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Probe: ECMP Imbalance (Fabric Interfaces)

Purpose

This probe calculates ECMP imbalance on fabric ports.

A given set of ECMP links (only calculated on leaf-to-spine links), identified by common system_id, is determined to be imbalanced if the standard-deviation of the tx_bytes counter (averaged periodically over the specified period) for the involved leaf-interfaces is above "Max Standard Deviation".

If such imbalance is observed for more-than "Threshold Duration" over the last"Duration" time period, we raise an anomaly.

The last "Anomaly History Count" anomaly state-changes are stored for observation.

If more-than "Max Imbalanced Systems" systems are imbalanced, we raise a distinct anomaly.

We maintain for inspection the number of imbalanced systems over the last "System Imbalance History Count" samples.

Source Processor
leaf fabric interface traffic (Interface Counters-)

Purpose: wires in interface traffic samples (measured in bytes per second) from each spine-facing interface on each leaf.

Output Stage: leaf_fabric_int_traffic

Set of traffic samples (for each spine-facing interface on each leaf). Each set member has the following keys to identify it: label (human-readable name of the leaf), system_id (id of the leaf system, usually serial number), interface (name of the interface).

Additional Processor(s)
leaf fabric interface traffic avg (Periodic Average)

Purpose: Calculate average traffic during period specified by average_period facade parameter. Unit is bytes per second.

Input Stage: leaf_fabric_int_traffic

Output Stage: leaf_fabric_int_tx_avg

Set of traffic average values (for each spine-facing interface on each leaf). Each set member has the following keys to identify it: label (human-readable name of the leaf), system_id (id of the leaf system, usually serial number), interface (name of the interface).

leaf fabric interface std-dev (Standard Deviation)

Purpose: calculate standard deviation for a set consisting of traffic averages for each spine-facing interface on a given leaf. Grouping per leaf is achieved using 'group_by' property set to 'system_id'.

Input Stage: leaf_fabric_int_tx_avg

Output Stage: leaf_fab_int_std_dev

Set of values, each indicating standard deviation (as a measure of ECMP imbalance) for traffic averages for each spine-facing interface on a given leaf. Each set member has system_id key to identify leaf whose ECMP imbalance the value represents.

std-dev percentage (Ratio)

Input Stage: leaf_fab_int_std_dev

Output Stage: std_dev_percentage

live ecmp imbalance (Range)

Purpose: Evaluate if standard deviation between spine-facing interfaces on each leaf is within acceptable range. In this case acceptable range is between 0 and std_max facade parameter (in bytes per second unit).

Input Stage: std_dev_percentage

Output Stage: live_ecmp_imbalance

Set of true/false values, each indicating if standard deviation (as a measure of ECMP imbalance) for traffic averages for each spine-facing interface on a given leaf is within acceptable range. Each set member has system_id key to identify leaf whose ECMP imbalance the value represents.

sustained ecmp imbalance (Time in State)

Purpose: Evaluate if standard deviation between spine-facing interfaces on each leaf has been outside acceptable range, (as defined by 'live ecmp imbalance' processor) for more than 'threshold_duration' seconds during last 'total_duration' seconds. These two parameters are part of facade specification.

Input Stage: live_ecmp_imbalance

Output Stage: system_imbalance

systems imbalanced count (Match Count)

Purpose: Count how many systems have ecmp imbalance anomaly true at any instant in time.

Input Stage: system_imbalance

Output Stage: system_imbalance_count

Number of systems with ecmp imbalance.

imbalanced system count out of range (Range)

Purpose: Evaluate if the number of imbalanced systems is within acceptable range, which in this instance means less than 'max_systems_imbalanced' value which is a facade parameter.

Input Stage: system_imbalanced_count

Output Stage: imbalanced_system_count_out_of_range

Boolean indicating if the number of imbalanced systems is within accepted range, i.e. less than 'max_systems_imbalanced" which is a facade parameter.

For more information about this probe, from the blueprint, navigate to Analytics > Probes, click Create Probe, then select Instantiate Predefined Probe from the drop-down list. Select the probe from the Predefined Probe drop-down list to see details specific to the probe.