can occur. This
technique ensures that all forwarded frames are of a valid length and have the correct CRC, (i.e.,
are good packets). This eliminates the propagation of bad packets, enabling all of the available
bandwidth to be used for valid information.
While other switching technologies such as "cut-through" or "express" impose minimal
frame latency, they will also permit bad frames to propagate out to the Ethernet segments
connected. The "cut-through" technique permits collision fragment frames, which are a result of
late collisions, to be forwarded to add to the network traffic. Since there is no way to filter frames
with a bad CRC (the entire frame must be present in order for CRC to be calculated), the result of
indiscriminate cut-through forwarding is greater traffic congestion, especially at peak activity.
Since collisions and bad packets are more likely when traffic is heavy, the result of store-and-
forward operation is that more bandwidth is available for good packets when the traffic load is
greatest.
To minimize the possibility of dropping frames on congested ports, each Magnum P62-
Series Hardened Switch dynamically allocates buffer space from an 1MB memory pool, ensuring
that heavily used ports receive very large buffer space for packet storage. (Many other switches
have their packet buffer storage space divided evenly across all ports, resulting in a small, fixed
number of packets to be stored per port. When the port buffer fills up, dropped packets result.)
This dynamic buffer allocation provides the capability for the maximum resources of the Magnum
P62-Series unit to be applied to all traffic loads, even when the traffic activity is unbalanced
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