I have a few questions on your proposal to use an IPP redirect mechanism.
But it does seem to be simple and allows scalability where a print job could
be performed on a different server than to which it was originally
submitted. This was a feature that Kinko's liked.
Also, as you point out, it allows an implementor and/or system administrator
to decide on an operation by operation basis, which operations needs
more security and which do not.
The key is that all clients MUST support the redirect mechanism.
I'm trying to compare your scheme with Carl-Uno and Larry's
of having a single multi-valued "printer-uri-supported" Printer attribute
and a single-valued "printer-uri" operation attribute. The directory
entry would also be the multi-valued "printer-uri-supported" attribute.
Both schemes simplify our current document and have a single attribute.
See comments marked TH> below on your proposal.
Tom
Here is your attachment as text:
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 3.1.3.2 Response Operation Attributes
An additional operation response
attribute would be defined:
server-redirect-uri
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
redirected.
TH> Presumably, this "server-redirect-uri" Operation attribute is
TH> MANDATORY for a Printer to support, but is only returned on
TH> a redirect response, correct?
TH> Also we need to add a redirect status code in section 13.1.3
TH> Redirection Status Codes, say, "server-redirect", correct?
clients MUST recognize and use redirects.
----
For all operations, an additional operation
attribute MAY be included by clients:
client-TLS-requested
TH> Presumably, a 'boolean' attribute, correct?
TH> How about making the value of this attribute specifying what
TH> security is requested, perhaps as a keyword value?
TH> Something like "client-security-requested" with values: 'tls' and
TH> 'digest'.
This attribute would indicate to the server
that the client wishes to use TLS for the
session.
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
client.
TH> Presumably the server rejects the request as well, correct?
TH> Also this attribute is MANDATORY for a server to support,
TH> but which values depends on implementation.
----
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 advantages:
-- 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 feature
TH> This is a good feature. However, if a client wants security and TH> only has an HTTP URL, how does it get started? It certainly doesn't TH> want to do a Print-Job and send valuable data, before gettting the TH> TLS URL. So this means that the client that wants security is forced TH> to do a Validate-Job with the HTTP://... URL in order to get back TH> the redirect HTTPS://... URL, correct?
TH> After getting back the HTTPS:// URL, the client can either do another TH> Validate-Job operation to validate the attributes before wasting time TH> sending the data, or it can do the Print-Job operation and send the TH> data and risk wasting the time sending the data for a job that is TH> rejected.
TH> Presumably, before doing the second validate or Print-Job, the TH> client and server perform the TLS handshake.
TH> Presumably, the TLS handshake doesn't have to be repeated for the TH> Print-Job, after the second Validate-Job, correct? In other words, TH> the TLS handshake is for the session, not for each operation? TH> Only after a redirect, does the client have to repeat the TLS TH> handshake, correct?
-- 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".
At 23:46 12/20/1997 PST, Turner, Randy wrote: > >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 >handling... > >Randy > > > >Attachment Converted: "C:\WINNT\Profiles\hastings\Personal\Attach\redir.txt" >