GarrettCom 8000X - Manual (Page 19)

Magnum 8000X Mixed-Media Fiber Hubs Installation and User Guide (05/ 02)
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no software configuring and is transparent to system and application software, including
network management software.
2.5.1 Magnum SPM-FDST
The significant feature of the SPM-FDST is that the fiber
bonus port operates in full-duplex mode, sending packets on
one fiber filament while simultaneously and independently
receiving packets on the other. There is no “collision
domain” with full- duplex, and while this violates the specs
of traditional Ethernet, it is accepted in most situations.
Therefore, the SPM-FDST extends the distance limits of Fast
Ethernet. In particular, with multi-mode fiber, it permits Fast
Ethernet cable distances of up to 2km, much more than the 412m half-duplex distance
limit otherwise obtainable.
These SPMs can also be configured to operate as a half-duplex switch port.
As shown in the figure, the jumper located on the SPM board by default is factory set
to full-duplex mode (position 2-3).
By setting the jumper in position 1-
2, it will operate as shared (half
duplex). To operate properly in
either half- or full-duplex mode, the
device on the other end of the fiber
segment must also be a
corresponding device. Since full-
duplex Fast Ethernet (802.3x) is a
recent 1997 standard, it is
recommended that the device on the
other end of the segment be another
full-duplex fiber SPM or equal.
As is typical for bridges and switches, the internal packet buffer space of the
SPM-FDST temporarily stores unfiltered packets. It is desirable to have a large packet
buffer for temporary storage, particularly when operating at different speeds (such as 10
and 100) or with different traffic types (shared and full-duplex). The SPM-FDST packet
Magnum SPM-FDST
R X L IN K
FULL
DUPLEX
Magnum SPM-FDST
R X L IN K
FULL
DUPLEX
HALF FULL
DUPLEX MODE
1
HALF FULL
1
HALF DUPLEX
HALF FULL
1
FULL DUPLEX
(Default)
FULL/HALF JUMPER