diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/HTTP2.md | 99 | ||||
| -rw-r--r-- | docs/Makefile.am | 4 |
2 files changed, 101 insertions, 2 deletions
diff --git a/docs/HTTP2.md b/docs/HTTP2.md new file mode 100644 index 000000000..e9084233b --- /dev/null +++ b/docs/HTTP2.md @@ -0,0 +1,99 @@ +HTTP2 with libcurl + + Spec: http://www.rfc-editor.org/rfc/rfc7540.txt + + Document explaining it: http://daniel.haxx.se/http2/ + + Build prerequisites + - nghttp2 + - OpenSSL, NSS, GnutTLS or PolarSSL with a new enough version + + nghttp2 (https://github.com/tatsuhiro-t/nghttp2) + + libcurl uses this 3rd party library for the low level protocol handling + parts. The reason for this is that HTTP/2 is much more complex at that layer + than HTTP/1.1 (which we implement on our own) and that nghttp2 is an already + existing and well functional library. + + We require at least version 1.0.0. + + Over an http:// URL + + If CURLOPT_HTTP_VERSION is set to CURL_HTTP_VERSION_2_0, libcurl will + include an upgrade header in the initial request to the host to allow + upgrading to http2. + + Possibly we can later introduce an option that will cause libcurl to fail if + not possible to upgrade. Possibly we introduce an option that makes libcurl + use http2 at once over http:// + + Over an https:// URL + + If CURLOPT_HTTP_VERSION is set to CURL_HTTP_VERSION_2_0, libcurl will use + ALPN (or NPN) to negotiate which protocol to continue with. Possibly + introduce an option that will cause libcurl to fail if not possible to use + http2. Consider options to explicitly disable ALPN and/or NPN. + + ALPN is the TLS extension that http2 is expected to use. The NPN extension + is for a similar purpose, was made prior to ALPN and is used for SPDY so + early http2 servers are implemented using NPN before ALPN support is + widespread. + +SSL libs + + The challenge is the ALPN and NPN support and all our different SSL + backends. You may need a fairly updated SSL library version for it to + provide the necessary TLS features. Right now we support: + + OpenSSL: ALPN and NPN + NSS: ALPN and NPN + GnuTLS: ALPN + PolarSSL: ALPN + +Multiplexing + + Starting in 7.43.0, libcurl fully supports HTTP/2 multiplexing, which is the + term for doing multiple independent transfers over the same physical TCP + connection. + + To take advantage of multiplexing, you need to use the multi interface and + set CURLMOPT_PIPELINING to CURLPIPE_MULTIPLEX. With that bit set, libcurl + will attempt to re-use existing HTTP/2 connections and just add a new stream + over that when doing subsequent parallel requests. + + While libcurl sets up a connection to a HTTP server there is a period during + which it doesn't know if it can pipeline or do multiplexing and if you add + new transfers in that period, libcurl will default to start new connections + for those transfers. With the new option CURLOPT_PIPEWAIT (added in 7.43.0), + you can ask that a transfer should rather wait and see in case there's a + connection for the same host in progress that might end up being possible to + multiplex on. It favours keeping the number of connections low to the cost + of slightly longer time to first byte transfered. + +Applications + + We hide http2's binary nature and convert received http2 traffic to headers + in HTTP 1.1 style. This allows applications to work unmodified. + +curl tool + + curl offers the --http2 command line option to enable use of http2 + +HTTP Alternative Services + + Alt-Svc is a suggested extension with a corresponding frame (ALTSVC) in + http2 that tells the client about an alternative "route" to the same content + for the same origin server that you get the response from. A browser or + long-living client can use that hint to create a new connection + asynchronously. For libcurl, we may introduce a way to bring such clues to + the applicaton and/or let a subsequent request use the alternate route + automatically. Spec: + http://tools.ietf.org/html/draft-ietf-httpbis-alt-svc-05 + +TODO: + + - Provide API to set priorities / dependencies of individual streams + + - Implement "prior-knowledge" HTTP/2 connecitons over clear text so that + curl can connect with HTTP/2 at once without 1.1+Upgrade. + diff --git a/docs/Makefile.am b/docs/Makefile.am index 1f92911a4..d745c4844 100644 --- a/docs/Makefile.am +++ b/docs/Makefile.am @@ -5,7 +5,7 @@ # | (__| |_| | _ <| |___ # \___|\___/|_| \_\_____| # -# Copyright (C) 1998 - 2014, Daniel Stenberg, <daniel@haxx.se>, et al. +# Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al. # # This software is licensed as described in the file COPYING, which # you should have received as part of this distribution. The terms @@ -38,7 +38,7 @@ EXTRA_DIST = MANUAL BUGS CONTRIBUTE FAQ FEATURES INTERNALS SSLCERTS \ KNOWN_BUGS BINDINGS $(man_MANS) $(HTMLPAGES) HISTORY INSTALL \ $(PDFPAGES) LICENSE-MIXING README.netware DISTRO-DILEMMA INSTALL.devcpp \ MAIL-ETIQUETTE HTTP-COOKIES LIBCURL-STRUCTS SECURITY RELEASE-PROCEDURE \ - SSL-PROBLEMS + SSL-PROBLEMS HTTP2.md MAN2HTML= roffit < $< >$@ |