You want to know how the CPL http.client.persistence(preserve) works.
 

CPL on SGOS:

<Proxy>

http.client.persistence(yes|no|preserve)

The preserve option reflects the server's persistence to the client connection. In other words, if the server has chosen not to maintain persistence (and closes its connection after serving its response to the first request), the proxy will force the client to use a new connection for each request, and conversely, if the server chooses to maintain persistence, the proxy will attempt to do so on the client side also. (Note however that a client configured to never use persistence, for example a browser or application which only do HTTP 1.0, will ignore such attempts and use a new connection for each request regardless).

Refer to page 367 of the SGOS CPL guide.