IPP> Additional proposal details

IPP> Additional proposal details

IPP> Additional proposal details

Turner, Randy rturner at sharplabs.com
Sun Dec 21 02:46:28 EST 1997

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Please review the attached details to the
proposal I loosely suggested earlier. This
proposal addresses Bob's concerns with
the problems of printer-uri and printer-tls-uri



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TLS Redirection Modifications

The following changes to the model document
would be required in order to support my
earlier redirection proposal. The changes
appear to be simple, and would allow us to
use the term "printer-uri" throughout the
document, without all the "hand waving"
(similar to Bob's proposal).

Section Response Operation Attributes

An additional operation response
attribute would be defined:


This is a generic redirect (not TLS specific)
that allows servers to redirect requests to
another URI. NOTE: The redirect only applies
to each request. A client should not assume
the lifetime of a redirect to last beyond the
particular request that was originally

clients MUST recognize and use redirects.


For all operations, an additional operation
attribute MAY be included by clients:


This attribute would indicate to the server
that the client wishes to use TLS for the

If the server supports TLS, it would return
the generic redirect response attribute
described above. If the server DOES NOT
support TLS, then the server would return the
"scheme-not-supported" error code to the


On a get-printer-attributes request, the
"printer-uri" returned would always be the
URI that was used to issue the get-attributes
request (like Bob's proposal)

On a get-job-attributes request, the 
"containing-printer-uri" would be either the
base "printer-uri" (non-TLS), or a
redirected TLS URI that was actually used to
submit the job. I submit that we can leave
this up to implementations since I think the
client results would be the same.


On a get-jobs request to a printer-uri, the
"containing-printer-uri" attribute returned
for each job would be implementation-specific.
It would either be the "printer-URI" (non-TLS)
for the printer, or it could be a redirected
TLS URI. This needs to be implementation-specific
so as to allow servers to decide how job-
specific information is displayed for a 
particular client.


In addition to addressing Bob's concerns
with printer-uri and printer-tls-uri, this
proposal also offers the following

-- It allows a TLS-capable server the ability
   to only require TLS negotiation for 
   particular operations that require the server
   to allocate resources. For instance, a
   server that requires all print jobs to be
   authenticated might still want all clients
   to be able to get attributes for the printer,
   as well as validate job parameters, without
   going to the expense of performing TLS
   negotiation. It basically allows an 
   administrator to decide what types of 
   operations should be authenticated. In the
   current spec, ALL operations are authenticated
   or NONE are. This is a nice scalability

-- We no longer have to worry about publishing
   multiple URI strings in directories or other
   places in order to support TLS sessions to
   a server. There's only one URI for the 
   printer. If a client attempts an operation to
   the printer URI, and the server deems that
   authentication is required, then it 
   automatically issues a redirect, similar to
   the way current web browsers bounce back and
   forth from SSL and non-SSL connections to a
   a particular web "service".

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