CISCO-VISM-CAC-MIB

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Organization: Cisco Systems, Inc.

Last Updated: 2004-02-20

Category: Cisco Devices, Telephony and VoIP

Description: Manages Connection Admission Control (CAC) policies and bearer channel capacity on Cisco VISM ATM voice gateway.

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What Is CISCO-VISM-CAC-MIB?

CISCO-VISM-CAC-MIB manages Connection Admission Control (CAC) for Cisco's Voice Interworking Service Module (VISM), an ATM-based voice gateway card used on Cisco MGX platforms. It exposes per-channel CAC data such as accepted and rejected connection counts, rejection policy, carrier-loss policy, and voice activity detection (VAD) tolerance/duty-cycle parameters, plus card- and port-level CAC failure statistics. The MIB is squarely aimed at monitoring the health and capacity behavior of voice trunking hardware: administrators track passed versus rejected connection counts to gauge whether a channel or card is being overloaded, and card/port CAC failure counters to detect provisioning or PVC failures. It depends on the broader CISCO-VISM module family, such as CISCO-VISM-MODULE-MIB, for the underlying module/card context it references. It is deployed in legacy Cisco MGX 8000-series ATM voice gateway networks carrying voice-over-ATM traffic with call-admission constraints. Network engineers evaluating or troubleshooting this functionality can download the CISCO-VISM-CAC-MIB file directly to load it into their MIB browser.

IPNetwork Monitor allows you to monitor SNMP objects defined in CISCO-VISM-CAC-MIB. Use the built-in SNMP Monitoring Browser to explore available variables, view their current values and descriptions, and select the objects you want to monitor. You can then create SNMP monitors, configure thresholds, and receive alerts when monitored values change.

Supported Devices

Cisco VISM voice service module (MGX platform)
Cisco MGX 8000-series ATM voice gateway

Monitoring Examples

A NOC engineer would poll vismChanCacTable, indexed by vismChanNum, comparing vismChanCacPassedCons to vismChanCacRejectedCons over time to detect a channel that is rejecting an increasing share of new voice calls due to capacity limits or its vismChanCacRejectionPolicy setting. Rising vismPortCacPvcAddFailures on a port would signal that PVCs cannot be admitted, pointing to a resource exhaustion issue on that VISM card, and vismCardCacFailuresGrp would be checked for card-wide CAC failure trends. The networkCacConfigState object indicates whether network-wide CAC is currently enabled, which is checked before diagnosing individual channel rejections.

What Can Be Monitored

passed vs rejected connection counts per channel
channel rejection policy
carrier loss policy
VAD tolerance and duty cycle
port-level PVC add failures
card-level CAC failures
network-wide CAC configuration state

Imported Objects

From BASIS-MIB

vismChanCnfGrp	OBJECT-IDENTITY
voice	OBJECT-IDENTITY

From CISCOWAN-SMI

ciscoWan

OBJECT-IDENTITY

From SNMPv2-CONF

MODULE-COMPLIANCE
OBJECT-GROUP

From SNMPv2-SMI

Counter32
Integer32
MODULE-IDENTITY
OBJECT-TYPE

How to Use in IPNetwork Monitor

Example using vismPortCacPvcAddFailures OID:

Select a Cisco VISM (Voice Interworking Service Module) card, MGX platform (legacy) as the target host to create a monitor — the SNMP service should be up and running on it. Click New Monitor, then check SNMP Custom on the Favorites tab, click Next, and confirm the host. On the next page, click Select... to open the built-in SNMP MIB Browser and type vismPortCacPvcAddFailures into the Find box to locate it in the OID tree, then select it and click OK. It reports the total number of attempts to add or modify a PVC to VISM virtual port that were rejected by port level CAC. On the monitor's Main parameters page you can set the target's SNMP port (default 161), credentials, polling interval, and other settings — see the SNMP Monitor help for details. On the State conditions and Alerting tabs, configure when the monitor should change state and trigger an alert; since this is a Counter32-type OID, Value bounds is the most useful condition here — trigger an alert if the counter increases between polls, since a rising count of errors, failures, or discards often points to a real underlying problem. Click Finish to create the monitor; you can adjust any parameter later.

