It strange for me because If IPP server accept empty HTTP request,
why client has to send Validate-Job Request.
I think authentication is done by URL. Clinet send HTTP requst to make
sure whether the URL requires authentication or not. Further more, the authentication message is in the HTTP header not IPP request.
Since URL and all authenticate informations are in the HTTP header, authentication should be done in the HTTP layer not IPP layer.
So I supporsed content length zero should be work fine and the
best way to reduce network traffic. This isn't simple?
Atsushi / EPSON
At 2:41 PM -0400 10/26/00, Zehler, Peter wrote:
>BO3-2: Some IPP Clients issues a zero length HTTP Post. The Client assumed
>that this would force a challenge if security is enabled on the Printer.
>The Client would have a problem if a subsequent print operation were
> Proposed Resolution: The Client should use the IPP operation
>"validate-job" to check if a job will be accepted. This operation will
>cause the Printer to issue a challenge and check the print request before
>sending the data. The IPP Client should also be able to handle a challenge
>when issuing an IPP operation since there is no guarantee the connection has
>not been torn down.
> Furthermore, a Printer should accept an empty HTTP post and
>issue a challenge based on the URL of the post.
> Action Item: Bob Herriot: Some clients determined if a
>Printer requires authentication by sending an
> empty HTTP request. Some Printers treated this as an error.
> was for clients to send a ValidateJob operation and by
>inference to allow
> Printers to reject empty HTTP requests.
>> I raised the issue about whether a Printer should perform
> challenge based solely on the URL or whether it could react
> an empty request than to a Validate-Job request.
>> I asked an HTTP expert and received the following
>> 1) An HTTP server can have any policy.
>> This means that our decision is allowable.
>> 2) It is best for a client if it can associate the URL
> the authentication space.
>> This means that our decision could be better. That is,
> require an IPP Printer to decide whether to issue an
> challenge by examining the URL and nothing else, e.g.
> receiving a request for a particular URL, gives the
> challenge to an empty request as to a Validate-Job
>> This solution allows a client to use Validate-Job to request
>a challenge as
> we decided to allow. It also allows a client to use the
>> The important difference between our decision and what I am
> that the Printer must perform an authentication challenge
>consistently for a
> URL regardless of the contents of the message body. This
>rule make IPP
> behavior consistent with good HTTP policy.
>>> Peter Zehler
> Xerox Architecture Center
> Email: Peter.Zehler at usa.xerox.com> Voice: (716) 265-8755
> FAX: (716) 265-8792
> US Mail: Peter Zehler
> Xerox Corp.
> 800 Phillips Rd.
> M/S 139-05A
> Webster NY, 14580-9701