Specifications

December 2008 Page 5–7
Chapter 5. Alternate Path Mode (APM)
5
Bad, Fail Direction: XCVR1-2.” will be
logged.
• APM Status of Node 565 will be FLIPPED,
FLIPPED LED will be ON. Target “APM
Loop 1 Going FLIPPED.” will be logged.
• APM Status of Node 140 will be FLIPPED,
FLIPPED LED will be ON. Target “APM
Loop 1 Going FLIPPED.” will be logged.
• No Channels will be rerouted.
Figure 5–1. APM Re-routing Example.
5.1.4.4 Alternate Path Mode with PLD
Modules
If you want to use APM with PLD modules, you
should not use DS0 channel 24 (30/E1) for the
PLD. This is because the algorithm for “Flipping”
PLD channels when a link goes down is to use an
additional channel. The channel used for this is the
current PLD DS0 assignment channel plus one.
Thus, if channel 24/30 is used as the primary
channel for PLDs, alternate path will not work for
the PLD chain.
5.1.4.5 Spur Applications
APM supports the rerouting of broken channels
entering a ring via a third or fourth transceiver.
5.1.4.6 Using the “Disable Auto-sync”
Feature
The “disable Auto-sync” feature is one of your
options when defining an APM loop (see
“Defining APM Loops” earlier in this chapter).
Selecting the feature is as simple as clicking on
the checkbox for the “Disable Auto-sync into
loop” field in the “APM Loop Definition” dialog
box. But when should you select this feature?
Typically, you should select the “disable Auto-
sync” feature whenever the data leaving the loop
is more important than the data moving within the
loop. The exception is when either side of the loop
you are defining is the same as the programmed
sync direction (i.e., the “Sync on” direction
checked on the FCS Mode menu). In these cases,
selecting the “disable Auto-sync” feature causes
the chassis to not switch to the appropriate
slave/master mode when a break is in this loop.
With the default setting, Auto-sync enabled (i.e.,
the “Disable Auto-sync into loop” field is not
checked), the APM function automatically
changes the synchronization direction toward the
broken loop. This technique minimizes sync slips
within the broken loop, but increases the likeli-
hood of sync slips at any spurs or second loops.
This is desirable if the data within the loop is more
important than the data leaving the loop.
The following examples show an APM loop
during normal operation and the results of a break
in the loop with the “Disable Auto-sync into loop”
feature both selected (disabled) and not selected
(enabled).