Responses from origin web servers include entity tags (ETags), which are arbitrary strings attached to a document that specify some characteristic of the document, such as a version, serial number, or checksum of content. A changed document includes a different ETag, enabling a client's GET request to use an If-None-Match conditional header to acquire a new copy of the document. Because not all web applications generate ETags consistently, the BIG-IP device creates its own ETag for each cached document that is based on a signature, or checksum, of the document's content. The BIG-IP device stores content signatures in the Metadata cache for other optimizations, including Intelligent Browser Referencing.

BIG-IP applications provide options to always or never send metadata. Additionally, you can specify a maximum size for the Metadata cache, in megabytes. All BIG-IP applications share the same Metadata cache.

BIG-IP policies cache ETag headers, which include the following:

• Request URL
• Content signature of the response body
• Application name for the matching request
• Metadata, including the expiration time, read time, and update time for content

1. On the Main tab, click Acceleration > Web Application > Applications. The Applications List screen opens.
2. Click the name of an application.
3. From the General Options list, select Advanced.
4. From the Send Metadata list, select Always.
5. In the Metadata Cache Max Size field, type a size in megabytes (MB) for the maximum cache size.
6. Click Save.

1. On the Main tab, click Acceleration > Web Application > Applications. The Applications List screen opens.
2. Click the name of an application.
3. From the General Options list, select Advanced.
4. From the Send Metadata list, select Never.
5. Click Save.