CANOGA PERKINS 9119 Rack Mount 100BASE-TX/FX Media Converter - Manual (Page 15)

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9119 Media Converter Canoga Perkins
Figure 2-6
Fiber Break Responses
2.4.3 10/100 Auto Negotiation Application Note
The 100BASE-FX specification for fiber optic interfaces as implemented in the 9119 media converter, does not provide
support for the auto negotiation of speed or mode. Therefore, any attachment to the 9119 fiber optic interface must be
100Mbps. The 9119 optical interfaces are fixed Full-duplex (FDX) devices that also support half-duplex (HDX) port attachments.
While the 9119 supports the 100BASE-TX interface specifications for speed and mode, it does not implement the N-Way
auto negotiation feature that communicates speed and mode changes (10 to 100Mbps and HDX to FDX) between UTP
interfaces. In order to support N-Way speed changes, packet buffering, which flow controls frames from the 100Mbps
interface down to a 10Mbps interface, must be implemented for normal operation. Since packet buffering is typically em-
ployed in layer 2 switches, and not the physical layer, the 9119 does not provide buffering, cannot support speed changes
and must operate at 100Mbps.
Since N-Way auto negotiation is normally implemented in 100BASE-TX switch interfaces, if left to auto negotiate with the
9119 fixed interface, there is a strong likelihood that it will default to HDX operation rather than FDX. Since most 100Mbps
circuits require FDX data transfer for optimal operation, defaulting to the lowest speed (100Mbps in the case of the 9119)
and lowest mode, (HDX rather than FDX) can potentially cause operational issues.
Therefore, where practical, rather than allow the interface to auto negotiate with the fixed 9119 UTP interface, it is recom-
mended that the switch interface be set to 100Mbps and the users choice of mode (HDX/FDX).
2.4.4 Fiber Link Loss Forwarding Application Note
The 9119 Media Converter incorporates a Fiber Link Loss Forwarding feature which allows indirect sensing of a Fiber Link
Loss via the 100BASE-TX UTP connection. Whenever the 9119 Media Converter detects a Link Loss condition on the
Receive fiber (Fiber LNK OFF), it disables its UTP transmitter so that a Link Loss condition will be sensed on the UTP port
to which the 9119 Media Converter is connected. (See Figure 2-6). This link loss can then be sensed and reported by a
Network Management agent in the remote UTP port's host equipment.
This feature has no effect on the 9119s UTP LNK LED, which continues to function normally, independent of the state of
the Fiber LNK LED and the UTP transmitter.
NOTE: Some UTP interfaces will disable the transmission of idle signals towards the 9119, when a loss of link from
the 9119 is detected. The 9119 does not disable the UTP Port and will show link if the attached UTP interface
continues to send good link pulses.
In addition, the 9119 will invoke LLF when a legitimate remote fault alarm (RMTF) is received from the
remote 9119. This implies that the local 9119 transmitter, remote receiver, or cable between the two, is
faulty.