GigaStream Imbalance Notification

In GigaVUE-OS nodes, traffic is distributed across the ports in a GigaStream based on the following criteria:

• Type and volume of the incoming traffic
• Configurations defined in the Advanced Hash Settings page for the selected line card or chassis. Refer to the Advanced Hashing section in the Fabric Management guide for more details.

Consider a scenario in which ip4src and ip4dst are configured as advanced hash methods. Accordingly, traffic is distributed based on the matching IP source and IP destination addresses.

• In case of high traffic volume on a particular IP address or subnet, one or more ports within the GigaStream group will receive more traffic compared to the other ports.
• Alternatively, if there is a low traffic volume on a particular IP address or subnet, one or more ports within the GigaStream group will receive lower traffic compared to the other ports.

A small variation in traffic volumes across the ports in a GigaStream is expected and is acceptable. Large variation in traffic volume causes packet drops due to over subscription or under subscription of ports. With the GigaStream imbalance notification functionality, the port statistics of the member ports in a GigaStream are validated to determine if the variation in traffic distribution across the ports does not exceed or fall below a user-defined threshold value limit. If traffic distribution is not within the allowed variance limit, the GigaVUE HC Series and TA Series devices generate SNMP traps that are sent to GigaVUE-FM based on which GigaStream imbalance alarms are triggered.

SNMP traps are generated in the devices based on the following criteria:

• Variance threshold % configured either through GigaVUE-FM or CLI (refer to the Example for more details)
• Distribution of traffic between the ports (on a 30 second interval)

The following SNMP traps are triggered in the devices:

• For imbalanced traffic distribution: gigamonSnmpGigastreamImbalanceNotification
• On recovery of balanced traffic: gigamonSnmpGigastreamRecoveryNotification

To manage the SNMP traps, you can either use the SNMP throttling feature or the GigaStream Imbalance notification feature. With SNMP throttling, it is possible for some of the recovery traps to get throttled resulting in inappropriate health status of the ports in the GigaVUE-FM GUI. Use the GigaStream Imbalance Notification feature to generate traps and trigger appropriate alarms.

Note:  GigaStream Unhealthy alarm is raised to signify the imbalance in traffic distribution ( alarm description includes all the affected ports).

GigaStream Imbalance Threshold Priority Levels

Threshold values for GigaStream imbalance can be configured at the following levels:

Configuration Level	Description	Notes
Per GigaStream Level Configuration	Applies to a specific GigaStream in a device.	Has the highest priority and overrides the type level and global level configuration.
Type Level Configuration	Applies to all GigaStreams of a particular type.	Has the second highest priority and overrides the global level configuration .
Global Level Configuration	Applies to all GigaStreams.	Has the lowest priority.

The following table shows the various configurations that can be performed from the GUI:

Configuration Level	Details	Refer to
Per GigaStream Level Configuration	Allows you to configure GigaStream Imbalance notification for a specific GigaStream in a device.	Configure GigaStream Imbalance per GigaStream
Device Level Configuration	Allows you to configure GigaStream Imbalance notification for all the GigaStreams in a device.	Configure GigaStream Imbalance Threshold in Devices
GigaVUE-FM Level Configuration	Allows you to configure GigaStream Imbalance notification for all the GigaStreams in all devices managed by GigaVUE-FM.	Configure GigaStream Imbalance Threshold in GigaVUE-FM

Note:  For configuration using CLI, refer to the GigaVUE-OS CLI Reference Guide.

You can configure threshold values for GigaStream imbalance for the following GigaStream types:

• All GigaStreams
• Tool GigaStream
• Circuit GigaStream
• Hybrid GigaStream
• Stack GigaStream

Note:  GigaStream Imbalance threshold notification functionality is applicable only for regular GigaStreams. Controlled GigaStreams and weighed GigaStreams are not within the scope of this functionality as traffic distribution is uneven within the ports.