What is an HP Jetdirect?
When printers were directly connected to network spoolers, often a simple hardware protocol was
used to send data from the PC to the printer. Centronics mode on a parallel port would be an
example. As customers demanded faster data transfer speeds and richer status, these protocols
became more complex as in IEEE 1284.4. In short, a printer had direct connect ports (e.g., serial,
parallel) that implemented a hardware protocol and converted encapsulated data into just data for
printer consumption. As customers began to network their printers, HP decided to embark on a
strategy that still remains in use to this day: Use a smart networking card to implement the various
networking infrastructure components to convert encapsulated network data into data for printer
consumption. Thus, the HP Jetdirect was born – one of the first Networking Protocol offload engines.
Let's refer to Figure 1 – Functional Diagram
Figure 1 - Functional Diagram
In Figure 1, you can see the standard diagram of an offload engine. This diagram is by no means
comprehensive, but does convey the difference between HP Jetdirect and Printer/MFP platforms.
Why is this diagram important? First and foremost, we can understand what HP Jetdirect can do to
help in the security of your printing infrastructure. Secondly, we can also understand what HP
Jetdirect cannot do. As an example, some information on the Internet conveys that the PJL parser is
implemented on HP Jetdirect. Based upon this diagram, we know that is false. Upgrading your HP
Jetdirect card to provide your printer more PJL parsing protection is not going to be a good
investment. Upgrading your HP Jetdirect card to control who can and who cannot interact with your
printer is a good investment.