Google.com and clients1.google.com/generate_204

Question

I was looking into google.com\'s Net activity in firebug just because I was curious and noticed a request was returning \"204 No Content.\"

It turns out that a 204 N

Answer 1

This documents explains:

http://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1417&context=ecetr&sei-redir=1

(Search for generate204)

Relevant section:

Among the different objects, a javascript function triggers a generate204 request sent to the video server that is supposed to serve the video. This starts the video prefetch, which has two main goals: first, it forces the client to perform the DNS resolution of the video server name. Second, it forces the client to open a TCP connection toward the video server. Both help to speed-up the video download phase.

In addition, the generate204 request has exactly the same format and options of the real video download request, so that the video server is eventually warned that a client will possibly download that video very soon. Note that the video server replies with a 204 No Content response, as implied by the command, and no video content is downloaded so far.