112 lines
7.2 KiB
HTML
112 lines
7.2 KiB
HTML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<meta name="DC.Type" content="topic" />
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<meta name="DC.Title" content="File compression for HTTP Server (powered by Apache)" />
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<meta name="abstract" content="This topic provides information on file compression and how output from your server is compressed before being sent to the client over the network." />
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<meta name="description" content="This topic provides information on file compression and how output from your server is compressed before being sent to the client over the network." />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2002,2006" />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<title>File compression for HTTP Server (powered by Apache)</title>
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</head>
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<body id="rzaiecompression"><a name="rzaiecompression"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">File compression for HTTP Server (powered by Apache)</h1>
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<div><p>This topic provides information on file compression and how output
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from your server is compressed before being sent to the client over the network.</p>
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<div class="important"><span class="importanttitle">Important:</span> Information
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for this topic supports the latest PTF levels for HTTP Server for i5/OS .
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It is recommended that you install the latest PTFs to upgrade to the latest
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level of the HTTP Server for i5/OS. Some of the topics documented here are
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not available prior to this update. See <a href="http://www-03.ibm.com/servers/eserver/iseries/software/http/services/service.html" target="_blank">http://www.ibm.com/servers/eserver/iseries/software/http/services/service.htm</a> <img src="www.gif" alt="Link outside Information Center" /> for more information. </div>
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<p>Compressed output is transferred to requesting client browsers at a higher
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rate of speed than noncompressed output. This decreases the amount of data
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that the server needs to send over the network and improves network performance
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and response times. </p>
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<p>Compression and decompression is implemented by the DEFLATE filter, located
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in <a href="rzaiemod_deflate.htm">Module mod_deflate</a>. The DEFLATE filter
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is always inserted after RESOURCE filters like PHP or SSI. It never touches
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internal subrequests. See <a href="http://httpd.apache.org/docs-2.0/mod/mod_deflate.html" target="_blank">Apache HTTP Server Version 2.0 Documentation</a> <img src="www.gif" alt="Link outside Information Center" /> for additional
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information and examples on configuring the Apache server to use compression.</p>
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<p>When the DEFLATE filter is used, a LoadModule is required in order to recognize
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the associated directives.</p>
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<blockquote><pre>LoadModule deflate_module /QSYS.LIB/QHTTPSVR.LIB/QZSRCORE.SRVPGM</pre>
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</blockquote>
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<div class="section" id="rzaiecompression__output"><a name="rzaiecompression__output"><!-- --></a><h4 class="sectiontitle">Output compression</h4><p>Files can be compressed
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by the server before output to the client. The server can be configured to
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only compress files which are located in specific containers or globally.
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Directive SetOutputFilter enables compression for files in the container
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where it is placed. For example:</p>
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<blockquote><pre>SetOutputFilter DEFLATE</pre>
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</blockquote>
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<p>Files
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being compressed can also be restricted to specific MIME types. In order
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to configure the server to restrict compression based on MIME types, the AddOutputFilterByType
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directive should be used. For example, to enable compression
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only for the HTML files located in a specific directory:</p>
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<blockquote><pre><Directory "/your-server-root/htdocs">
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AddOutputFilterByType DEFLATE text/html
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</Directory></pre>
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</blockquote>
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</div>
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<div class="section" id="rzaiecompression__input"><a name="rzaiecompression__input"><!-- --></a><h4 class="sectiontitle">Input compression</h4><p>Compressed files require
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decompression before they can be used. A filter is necessary for decompressing
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a GZIP compressed request body. The DEFLATE filter is required in the input
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filter chain and is set by using the SetInputFilter or the AddInputFilter.
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For example:</p>
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<blockquote><pre><Location /dav-area>
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SetInputFilter DEFLATE
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</Location></pre>
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</blockquote>
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<p>Requests containing a Content-Encoding:
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GZIP header are automatically decompressed. The Content-Length header specifies
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the length of incoming data from the client, not the byte count of the decompressed
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data stream. The actual length of the data will be greater than the Content-Length
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header indicates after the decompression has been done.</p>
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<div class="note"><span class="notetitle">Note:</span> Check your
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browser to ensure it supports GZIP request bodies.</div>
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</div>
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<div class="section" id="rzaiecompression__proxy"><a name="rzaiecompression__proxy"><!-- --></a><h4 class="sectiontitle">Proxy servers</h4><p>Proxy servers receive a
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Vary: Accept-Encoding HTTP response header to identify that a cached response
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should be sent only to clients that send the appropriate Accept-Encoding request
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header. The response header prevents compressed content from being sent to
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a client that cannot support it.</p>
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<p>Dependencies on special exclusions,
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for example, the User-Agent header, can be specified with an addition to the
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Vary header. The Vary header must be manually configured in order to alert
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proxies of the additional restrictions. For example, where the addition of
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the DEFLATE filter depends on the User-Agent, the following Very header should
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be added:</p>
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<blockquote><pre>Header append Vary User-Agent</pre>
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</blockquote>
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<p>If
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compression depends on information other than request headers, set the Vary
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header with a value of "<samp class="codeph">*</samp>". The "<samp class="codeph">*</samp>" prevents
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compliant proxies from caching entirely. For example:</p>
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<blockquote><pre>Header set Vary *</pre>
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</blockquote>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaieconcepts.htm" title="This topic provides concepts of functions on HTTP Server and IBM Web Administration for i5/OS interface.">Concepts of functions of HTTP Server</a></div>
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</div>
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</div>
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</body>
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</html> |