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One of my customers has something installed on their site, which makes all their resources load from domain. All HTTP requests also have the following header:

Via: HTTP/1.1 GWA

All my searches of this particular header show "Google Web Accelerator", a client-side technology discontinued ca in 2006. I certainly don't have it installed (and even if I did, I'm pretty sure wget -S wouldn't make use of it).

Can you point me to a product that's used on this website? It's likely some kind of cache like Cloudflare or Torbit, but from Google.

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up vote 3 down vote accepted

The Via: header is added by proxies, both forward and reverse, and can appear in the request headers and the reply headers. That field containing "GWA" is notionally the hostname or pseudonym field, possibly an identifier for the proxy/firewall, e.g. "gateway A", :

  Via =  "Via" ":" 1#( received-protocol received-by [ comment ] )
  received-protocol = [ protocol-name "/" ] protocol-version
  received-by       = ( host [ ":" port ] ) | pseudonym

Since you're seeing that in the request headers (presumably on the web server itself), and you're not sending it, it must be a server side reverse-proxy/accelerator. My best guess is Google PageSpeed, you should be able to confirm it by checking the DNS CNAME for the web site, PageSpeed uses names matching * for content caching. I cannot confirm its behaviour with the Via header though, that could be added at any step on the way. You may be able to bypass the PageSpeed servers to confirm (or deny) if they add it by using something like:

wget -S --header "Host:"

Where is the real public IP of the hosted website (i.e. not a PageSpeed server), and is the real address.

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Indeed, I just learned it's PageSpeedService. It seems to be mod_pagespeed combined with a cache. The setup is described here: – GDR Apr 2 '13 at 19:43
Great, and thanks for the feedback! – mr.spuratic Apr 2 '13 at 22:46

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