Marconi OMS 1200
Technical Product Description
221 02-ZAP 701 25/1 Rev C 2006-08-04
© Ericsson AB 2006
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Note:
Forced Switch can only be revoked by a Clear command or another
Forced Switch).
Note:
A subsequent failure of the selected core-unit does not cause traffic
to be selected from the other core-unit.
3
Clear.
Clears all the above forced switch commands.
The protection state of the currently selected core unit is displayed to you.
7.7.6
Protection Switching Control
7.7.6.1 Protection
Switching Operation
In a system configured for switch protection, there are two states for the selector at
each destination port, receiving traffic from Core A and receiving traffic from Core B.
The clock selected is derived from the same core unit as the selected traffic. Except
for a transient period between detection of a failure at one destination port and
switchover of all other destination port selectors, all selectors in the SMA are in the
same state.
The state of each selector on each peripheral tributary card/core line interface module
is governed by the state of core failure indications within the SMA and by commands
entered by the operator via the LCT (refer to the “LCT/LCTS Operating Procedures”
handbook). The state of the selectors is also affected by previous history, in that
switching is non-Revertive and the fault that instigated a changeover may no longer be
present.
An instruction to select a core unit received from the Multiplexer Controller overrides
all locally detected conditions.
In case of two or more detected failures, with (at least) one failure of each core
indicated, the selected core is chosen according to the first failure indication received
by the core unit. Any subsequent failure detections will not cause the destination ports
to switch to the unit that was first detected as having failed until all failures on that unit
are cleared.
With core switchplane protection operation, peripheral tributary cards select internal
traffic interfaces between Cores A and B. This is also true of the core cards’ own SDH
line interface modules. However, as discussed earlier, linear MSP/SNCP protection
schemes involving the core line interfaces will operate independently, if (say) a core
card fails or is removed.
In OMS1240, 2Mbit/s traffic is provided by the Core Tributary cards. Each Core Trib
Card is a dependant of the Core Card, such that the Core A Card is associated with
the Core A Trib and the Core B Card is associated with the Core B Trib. If a Core Card
Master/Slave status switch occurs, then Core Tributary worker status will switch in
common. This switch (controlled on the tributary cards) determines which Core Trib
drives traffic to and from the 2M PDH core tributary traffic LTUs. The result is that 2M
PDH traffic is affected when core protection switching occurs.
Version 1 Core Trib cards must be protected if the Core Cards are protected.
Version 2 Core Trib Cards can operate independently of the Master/Slave status when
only one Core Trib card is fitted. This allows for Core Trib cards to be unprotected
when the system has protected Core Cards.
