Simulation help: Queue Settings

• FIFO Queueing
  The simplest form of queuing. Perfect reference.
• LDoLL Queuing
  A simple priority system with two different priorities
• LDoLL with limited LD buffer
  A slightly modified LDoLL Queue. The modifications improve the delay characteristics of Low Delay traffic.
• LDoLL Extended
  An queue based on LDoLL but with a far greater number of priorities.
• Voice First
  A very simple mechanism with limited possibilities, but attractive capabilities
• FIFO-Tail drop
  A normal FIFO queue that uses tail drop instead of head drop.

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LDoLL provides two different treatments for packets. One is concentrated on providing the lowest possible delay; the other is concentrated on providing the lowest possible loss. Serving the low delay packets first fulfills this objective, and only serving the low loss packets when there are no low delay packets left. However, when too much low loss packets are in the buffer waiting, their loss probability increases. Therefor, a threshold value is used. When the number of Low Delay bytes in the buffer exceeds the threshold, Low Loss packets are serviced first.

LDoLL has three parameters: The queue's size must be specified in bytes. The second parameter defines when an incoming packet is specified as Low Loss or low delay. It is the lowest class code used for Low Delay. Every packet with a class code (traffic type) equal or higher than this number is treated as Low Delay. Packets with lower numbers are treated as Low Loss
The last parameter is the threshold used to determine when Low Loss traffic receives service.

The traffic types are numbered as follows:

LDoLL also has some extensions. LDoLL with limited LD buffer limits the number of bytes that may be used by LD traffic. This implies that LD packets will have a higher loss probability than they used to have. It will also decrease their delay. LDoLL with limited LD delay drops Low Delay packets when their delay would be above a preset threshold. This also leads, of course, to a higher loss probability.

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LDoLL Extended is an extension of the LDoLL mechanism to allow more different priorities.
This queue organizes the different classes in four groups as shown in the picture below.

The groups indicated with the diagonal gray bars each have a time-slice assigned to them. You must specify these time-slices in bytes.
Within each group, LDoLL is used to determine which packet receives service. You can specify these thresholds on two levels. One is the threshold that determines when EE, CL or VI receives service. The second determines when BE or CL- receives service. XS is treated in a different way: It will only receive service when neither EE, BE nor BK has any packet waiting.

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The same as FIFO-Queuing, with one difference: Instead of dropping packets at the front of the queue, packets are dropped at the back of the queue. This will result in a different delay.

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