Tag Archives: HTTP2

cURL and libcurl, Web

HTTP2, SPDY and spindly right now

1 Comment

SPDYOn November 28, the HTTPbis group within the IETF published the first draft for the upcoming HTTP2 protocol. What is being posted now is a start and a foundation for further discussions and changes. It is basically an import of the SPDY version 3 protocol draft.

There’s been a lot of resistance within the HTTPbis to the mandated TLS that SPDY has been promoting so far and it seems unlikely to reach a consensus as-is. There’s also been a lot of discussion and debate over the compression SPDY uses. Not only because of the pre-populated dictionary that might already be a little out of date or the fact that gzip compression consumes a notable amount of memory per stream, but also recently the security aspect to compression thanks to the CRIME attack.

Meanwhile, the discussions on the spdy development list have brought up several changes to the version 3 that are suggested and planned to become part of the version 4 that is work in progress. Including a new compression algorithm, shorter length fields (now 16bit) and more. Recently discussions have brought up a need for better flexibility when it comes to prioritization and especially changing prio run-time. For like when browser users switch tabs or simply scroll down the page and you rather have the images you have in sight to load before the images you no longer have in view…

I started my work on Spindly a little over a year ago to build a stand-alone library, primarily intended for libcurl so that we could soon offer SPDY downloads for it. We’re still only on SPDY protocol 2 there and I’ve failed to attract any fellow developers to the project and my own lack of time has basically made the project not evolve the way I wanted it to. I haven’t given up on it though. I hope to be able to get back to it eventually, very much also depending on how the HTTPbis talk goes. I certainly am determined to have libcurl be part of the upcoming HTTP2 experiments (even if that is not happening very soon) and spindly might very well be the infrastructure that powers libcurl then.

We’ll see…

cURL and libcurl, Network

HTTP2 Expression of Interest: curl

For the readers of my blog, this is a copy of what I posted to the httpbis mailing list on July 12th 2012.

Hi,

This is a response to the httpis call for expressions of interest

BACKGROUND

I am the project leader and maintainer of the curl project. We are the open source project that makes libcurl, the transfer library and curl the command line tool. It is among many things a client-side implementation of HTTP and HTTPS (and some dozen other application layer protocols). libcurl is very portable and there exist around 40 different bindings to libcurl for virtually all languages/enviornments imaginable. We estimate we might have upwards 500
million users or so. We’re entirely voluntary driven without any paid developers or particular company backing.

HTTP/1.1 problems I’d like to see adressed

Pipelining – I can see how something that better deals with increasing bandwidths with stagnated RTT can improve the end users’ experience. It is not easy to implement in a nice manner and provide in a library like ours.

Many connections – to avoid problems with pipelining and queueing on the connections, many connections are used and and it seems like a general waste that can be improved.

HTTP/2.0

We’ve implemented HTTP/1.1 and we intend to continue to implement any and all widely deployed transport layer protocols for data transfers that appear on the Internet. This includes HTTP/2.0 and similar related protocols.

curl has not yet implemented SPDY support, but fully intends to do so. The current plan is to provide SPDY support with the help of spindly, a separate SPDY library project that I lead.

We’ve selected to support SPDY due to the momentum it has and the multiple existing implementaions that A) have multi-company backing and B) prove it to be a truly working concept. SPDY seems to address HTTP’s pipelining and many-connections problems in a decent way that appears to work in reality too. I believe SPDY keeps enough HTTP paradigms to be easily upgraded to for most parties, and yet the ones who can’t or won’t can remain with HTTP/1.1 without too much pain. Also, while Spindly is not production-ready, it has still given me the sense that implementing a SPDY protocol engine is not rocket science and that the existing protocol specs are good.

By relying on external libs for protocol and implementation details, my hopes is that we should be able to add support for other potentially coming HTTP/2.0-ish protocols that gets deployed and used in the wild. In the curl project we’re unfortunately rarely able to be very pro-active due to the nature of our contributors, which tends to make us follow the rest and implement and go with what others have already decided to go with.

I’m not aware of any competitors to SPDY that is deployed or used to any particular and notable extent on the public internet so therefore no other “HTTP/2.0 protocol” has been considered by us. The two biggest protocol details people will keep mention that speak against SPDY is SSL and the compression requirements, yet I like both of them. I intend to continue to participate in dicussions and technical arguments on the ietf-http-wg mailing list on HTTP details for as long as I have time and energy.

HTTP AUTH

curl currently supports Basic, Digest, NTLM and Negotiate for both host and proxy.

Similar to the HTTP protocol, we intend to support any widely adopted authentication protocols. The HOBA, SCRAM and Mutual auth suggestions all seem perfectly doable and fine in my perspective.

However, if there’s no proper logout mechanism provided for HTTP auth I don’t forsee any particular desire from browser vendor or web site creators to use any of these just like they don’t use the older ones either to any significant extent. And for automatic (non-browser) uses only, I’m not sure there’s motivation enough to add new auth protocols to HTTP as at least historically we seem to rarely be able to pull anything through that isn’t pushed for by at least one of the major browsers.

The “updated HTTP auth” work should be kept outside of the HTTP/2.0 work as far as possible and similar to how RFC2617 is separate from RFC2616 it should be this time around too. The auth mechnism should not be too tightly knit to the HTTP protocol.

The day we can clense connection-oriented authentications like NTLM from the HTTP world will be a happy day, as it’s state awareness is a pain to deal with in a generic HTTP library and code.