How to Test a Quality of Service Configuration

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Article ID: 5407 

Protocols/Features
QoS
CoS
ToS

Standards
802.1p
802.1d

Goals
Test a Quality of Service configuration
Verify the packet count in each priority transmit queue

Symptoms
Priority

Solution
Generally speaking, it is not possible to directly verify the count of packets that enter into, drop from, or are transmitted from each of the hardware transmit queues of an Enterasys device.

That being said, here are some possibly helpful test procedures:

  • To determine whether configured ToS/Priority/VLAN reassignments are functioning, inject a known mix of ingress traffic and then analyze (with a "Sniffer") the mix of egress traffic. The transmitted ToS value will be apparent on IP frames, and the transmitted 802.1p Priority and 802.1q VLAN will be apparent if 802.1Q Tagging is enabled on egress (5811).
  • To gain insights regarding transmit queue (7584) behavior, perform a similar test after (a.) ensuring that any given priority is mapped to a unique transmit queue and (b.) ensuring that the injected traffic is of sufficient volume to over-subscribe the available transmit bandwidth (possibly reduced via Outbound Rate Limiting). Only lower-priority traffic should be dropped as necessary to conform with available bandwidth constraints, unless only higher-priority traffic remains to be dropped.
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Posted 4 years ago

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