WEB SERVERS

Improving file-download performance for Web clients
Web clients can download a file that is attached to a page or that is in a server directory that is mapped by a URL. If a client is using a product that supports byte-range serving (available in HTTP 1.1 and higher) the client downloads the file in sections -- ranges of bytes -- and tracks the progress of each file download. If an interruption occurs, the client can resume the download from the point where it was interrupted. Without byte-range serving, users must repeat interrupted downloads from the beginning.

IBM® Lotus® Domino® is compatible with clients that support the HTTP 1.1 specification. The clients may be implemented in a variety of ways -- for example, as browser plugins, applets, or stand-alone programs.

Attached files must be decompressed so that clients that support byte-range serving can access them. When you attach a file, you must deselect the Compress option. To verify that an existing attachment is decompressed, from an IBM® Lotus® Notes® client choose File - Document Properties, select the $FILE item, and verify that the Compression Type property is NONE.

Example of downloading a file from the server's file system

The file INSTALL.EXE is located in a directory that is enabled for downloading using a URL-mapping. A GetRight 3.1 client can use the following URL to download the file:


where hostname is the name of the site.

If the download is interrupted, the client can restart the download from the point where it was interrupted.

Example of downloading a file attachment

A user can download a PDF file one page at a time if the PDF file is attached to a document and the user has set the configuration option in Adobe Acrobat to download a page at a time. Downloading one page at a time can greatly improve performance if the user is interested in only a portion of a large file. For example, a user accesses the PROJECT.PDF file using the following URL:


where hostname is the name of the site, dbname is the name of the database that stores the attachment, viewUNID is the Universal ID of the view for the attachment, and docUNID is the Universal ID of the document to which the file is attached.

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