Default, IIRC, is either 4 or 6 on IE8 / W7 and 2 on older browsers/OSs., which was fine in the days of dial-up and 1st generation DSL, but not much use for high speed fibre.
I read many moons ago ten is the limit, although I can't (for the life of me) work out why that should be the case. Decimal 10 is an unusual top-out for a hex number and a PITA (well; at least a waste) to store as a binary (1010 in a 4-bit word and 00001010 in an 8-bit word). Ten (as a limit) doesn't seem to make any sense (but we are talking about MS software here
). Unless the max connections per server value shares a word with something else (but still a stupid value, even if it's only allocated four bits - surely the limit would be 15 - or 16, depending on whether '0' is counted as zero or one).
but I don't know what to look for except snappier complex website loading
That's basically it...FWIU if allows IE to grab ten items at the same time, rather than two or six.
Less of a difference with IE8 / W7 (although 2/3rds as many items at once), but a massive increase from the default 2 of older browser/OS combinations.
In reality it makes little difference for largely txt based web sites, but does considerably speed up sites with large amounts of photos, Java, Flash embedded, etc.
BTW; it's a similar tweak (although in a totally different place in the registry for IE7.
No idea about IE9 - my guess is MS have either already adapted their latest browser (for faster connections) or moved it again!
The tweak does have a strange side-effect... Once enabled there's a slight pause when you load a new web page.
My guess is built into the browser (somewhere - good hunting) is a feature where IE (or Windows) waits until it has a response from all threads before loading anything on the page.
So you get a very slightly longer (albeit still quite short) initial pause, but then the page and all elements load much faster.
vDSL2 FTTC Infinity with BT
DL Sync 80Mbps
UL Sync 20Mbps