HTTP compression reduces file sizes by using algorithms to eliminate redundant data. When compression is enabled, you can obtain information about its use from the Forefront TMG logs. To do this, you must specify that compression information is displayed when a log queries runs, as described in the following procedure.

Adding HTTP compression information to the log viewer

To add HTTP compression information to the log viewer

  1. In the Forefront TMG Management console tree, select Logs and Reports.

  2. In the details pane, select the Logging tab.

  3. Click Start Query.

  4. In the log that appears, right-click any column heading, and then click Add/Remove Columns. Use Move Up and Move Down to specify where the information should appear in the log headings.

  5. In the Add/Remove Columns dialog box, select the Filter Information column, click Add, and then click OK. The following information may appear in the Filter Information column:

    • Client—Indicates whether compression is enabled between Forefront TMG and the client, as well as whether the client requested compression. If both conditions are true, this will show Y (yes). If either condition is false, this will show N (no).

    • Server—Indicates whether Forefront TMG requested compression from the Web server.

    • Cache—Indicates whether content was served to the client from the cache. This sometimes mistakenly indicates Y (yes).

    • Compression Rate—The amount of compression that has taken place on a specific response. This is calculated as:
      (size of original response - size of compressed response) x 100/size of original response

    • Decompression Rate—The amount of decompression that has taken place on a specific response. This is calculated as:
      compressed output x 100/decompressed output

    A simple way to check whether compression is operational is to verify if either the compression rate or decompression rate is greater than 0.

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