OIDs

OID symbolic	OID numeric	Type	Access	Description
ciscoVismCacCompliance	1.3.6.1.4.1.351.150.96.2.2.1			The compliance statement for objects related to VISM CAC module.
ciscoVismCacMIB	1.3.6.1.4.1.351.150.96			The MIB module containing the CAC information for VISM service module.
ciscoVismCacMIBCompliances	1.3.6.1.4.1.351.150.96.2.2
ciscoVismCacMIBConformance	1.3.6.1.4.1.351.150.96.2
ciscoVismCacMIBGroups	1.3.6.1.4.1.351.150.96.2.1
ciscoVismCardCacFailuresGrp	1.3.6.1.4.1.351.150.96.2.1.2			A collection of objects providing CAC statistics for both SVC and PVC connection.
ciscoVismChanCacGroup	1.3.6.1.4.1.351.150.96.2.1.1			A collection of objects providing CAC feature on PVC.
INT networkCacConfigState	1.3.6.1.4.1.351.110.5.5.3.1.3.1.9	INTEGER	read-only	This attribute defines whether the originating and terminating VISMs are configured properly or not, by default the configuration is assumed to be 'ok' and this object is set to 'ok', if later during upspeed if we discover that both the originating and terminating VISMs are configured as either CAC master or slave then it is considered as an invalid configuration and this object will be set to 'notOk' and trapNetworkCacConfigState(defined in CISCO-VISM-TRAPS-MIB MIB) change trap will be sent. This parameter is applicable only in trunking applications.
vismCardCacFailuresGrp	1.3.6.1.4.1.351.110.5.5.20
vismChanCacEntry	1.3.6.1.4.1.351.110.5.5.3.1.3.1		not-accessible	Each entry in this table corresponds to a PVC, since the CAC functionality is applied on a per PVC basis. The bandwidth is allocated on a per PVC basis and the connection admission control is done by comparing the available bandwidth on a PVC with the required bandwidth as a result of new connection setup request or upspeed request.
INT vismChanCacMaster	1.3.6.1.4.1.351.110.5.5.3.1.3.1.2	INTEGER	read-write	This attribute defines whether the PVC is the master end or slave end. CAC functionality is applied only at the master end of the PVC. It is not necessary if the PVC end is configured as the slave end. This is to prevent the glare condition resulting from the simultaneous allocation of the same bandwidth for different calls from both ends. This parameter is applicable only in the trunking mode.
C32 vismChanCacPassedCons	1.3.6.1.4.1.351.110.5.5.3.1.3.1.3	Counter32	read-only	This attribute defines the count of connections that passed successfully the CAC function. CAC functionality is applied either due to 1) The CRCX message sent to VISM from the Call Agent to set up a new connection OR at the time of 'addcid' command in AAL2 trunking application. 2) Upspeed request due to fax/modem tone detection on a connection configured for compression.
C32 vismChanCacRejectedCons	1.3.6.1.4.1.351.110.5.5.3.1.3.1.4	Counter32	read-only	This attribute defines the count of connections that got rejected due to CAC function. The CAC rejection was due to the bandwidth not being available on a given PVC.
INT vismChanCacRejectionPolicy	1.3.6.1.4.1.351.110.5.5.3.1.3.1.5	INTEGER	read-write	This attribute defines the policy that needs to be applied once the CAC function rejects the upspeeding of a connection, due to a fax/modem switchover request. The applicable options are 'delete' - to delete the connection that got rejected by CAC for upspeed. 'maintain' - to maintain the connection with the prior compression scheme. 'unspecified' - The CAC rejection policy as defined in the card level object vismCacRejectionPolicy(defined in CISCO-VISM-MODULE-MIB MIB) will be used, else the value of this object will be used. Note that the default value of maintaining the prior encoding scheme is applicable in the trunking application only since the connection is not deleted after the fax/modem switchover.In the case of switching application, the connection is deleted after the fax/modem switchover. Configuring this object will not have any affect when card level CAC object vismCacEnable(defined in CISCO-VISM-MODULE-MIB MIB) is disabled.
