SDH alarm Performance Analysis

1. Los: Alarm for signal loss
It indicates that the local end cannot receive light or electrical signals. When the signal amplitude remains below a preset threshold value (the threshold value is very small, far lower than or equal to 10-3) within a given time (for example, 100 ms, the SDH device enters the Los state. If two consecutive valid frame locating patterns are detected and no los is detected, the SDH device should exit the Los state.

(1) optical port los:
Network Management alarm: Light receiving signal loss, low light input.
The main cause is:
① Optical Cable disconnection, optical cable failure or optical cable failure;

② The opposite end does not send optical signals;
③ The local optical transceiver is broken;
④ The optical transceiver power is not within the indicator range of the optical transceiver module.

Solution:
① Use an Optical Fiber Self-ring for the local end first (the self-ring must ensure that the optical power of the receiving port is within the sensitivity and overload point range). If the alarm disappears, it indicates that the local end is good, the problem lies at the peer end. If the peer self-ring is good, the optical fiber between the two ends is definitely broken. (Note: The degree of tightening of the flange connection directly affects the optical power sending and receiving)

② If the end-to-end self-ring is not good, it is also a los alarm. The optical power meter is used to measure the optical power. If the power is too small
(-50 dB or lower) it can be determined that the optical fiber is broken;
③ If the power is normal, it is caused by no clock. If the clock board is replaced, the alarm disappears;
④ If the local self-loop or Los alarm occurs, the light receiving module is broken and the alarm disappears after the switch.
(2) Electrical port los:
Network Management alarm: 2 M terminal (receive) signal loss.
Check whether there is a signal sent from the interface to the SDH device on the PDH side. If the branch board does not receive the input signal, it detects that the signal level uploaded from the 2 M interface box has not changed for a period of time.
Los is only related to the local network element, which is generally due to the following reasons:
Interface cable error or poor contact with the interface box. In special circumstances, if a hardware fault occurs on the branch board of 2 MB, the above two types of alarms may occur.
2. Oof Frame loss, lof Frame loss, and Lom Frame loss
A1 and A2 have a fixed value, that is, a fixed bit pattern. A1: 11110110 (F 6 h), A2: 00101000 (28 h ). The receiver detects each byte in the signal stream. When n f 6 h records are found consecutively, and followed by the emergence of N 26h bytes (in the STM-1 frame A1 and A2 bytes have 3), it is concluded that now began to receive a STM-N frame, the receiving end identifies different STM-N frames by locating the starting point of each STM-N frame to separate different frames. When n = 1, The STM-1 frame is distinguished.

When more than five consecutive frames (US) fail to receive the correct A1 and A2 bytes, that is, more than five consecutive frames cannot identify the frame header (separate different frames ), then, the receiving end enters the frame out-of-progress state, and generates a frame out-of-Progress alarm-Oof; If oOf continues for 3 ms, it enters the frame loss State-the device generates a frame loss alarm LOF, and the SDH device inserts the AIS signal downward, the entire business is interrupted. In the lof State, if the receiver is in the Fixed Frame State for more than 1 ms, the device returns to the normal state.

Network Management alarm: There are oOf and lof alarms on the optical board.
The main cause is:
① Optical Cable disconnection or optical cable failure;
② Clock;
③ Start optical module;
④ Receiver optical module;
⑤ Cross Board;
6. Backplane (2.5 GB ).
Processing Method: Same optical port los processing.
3. Lop pointer loss
When a specified number of times continuously occurs for conditions that cause uncertain pointer values, the SDH device enters the Lop state. The SONET standard clearly stipulates [4] that the device enters the Lop state when a valid pointer is found for eight consecutive frames or eight consecutive NDF is detected. When a valid pointer or cascade indicator with a normal NDF is detected for three consecutive frames, the device should exit the Lop state.

