Assess Compression Results

Instructions to increase WAN-link capacity and examine your gains due to compression

Packeteer's Xpress acceleration increases WAN-link throughput without imposing cumbersome administrative overhead. It makes it seem as if your WAN link offers more bandwidth than it really does.

For more background, see PacketGuide's Compression Overview and the white paper titled "Accelerating Throughput."

How much bandwidth savings are you getting from compression? Follow the steps below to find out.

1. Wait some time after enabling compression or changing compression's settings to allow traffic to pass and the changes to have an effect.
   
   
2. Display the compression summary. Compare throughput rates with and without compression, and examine the bytes saved due to compression.
   
   If traffic is light or from applications that are not compressible (VoIP, encrypted, and others), rates will not show a dramatic difference. Also, overall savings for the entire link can look minimal due to much non-compressible traffic. Class-based reports show more representative savings.
   
   In addition, high-level or overall results can be misleading if some traffic goes to locations with Xpress units at the destination (compression is possible), and some traffic goes to destinations without Xpress units (compression is not possible). The summary figures average all traffic, compressed and not compressed, together.
   
   
3. Create the graph for Link Compression Bytes Transferred. This graph provides a visual impression of the difference compression has made. This one graph supplies a very big picture. It shows traffic volume that you:
   • Would have had without compression
   • Actually did have with compression
   • Saved due to compression
   • Could not compress (VoIP, encrypted, and so on)
     
     
4. Explore the variety of other compression-related graphs for individual classes (especially your critical and high-volume classes), partitions, and the link.
   
   Note that compression results are most informative when you display a graph or chart for one particular class, and the class has only one particular type of traffic.
   
   For example, suppose you have an Outbound traffic class for POP3 that contains both standard and encrypted email. Examining compression results for that POP3 class might not be very impressive. If your organization had a sudden burst of secure email (encrypted traffic does not compress well) then your overall compression figures for email would look rather poor. But if you were to separate the POP3 class into two subordinate classes, then you could run a compression report for the standard email class and see some great results.
   
   You might have a similar pattern with other classes that contain multiple types of traffic.
   
   If you need help or ideas in dividing your traffic tree into more granular classes, see Create an Application-Based Traffic Tree and Classification Hints and Examples.
   
   
5. Examine the output of the CLI command compression show.
   
   It offers information about several aspects of compression status: whether compression is enabled, the IP address and status of active tunnel partners, details about the services that have active flows being compressed, bytes saved due to recent compression, memory figures for amounts in use and available, and other information.
   
   The information can be helpful, but keep in mind that it shows status for only the most recent few packets. So whether your byte savings look stellar, dismal, or somewhere in-between, they are probably not representative of your overall savings.
   
   
6. If your compression seems not to be working well, see Compression Troubleshooting. If you want to tune Xpress for better compression results (an advanced project), see Accelerate Traffic.