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Cisco ONS 15454 DWDM Reference Manual, R8.5
78-18343-02
Chapter 8 Transponder and Muxponder Cards
8.13.1 Y-Cable Protection
To create Y-cable protection, you create a Y-cable protection group for two TXP, MXP, GE_XP or
10GE_XP cards using the CTC software, then connect the client ports of the two cards physically with
a Y-cable. The single client signal is sent into the RX Y-cable and is split between the two TXP, MXP,
GE_XP or 10GE_XP cards. The two TX signals from the client side of the TXP, MXP, GE_XP or
10GE_XP cards are combined in the TX Y-cable into a single client signal. Only the active card signal
passes through as the single TX client signal. The other card must have its laser turned off to avoid signal
degradation where the Y-cable joins.
When an MXP_MR_2.5G, MXP_MR_10DME_C, or MXP_MR_10DME_L card provisioned with
Y-cable protection is used on a storage ISL link (FC1G, FC2G, FC4G, FICON1G, FICON2G, or
FICON4G), a protection switchover resets the standby port to active. This reset reinitializes the
end-to-end link to avoid any link degradation caused due to loss of buffer credits during switchover. This
results in an end-to-end traffic hit of 15 to 20 seconds.
Use the TXP_MR_2.5G card to avoid the 15 to 20 second traffic hit. When a Y-cable protection
switchover occurs, the storage ISL link does not reinitialize and results in an end-to-end traffic hit of less
than 50ms.
Note Y cable connectors will not work with copper SFPs as Y cable is made up of optical connectors and their
is no way to physically connect this to a copper SFP.
Note There is a traffic hit of upto a couple hundred milliseconds on the MXP_MR_2.5G and
MXP_MR_10DME cards in Y-cable configuration when a fiber cut or SFP failure occurs on one of the
client ports.
Note If you create a GCC on either card of the protect group, the trunk port stays permanently active,
regardless of the switch state. When you provision a GCC, you are provisioning unprotected overhead
bytes. The GCC is not protected by the protect group.
Figure 8-29 shows the Y-cable signal flow.
Note Loss of Signal–Payload (LOS-P) alarms, also called Incoming Payload Signal Absent alarms, can occur
on a split signal if the ports are not in a Y-cable protection group.
Note Removing an SFP from the client ports of a Y-cable protection group card causes an IMPROPRMVL
(PPM) alarm. The working port raises the CR,IMPROPRMVL,SA alarm and the protected port raises
the MN,IMPROPRMVL,NSA alarm. The severity on the client ports is changed according to the
protection switch state.
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