[osth]

Yes, a major appeal of pipelining to me is efficiency with respect to open connections. It's easier to monitor the progress of one connection sending multiple HTTP verbs than multiple connections each sending one verb.

Whether multiple verbs over one connection are processed by the given httpd more efficiently than single verbs over single connections is another issue. IME, a purely client-side perspective, pipelining does speed things up. But then I'm not using Firefox to do the pipelining.

I'm sure the team reponsible for Googlebot would have some insight on this question. (And I wonder how much SPDY makes the bot's job easier?)

In any event, multiplexing would appear to solve the open connections issue. And I don't doubt it will consistently beat HTTP/1.1 pipelining alone. I'm a big fan of multiplexing (for peer-to-peer "connections"), but I am perplexed by why it's being applied at the high level of HTTP (and hence restricted to TCP, and all of its own inefficiencies and limitations).

I'm curious about something you said earlier. You said something about the "overhead" of using netcat. It's relatively a very small, simple program with modest resource requirements. What did you mean by overhead?

[akalin]

Re. multiplexing at the HTTP layer, because an HTTP replacement has to be deployable and testable. However, now that the ideas in SPDY have been proven and are on their way to being standardized, you can look at QUIC to see what can be done when not limited to TCP and HTTP.

By overhead I mean latency overhead -- running a program to download a site to a local file and then displaying it in a browser will almost certainly have a higher time to start render. Not to mention you're hitting everything cold (i.e., not using the browser's cache).

[osth]

I don't measure latency as including rendering time. Maybe I'm not "rendering" anything except pure html.

I measure HTTP latency as the time it takes to retrive the resources.

Whatever happens after that is up to the user. Maybe she wants to just read plain text (think text-only Google cache). Maybe she wants to view images. Maybe she wants to view video. Maybe she only wants resources from one host. Maybe she does not want resources from ad servers. We just do not know. Today's webpages are so often collections of resources from a variety of hosts. We can't presume that the user will be interested in each and every resource.

Of course those doing web development like to make lots of presumptions about how users will view a webpage. Still, these developers must tolerate that the speed of users' connections vary, the computers they use vary, and the browsers they use vary, and some routinely violate "standards". Heck, some users might even clear their browser cache now and again.

But HTTP is not web development. It's just a way to request and submit resources. Nothing more, and nothing less.