Generally, it is generated along with lof and oof. pointers include au ptr and Tu PTR.
Network management warning: pointer loss Detected
The main cause is:
① Optical Cable disconnection or optical cable failure;
② Clock Board;
③ Cross Board;
④ Light board;
⑤ Backboard (2.5 GB ).
Solution:
4. AIS Alarm Indication signals: including MS-AIS, Au-AIS, and Tu-AIS.
(1) MS-AIS:
Multiplexing range alarm signal (MS-AIS): utilizes K2 (b6-b8) overhead bytes.
The multiplexing period alarm signal refers to the STM-N signal that contains valid rsoh and the rest of the signal is "1.
Reuse segment Remote Defect indication (MS-RDI) byte: K2 (b6-b8 ).
This is a message sent back from the receiver (sink) to the sender (source), indicating that the receiver detects a fault or is receiving an alarm signal for the reuse segment. That is to say, when the receiving end receiving deterioration, then back to the sender MS-RDI alarm signal, so that the sender knows the receiving end status. If the received K2 b6-b8 is 110 code, this signal is the peer to the end of the MS-RDI alarm signal; if the received K2 b6-b8 is 111, this signal is the end of the received MS-AIS signal, at this time to the end of the MS-RDI signal, that is, to the end of the signal frame to the STM-N of K2 b6-b8 into the 110 bit pattern. MS-AIS is usually accompanied by the appearance of remote LOS/LOF, or insert the alarm from the network management.

Example of MS-AIS: see Figure 11
◆ A end to get the MS-AIS, write K2 MS-RDI, return to B End.
◆ B terminal get MS-RDI,
Station A writes B5-B7 to G1 at the same time --> HP-RDI,
Write B5-B8 --> LP-RDI to V5 at the same time, as detailed later.
Figure 11 example of a MS-AIS

The main cause is:
① Optical Cable disconnection or optical cable failure;
② Light board.
3. crosstab chart
Solution:
If the local self ring also has the alarm MS-AIS, then change the light board.
② If the Local Self-loop is good and there is no los alarm on the peer end, the AIS alarm may be inserted on the network management, and the AIS operation will be inserted on the network management. If this process does not eliminate the alarm, the remote light board is replaced.
3. crosstab changes
(2) AU-AIS:
Au-AIS, AU-LOP: High-Order channel Alarm Indication Signal, AU Management Unit pointer loss.
The main cause is:
① Optical Cable disconnection or optical cable failure;
② Clock Board;
③ Cross Board;
④ Light board;
⑤ Branch board bus;
6. Backplane;
7. Incorrect time slot configuration.
Solution: locate the fault through loopback, change the board or modify the time slot configuration.

(3) TU-AIS
Tu-AIS, TU-LOP: branch warning indicator signal, branch pointer loss.
The main cause is:
① Optical Cable disconnection or optical cable failure;
② Clock Board;
③ Cross Board;
④ Light board;
⑤ Branch board bus;
⑥ Branch board;
7. Backplane;
The timeout time slot is incorrectly configured.
Solution: locate the fault through loopback, change the board or modify the time slot configuration.
5. B1 performance records and alarm generation
B1 uses bip8-bit inter-insertion parity to calculate and calculate data in the regeneration segment.
Working mechanism: the sender performs STM-N even verification on all the bytes after the last frame (1 # BIP-8) is disturbed, and the result is placed in the next frame to be disturbed (2 # STM-N) the receiver verifies all the bits of the current frame (1 # STM-N) to the BIP-8, and the result is compared with the next frame (2 # STM-N) the values of the B1 bytes after the disturbance are different or compared. If the two values are inconsistent, the values may be different or 1, depending on how many values are 1, then we can monitor the number of error blocks in the transmission of the 1 # STM-N frame.
B1 ends on various network element optical interface boards. Including Reg, ADM, and TM.
When the B1 error count exceeds the threshold, an alarm is reported as the B1 performance value.
Including B1 bbe, B1 es, B1 SES, and B1 UAS.
B1 has no remote concept.
The main cause is:
① Optical Cable disconnection, optical cable failure or optical cable failure;
② The opposite end does not send optical signals;
③ The local optical transceiver is broken;
④ The received optical signal is different from the optical module's speed level;
⑤ The optical transceiver power is not within the indicator range of the optical transceiver module.
Solution:
① Use an Optical Fiber Self-ring for the local end first (the self-ring must ensure that the optical power of the receiving port is within the sensitivity and overload point range). If the alarm disappears, it indicates that the local end is good, the problem lies at the peer end. If the peer self-ring is good, the optical fiber between the two ends is definitely broken. (Note: The degree of tightening of the flange connection directly affects the optical power sending and receiving)
② If the end-to-end self-ring is not good, it is also a los alarm. The optical power meter is used to measure the optical power. If the power is too small
(-50 dB or lower) it can be determined that the optical fiber is broken;
③ If the power is normal, it is caused by no clock. If the clock board is replaced, the alarm disappears;
④ If the local self-loop or Los alarm occurs, the light receiving module is broken and the alarm disappears after the switch.
6. J0 overhead bytes
Trace bytes of the regeneration segment: J0
Alarm information on network management:
This byte is used to repeatedly send the segment Access Point identifier so that the receiving end can confirm that it is in a persistent connection with the specified sending end. This byte can be any character in the network of the same operator, And the J0 byte at both ends of the device receiving and sending must be the same at the network boundary of the two operators -- match. With J0 bytes, operators can detect and solve faults in advance, shortening the network recovery time.
7. B2 (M1) performance records and alarm generation:
(1) B2 uses the bip24 bit interlace parity check to calculate and calculate the data in the multiplexing segment.
Working mechanism: it is the beginning of B2 bytes on the previous STM-1 frame to be disturbed except rsoh (rsoh in B1) and all the bits of the Management pointer for BIP-24 calculation, the result is placed in the B2 byte location of the frame to be disturbed by the STM-1.