vismChanCacTable	1.3.6.1.4.1.351.110.5.5.3.1.3		not-accessible	This table defines the CAC success or failure statistics. CAC functionality is applied on a per PVC(Permanent virtual circuit) basis for accepting the new calls in a switching model (i.e when CRCX(CreateConnection) message is received from the call agent) and when adding a new binding between a CID(Channel Identifier) and a PVC in the AAL2 trunking application ('addcid' command). In both switching and trunking models, the CAC functionality is applied for upspeeding the connections due to the detection of fax/modem tone on a connection configured with voice compression. The entries in this table are implicitly created and deleted with the creation and deletion of entries in vismChanCnfGrpEntry (defined in CISCO-VISM-CONN-MIB MIB).
INT vismChanCarrierLossPolicy	1.3.6.1.4.1.351.110.5.5.3.1.3.1.6	INTEGER	read-write	This object defines the policy that needs to be applied when a carrier loss is detected. The possible policies are defined as follows: 'previousCodec' - switch to the pre-upspeed codec when a a carrier loss is detected. 'upspeedCodec' - remain with the upspeed codec when a carrier loss is detected. 'unspecified' - The card level object value vismCarrierLossPolicy(defined in CISCO-VISM-MODULE-MIB MIB) will be used. Configuring this object will not have any affect when card level CAC object vismCacEnable (defined in CISCO-VISM-MODULE-MIB MIB) is disabled.
I32 vismChanNum	1.3.6.1.4.1.351.110.5.5.3.1.3.1.1	Integer32	read-only	This attribute defines the index for the vismChanCac Table. The LCN(Logical channel number) number is the same as the LCN value used as the index for the vismChanCnfGrpTable (defined in CISCO-VISM-CONN-MIB MIB) i.e. vismCnfChanNum.
I32 vismChanVADDutyCycle	1.3.6.1.4.1.351.110.5.5.3.1.3.1.8	Integer32	read-write	This object refers to the talk-spurts duty cycle. A value of zero indicates the card level object vismVADDutyCycle(defined in CISCO-VISM-MODULE-MIB MIB) value will be used. Configuring this object will not have any affect when card level CAC object vismCacEnable(defined in CISCO-VISM-MODULE-MIB MIB) is disabled.
I32 vismChanVADTolerance	1.3.6.1.4.1.351.110.5.5.3.1.3.1.7	Integer32	read-write	The value in this object refers to the customer accepted drop rate for voice connections when the bandwidth usage exceeds allowed value. A value of zero indicates the card level object vismVADTolerance(defined in CISCO-VISM-MODULE-MIB MIB) value will be used. Configuring this object will not have any affect when card level CAC object vismCacEnable(defined in CISCO-VISM-MODULE-MIB MIB) is disabled.
C32 vismPortCacPvcAddFailuresEx	1.3.6.1.4.1.351.110.5.5.20.1	Counter32	read-only	Total number of attempts to add or modify a PVC to VISM virtual port that were rejected by port level CAC.
C32 vismPortCacSvcAddFailures	1.3.6.1.4.1.351.110.5.5.20.2	Counter32	read-only	Total number of attempts to add a SVC (Switched Virtual Circuit) to VISM virtual port that were rejected by port level CAC.
C32 vismPortCacSvcUpspeedFailures	1.3.6.1.4.1.351.110.5.5.20.5	Counter32	read-only	Total number of attempts to upspeed voice connections over bearer SVC connections that were rejected by port level CAC.
C32 vismVcCacPvcFailures	1.3.6.1.4.1.351.110.5.5.20.3	Counter32	read-only	Total number of attempts to admit voice connections over bearer PVC connections that were rejected by voice CAC. It is sum of all voice CAC failures for all VISM bearer PVC connections.
C32 vismVcCacPvcUpspeedFailures	1.3.6.1.4.1.351.110.5.5.20.4	Counter32	read-only	Total number of attempts to upspeed voice connections over bearer PVC connections that were rejected by port level CAC.

RFC description

Cisco VISM Voice Interworking Service Module MIB that provides Connection Admission Control (CAC) statistics for SVC and PVC connections, maintaining bandwidth calculations and call admission decisions.

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Download CISCO-VISM-CAC-MIB