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Don’t mess with my page, bro

March 7, 2014

One of my clients reported an issue – they were seeing “Waiting for 1.2.3.4″ and a blank screen when they tried to access the Apex web site I’d built for them. They were using Mozilla on a Windows PC, connecting via Vodaphone 3G – the problem was consistent, and it went away when they used their ADSL connection.

My initial response was “don’t use Vodaphone 3G” because the problem seemed to be outside of my area.  It appears to be a common issue, something that some mobile operators do to reduce image sizes – c.f. https://support.mozilla.org/en-US/questions/791180  and http://www.geekstogo.com/forum/topic/277895-suspected-issue-waiting-for-1234-in-firefox-on-at/

My client did a little more digging (he’s a techie as well) and found this: http://stackoverflow.com/questions/4113268/how-to-stop-javascript-injection-from-vodafone-proxy

After reading that I said I’d give it another go and see what could be done. As far as I could see, the only really viable solution is to add the “Cache-Control: no-transform” header to the responses. Since I’m using Apache, to do this I added the following to my apache config as per http://httpd.apache.org/docs/current/mod/mod_headers.html:

Header merge Cache-Control no-transform

That seemed to fix the problem. What this header does is instruct all intermediaries to not modify the content in any way – i.e. don’t try to recompress the images, don’t inject any extra CSS or javascript into the page, nothing. Adding this header does carry the risk that performance on some mobile networks may suffer (because they will no longer do the image compression), so it’s now up to me to make sure my pages and images are as small as possible.

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4 Comments
  1. What’s the syntax to stop the NSA sniffing packets?

  2. Can’t tell you Scott, I had to sign an NDA :)

  3. rimblas permalink

    Wow, very interesting.

  4. In Australian mobile telco’s we refer to the “Radio Frequency National Site Archive” (www.rfnsa.com.a) as the NSA. It’s fun to see people’s faces when they overhear us talking about NSA compliance for new cell towers.

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