Why is a partition not getting all the bandwidth that has been allocated?

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Article ID: 167571

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Updated On:

Products

PacketShaper

Issue/Introduction

There are several situations in which a partition may not get all of its reserved bandwidth.

  • Overcommitted bandwidth
  • Partition minimum too low to satisfy the guaranteed rate

The Answer section below describes each of these situations in more detail.

Resolution

Overcommitted Bandwidth

This issue may be related to overcommitted bandwidth. If you have a unit with a link size of 10M and you have guaranteed partitions which aggregates to 20M, you are overcommitting by 10M.

In order to make the size of the guaranteed partitions equal to the specified link size, PacketWise will dynamically scale down all the partition sizes so that total of all the guaranteed partition sizes will be 10M — exactly equal to the specified link size. 

In order to get around this, do not overcommit the bandwidth. Do not guarantee more than you have specified on the link size. You can make the partitions burstable to a higher limit if you want.

The overcommittment applies only to the guaranteed portion of the partition, not to the burstable portion.For Packetwise version 5.1.1 or above:

If you look at the Partition Summary, you will be able to see whether you are overcommitting or not.

For more information, see View Partition Information in PacketGuide.

Partition Minimum Too Low

Another possibility is that the partition minimum is too low to satisfy the guranteed rate.

For example, suppose a guaranteed rate policy on a class is 100k and the partition size is 150k. In this configuration, only one flow can be admitted, and the rest would be refused (assuming admissions control is set to refuse). The partition would have 50k unused and unusable.