I was at a customer location recently and they asked me, "Why is your control so big? My performance is being hurt by having to reload this huge map control every time I load my page." Hmm, time to investigate....

I opened up Firebug in Firefox and took a quick peek at the Virtual Earth Map Control...


891kb!!! Wow! That is huge. Something's wrong.

I'll give you the abridged version of what I found. Some corporate networks using proxy servers strip gzip compression. We use compression to shrink the size of the control to improve performance when distributing it to end users. If your proxy is removing the compression you get the 891kb version of the control (as seen above). The good news is most likely this WILL NOT filter down to your end users who are home using your web site - they'll be on a network connection without a proxy (or a broad proxy with compression honored); however, for your testing purposes you may see significant latency when downloading the control. You may also see a 891kb file! Don't freak out. Just send a nice e-mail to your friendly IT guys and ask them to enable gzip compression on the proxy server.

With compression, the control is sized 202kb. So, enable compression. Your network will thank you for it.

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