This is my first blog entry in this new AppExpert Community site.
I am excited that we are now ready to tap into the power of the community to spread the
knowledge power of AppExpert amongst the user base of Citrix application networking products!
The first thing I would like to share is my core belief in the strength of AppExpert Policy system,
which is its ability to provide powerful, extensive, flexible and expressive policy control while keeping
the simple tasks extremely simple.
AppExpert blends the power of extremely advanced application layer policy control with the ease of point and
click ease of use in its declarative rule setting model. Also, while administrators can compose
very complex expressions and combine them into powerful predicates and rule sequences,
AppExpert does not forget to keep simple things simple – rules that are needed most often are
often just a click or two away!
This is in keeping with my often expressed analogy of Digital SLR camera model of admin interfaces.
(yes, my esteemed colleagues are indeed quite sick of hearing me expound on this analogy, but I will do so
here for this new audience! )
Even the most complex Digital SLR cameras come with a fully automatic “A” mode for point-and-shoot
simplicity, while presenting an “PA” mode for more advanced users who want to customize only a couple of
key settings and a fully custom “M” (manual) mode for full power and control of all the aperture, speed,
Lens, focus etc settings of the camera.
AppExpert similarly, makes it a quite simple click for simple content switching type rules. But it goes on to
provide full power of pattern matching, predicates and rule sequences, for the more advanced users.
Granted it does not provide the “M” mode of a “Turing-complete” programming language or custom
script exits – yet. The reason, is that Citrix architects have wanted to first natively provide
the advanced capabilities in the PA mode, rather than just punting
the task of key application layer policy rules to be programmed in scripting languages by the administrator
without first carefully understanding the customer requirements.
Other systems have jumped to “outsource” development of such policy capabilities to their users,
thus subjecting them to the rigors of hiring programming and scripting experts even for simple
app layer rules! And, sometimes they claim to provide a grab bag of such scripts on web-sites to
copy and paste for their use. That’s great, but have they stopped to think if that’s the way someone
can set up rules for their system without a scripting expert, what happens when something breaks in that
script or it is not 100% suited to their specific installation? Who troubleshoots when things go bump
in the middle of the night or user traffic shoots up on a popular web2.0 application and the script breaks?!
Further, most often such scripting system provide a level of performance that is an order of magnitude
slower than the native rules. So while tempting with complete freedom, these scripting environments
very often flatter to deceive, and are unsuitable for many demanding, high throughput applications.
Citrix architects have taken the approach of providing the best of both worlds by providing
powerful capabilities within the native AppExpert system so that even very demanding
policies can be set using the visual, declarative point and click paradigm. And, these rules execute
at the speed of the core switching engine, preserving the high throughputs. This means that
customers can achieve what they need with the robustness and speed and express it with the
ease of visual+declarative interface and leave it to the system to carry out their wish in the fastest
possible way. The engine keeps getting optimized, so they continue to get performance improvements
as well, completely transparently. With a script, they have to reprogram, retest, and suffer through
a new test of hard to troubleshoot corner case bugs!
But does that mean that AppExpert will never ever offer the M mode? To the contrary.
Long time users of AppExpert will note that it has consistently evolved
release after release to include more powerful features and more flexible capabilities.
This will continue and AppExpert will add more flexible and extensible policycapabilities.
Moreover, the Citrix architects are carefully examining a structured way
to allow customers to leverage their investments in gateway logic to be applied to customize
policy processing. You all will hear more about it as the plans get more concrete and closer to
Watch this space for exciting AppExpert improvements in an Citrix app networking system near you!
CTO, Application Networking Group,
Citrix Systems, Inc