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Switch Bandwidth SLE

Switch Bandwidth is one of the Service-Level Expectations (SLEs) that you can track on the Wired SLEs dashboard.

Switch Bandwidth SLE Example
Note:

To find the Wired SLEs dashboard, select Monitor > Service Levels from the left menu of the Juniper Mist™ portal, and then select the Wired button.

What Does the Switch Bandwidth SLE Measure?

Juniper Mist™ measures the available bandwidth on your network based on the queued packets and dropped packets for each configured queue. The ratio between total_DropppedPackets and total_QueuedPackets is used to determine congestion at the interface level. Thee most dropped queue is also noted in the details for distribution/affected items. This SLE can help you to determine if you need more wired bandwidth on your site.

You can click the Settings button (above the SLE blocks) to set the percentage to use as the success threshold for this SLE. The percentage represents the total_DropppedPackets as a portion of total_QueuedPackets.

Setting the Switch Bandwidth Threshold

Classifiers

When the Switch Bandwidth threshold is not met, Juniper Mist sorts the issues into classifiers. The classifiers appear on the right side of the SLE block. In this example, 33 percent of the issues are attributed to Congestion and 67% to Bandwidth Headroom. (See the classifier descriptions below the example.)

Switch Bandwidth SLE Example

  • Congestion—This classifier measures the number of output drops. When packets come into a switch interface, they are placed in an input queue (buffer). When the buffer becomes full, it will start to drop packets (TxDrops). We use a formula that takes into account the following ratios to determine if there are bad user minutes due to congestion:

    • TxDrops to TxPackets—Total transmitted bytes dropped to total packets transmitted.

    • Txbps to Link speed—Total bytes transmitted per second to link speed.

    • RxSpeed to Link speed—Total bytes received per second to link speed.

  • Bandwidth Headroom—This classifier is triggered if the bandwidth usage exceeds the threshold for this SLE.

  • Congestion Uplink—The SLE dashboard shows high congestion uplink when:

    • One of the neighbors is a switch or a router (known through LLDP).

    • The port is a Spanning Tree Protocol (STP) root port.

    • The uplink port has a higher number of transmitted and received packets compared to the other ports.

    • There is congestion due to aggregated Ethernet links and module ports.