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Manual Chapter: BIG-IP Local Traffic Manager version 9.3 Implementations: Using RAM Cache for HTTP Traffic
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13

Using RAM Cache for HTTP Traffic


Introducing HTTP RAM Cache

An optional feature of the BIG-IP® system is its HTTP RAM cache. A RAM cache is a cache of HTTP objects stored in the BIG-IP system's RAM that subsequent connections can reuse to reduce the amount of load on the back-end servers.

When to use the RAM Cache

The RAM Cache feature provides the ability to reduce the traffic load to back-end servers. This ability is useful if an object on a site is under high demand, if the site has a large quantity of static content, or if the objects on the site are compressed.

  • High demand objects
    This feature is useful if a site has periods of high demand for specific content. With RAM Cache configured, the content server only has to serve the content to the BIG-IP system once per expiration period.
  • Static content
    This feature is also useful if a site consists of a large quantity of static content such as CSS, javascript, or images and logos.
  • Content compression
    For compressible data, the RAM Cache can store data for clients that can accept compressed data. When used in conjunction with the compression feature on the BIG-IP system, the RAM Cache takes stress off of the BIG-IP system and the content servers.

The items you can cache

The RAM Cache feature is fully compliant with the cache specifications described in RFC 2616, Hypertext Transfer Protocol -- HTTP/1.1. This means that you can configure RAM Cache to cache the following content types:

  • 200, 203, 206, 300, 301, and 410 responses.
  • Responses to GET methods by default.
  • Other HTTP methods for URIs specified in the URI Include list or specified in an iRule.
  • Content based on the User-Agent and Accept-Encoding values. The RAM Cache holds different content for Vary headers.

To use the RAM Cache feature, you need to:

  • Create a custom HTTP profile.
  • Create a virtual server.

For more detailed, background information on configuring the RAM Cache feature, see the Configuration Guide for BIG-IP® Local Traffic Management.

Creating a custom HTTP profile

The first task in configuring the HTTP RAM Cache feature on the BIG-IP system is to create a custom HTTP profile. An HTTP profile defines the way that you want the BIG-IP system to manage HTTP traffic.

After you create the custom HTTP profile, you create a virtual server and assign the custom profile to that virtual server.

To create a custom HTTP profile

  1. On the Main tab of the navigation pane, expand Local Traffic, and click Profiles.
    This displays a list of any existing HTTP profiles, including the default profile http.
  2. In the upper-right corner of the screen, click Create.
    The New HTTP Profile screen opens.
  3. In the Name box, type a name for the custom profile, such as http_ramcache
  4. Ensure that the Parent Profile setting is set to http.
  5. In the Settings area of the screen, retain all default values.
  6. Scroll down to the RAM Cache area of the screen.
  7. For the RAM Cache setting, on the far right side of the screen, click the Select box, and select Enabled from the RAM Cache list.
  8. For all other settings in the RAM Cache area of the screen, retain the default values, or configure them to suit your needs.
  9. Click Finished.

Creating a virtual server

The next task in configuring the RAM Cache feature is to define a virtual server that references the custom HTTP profile that you created in the previous section.You use the Configuration utility to create the virtual server.

To create a virtual server for HTTP RAM Cache

  1. On the Main tab of the navigation pane, expand Local Traffic, and click Virtual Servers.
    The Virtual Servers screen opens.
  2. In the upper-right corner of the screen, click Create.
    The New Virtual Server screen opens.
  3. Note: If the Create button is unavailable, this indicates that your user role does not grant you permission to create a virtual server.
  4. In the Name box, type a name for the virtual server, such as vs_http_compress.
  5. In the Destination box, verify that the type of virtual server is Host, and in the Address box, type an IP address for the virtual server.
  6. In the Service Port box, type 80, or select HTTP from the list.
  7. In the Configuration area of the screen, retain the value of the Protocol setting, TCP.
  8. From the HTTP Profile list, select the custom HTTP profile that you created in the previous section. In our example, this value would be http_ramcache.
    This assigns the custom HTTP profile to the virtual server.
  9. In the Resources area of the screen, locate the Default Pool setting and select a pool name.
  10. From the Default Persistence Profile list, select source_addr.
    This implements the default profile for source address affinity persistence.
  11. Click Finished.



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