Black Box Mixed-Media Fiber Hubs
Installation and User Guide (4/99)
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4.0 Operation
The operation of the LH8050A is described in this section.
4.1 Repeater
Functionality
The LH8050A operates as a Mixed-Media Ethernet Hub to support multiple port
segments within two (10 and 100Mbps) collision domains. The following describes
the basic functionality of the LH8050A Fiber Hub.
1. Repeater Functions:
Each front port operates in conjunction with the controller
functions of the LH8050A chassis as a fully compliant Ethernet repeater. The entire
hub (or a stack of multiple units) counts as a single Dual-Speed repeater.
2. Collisions:
When a collision is detected at a port other than the original receiving
port, it generates a jam pattern to the other ports in that domain. When a collision
signal is detected at a receiving port, it generates a jam pattern to the other ports. The
sequence of jam signals depends on the sequence and location of collisions.
3. Partitioning and Re-connection:
An LH8050A will automatically disconnect
(partition) any segment (port) when 64 consecutive collisions occur or after 6.5 ms of
continuous transmissions. Network integrity is checked every 800 ms and segment
(port) reconnection occurs after a 512-bit packet is transmitted without error.
4. Link Status:
The LH8050A PMs indicate link integrity for fiber optic and
twisted pair segments. LINK is normally lit. Broken cables or a loss of power at any
point in such segments will turn off the LINK LED.
4.2 Dual-Speed
Functionality
The LH8050A handles the two different traffic domains separately . The LH8050A
provides switched (bridged) connectivity between the Ethernet (10 Mbps) and Fast Ethernet
(100Mbps) domains. It joins the two network domains for unified operation, and filters/
forwards packets in both directions to maximize bandwidth utilization and performance.
LH8050As are hardware plug-and-play devices. There is no software set-up to be done at
installation or for maintenance. The functions of the LH8050A are described in this manual.
Each time a packet is received on one domain of the bridge module, the decision is
taken to either to filter or forward the packet. Errored packets are always filtered. For good
packets, the filter and forward decisions are made based on the destination address contained in
each packet. If the destination address is on the same domain from which the packet originated,
then it is filtered and not forwarded to the other domain. If the destination address is not found
