Stampa via Internet Printing Protocol (IPP)

con nessuno dei due printserver sembra sia possibile stabilire una connessione IPP sulla porta standard per questo protocollo

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The standard way of printing over the Internet is Internet Printing Protocol (IPP). IPP, which dates back to work done in the mid-90s by Novell and Xerox, uses the Web’s Hypertext Transfer Protocol (HTTP) as its primary protocol.

To use IPP, you need your print server to work in concert with a Web server. When a desktop client connects to the IPP server, it sends a printer request with the Multipurpose Internet Mail Extensions (MIME) media type “application/ipp” in a HTTP POST request. The server then sends the print request to your local printer.

For authorization and security, you must use a HTTP compatible system. Thus, for authentication you might use Generic Security Services Application Program Interface (GSSAPI) as a front-end to a Kerberos service. For security, you should use Hypertext Transfer Protocol Secure (HTTPS), which adds the SSL/TLS protocol.

By default, IPP uses TCP port 631, which probably requires the network staff to open up this port on the firewall. IPP doesn’t have to use that port though. With Windows, for example, you can use the usual Web 80 port or the more secure HTTPS port 443. On Macs and on Linux systems, which both use the open-source Common UNIX Printing System (CUPS) printing system, the IPP printing systems default to HTTP’s port 631.

An IPP-enabled print server should let remote users query the printer capabilities via a Web browser, such as whether they can print in color or black and white, choose 600 vs. 1200 dpi, get the printer’s status, monitor the printer’s print jobs, and, of course, submit and cancel print jobs. What data it actually provides depends on the specific capabilities of your IPP print servers.

With Windows Server 2003 and higher, users can also access IPP-enabled printers with an asynchronous remote procedure call (RPC) printer connection. This method, however, is reported to not work well with Windows XP’s print spooler, which doesn’t support asynchronous RPC. Other Microsoft reports state that asynchronous RPC was only introduced in Windows Server 2008 and up, and can only be used with Windows Vista and Windows 7. This results in Vista and Windows 7 PCs failing when they first try to print to a Windows 2003 RPC IPP printer.

There are three possible solutions:

• Upgrade your Internet print server to Windows 2007 or 2008 R2.
• Use straight IPP without the use of RPC, albeit this may result in slow print jobs.
• If you want to use RPC and you’re still using Windows 2003, you can disable Async RPC by adding the following registry key on the Windows 7 or Windows Vista clients:
  
  

Codice:

HKLM\Software\Policies\Microsoft\Windows NT\Printers\EnabledProtocols

Type: DWORD

Data: 6

Regardless of how you handle IPP, your local clients must also have the appropriate printer drivers. While “driverless” printing is on its way with IPP Everywhere (PDF), this is still a work in progress. In the long run, the IPP working group also plans to enable you to use scanners over the Internet.

That’s all fine and well if you have Web and print servers at your beck and call, but what if your office isn’t that big? True, you can use IPP on a client operating system such as Windows XP, but you risk your office’s security by using a client operating system to provide an Internet service.

Fortunately, there are other answers.

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