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Note that in this kind of scenario the performance benefit of caching is network
performance, since the reverse proxy is normally sitting close to the back-end
server. A significant motive for caching with a reverse proxy is to offload the
serving of static cacheable content from back end application servers. This
leaves the often more expensive back end application servers free to focus their
CPU bandwidth on more complex dynamic and transaction-oriented tasks.
However, when caching is enabled on a reverse proxy, it is important that the
reverse proxy be properly protected. All content, even if it is completely static,
still needs to be protected. You do not want to wake up and find that the static,
non-confidential part of your Web site has been completely defaced by hackers
within the reverse proxies cache.
Reverse proxies with additional security
Reverse Proxies Secure Servers (RPSS) combine, in one box or product, the
functions of a pure reverse proxy and the functions of a security proxy as
described earlier.
Often, such RPSS products will have a plug-in component on the reverse proxy
that handles access control and authorization requests, combined with a back
end enterprise access system that actually verifies the access and authorization
rights of the user or client. This plug-in component is sometimes referred to as a
blade. For example, you may be using IBM Tivoli Access Manager as your
Enterprise Security Solution; you still have the choice of what blade to use at the
proxy level (WebSeal or the lighter plug-in sometimes called WebSeal-lite).
5.4 Reverse proxies and Lotus technologies
The majority of the Lotus Domino-based technologies have supported reverse
proxy scenarios for a number of years. That is with the exception of the Lotus
Sametime product, which only recently gained reverse proxy support. This is
described in more detail in the next section.
For the traditional Lotus Domino-based technologies (Notes/Domino, iNotes,
QuickPlace, and so forth) the following reverse proxy requirements for Domino
must be considered.
5.4.1 Domino caching considerations
The first consideration for caching is that Domino-based applications, sites, and
technologies can be very dynamic in nature. Based on this, any reverse proxy
implementation with caching enabled should be sure to honor the HTTP header
Chapter 5. Proxies 171