Michael, Thanks for the comprehensive response to my questions on IPP USB and confirming my assumptions.
The only remaining question I have for the list at this time is - are there any Hosts, including model, OS and OS version (or other S/W requirements), presently available on the market (or otherwise) which support IPP USB as per the Specification? Thanks again, Carlos Rimola On Thu, Feb 27, 2014 at 7:37 AM, Michael Sweet <[email protected]> wrote: > Carlos, > > On Feb 26, 2014, at 9:33 PM, Carlos Rimola <[email protected]> wrote: > > Hi All, > > I have some quick and general questions regarding IPP over USB ("IPP USB" > for short). Some are related to Till's proposed project "Google Summer of > Code 2014 - IPP-over-USB printer support". Any help and feedback will be > greatly welcomed. I should mention that I am in favor of the proposed > project for this event. > > Assumptions (please confirm or correct): > > 1) This first one may be obvious but to be sure - I am assuming that we > are referring to IPP USB as defined in the "USB Print Interface Class IPP > Protocol Specification Revision 1.0" dated 12/5/2012 and published by > USB-IF and authored by HP's Smith Kennedy and Andrew R. Mitchell. I'll > refer to it as the "IPP USB Spec". > > Correct. > > 2) As I understand the IPP USB Spec, there is NO network interface, NOR > TCP/IP involved. The Communication Protocol to be used between Host and > Device (Printer) is *purely HTTP + IPP directly over USB*. A place where > this is noted is section 6.2 - "HTTP Headers" which states the following: > > *Since there is NO network interface connection, NO DNS hostnames or IP > addresses, and NO TCP port numbers associated with USB connection, the > requirements of the HTTP Host field is addressed by requiring that the > value of this header MUST be "localhost".* > > Please correct me if I am wrong on either of these assumptions. > > > Correct (a port number can be passed by the "client" over USB to allow > gateways/proxies to work...) > > Questions: > > 1) I know the Spec is already cast in stone but I would like to understand > what function HTTP serves and if it is only used for identifying "Host: > localhost" and the "/ipp/printer" path? In other words, could pure IPP > Requests/Responses and IPP expected format "Print Data" have sufficed? > > While you might get away with that for simple IPP messages, that wouldn't > work for document data since IPP by itself has no framing or other niceties > - you'd never know when the data ended. > > Also, the HTTP portion is used for the embedded web server, doing firmware > updates, and so forth. > > 2) Section 3.2 "Interface Set" paragraph 2 states that "All IPP USBcapable > Print class interfaces provided by a device MUST be functionally equal > from an IPP operation or HTTP perspective. In other words, any IPP > operation or resource path that is valid over one IPP USB interface MUST > be reachable via any and all of the IPP USB interfaces." > > Does this imply that, for example, a Request from the host can be sent > over one interface (I/F #1) and the response received over a different > interface (e.g., I/F #2)? > > No, each interface is an independent channel to the printer. > > The reason for this requirement is to prevent having an IPP USB endpoint > just for printing, and another just for scanning, and so forth. > Effectively IPP USB defines an interface protocol that allows arbitrary > HTTP and IPP requests to be performed. > > 3) The last question is much simpler but would be helpful to an > implementor - what specific printers (manufacturer, line and model) *on > the market* support IPP USB? I have seen references to HP Photosmart and > OfficeJet but no model given. Similarly, what Host(s) on the market, > including OS and version, support the IPP USB protocol with these Printers? > > Here is the latest list we have from HP: > > Deskjet 3520 > Envy 120 > Envy 4500 > Envy 5530 > Officejet 3620 > Officejet 4630 > Officejet 7610 > Officejet Pro 276 MFP > Officejet Pro X576 dw > Photosmart 5520 > Photosmart 6520 > Photosmart 7520 > > I know of four other manufacturers that either have shipping products or > will soon be shipping - will post here when I can do so publicly... > > _________________________________________________________ > Michael Sweet, Senior Printing System Engineer, PWG Chair > >
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