Monitoring HTTP compression

HTTP compression reduces file sizes by using algorithms to eliminate redundant data. For more information, see Overview of HTTP compression. When compression is enabled, you can obtain information about its use from the Forefront TMG logs. To do this, you need to specify that compression information is displayed when a log queries runs, as follows:

Adding HTTP compression information to the log viewer

1. In the Forefront TMG Management console tree, select Monitoring.

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 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—**This 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—**This indicates whether Forefront TMG requested compression from the Web server.
   • **Cache—**This 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 follows:(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

   Note

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