Description of the problem

After enabling the ASON clock in the ASON network, the customer found that some of the network elements tracked the internal clock source and the network elements entered the free oscillation mode. The network element version is: V1R10C01SPC100 (5.21.20.31).

Alarm Message

CLK_NO_TRACE_MODE MN start 2011-12-14 13:42:14 None 0x01 0x00 0x01 0xff 0xff

Processing

This issue has been resolved in V1R8C02SPC500 and V1R10C03SPC100. It is recommended that customers can simply use one of the following solutions:

1. Don't use smart clock for the whole network, change to normal clock mode.

2. Upgrade the network element to V1R10C03SPC100 and later versions.

3. Replace the docking optical port with a 1-optical port, or use a different veneer.

Root cause

1. After enabling the intelligent clock, the intelligent platform will assign each network element a unique clock tracking path, and the network element can only track the clock source on this path. And the low 4 bits of the S1 byte on this path are set to f (the high 4 bits are the quality of the clock source), such as 0xf2.

Query the current clock source S1 information of the problematic network element and find that no such S1 value exists:

#5-7:szhw [Blnb-S3.DXC64.1201 ][][2011-12-16 12:49:24+01:00]>

:cfg-get-alls1:9

ALL-SYN-S1

SYN-SOURCE S1-VALUE

0x0801 QL_DNU

0x0802 QL_DNU

0x0b01 QL_DNU

0x1a01 QL_PRC

0x1d01 QL_PRC

0xf101 QL_SEC

Total records :6

#5-7:szhw [Blnb-S3.DXC64.1201 ][][2011-12-16 12:49:21+01:00]>

Querying the S1 reported on the line veneer.

:optp:9,0,90,1,0e,50

Optp cmd : 0e50

00 06 08 01 0f 08 02 0f 0b 01 0f 1a 01 02 1d 01 02 f1 01 0b

2. Query the smart clock path and find that it should be tracking the 1 optical port of the 8-slot circuit board (Clock Path Piece Attachment).

:cspf-get-curr-clkpath

CSPF_CURRENT_TRACK_PATH

node id board/port

1.1.5.3 0xf001

1.1.5.16 0x0b01

1.1.5.7 0x0802

Total records :3

3. Query the S1 value of the optical port receive clock of 8-slot board 1 is 0f, which is not the S1 value required by the intelligence:

#5-7:szhw [Blnb-S3.DXC64.1201 ][][2011-12-16 12:51:12+01:00]>

:optp:8,0,9b,1,09,13,0

Optp cmd : 0913

00 0f 0f

4. query upstream 1.1.5.16 Network element 11 slot 1 optical port receive S1 value is 02, which is also not the intelligent required S1 value:

#5-16:szhw [Pra-S1.DXC64.1201 ][][2011-12-16 20:07:20+08:00]>

Query receive S1 for all optical ports

:optp:b,0,9b,1,09,13,0

Optp cmd : 0913

00 02 0b

5. query the base site 1.1.5.3 for the transmit S1 value of slot 7 optical port 2 as f2, which is exactly the S1 value of the smart clock. While the downstream optical port is erroneously receiving the S1 value of optical port 1:

#5-3:szhw [Ffm-S1.DXC64.1201 ][][2011-12-16 12:55:45+01:00]>

:optp:7,0,9b,1,09,11,0

Optp cmd : 0911

00 02 f2

Query this board as SSN4SLD64

#5-3:szhw [Ffm-S1.DXC64.1201 ][][2011-12-20 09:47:33+01:00]>

:cfg-get-phybd

PHY-BOARD

BID BOARD-TYPE

3 ssn1ems4

4 ssn1eas2

5 ssn4slq16

6 ssn1sf64

7 ssn4sld64

9 sst1sxcsa

6. Due to a defect in the SSN4SLD64 single-board software, the S1 value sent by the second optical port will be the same as that of the first optical port. When the downstream network element tracks the clock of the second optical port of the N4SLD64, the S1 value does not reflect the real clock situation of the current network element resulting in the downstream network element judging the S1 value to be incorrect, so that the downstream network element is unable to track the clock and enters the free oscillation mode to report the alarm.

Suggestion and Summary

1. smart clock tracking process:

a.After configuring the intelligent clock information, the intelligent will flood the clock information in the group network routing domain.

b. Each network element receives the update information of the intelligent clock, and starts the algorithm to calculate the optimal clock tracking path

c.After successful calculation of the intelligent clock, the host is notified to switch the clock, thus completing the automatic configuration of clock tracking.

When the intelligent clock information changes, or there are fiber optic interruptions, segment level error codes reported, the change information will flood to the whole network, each network element will recalculate the clock tracking relationship and automatically adjust, always ensure that the current clock tracking relationship is optimal.

2. The shortcomings of intelligent clock reversal:

Traditional clock reversal conditions are RLOS, MSAIS, B2EXC, but MSAIS, B2EXC default is not as clock reversal conditions, unless set manually. The smart clock will recognize these as reversal conditions, and can not be set. From the above smart clock tracking process can be seen, the smart clock is characterized by the configuration of the basic relationship between the clock, the smart domain tracking relationship does not need to be configured, the smart will be like re-routing the same way as the calculation of the tracking path, and in the optical fiber or after the report of the error code and then re-calculate the tracking relationship and sent to the host. In this way, when the fiber quality is unstable and there are frequent BERs, it will trigger the smart to keep sending trace relationship changes, resulting in S1 alarms. Therefore, the intelligent clock is suitable for use in the fiber quality is more stable, less BER, even if the interruption is the real interruption of the cable to use, is not suitable for the use of more BER network.

This chapter of related technical information and SDH equipment troubleshooting process is collected and organized by Shenzhen Optical Transmission Network Technology Co. Our company specializes in Huawei SDH optical transmission equipment, SDH transmission equipment sales.