Benchmarking Differentiated Service

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Benchmarking Differentiated Service
Metrics for Measuring Differentiated Service
Performance Jerry Perser
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Abstract

• Previous effort has been concentrated on
  measuring the maximum performance under no loss
  environment.
• Differentiated Services and IP precedence should
  be measured only when their mechanisms are
  actively discarding frames.
• These mechanisms intelligently discard during
  congestion.

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Graph of Offered Load versus Forwarding Rate

• Starts as a linear equation.

Forwarding Rate
Offered Load
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Offered Load and Frame Loss

• Throughput is just one point on the graph.

Frame Loss
No Loss
Forwarding Rate
Throughput
Offered Load
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Metrics with frame loss present

• Measure performance beyond throughput.

Frame Loss
No Loss
Forwarding Rate
Throughput
Offered Load
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Current Metric

• Throughput
• Well known.
• Well defined.
• Does not measure all no frame loss conditions.
• Does not measure any frame loss conditions.
• Based on input and output observations.
• Not Atomic for devices with queues.
• Queues will increase perceived performance.

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Proposed Metrics

• Channel Capacity
• The maximum forwarding rate at which none of the
  frames are dropped by the device.
• Pure output-based measurement.
• Opposite of throughput.
• Compensates for queue size.
• May be less than Throughput rate.
• Code Point Forwarding Rate (CPFR)
• Measured by code point.

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Proposed Metrics on the Graph
CPFR
Frame Loss
No Loss
Channel Capacity
CPFR
Forwarding Rate
Throughput
CPFR
Offered Load
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Current Metric

• Latency
• Defined differently based on devices
  architecture.
• FIFO bit forwarding.
• LIFO Store and Forward.
• Not Atomic
• Measured at the throughput rate (RFC2544).
• Measures the Queue time.

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Proposed Metric

• Delay
• Measured from last bit in to the last bit out
  (LILO) of the IP datagram.
• Same method for any device.
• Not affected by back pressure.
• Uses the Relay Race Mentality
• You can not run until the previous guy lets go!
• Measured with AND without the queue time.
• Crosses different layer 1 and layer 2
  technologies.
• Measure more than one frame for minimum, maximum,
  average, and jitter delay.

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Proposed Metric

• Queue Size
• The maximum amount of space inside the device
  used to hold frames for a particular Class of
  Service.
• Forwarding of a frame may be on hold while a
  higher priority frame is forwarded.
• Measured independently from Delay.
• Units in frames or octets.
• Atomic measurement.

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The End
Fin