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Cisco ONS 15454 SDH Reference Manual, R5.0
April 2008
Chapter 7 Card Protection
7.2 STM-N Card Protection
The ONS 15454 SDH automatically detects and identifies a 1:N protect card when the card is installed
in Slot 3 or Slot 15. However, the slot containing the 1:N card in a protection group must be manually
provisioned as a protect slot because by default, all cards are working cards.
7.2 STM-N Card Protection
With 1+1 port-to-port protection, any number of ports on the protect card can be assigned to protect the
corresponding ports on the working card. The working and protect cards do not have to be placed side
by side in the node. A working card must be paired with a protect card of the same type and number of
ports. For example, a single-port STM-4 must be paired with another single-port STM-4, and a four-port
STM-4 must be paired with another four-port STM-4. You cannot create a 1+1 protection group if one
card is single-port and the other is multiport, even if the STM-N rates are the same. The protection takes
place on the port level, any number of ports on the protect card can be assigned to protect the
corresponding ports on the working card.
For example, on a four-port card, you can assign one port as a protection port on the protect card
(protecting the corresponding port on the working card) and leave three ports unprotected. Conversely,
you can assign three ports as protection ports and leave one port unprotected.
With 1:1 or 1:N protection (electrical cards), the protect card must protect an entire slot. In other words,
all the ports on the protect card are used in the protection scheme.
1+1 span protection can be either revertive or nonrevertive. With nonrevertive 1+1 protection, when a
failure occurs and the signal switches from the working card to the protect card, the signal stays switched
to the protect card until it is manually switched back. Revertive 1+1 protection automatically switches
the signal back to the working card when the working card comes back online.
You create and modify protection schemes using CTC software. For more information, refer to the “Turn
up Node” chapter in the Cisco ONS 15454 SDH Procedure Guide.
7.3 Unprotected Cards
Unprotected cards are not included in a protection scheme; therefore, a card failure or a signal error
results in lost data. An unprotected configuration is sometimes called 1:0 protection. Because no
bandwidth is reserved for protection, unprotected schemes maximize the available ONS 15454 SDH
bandwidth. Figure 7-3 shows the ONS 15454 SDH in an unprotected configuration. All cards are in a
working state.