Measuring Reliable Session Speed

What kind of a performance impact does ensuring reliable delivery have? A common rule of thumb that I've heard circulated in the past is that turning on a feature such as reliable messaging or security cuts your throughput roughly by half. I decided to put this rule of thumb to a test by taking some measurements. I instrumented a simple service to collect data over the course of many calls. I used HTTP. I used custom bindings to match up exactly the same settings both with and without reliable sessions. All of this is completely irrelevant because your service has different message sizes, different processing times, a different network, or what have you. Your service simply won't have the same numbers.

Nevertheless, I looked at the data and decided how to best organize it. The striking feature was how much (or in some cases how little) the throughput impact changed when I varied the number of messages in each reliable session. Rather than give you numbers with unhelpful units, I created a unitless measure by dividing the throughput with reliable messaging on by the throughput with reliable messaging off.

As you can see, the throughput was roughly cut to a third when the sessions were ridiculously small and recovered to around 90% when the sessions were ridiculously large. I think that for reasonably sized sessions though, a number between 50 and 75 percent would not be out of the question. The rule of thumb seems pessimistic.

These measurements were taken under conditions where none of the packets were actually dropped of course. The efficiency gets worse if you need to retransmit something. However, it's meaningless to consider dropped packets when one part of the measurement is non-reliable transfer. Non-reliable transfer doesn't work when packets are dropped. You can make something extremely fast if it doesn't need to be correct.

Next time: Measuring Reliable Session Speed with Duplex

Comments

• Anonymous
  August 22, 2007
  MSMQ has gotten a bit of an upgrade in the latest releases, particular in the area of poison message