[IPP] Impressions vs. images for IPP FaxOut service

[IPP] Impressions vs. images for IPP FaxOut service

Michael Sweet msweet at apple.com
Fri Nov 4 16:49:21 UTC 2011

On Nov 3, 2011, at 2:57 PM, William Wagner wrote:
> Hi Mike,
> Your option 1 is consistent with the decision to follow the 5106.1 distinction between images and impressions. As IPP is extended to include the MFD services beyond print, I think it is important to maintain the distinction. With respect to FaxOut, I appreciate that some applications may have lumped this service in with print, in which case using a different attribute is a disruption. If we were just extending IPP to FaxOut, fudging impression to mean images might be reasonable; but as Ira has suggested, it would be particularly confusing in some other services.

I think we have general consensus that option 1 is the right approach. The current draft already has the per-destination image count, so job-images-completed will just be a roll-up count.

> However, although the impressions/images/sheets/pages issue has seemed fairly clear for those of us who worked on 5106.1, it apparently has been an issue for you; so I wonder if we are missing something?

The confusion for me (and many vendors, based on the implementations I have seen) has been the plethora of definitions to date, the lack of concrete examples for the edge cases, and the lack of any normative references to 5106.1 in any IPP specification. I know I personally only ever thought of 5106.1 as a counter MIB and not as something that had broader reach/implications for higher-level protocols.

(Obviously we are going to fix the referencing issue, and I am preparing an errata for RFC 2911 to provide a normative reference to 5106.1 for job-media-sheets/-completed and job-impressions/-completed)

Michael Sweet, Senior Printing System Engineer, PWG Chair

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