IBM 6.1.X manual Real-World Network Considerations

Real-World Network Considerations

In our lab environment, we had the luxury of our clients and servers being on the same LAN segment, so that they could take advantage of a high-bandwidth, low-latency network connection. However, this is typically not the case for real clients. Over a wide-area network, latencies can be significant, and bandwidth limited. In this case, the time to transfer the page content from the server to the client can become a significant contributor to overall page response time.

Here are some steps which can help alleviate this situation:

∙Compress content on the HTTP server

∙Allow client-side caching of images, Javascript files, and stylesheets, Details on these steps will be given below.

C O M P R E S S C O N T E N T O N T H E H T T P S E R V E R

Much of the content served by a WebSphere Portal site can be compressed to reduce transmission time and save network bandwidth. Typically, images should not be compressed (as they are usually stored in a compressed format), but other types of content can show a significant size reduction from compression.

IBM HTTP Server supports Deflate compression through the mod_deflate module. When it is enabled, the HTTP server checks the Accept-Encoding:header sent by the browser to see if it can accept a compressed version of the content. If so, the HTTP server will compress the content before sending it to the browser.

In one measurement, we observed an average of 65% network traffic reduction when Deflate compression is enabled. However, the compression operation does not come free as we also observed approximately a 10% processor utilization increase on the HTTP server.

To enable deflate compression in IBM HTTP Server, add the following lines in httpd.conf:

# compress everything but images

LoadModule deflate_module modules/mod_deflate.so DeflateFilterNote Input instream DeflateFilterNote Output outstream DeflateFilterNote Ratio ratio

#Insert filter SetOutputFilter DEFLATE

#Netscape 4.x has some problems...

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W E BS P HE R E P O R T AL V 6 . 1 T U N I N G G U I D E