Ira McDonald, Bob Herriot, Harry Lewis, Carl Kugler, and I have made a
number of passes over the new PWG draft standard 5100.6-D0.1. Its entitled:
"IPP Distributed Notification Service and IPPGET Client Behavior". It has
the redirection mechanism that was removed from the IETF IPPGET Delivery
Method spec. The conformance requirements for IPPGET clients is unchanged
in this document from what they were in the IETF IPPGET draft. We think the
redirection mechanism is still very sound from a security point of view, but
we're being cautious by moving it to this PWG spec, while we send the IETF
IPPGET and Base Notification spec drafts forward to the IESG.
ISSUE for the IPPFAX WG, which is REQUIRING support of IPPGET Delivery
Method: Is redirection an option of an IPPFAX Receiver? If yes, then the
IPPFAX Sender MUST support redirection as specified in this document.
The files are available at:
ftp://ftp.pwg.org/pub/pwg/ipp/new_NOT/ipp-dist-not-service-021010.pdf
ftp://ftp.pwg.org/pub/pwg/ipp/new_NOT/ipp-dist-not-service-021010.doc
Here is the Abstract:
Abstract: This document specifies an OPTIONAL IPP Distributed Notification
Service for use with the "Internet Printing Protocol (IPP): Event
Notifications and Subscriptions" specification (ipp-ntfy). This IPP
Distributed Notification Service enables multiple trusted IPP Printers to
off-load IPP Event Notification Delivery to a shared Notification Server for
any Event Delivery Method. The Notification Server (instead of the Printer)
deals with the burden of delivering Event Notifications. For the IPPGET
Delivery Method (get-method), the Notification Server, rather than the IPP
Printer, takes over the burden of keeping a large number of long duration
connections open for outstanding Get-Notifications operations.
This document also specifies additional REQUIRED behavior for any client
supporting the IPPGET Delivery Method.
Conformance: This extension is REQUIRED for all IPP clients that support
the IPPGET Event Notification Delivery Method. This extension is OPTIONAL
for IPP Printers that support the IPPGET or any other Event Notification
Delivery Method.
Ira McDonald has written a companion spec for the protocol between the
Printer and the Notification Server which we will post shortly as another
PWG Draft. Its entitled: "Distributed Notification Service - Printer to
Notification Protocol (PNSP). We briefly considered combining them, but
didn't because using PNSP isn't required in order to redirect the
Get-Notifications request. Also having too many conformant interfaces in a
single document becomes too cumbersome to understand which statements apply
to which interface.
Here are the Changes from the redirection in the original IPPGET Delivery
Method [get-method]:
17.1 Changes from [get-method] to make version 0.1
1. Invented the title: "The Printer Working Group Standard for
Internet Printing Protocol (IPP): Distributed Notification Service and
IPPGET Client Behavior"
2. Removed this redirection functionality from the IETF IPPGET
[get-method] specification and put it in this document.
3. Section 2.2: Defined "IPPGET Client", "Notification Server",
and "Distributed Notification Service" terms.
4. Clarified that this specification is the Interface between
an IPP Client and a Distributed Notification Service, in case the IPP
Printer exercises the option of using a Notification Server to deliver Event
Notifications.
5. Section 5.3: Maintained the client requirement to support
the redirection for any client that supports the IPPGET Event Delivery
Method (see [get-method]). In other words, any client that supports the
Get-Notifications operation is required to support the redirection in case
the Printer exercises this option.
6. Clarified that this Notification Server may deliver Event
Notifications for any Push Delivery Method and for the IPPGET Pull Delivery
Method.
7. Section 4.1: Added the "printer-notify-server-uri" (1setOf
uri) Printer Description attribute so that the Printer could be configured
for none ('no-value' out-of-band value), one, or more than one Notification
Server.
8. Sections 5.2 and 6.1: Clarified that the "redirect-uri"
(uri) operation attribute and the 'redirection-other-site' status code are
for use with the Get-Notifications operation response only, but could be
used by operations defined in the future or existing operations if the IPP
protocol minor version number incremented.
9. Section 5.1: Clarified that the Printer MAY return the
"redirect-uri" (uri) operation attribute depending on any
implementation-defined reasons which could be dynamically varying. Gave
examples, such as on the number of open channels and the authorization of
the user.
10. Section 7.3: Added conformance requirements for a
Notification Server, acting in combination with a Printer, to provide a
Distributed Notification Service.
11. Section 15: Added the Informative Appendix that describes
PNSP.
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