QoS policy profiling

This test runs TCP and UDP sessions between two Test Agents to verify QoS class based bandwidth shaping for up to six different QoS (quality-of-service) classes.

You can specify the total expected throughput between the Test Agents, and also its expected distribution among the QoS classes for which throughput is important. Throughput is measured as TCP bandwidth. Each measured rate is allowed to deviate from the expected value by a specified percentage. If any of these deviation thresholds is exceeded, the test fails.

The picture below shows an example with three QoS classes.

For QoS classes where delay is more important than throughput, you can measure UDP buffer delay instead of TCP bandwidth. The critical metric here is the difference (increase) in UDP buffer delay when TCP streams in other QoS classes are running concurrently. A permissible UDP buffer delay deviation is specified for each class.

When the test is started, the UDP streams are started first and left running for 10 seconds. During this time, the average one-way delay is measured. Then the TCP streams are also started, and one-way delay is measured once more for the UDP streams. All streams are then left running for the specified duration.

The difference between the UDP buffer delay values with and without the TCP traffic must not exceed the specified UDP delay deviationotherwise the test fails.

The test also fails if any of UDP packet loss, (absolute) delay, or jitter goes above its respective threshold.

The DSCP and PCP (VLAN priority) value can be configured for each class.

The UDP streams are running at 50 kbit/s rate with configurable packet size.

When the TCP streams are started, the results for the first 2–3 seconds are skipped in order to give the TCP sessions time to stabilize.

Prerequisites

To run a QoS policy profiling test, you need to have two Netrounds Test Agents installed. If you haven't already done the installation, consult our quick start guides for various types of Test Agents in the section Netrounds Test Agents.

Note that the test requires exclusive access to the Test Agents; no other test nor monitoring can be active on the Test Agents during this test.

Create a new QoS policy profiling test and fill in the mandatory parameters below:

Parameters

All deviations are calculated as | measuredexpected | / expected × 100 %.

General

  • Server: The server interface.
  • Client: The client interface.
  • Traffic direction: Traffic direction. One of: Upstream (from client to server) or Downstream (from server to client). Default: Downstream.
  • Test duration (seconds): The duration of this test step in seconds. Min: 20 s. Max: 300 s. Default: 60 s.
  • Wait for ready: Time to wait before starting the test. The purpose of inserting a wait is to allow all Test Agents time to come online and acquire good time sync. Min: 1 min. Max: 24 hours. Default: "Don't wait", i.e. zero wait time.

Aggregate 

  • Total expected TCP rate (Mbit/s): The total expected TCP payload rate for all TCP streams combined. Range: 0.1 ... 10,000,000 Mbit/s. No default.
  • Max deviation from expected TCP rate (%): The allowed deviation from the expected total TCP rate, expressed as a percentage. Range: 0 ... 100 %. No default.

Advanced

  • Pause NTP on client: Pause the time synchronization during test. This might reduce time sync problems that can occur if the test is overloading the management interface. Value: Yes or No. Default: No. 

Class 1 ... Class 6 

  • Class name: The name of the class. Default names are simply "1" ... "6". 
  • Type of measurement: Bandwidth (TCP) or delay (UDP). Default: None. 
  • Number of TCP streams: Number of TCP streams. Range: 0 ... 15. Default: 1.
  • Server port: The TCP/UDP server port. Range: 1 ... 65535. Default: 5000. 
  • DSCP value TCP/UDP: DiffServ Code Point (DSCP) value for the TCP or UDP stream. Range: 1 ... 63. Default: 0.
  • VLAN priority (PCP): Priority bits in VLAN header. Range: 0 ... 7. No default.
  • Expected TCP rate (%): The expected combined TCP rate in this class as a percentage of the total rate. Range: 0 ... 100 %. No default.
  • Allowed TCP rate deviation (%): The allowed deviation from the expected TCP rate. Range: 0 ... 100 %. No default.
  • Frame size for UDP: Frame size for the UDP stream. Range: 64 ... 1518 bytes. Default: 1518 bytes.
  • Allowed UDP delay deviation (%): The allowed difference in UDP delay with concurrent TCP in other QoS classes as compared to the situation with no TCP. Range: 0 ... 1000 %. No default.
  • Loss threshold UDP (%): Maximum loss allowed for the UDP stream. Range: 0 ... 100 %. No default.
  • Delay threshold UDP (ms): Maximum (absolute) delay allowed for the UDP stream. Range: 0 ... 1000 ms. No default.
  • Jitter threshold UDP (ms): Maximum jitter allowed for the UDP stream. Range: 0 .. 1000 ms. No default. 

Result metrics – TCP bandwidth

  • Measured rate (Mbit/s): The measured TCP rate per class.
  • Measured rate (%): The measured TCP rate per class as percentage of the total rate. 
  • Rate deviation (%): The deviation from the expected TCP rate in percent.  

Result metrics – UDP delay 

  • Loss (%): The loss in the UDP stream before the TCP streams are started.
  • Loss under load (%): The loss in the UDP stream under TCP load.
  • Delay (ms): The delay for the UDP stream before the TCP streams are started.
  • Delay deviation (%): The delay for the UDP stream under TCP load.
  • Jitter (ms): The jitter for the UDP stream before the TCP streams are started. 
  • Jitter under load (ms): The jitter for the UDP stream under TCP load. 
The pictures below give some examples of results from a QoS policy profiling test.
 
The first screenshot shows measurements on a connection where three QoS classes share bandwidth according to a 60/30/10 partitioning.
 
 
The second screenshot shows TCP bandwidth results for two QoS classes ("BC", "BE") and UDP delay results for a real-time QoS class ("RT").
 
 
Both measurement types have pass/fail criteria defined according to the above description.
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