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I have a very strange network issue related to my PC (Win7 64bit pro) and http traffic. In general it is all about strange 5s/10s delays for resources obtained using http protocol.

I am 100% sure it is not related to the web browser – it all happens in firefox, chrome and IE9 – I’ve spent lot of time to verify that. It even happens when I access http using fiddler or via system sockets. So in general it is not related to the software I am using.

I can also say for sure (99.9% sure ;-) that some software or hardware is interfering in the traffic as delay occurs in very similar cases when the host is accessed using FQDN and resource's Content-Encoding is gzip and when http works on port 80. For example - say I am working on host A and trying to access

http://hostB_FQDN/test.txt file

Even if it is in my company LAN I wait 5seconds before it is retrieved. Moreover 'test.txt' has its Content-Encoding set to gzip. If I access jpg, gif, png there is no delay (but they have no gzip encoding set in http header).

Moreover if I access

http://hostB_IP/test.txt

there is no delay but it is not DNS related as delay happens after 3way handshake (Wireshark shows that) and before packet with 'GET /test.txt.'. DNS works fine from my PC – fast – no delays – it is not DNS related and happens with HTTP only no other protocols affected.

If that would be DNS related I would have delay before connection and not in the middle.

Weird but using IP instead of FQDN and setting web server to work on port other than 80 (81 for example) allows me to use FQDN without delays - for example:

http://hostB_FQDN:81/test.txt

works perfectly.

I suspect some software/hardware to interfere with my http traffic when HTTP header contains 'Host: FQDN' and 'Content-Encoding: gzip'.

Any suggestions? I have 'TREND MICRO Office scan' crap installed by IT on my pc that I cannot remove. Can this interfere?

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Suggestions-not in any particular order.. obviously consider the difficulty of the suggestion / time it takes / amount of bother / likelyhood, and do them / troubleshoot in an order according to such factors). Try another host with that file - could be a free hosted web server with the file. Try it from a Virtual Machine, try different operating systems in the virtual machine. Try it from another computer attached to your router(quick and easy to try). Try another router. If possible, try another ISP(in the UK, while DSL is contract, dialup is PAYG and one can pick any). You could take all your hardware(router,cable,computer etc) (easier if laptop produces same issue) to a friend's place he may have a different ISP. Try booting off a Live CD

Try with wget, and this has the added advantage that you can manually enter a header. download gnuwin32, with coreutils and wget. (coreutils isn't necessary but it's useful). C:\>wget -d --header="test:abc" www.whatismyip.com you may be able to experiment with that like with the Content-Encoding header.

It could also be something at their end, as you only mention HostB. So try another host e.g. HostB2, and try connecting to HostB and a Host B2, from another computer like I see you tried this from work. Try it from home, connecting to HostB.

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  • thanks for suggestions - it affects all servers I am accessing but I am trying to investigate it in LAN - other hosts accessing same resources do not have this problem as I have. On LAN I have access to both my machine and web servers. I've even started wireshark both on server and my host side. Both wiresharks show 5s delay between 3way handshake and 'GET /test.txt' packet. As if my host is waiting for something. There is another host attatched to the same switch - and it works fine. I'll try with fiddler to use FQDN to access test.txt but will place IP in 'Host:' header ;-)
    – Artur
    Feb 15, 2013 at 11:01
  • @Artur I don't think the Host header is for an IP. When present, it only ever takes a domain. The reason is the purpose of the Host header. We know the IP and it is of course that of a webserver as we http to it, so no need to repeat that IP in in a request header, but that IP may host many websites each in a different directory. sure the domains all translate to the same IP, but the web server sees the Host header and points to the right directory/folder for which website to show. Of my suggestions, booting off a Live CD or USB might be easy to try and may narrow things down a lot.
    – barlop
    Feb 15, 2013 at 12:12
  • I guess a Live CD won't have the problem. You could reinstall windows. Or you could do a repair installation. Put the Win 7 CD in, and for Win 7 this only works within Windows. You get options Custom and Upgrade. Choose Upgrade. I haven't tried it but apparently that is the repair installation.
    – barlop
    Feb 15, 2013 at 12:17
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    I've found the root cause - this is (as I suspected) related to Trend Micro Office Scan - TMProxy.exe (Office Scan NT Proxy Service) - Once I killed this all workd perfectly. Thanks for all suggestions.
    – Artur
    Feb 16, 2013 at 13:30

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