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I just noticed that when SO main page is loaded in Firefox with "Automatically load images" unchecked that single load consumes about 400 kilobytes of traffic - I used Net Limiter to measure that. That seems to happen on every reload.

Is that me and Firefox or is it how it is done on the site? Can anything (except opening the main page less often) be done to reduce traffic?

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only, 128kb for me for SO, do you have any proxy server that drops gzip compression headers? or have some extensions / userscripts that inject something to the pages? – YOU Mar 22 '11 at 8:48
It is worth noting that the 400kb are the uncompressed amount. I get 116 kb of overall compressed traffic when loading everything from scratch. Also, about 200kb out of the 400 are external, cached resources that will not usually be loaded when refreshing the front page. – Pëkka Mar 22 '11 at 8:48
@YOU: We have corporate ISA Server but I have no idea how to check whether it does something like what you mention. – sharptooth Mar 22 '11 at 9:00
Just FYI, I've found math.stackexchange.com site is 391kb, because it has embedded some fonts, scripts to render properly for math stuff. other beta SE sites are around 261 kb because of beta info stickers, so I'm afraid they cannot do any thing about that. – YOU Mar 22 '11 at 9:02
@sharptooth, Imm, I don't know how to configure ISA Server to allow accept-encoding, may be search on serverfault.com or superuser.com for howto? – YOU Mar 22 '11 at 9:04
for you reference, @sharptooth, here is my firebug screenshot with headers info, browsers sent "Accept-Encoding:gzip,deflate" and server use to response with "Content-Encoding:gzip" but some proxy server drops "Accept-Encoding" from request headers, server response non-gzipped contents back, so you got uncompressed big files as result. – YOU Mar 22 '11 at 9:18
@YOU: I see, I'll try to check that, however it will take some time. Thank you. – sharptooth Mar 22 '11 at 9:20
@YOU: Will Fiddler help me? I'm staring at the session inspector and it shows me that there's plain text returned - should I believe it? – sharptooth Mar 22 '11 at 9:34
@sharptooth, imm, I don't know fiddler, but it could be browser gunzipped first and give uncompressed version to browser plugins / scripts, so plain text or text/html could be ok for that case. May be, try to compare file sizes of your jquery.min.js, master.min.js, css files (with my firebug screenshot in above comment), and also check response headers for existance of "Content-Encoding:gzip" – YOU Mar 22 '11 at 9:41
@sharptooth we have a TMG firewall (the next version of ISA server) and as far as we can tell it does the deflation / decompression for you and we haven't found a way to test whether something external was compressed once it's inside your network. When we want to test if our servers are set up correctly we use something external to test compression. – Rup Mar 22 '11 at 10:01
@Rup: Do you count traffic for your employees? If so, is compressed or decompressed volume counted? – sharptooth Mar 22 '11 at 10:03
I don't know sorry. You'd hope it counts compressed but I'd be interested to know. (So that's where you're coming from - you want to keep your net usage stats down?) – Rup Mar 22 '11 at 10:07
@Rup: Yes, that's the primary problem for me at the moment. – sharptooth Mar 22 '11 at 10:11

2 Answers 2

up vote 3 down vote accepted

I just made two requests to the homepage http://stackoverflow.com/; the first one with an empty cache. Not counting images, here are the download volumes:

                   1. (full)    1. (gz)   2. (full)  2.(gz)
the page itself          187         30         184      30
jQuery                    77         26
master.min.js             65         24
all.css                   49         11
other JS                  37         19           7       7
total                    415        110         191      37

So assuming you're requesting gzipped content, the very first load has 110kb of network traffic; on subsequent loads (where your browser has the JS and CSS already cached), it's 37kb.

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Great, I guess the problem is on my side then. I'll try to check that. 110K is much better than 400K anyway. – sharptooth Mar 22 '11 at 10:20
I get 137 KB with an empty cache and 39KB with a primed cache. You can see the test results online at webpagetest here: webpagetest.org/result/110322_GY_783P – Ciaran Mar 22 '11 at 13:39
@Ciaran Yep, that's close enough. Note that I excluded images, and not all requests are identical (e.g. logged in or not, what ads are served, etc.) – balpha Mar 22 '11 at 15:11
Okay, I talked to our sysadmins and it turned out that ISA Server 2006 we're using was uncompressing the compressed traffic on the fly and even counted uncompressed amount and attributed that uncompressed amount to users. I don't know what exactly they changed - I only gave them link to this page technet.microsoft.com/en-us/library/bb794746.aspx but now the problem seems solved - Firefox receives compressed data and compressed amount is attrbuted. – sharptooth Mar 25 '11 at 7:41
@sharptooth: Makes a lot more sense -- glad it worked out! – balpha Mar 25 '11 at 8:24

I only see about 32 KB of compressed data for the homepage.

enter image description here

The only way to get more than this, is if

  • your browser or proxy is somehow interfering with normal browser / HTTP caching rules

  • your browser or proxy is somehow disabling standard HTTP compression

(you can view this same info in your copy of Google Chrome by pressing ctrl+shift+I then selecting the network tab in the panel at the bottom of your browser)

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