WebSphere Application Server V7.0: Concepts ... - IBM Redbooks

In this example, a reverse proxy in the DMZ listens on the HTTP and HTTPS port
(typically port 80 and 443) for requests. The reverse proxy intercepts the
incoming requests and verifies if there is a valid copy of the requested object in
its cache. If a valid, cached version is found, the cached copy is returned to the
client. If no valid copy of the requested object is found in the local cache it
forwards those requests to the Web server in the internal network. Responses
are returned through the reverse proxy to the Web client, hiding the Web server
from the clients and allowing the proxy server to store a copy of the object in the
local cache, if the configuration permits.
Reverse proxy configurations support high-performance DMZ solutions that
require as few open ports in the firewall as possible. The reverse proxy requires
only one open port per protocol to access the Web server behind the firewall.
Advantages
Advantages of using a reverse proxy server in a DMZ configuration are as
follows:
► Independent configuration
The reverse proxy installation has no effect on the configuration and
maintenance of a WebSphere application.
► Improved performance due to caching
As the reverse proxy server provides caching capabilities, in most cases it can
respond faster to client requests because objects can be served out of the
cache. In most cases the response time and performance will improve.
► Off loading the Web servers
The reverse proxy servers delivered with WebSphere Application Server V7.0
provide caching capabilities, off-loading the Web servers and the application
servers if dynamic caching is supported as well.
Disadvantages
Disadvantages of a reverse proxy server in a DMZ configuration are as follows:
► Increased complexity
This configuration requires an the Caching Proxy component to be installed
and maintained, increasing the installation and configuration complexity. As
the Load Balancer is running on a separate system there are more systems to
manage and to operate, which in turn, increases the cost for the operation of
the environment. Consider these costs against the advantages you realize.
► Increased latency for non-cacheable objects
Requests for non-cacheable objects increase network latency and lower
performance To be effective, a sufficiently high cache hit rate is required.
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