CSCF External Network Selection Table Loop Detected

Call Session Control Function

1	Introduction
1.1	Alarm Description
1.2	Prerequisites
2	Procedure

1 Introduction

This instruction concerns alarm handling.

1.1 Alarm Description

The alarm is issued when the number of External Network Selection (ENS) criteria tables started in a single gateway selection request exceeds the value of the configurable parameter extNetSelectionMaxTables, refer to Managed Object Model (MOM). The alarm is caused by the ENS configuration instance (ExtNetSelection or ExtNetSelection2) that was active at the time of the alarm.

The possible cause is ENS configuring error. A loop can be present in the tables. The selection process cannot converge to a pool.

The possible alarm causes and the corresponding fault reasons, fault locations, and impacts are described in Table 1.

Table 1 Alarm Causes
Alarm Cause	Description	Fault Reason	Fault Location	Impact
External Network Selection (ENS) table loop was detected.	The number of ENS criteria tables that were started in a gateway request exceeded the `extNetSelectionMaxTables` maximum configured parameter value.	The possible cause is ENS configuring error. A loop can be present in the tables. The selection process cannot converge to a pool.	The fault is caused by a loop that is detected or that the analysis is so complex that the `extNetSelectionMaxTables` is configured too small. The attribute `extNetSelectionMaxTables` is placed in the MOC `ExtNetSel-Application`, which describes the maximum number of times ENS table can be started in a single gateway selection request before the alarm is triggered.	The SIP message that triggered the alarm is routed to the gateway identified in the `extNetSelectionDefaultPoolName` parameter. If the parameter is not defined, the SIP message is answered with a `500 PSTN Gateway unreachable` error response.

Note:: An alarm can appear as a result of maintenance activity.

The alarm attributes are listed and explained in Table 2.

Table 2 Alarm Attributes
Attribute Name	Attribute Value
Major Type	193
Minor Type	6684696
Managed Object Class	ExtNetSel-Application
Managed Object Instance	`ManagedElement=<node_name>,CscfFunction=1,ExtNetSel-Application=ExtNetSelection or ExtNetSelection2`
Specific Problem	CSCF External Network Selection Table Loop Detected
Event Type	processingErrorAlarm (4)
Probable Cause	x733ConfigurationOrCustomizationError (307)
Additional Text	ENS tables input information ⁽¹⁾⁽²⁾
Perceived Severity	major (4)

(1) Example: SipMessage=[INVITE tel:+468000000000 SIP/2], SdpMediaType=[]

(2) Input information includes the SIP request received by ENS. The SIP request information includes SDP media information without the message body part. A SIP request with length exceeding the display limit is truncated.

1.2 Prerequisites

This section provides information on the documents, tools, and conditions that apply to the procedure.

1.2.1 Documents

This instruction references the following document:

1.2.2 Tools

No tools are required.

1.2.3 Conditions

No conditions.

2 Procedure

This section describes the procedure to follow when this alarm is received.

Do the following:

To get the input to the ENS analysis:
1. Identify the input parameters that caused the alarm by looking in the Additional Text field of the alarm.
2. Identify the affected configuration instance (ExtNetSelection or ExtNetSelection2) by looking in the Managed Object Instance field.
3. Get the input to use for the ENS analysis, by checking when the alarm was raised. This can be done if the ENS analysis matches on the EnsDateMatchTable or EnsTimeMatchTable.
Note:
The time can differ on second level, and that the configured times in the ENS analysis are using UTC format.
If the ENS is configured to use both configuration instances, ensure that the affected configuration instance is configured as passive. To do so, set extNetSelectionActiveConfiguration to the other instance.
For example, if the affected configuration is ExtNetSelection2, set the parameter to ExtNetSelection.
For more information about the parameter extNetSelectionActiveConfiguration, refer to Managed Object Model (MOM)and CSCF Configuration Management.
Examine and correct the ENS table entries to ensure that the identified combination of input criteria values lead to the selection of a pool. Increase the value of the configurable parameter extNetSelectionMaxTables, if appropriate.
Set the extNetSelectionTablesSynchronization to true in the targeted configuration instance. The ENS application is now notified that a new configuration must be used, and the alarm ceases.
For more information about the parameter extNetSelectionTablesSynchronization, refer to Managed Object Model (MOM) and CSCF Configuration Management.
Confirm that the alarm has ceased. If the alarm is not ceased, consult the next level of maintenance support. Further actions are outside the scope of this instruction.
Job is completed.