This filter and policy rewrites the TOS value on every TCP packet. Note: rewriting the TOS value in IP packet involves recalculating and resetting the checksum value for each IP packet.

Interpretation of Results

netperf does not provide per packet processing numbers. Service demand numbers are the closest approximation to the per packet overhead. Service demand indicates the amount of processing done per 1KB of data. For a TCP packet payload of 1460 bytes (MTU of 1500 bytes minus 40 bytes of TCP and IP header), the service demand numbers can be multiplied by 1.46 to get the approximate per packet processing time.

Another important measurement is CPU utilization. In the netperf tests, the CPU utilization numbers show that, for the 1000BaseT interface, more data (and hence more packets) were handled in a given time interval, requiring more processing time. As described in the introduction, this behavior is expected with HP-UX IPQoS.

Typical results from a netperf output indicate an increase in service demand by anywhere from 5 to 45 microseconds in a system with HP-UX IPQoS installed and a simple filter and policy configured, compared to a system without HP-UX IPQoS installed.

CPU utilization increases anywhere from 1% to 15% when HP-UX IPQoS is installed with a simple filter and policy on both 100BaseT and 1000BaseT connections. For faster connections, expect the CPU utilization to be higher.

Throughput utilization decreases anywhere from 1% to 10% when HP-UX IPQoS is installed with the simple filter and policy configured, especially on the 1000BaseT interface since more packets are processed.

Each test was repeated because of varying confidence level in the results reported by netperf. Only one set of data for each type of test is provided here.

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