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That's a very simple approach which has some disadvantages. It just adds the Window-ID to all URLs. That works if users don't open e.g. a link in a new tab (it would clone a window - that isn't nice but not worse than the HTTP session itself). Furthermore, a "drop" script detects the "open in new tab" use-case and drops the current window-id and requests the page again with a new window-id.
There must be a per-use way to disable the inclusion of the URL in a link.

custom-Mode

This mode allows that a JSF implementation or RenderKit provides a proprietary mode which is even more optimized - e.g. using an intermediate page which can be stored in the local-storage of HTML5.
Values: custom:name of the mode e.g.: <param-value>custom:intermediate-page</param-value>

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