Changes to Trickle Transfer in WebMarshal 6.5.5 and above

This article applies to:

• WebMarshal 6.5.5 and above

Question:

• How has Trickle Transfer changed in WebMarshal 6.5.5?
• How do I use Trickle Transfer and Streaming Content Types in WebMarshal 6.5.5 or above?

Information:

WebMarshal behavior and configuration for large files and streaming media is enhanced in version 6.5.5 and above.

For most installations, no action is required. The change will be handled automatically during upgrade.

Background:

WebMarshal Content Analysis rules (such as TextCensor and virus scanning) require the entire file to be available. This fact can cause several issues for web browsing.

1. For large files, if a download is held back until the entire file is available, the user's browsing experience is affected.
2. Software downloads and other very large files could be delayed long enough that the browser times out.
3. Streaming media present an additional issue because the file will effectively never be complete.

To address these issues, WebMarshal can send part of the file to the browser before completing processing. WebMarshal waits for a configurable time and/or amount of data before beginning to send the file.

Previous behavior:

Versions of WebMarshal before 6.5.5 "trickle" a configurable percentage of large files to the browser. This behavior displays file progress to the user, and also keeps the browser session alive. To resolve the issue of streaming media, certain MIME types could be defined as exempt from content analysis using the Streaming Content Types setting. However, the user still experiences "slow" file download, and streaming media settings can be complex to configure.

Changes in Version 6.5.5 and above:

In version 6.5.5 and above, the percentage trickle setting no longer applies. WebMarshal holds back a small amount (20KB or less) of all incomplete files that it is sending.

• This behavior does not increase virus or malware risk from file downloads, because the files will not be completely sent until they are scanned. If the scan indicates an infected file, the download is aborted.
• This behavior greatly enhances the perceived speed of downloads.
• This behavior also resolves the issue of streaming media. The list of Streaming Content Types is no longer required and it has been removed from the user interface.

Notes:

You can configure WebMarshal 6.5.5 and above to use the previous behavior (trickle a percentage of the file and explicitly define streaming types).

To configure this behavior, edit the file WMProxy.config.xml using an XML editor or a text editor

Add settings as follows:

<WebMarshal>
   <Proxy>
     <Config>
        <TrickleTransfer enabled="true" rate="{percentage rate}">
           <Streaming type="{type}" />
           <Streaming type="{type}" />
        </TrickleTransfer>
     </Config>
  </Proxy>
</WebMarshal>

• The file WMProxy.config.xml is located on the processing server. If you have more than one processing server, you must make the changes on each server.
• When entering the percentage rate and streaming types, do not include the braces {}, but do include the quote marks.
• You can add as many streaming type entries as you require.
• For instance, a common type is video/flv
• Back up configuration before making changes.
• The file WMProxy.config.xml normally contains additional settings. For this specific change, do not alter any other settings.
• For general information about editing XML settings files, see article Q12705.