Return-Path: X-Original-To: apmail-httpd-cvs-archive@www.apache.org Delivered-To: apmail-httpd-cvs-archive@www.apache.org Received: from mail.apache.org (hermes.apache.org [140.211.11.3]) by minotaur.apache.org (Postfix) with SMTP id AAD9B180D1 for ; Thu, 17 Mar 2016 07:58:09 +0000 (UTC) Received: (qmail 72429 invoked by uid 500); 17 Mar 2016 07:58:09 -0000 Delivered-To: apmail-httpd-cvs-archive@httpd.apache.org Received: (qmail 72363 invoked by uid 500); 17 Mar 2016 07:58:09 -0000 Mailing-List: contact cvs-help@httpd.apache.org; run by ezmlm Precedence: bulk Reply-To: dev@httpd.apache.org list-help: list-unsubscribe: List-Post: List-Id: Delivered-To: mailing list cvs@httpd.apache.org Received: (qmail 72354 invoked by uid 99); 17 Mar 2016 07:58:09 -0000 Received: from pnap-us-west-generic-nat.apache.org (HELO spamd1-us-west.apache.org) (209.188.14.142) by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 17 Mar 2016 07:58:09 +0000 Received: from localhost (localhost [127.0.0.1]) by spamd1-us-west.apache.org (ASF Mail Server at spamd1-us-west.apache.org) with ESMTP id 15900C3071 for ; Thu, 17 Mar 2016 07:58:09 +0000 (UTC) X-Virus-Scanned: Debian amavisd-new at spamd1-us-west.apache.org X-Spam-Flag: NO X-Spam-Score: 0.999 X-Spam-Level: X-Spam-Status: No, score=0.999 tagged_above=-999 required=6.31 tests=[KAM_LAZY_DOMAIN_SECURITY=1, RP_MATCHES_RCVD=-0.001] autolearn=disabled Received: from mx2-lw-eu.apache.org ([10.40.0.8]) by localhost (spamd1-us-west.apache.org [10.40.0.7]) (amavisd-new, port 10024) with ESMTP id Ri-YHgEy04Mc for ; Thu, 17 Mar 2016 07:58:07 +0000 (UTC) Received: from mailrelay1-us-west.apache.org (mailrelay1-us-west.apache.org [209.188.14.139]) by mx2-lw-eu.apache.org (ASF Mail Server at mx2-lw-eu.apache.org) with ESMTP id E80975F23E for ; Thu, 17 Mar 2016 07:58:06 +0000 (UTC) Received: from svn01-us-west.apache.org (svn.apache.org [10.41.0.6]) by mailrelay1-us-west.apache.org (ASF Mail Server at mailrelay1-us-west.apache.org) with ESMTP id D61D2E0097 for ; Thu, 17 Mar 2016 07:58:05 +0000 (UTC) Received: from svn01-us-west.apache.org (localhost [127.0.0.1]) by svn01-us-west.apache.org (ASF Mail Server at svn01-us-west.apache.org) with ESMTP id AB98E3A0734 for ; Thu, 17 Mar 2016 07:58:05 +0000 (UTC) Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: svn commit: r1735373 - /httpd/httpd/trunk/docs/manual/howto/http2.xml Date: Thu, 17 Mar 2016 07:58:05 -0000 To: cvs@httpd.apache.org From: elukey@apache.org X-Mailer: svnmailer-1.0.9 Message-Id: <20160317075805.AB98E3A0734@svn01-us-west.apache.org> Author: elukey Date: Thu Mar 17 07:58:05 2016 New Revision: 1735373 URL: http://svn.apache.org/viewvc?rev=1735373&view=rev Log: Added some notes to the HTTP/2 howto Modified: httpd/httpd/trunk/docs/manual/howto/http2.xml Modified: httpd/httpd/trunk/docs/manual/howto/http2.xml URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/docs/manual/howto/http2.xml?rev=1735373&r1=1735372&r2=1735373&view=diff ============================================================================== --- httpd/httpd/trunk/docs/manual/howto/http2.xml (original) +++ httpd/httpd/trunk/docs/manual/howto/http2.xml Thu Mar 17 07:58:05 2016 @@ -47,6 +47,15 @@ better document to start with is http2 explained by Daniel Stenberg, the author of curl. It is available in an ever growing list of languages, too!

+

Too Long, Didn't read: there are some new terms and gotchas that need to be kept in mind while reading this document:

+
    +
  • HTTP/2 is a binary protocol, as opposed to HTTP 1.1 that is plain text. The latter is meant to be human readable (for example sniffing network traffic) meanwhile the former is not. More info in the official FAQ question.
    • +
  • h2 is HTTP/2 over TLS (protocol negotiation via ALPN).
    • +
  • h2c is HTTP/2 over TCP.
    • +
  • A frame is the smallest unit of communication within an HTTP/2 connection, consisting of a header and a variable-length sequence of octets structured according to the frame type. More info in the official documentation section.
    • +
  • A stream is a bidirectional flow of frames within the HTTP/2 connection. The correspondent concept in HTTP 1.1 is a request/response message exchange. More info in the official documentation section.
    • +
  • HTTP/2 is able to run multiple streams of data over the same TCP connection, avoiding the classic HTTP 1.1 head of blocking slow request and avoiding to re-instantiate TCP connections for each request/response (KeepAlive patched the problem in HTTP 1.1 but did not fully solve it).
    • +
@@ -112,8 +121,11 @@ Protocols http/1.1

This allows only HTTP/1 on connections, except SSL connections to test.example.org which offer HTTP/2.

+ Choose a strong SSLCipherSuite +

The SSLCipherSuite needs to be configured with a strong TLS cipher suite. The current version of mod_http2 does not enforce any cipher but most clients do so. Pointing a browser to a h2 enabled server with a inappropriate cipher suite will force it to simply refuse and fall back to HTTP 1.1. This is a common mistake that is done while configuring httpd for HTTP/2 the first time, so please keep it in mind to avoid long debugging sessions! If you want to be sure about the cipher suite to choose please avoid the ones listed in the HTTP/2 TLS blacklist.

+

The order of protocols mentioned is also relevant. By default, the first one is the - most peferred protocol. When a client offers multiple choices, the one most to the + most preferred protocol. When a client offers multiple choices, the one most to the left is selected. In

Protocols http/1.1 h2 @@ -172,11 +184,11 @@ ProtocolsHonorOrder Off never sent and the response to it will arrive soon..."

But there are restrictions: the client can disable this feature and the server may only ever PUSH on a request that came from the client.

-

The intention is to allow the server to send resources to the clien that +

The intention is to allow the server to send resources to the client that it will most likely need: a css or javascript resource that belongs to a html page the client requested. A set of images that is referenced by a css, etc.

The advantage for the client is that it saves the time to send the request which - may range from a few milli seconds to half a second, depending on where on the + may range from a few milliseconds to half a second, depending on where on the globe both are located. The disadvantage is that the client may get sent things it already has in its cache. Sure, HTTP/2 allows for the early cancellation of such requests, but still there are resources wasted.