GarrettCom 500-Series User Manual
Page 12
Magnum 500-Series Switching Hubs
Installation and User Guide (08/98)
GARRETT
7
2.2.3 100Mb/s Fiber Port, ST or SC type (Single-Mode or Multi-Mode) 100Mb1@
1 @ 100Mb Fiber port, type ST or SC (Magnum 528F models only)
The two Fast Ethernet switched ports on the Magnum 528F normally are set (by factory
default) to operate at fixed 100Mb speed for guaranteed high-speed performance. The
528F’s fiber ports can be connected using a multi-mode ST, SC or single-mode ST, SC
connector. In the factory-default setting, each of the 100Mb RJ-45 ports and/or the
100Mb Fiber port will run at 100Mb/s speed at all times
On the Magnum 528 and 528F models, the user may select full- or half-duplex
mode per-port with a manual switch for flexibility to adapt to any type of Fast Ethernet
devices. The Full/Half-duplex manual switches are located on the front panel under the
corresponding Fast Ethernet ports for convenient access.
On Magnum 528F units, there are three LED’s per Fiber Optic port. One (LK)
indicates ready for operation at 100Mb when lit, one indicates operation in full-duplex
mode when ON (when it is OFF, operation is half-duplex), and one indicates Receiving
Activity (RX). A fiber cable must be connected to each 100Mb port and a proper link
(LK lit) must be made with the device at the other end of the cable in order for these
LEDs to provide valid indications of operating conditions.
2.2.3
Frame Buffering and Latency
The Magnum 500-Series are store-and-forward switches. Each frame (or
packet) is loaded into the Magnum 500’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
PWR
RX
LK
AUTO
F/H
F
H
F
H
L K RX
F/H
100
10
TX
RX
100 M b
ST Connector (Magnum 528F-ST)
SC Connector (Magnum 528F-SC)
PWR
RX
LK
AUTO
F/H
F
H
L K RX
F/H
100
10
TX
RX
100 M b