Internet Printing – How Windows decides if http or RPC is used for a Print Connection to an IPP Server

We often get asked from time to time how to force printers that a user has installed on their workstation using the IPP website to use RPC in lieu of the Internet printing protocol. There is a document available on TechNet that explains how to accomplish this:

http://technet.microsoft.com/en-us/library/cc757981(WS.10).aspx

(It’s as simple as changing the IE Zone Security to Medium-Low)

Often though, we run into customers who have already customized the settings in their IE Zone security and would still like to force the use of RPC for IPP printers without resetting those IE Zone settings to Medium-Low.

So what settings is the IPP printer really checking to accomplish this?

The process Windows uses to decide how to connect to a printer looks like this:

1. The OS checks if the following Registry Key is set:

[HKEY_CURRENT_USER\Printers\Settings\PreferredConnection]

If this key exists and its value is 0, the printer connection is using HTTP.

2. If the Registry Key is not set we are looking for two Settings:

a. Java Permissions

This Setting cannot be made inside IE. You have to configure the Settings with GPO.

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Java Permissions need to be at least set to Medium Safety to use RPC.

b. ActiveX

Additionally the OS checks the Value from “Initialize and script ActiveX controls not marked as safe for scripting”.

If the Value is disabled we will use RPC otherwise we will use HTTP for the Print Connection.

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A last pre-requisite is that the Protected Mode in IE needs to be turned off to use RPC

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-Bernd Hogen