[youngtaff]

Multiple parallel connections increases the likelihood of packet loss due to network congestion, is also imposes a larger load on servers and intermediate proxies.

A TCP handshake has to take place for each connection and this isn't cost free, and there's the SSL negotiations on top (though techniques like OCSP stapling help)

Going massively parallel isn't free - Will Chan of Chrome did a good write up here: https://insouciant.org/tech/network-congestion-and-web-brows...

[vidarh]

True, but my point is that unlike what zaptheimpaler seemed to imply, if you don't see massively parallel downloads in the network tab already, you are not going to see massively parallel downloads just because you get multiplexed streams, and the sites that do see parallel downloads are already for the most part going to do well.

So the real world impact for users is likely to be small:

Lowering the cost of multiple streams will likely give you decent percentage wise improvements on page download times that are already so good that the absolute improvements are likely to be small, and likely minimal to no improvements on the pages that are actually slow.

[dcsommer]

The real world impact is incredible, not small. Opening new connections is horribly, horribly bad for internet performance. http://www.chromium.org/spdy/spdy-whitepaper

[youngtaff]

Akamai report a 5-20% increase with some sites seeing no improvement.

With the advent of the browser pre-loader then as long as the resources are declared in the markup then the browser should discover them and issue the request.

Currently browsers often seemed to blocked on waiting for a connection to come free