First : While doing the Manual Upgrade iOS using iTunes. Here I will give examples a chronological. This time, I have an iPhone with iOS 5.1.1 and I intend to do the upgrade to iOS 6.1 but I do not know if iOS 6.1.3 has been released in public, and I has been to download iOS 6.1 ipsw file and tried to Upgrade to iTunes and the result I get iTunes Error 3194, why is It happens? This is caused when the Apple has released a new version of iOS, you are do not longer allowed to do the upgrade to previous versions of iOS, the iOS 6.1. All you have to do is upgrade to iOS 6.1.3. Because of this is a new version of iOS is released by the Apple
Second : Do you try to Downgrade iOS on your iPhone iPad iPod. Maybe the reason, the latest iOS is very wasteful and do not stable. This also has a policy of the Apple. That you can no longer do the downgrade to a the previous iOS if the latest iOS has been released. the only way to be able to downgrade, without getting iTunes Error. you must have the previous iOS SHSH blobs and use the tool likes redsn0w or sn0wbreeze.
Third : Restore iOS uses the same iOS version. Do not ever think you can do it, if the latest iOS has been released By the Apple. The only way is to check if the latest iOS has been released By the Apple. if you find the latest iOS has been released By the Apple, The only way is to restore to that new iOS.
Understanding iTunes Error 3194 and How to Fix it
If you are not do things above and still get Error 3194, Please Try this way
Step 1: Close iTunes, if Open
Step 2: Find Hosts file on your computer by Location
Directory: / etc / hosts on Mac OS X:
Directory: c: \ windows \ system32 \ drivers \ etc \ hosts for Windows
Step 3: Open that hosts file, using notepad. then edit the file by adding the following text,
# 126.96.36.199 gs.apple.com
# 127.0.0.1 gs.apple.com
# 188.8.131.52 gs.apple.com
Step 4: Place the best way is the iPhone, iPad, your iPod in DFU MODE Conditions, Do it Upgrade or Restore as normal