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MSP Switching Fails When OptiX OSN 3500 Interconnects with WDM Equipment

Publication Date:  2012-08-12 Views:  112 Downloads:  0
Issue Description

Four OptiX OSN 3500 NEs form an MSP ring, as shown in Figure 1.

Figure 1 Networking diagram 

Table 1 shows fiber connection between the NEs.

Table 1 Fiber connection between the NEs
Local End Opposite End
NE Name Slot Board Name Port NE Name Slot Board Name Port
NE141 7 N1SL16 1IN NE144 12 N1SL16 1OUT
NE141 7 N1SL16 1OUT NE144 12 N1SL16 1IN
NE142 7 N1SL16 1IN NE141 12 N1SL16 1OUT
NE142 7 N1SL16 1OUT NE141 12 N1SL16 1IN
NE143 7 N1SL16 1IN NE142 12 N1SL16 1OUT
NE143 7 N1SL16 1OUT NE142 12 N1SL16 1IN
NE144 7 N1SL16 1IN NE143 12 N1SL16 1OUT
NE144 7 N1SL16 1OUT NE143 12 N1SL16 1IN

During the MSP ring switching test, only NE-143 and NE-144 are successfully switched and switching for the other NEs fails.

Alarm Information
Handling Process

Modify the MSP ring into an SNCP ring and then perform the SNCP switching. The switching is normal.  

Root Cause

All the K1/K2 bytes received at the west board (7-SL16) on NE-144 are "0". As a result, NE-144 and the downstream NEs fail to receive the K1/K2 byte from the east board (12-SL16) on NE-143. Hence, it is determined that NE-143 and NE-144 may be faulty. Table 2 lists the received and transmitted K1/K2 bytes.

Table 2 Transmitted and received K1/K2 bytes
NE-144 K1/K2 KC KM NE-143 k1/k2 KC KM
Transmitted K1/K2 byte 0x0230 0xcd 0xd3 Transmitted K1/K2 byte 0x0320 0xdc 0xd3
Received K1/K2 byte 0x0000 0xff 0xff Received K1/K2 byte 0x0230 0xfd 0xcf

Refer to Table 1. It is found that NE-143 can receive the K1/K2 bytes from NE-144 normally. The received K1/K2 bytes, however, are always "0x0000" regardless of whether NE-143 transmits any K1/K2 bytes whose values are "0x0000". In addition, the KC and KM bytes are abnormal. NE-144 fails to receive the K1/K2 byte that is normally transmitted from NE-143. The K1/K2 bytes received in slot 7 on NE-144 are always "0x0000". In addition, it is found that WDM equipment is located between NE-143 and NE-144. Hence, it is suspected that the WDM equipment changes the K1/K2 byte from NE-143 to NE-144. At the same time, WDM equipment in other segments may also affect the K1/K2 bytes, especially the KC and KM bytes.

To check whether the WDM equipment between NE-143 and NE-144 changes the K1/K2 byte, do as follows:
  1. Connect an SDH analyzer to NE-143 and an SDH analyzer to NE-144. The connection is as follows: #144-7-------SDH analyzer 1-------WDM equipment------- SDH analyzer 2-------#143-12.
  2. Shut down the laser on the board in slot 7 on NE-144. Then, MSP switching occurs.
  3. Record the K1, K2, KC, and KM bytes that are read from SDH analyzer 1 and SDH analyzer 2. The test results shows that the bytes read by the two SDH analyzers are different. Hence, it is verified that the WDM equipment changes the overhead