Persistent Connections & Performance - Web Performance

Persistent Connections & Performance

Reaping performance benefits from using persistent connections on your HTTP web server is nothing new. In a recent test of a SSL site, one of our clients enabled persistent connections on their servers as part of a new deployment. The results were quite impressive: for a single user & negligible server utilization, page durations dropped from 12 seconds to only 3.5 seconds. Persistent connections can contribute to much of this duration difference by reducing the amount of time needed establish new connections. The use of SSL makes this feature even more important, as the SSL layer requires additional session negotiation. Despite the potential for better performance, many systems still today do not utilize this feature for one reason or another.

Load Tester can be easily used to identify a system which may not be using persistent connections. The best place to start is in the Headers View. The Headers View will identify both the protocol used, as well as other HTTP Headers being sent back.
Load Tester Headers View

If you see the header: “Connection: close”, then your site is not using persistent connections. Some servers may also send back a response using HTTP 1.0, in which case the connection most likely is not persistent.

So why would sites not support persistent connections?

Given those conditions, persistent connections aren’t necessarily the best choice for every possible configuration. But before writing them off entirely, we do recommend testing that option first: it can be an easy setting to improve end user experience considerably!

-Frank, Engineer at Web Performance

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