It is accompanied by the following parameters ① b2bbe ② b2es ③ b2ses ④ b2uas
B2 sends an alert message at the same time when it ends the network element that processes the overhead of the multiplexing segment. For example, if Reg does not perform the B2 test and report, the B2 bytes of the reg net element will be sent to the next net element without any change, which will be processed by the next net element. Other items, including ADM and TM, end B2 and re-initiate verification records. In addition, B2 sends an advertisement message back to B2's original network element. For example, if the b2-record value exceeds the threshold value, the system will display an "over-performance alarm" on the network management, but there is no send-back alarm information.

(2) M1: B2 to the byte, reuse segment remote code block indication (MS-REI) bytes
This is a peer message, which is sent back to the sender by the receiver. M1 bytes are used to transmit the number of blocks detected by the BIP-N × 24 (B2), so that the sender can understand the receiver's receiving Error Code accordingly. After the receiver's network element detects B2, it stores the value in M1 bytes and sends it back to the initiator's network element. After the initiator's network element detects m2, returns the b2-fe value of the corresponding value (fees/febbe/feses/feuas) generally, bbe/ES/SES/UAS of a certain network element is generated along with B2 febbe/fees/feses/feuas of the peer network element.
8. J1 and C2 overhead bytes
C2 is used to indicate the re-Connection Structure of VC frames and the nature of the Net Load of information, such as whether the channel is loaded, the business types contained and Their ing methods.
The setting of J1 and C2 bytes must make the receiving/sending ends consistent -- send and receive match, otherwise the receiving device will have a HP-TIM (high-level Channel Tracking byte mismatch), HP-SLM (high-order channel signal flag byte mismatch ). Both alerts enable the device to insert a full "1" code to the lower-level tug3 of the vc4-A TU-AIS alarm indication.

9. B3 (G1) performance records and alarm generation
B3 is calculated through bip8 bit inter-insertion parity in High-Order channels.
Working mechanism: B3 bytes is responsible for monitoring the error performance of vc4 transmitted in the STM-N frame, the monitoring mechanism is similar to B1, B2, but B3 is to verify the BIP-8 of vc4 frame.
G1 is used to send the status and performance of the Channel Terminal Back To The vc4 channel source device, allowing you to monitor the status and performance of the entire two-way channel at either end of the channel or any point in the channel. The G1 bytes actually send the peer information, that is, the information sent from the receiver to the initiator, so that the receiver can learn about the situation where the receiver receives the corresponding vc4 channel signal.
If the receiver detects the Error Block, the performance monitoring event of the local device-HP-BBE (higher-level channel background Error Block) shows the number of corresponding error blocks, at the same time, the b1-b4 in G1 bytes is returned to the vc4 channel error number detected by B3 (BIP-8), that is, HP-Rei. When the receiving end receives AIS, the error code exceeds the upper limit, J1, C2 first configuration, by the G1 byte 5th bits send back to start a HP-RDI (high-end Channel Remote deterioration indication ), enable the initiator to understand the status of the corresponding vc4 received by the receiving end, so as to detect and locate faults in time. G1 bytes of B6 and B8 are not used currently.
The alert mechanism for over-performance B3 is the same as that for B1 and B2.
The main cause is:
① Optical Cable disconnection or optical cable failure;
② Clock Board;
③ Cross Board;
④ Light board;
⑤ Branch board bus;
6. Backplane;
7. Incorrect time slot configuration.
Solution:
Locate the fault through loopback, change the corresponding board or modify the time slot configuration.
Note: It is normal that the corresponding Au will generate B3 in an instant when the AU's time slot is reconfigured.