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OSN 500 550 580 V100R008C50 Alarms and Performance Events Reference 02

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VC_AIS

VC_AIS

Description

The VC_AIS is an alarm indication signal of the virtual channel (VC) connection. When a forward or backward VC connection that is configured with the segment/end point attribute receives AIS cells, the VC_AIS alarm is reported indicating that the upstream services are abnormal.

Attribute

Alarm Severity Alarm Type

Major

Communication alarm

Parameters

Name Meaning

Parameter 1

This parameter is used for the TDM-domain ATM board. The fixed value is 0x01 and the value is meaningless.

This parameter is used for packet-domain ATM boards and E1 interface boards, and indicates connection direction.

  • 0x01: forward
  • 0x02: backward

Parameter 2, Parameter 3

These parameters are used for the TDM-domain ATM board and indicate the connection ID and connection direction.

The value is the remainder of applying the algorithm ((ConnId - 1)×2 + ConnDir)/2048 to connection ID (Connld) and connection direction (ConnDir).

NOTE:
  • ConnDir: the value 1 means forward and the value 2 means backward.
  • ConnId: the value 1 means an odd number and the value 2 means an even number.

Parameter 2 is used for packet-domain ATM boards and E1 interface boards, and indicates segment/end attribute of the alarm.

  • 0x01: segment
  • 0x02: end

Parameter 4

This parameter is used for the TDM-domain ATM board and indicates the group number.

The value is the integer result of applying the algorithm ((ConnId - 1)×2 + ConnDir)/2048 to connection ID (Connld) and connection direction (ConnDir).

NOTE:

The unidirectional connections of the alarm are divided on the 2048 base.

Parameter 5

This parameter is used for the TDM-domain ATM board and indicates the source ATM port number of a certain connection in a certain direction.

  • For the ATM board with the IMA function, the value of this parameter ranges from 0x01 to 0x4A (1 to 74). The values 0x01 to 0x04 (1 to 4) represent external optical port numbers; the values 0x05 to 0x4A (5 to 74) represent internal VCTRUNK numbers.
  • For the ATM board without the IMA function, the value of this parameter ranges from 0x01 to 0x14. The values 0x01 to 0x04 (1 to 4) represent external optical port numbers; the values 0x05 to 0x14 (5 to 20) represent internal VCTRUNK numbers.
NOTE:

Internal VCTRUNK numbers are calculated by applying the algorithm (VCTRUNK ID - 0x8001 + 0x0005) to actual VCTRUNK IDs.

Impact on the System

  • The continuity check (CC) sink of an upstream connection is activated, but the related CC source is not activated, and no user cells are received because the current bandwidth is zero. In this case, the upstream NE reports the CC_LOC alarm, and the AIS cells are inserted at the downstream NE. Consequently, the local NE generates the VC_AIS alarm. Services are not interrupted, but are unavailable in the connection.
  • In other cases, the related VC connections have been interrupted when the VC_AIS alarm is reported. Moreover, the AIS cells are continuously inserted at the downstream station. In addition, the RDI cells are returned to the upstream station.

Possible Causes

Possible causes of the VC_AIS alarm are as follows:

  • An upstream NE of the connection fails to receive signals in the SDH path. For example, an SDH alarm, such as the R_LOS, R_LOF, MS_AIS, AU_AIS, AU_LOP, TU_AIS, or TU_LOP, is reported at the NE.
  • The LCD alarm is reported at an upstream ATM port of the connection.
  • The CC sink of an upstream NE on the connection is activated, but the relevant CC source is not activated, and no user cells are received because the current bandwidth is zero. In this case, the upstream NE reports the CC_LOC alarm, and the AIS cells are inserted at the downstream NE. Consequently, the local NE generates the VC_AIS alarm.
  • The ATM processing chip on the alarmed board is faulty.

Procedure

  1. View the VC_AIS alarm information on the U2000, and then confirm the connection where the alarm is generated according to alarm parameters 2 and 3.
  2. Check whether any alarm, such as the R_LOS, R_LOF, MS_AIS, AU_AIS, AU_LOP, TU_AIS, or TU_LOP, is generated in the SDH path of an upstream NE connected to the ATM port. If yes, clear it, and then check whether the VC_AIS alarm is cleared. If the VC_AIS alarm persists, go to the next step.
  3. Check whether the LCD alarm is reported at the ATM port on the ATM board of the upstream NE. If yes, clear it, and then check whether the VC_AIS alarm at the local station is cleared.
  4. If the VC_AIS alarm persists, check whether the CC sink is activated at an upstream NE of the connection but the CC source is not activated. If the CC sink is activated, deactivate it. Moreover, check whether the CC_LOC alarm is reported. If yes, clear the CC_LOC alarm at the upstream NE, and then check whether the VC_AIS alarm at the local NE is cleared.
  5. If the VC_AIS alarm persists, the ATM processing chip on the alarmed board may be faulty. Reset (cold) the board and check whether the VC_AIS alarm is cleared.

    If the services on the alarmed board are not configured with protection, the services are interrupted after the board cold reset.

  6. If the VC_AIS alarm persists, replace the board that generates the alarm.

Related Information

Unidirectional connection

A complete bidirectional connection is divided into a forward unidirectional connection and a backward unidirectional connection. The direction of the forward and backward connections is based on the same node.

End and segment

The end point refers to the termination point in the chain network, and it is used to monitor the whole virtual connection. The segment point is, generally, used to monitor a segment of the whole link.

Segment and end point

This is one of the segment end attributes. The segment end attributes include: segment point, end point, segment and end point, non-segment and end point.

  • If an NE is set with the segment end point attribute, it can retrieve the alarms that are generated at the segment and end.
  • If an NE is set with the segment point attribute, it can retrieve the alarms that are generated at a segment.
  • If an NE is set with the end point attribute, it can retrieve the alarms that are generated at an end.
  • If an NE is set with the non-segment end point attribute, it fails to retrieve the alarms that are generated at the segment and end.
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Updated: 2019-01-21

Document ID: EDOC1100020975

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