Brocade Fabric OS Administrators Guide (Supporting Fabric OS v7.3.0) - Manual (Page 389)

Bottleneck Detection
● Bottleneck detection overview ......................................................................................389
● Supported configurations for bottleneck detection........................................................ 391
● Enabling bottleneck detection on a switch.................................................................... 392
● Displaying bottleneck detection configuration details....................................................393
● Setting bottleneck detection alerts ............................................................................... 394
● Changing bottleneck detection parameters...................................................................397
● Logging frame timeouts due to bottlenecking............................................................... 400
● Advanced bottleneck detection settings........................................................................401
● Excluding a port from bottleneck detection................................................................... 402
● Displaying bottleneck statistics..................................................................................... 404
● MAPS and bottleneck detection.................................................................................... 404
● Disabling bottleneck detection on a switch................................................................... 404
Bottleneck detection overview
A bottleneck is a port in the fabric where frames cannot get through as fast as they should. In other
words, a bottleneck is a port where the offered load is greater than the achieved egress throughput.
Bottlenecks can cause undesirable degradation in throughput on various links. When a bottleneck
occurs at one place, other points in the fabric can experience bottlenecks as the traffic backs up.
The bottleneck detection feature does not require a license, and is disabled by default. The bottleneck
detection feature is configured on a per-switch basis, with optional per-port exclusions. The best
practice is to enable bottleneck detection on all switches in the fabric, and leave it on to continuously
gather statistics.
The bottleneck detection feature enables you to do the following:
• Prevent degradation of throughput in the fabric.
The bottleneck detection feature alerts you to the existence and locations of devices that are causing
latency. If you receive alerts for one or more F_Ports, you can use the CLI to check whether these
F_Ports have a history of bottlenecks.
• Reduce the time it takes to troubleshoot network problems.
If you notice one or more applications slowing down, you can determine whether any latency devices
are attached to the fabric and where. You can use the CLI to display a history of bottleneck
conditions on a port. If the CLI shows above-threshold bottleneck severity, you can narrow the
problem down to device latency rather than problems in the fabric.
You can use the bottleneck detection feature with other Adaptive Networking features to optimize the
performance of your fabric. For example, you can do the following:
• If the bottleneck detection feature detects a latency bottleneck, you can use TI zones or QoS
SID/DID traffic prioritization to isolate latency device traffic from high priority application traffic.
• If the bottleneck detection feature detects ISL congestion, you can use ingress rate limiting to slow
down low priority application traffic, if it is contributing to the congestion.
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