User`s guide

14 Metrobility 10/100Mbps Delta Class AutoTwister
Factory Settings
This section describes the preset features on the 10/100Mbps Delta
Class AutoTwister. These settings cannot be changed.
Full-Duplex Flow Control
The AutoTwister supports flow control on each port in full duplex only.
Full-duplex flow control is provided to avoid dropping packets during
network congestion. If there is no buffer space available for incoming
packets, the AutoTwister will issue a PAUSE frame. Full-duplex flow
control is only applicable to ports operating in full duplex with auto-
negotiation enabled. Additionally, during auto-negotiation, the port’s link
partner must advertise that it supports PAUSE frames.
For ports operating at half duplex, the AutoTwister does not support any
type of flow control. If there are not enough buffers available, incoming
packets will be dropped.
Auto-Recovery
The AutoTwister includes an auto-recovery circuit that allows you to
transparently connect a pair of AutoTwisters between two network
devices. This enables you to design a redundant path between 10Mbps
and 100Mbps devices, allowing both end devices to detect link loss if any
part of the connection fails.
To activate auto-recovery, all of the following conditions must be met:
• Auto-negotiation is disabled.
• LLR is enabled.
• LLCF is enabled.
When auto-recovery is enabled, the AutoTwister attempts to establish the
fiber link between two back-to-back units. When LLR is enabled on two
adjoining AutoTwisters, it creates a deadlock situation with each fiber
port waiting for the other to transmit first. Auto-recovery breaks the
deadlock by periodically sending out pulses from the fiber port allowing
the AutoTwister to reestablish its fiber link.