Qin,

Thank you for your review and feedback.  I provide responses to your feedback 
below.  Let me know if you have any additional questions or feedback.

Thanks,

-- 
 
JG



James Gould
Fellow Engineer
[email protected] 
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On 2/6/21, 6:58 AM, "Qin Wu via Datatracker" <[email protected]> wrote:

    Reviewer: Qin Wu
    Review result: Has Issues

    I have reviewed this document as part of the Operational directorate's 
ongoing
    effort to review all IETF documents being processed by the IESG.  These
    comments were written with the intent of improving the operational aspects 
of
    the IETF drafts. Comments that are not addressed in last call may be 
included
    in AD reviews during the IESG review.  Document editors and WG chairs should
    treat these comments just like any other last call comments.

    This document defines Extensible Provison Protocol (EPP) extension for
    unhandled namespace information conveyed to the client. It allow the server
    return unhandled namespace information that the client can process later. I
    think this document is well documented, however I do have a few questions 
for
    clarification. Major issue: Not found Minor issues: 1.Section 1: I am not 
sure
    how unhandled namespace information exchanging between the client and the
    service is compliant with the negotiated services defined in [RFC5730]. Why
    error response is not best choice to return this unhandled namespace
    information for later handling.

JG - Very good question. The first part of your question is associated with how 
the unhandled namespace information is returned back, which make it compliant 
with the negotiated services defined in RFC 5730.  The unhandled namespace 
information is returned in element (e.g., <extValue> <value> element) that is 
not processed by the XML parser so it won't cause a client-side XML parser 
error and is not located in a portion of the response (e.g., under <resData> 
for an object-level extension or under <extension> for a command-response 
extension) that would be a compliance issue with the RFC 5730 negotiated 
services.  For the second part of your question, why not return an error 
response, we need to look at the use case that raised this issue in the first 
place.  EPP includes a poll queue in RFC 5730 that enables the server to insert 
notifications (poll messages) for asynchronous consumption by the client using 
an ordered queue.  The poll queue is dequeued by the client one message at a 
time by receiving the message and acknowledging the receipt of the message with 
the server.  While working on the Change Poll Extension 
(https://tools.ietf.org/html/rfc8590), the question came up what occurs if the 
new poll message is in the queue, but the client does not support it?  If the 
lack of client support resulted in an error, the change poll message would 
represent a poison message that would halt the consumption of the poll queue 
messages.  Returning the message without consideration of the client services 
is a compliance issue and returning an error would result in a poison message, 
which was the driver to come up with a solution.  The EPP protocol already 
provided a mechanism to return XML information that is not processed by the XML 
parser, which enabled returning the poll message with the XML information and a 
signal that a service is not supported by the client that solved the compliance 
and the poison message issue.  This approach could also be used to optionally 
return the information and the unsupported service signal in general EPP 
responses.  The working group did discuss other options, such as changing the 
order of the messages in the queue, but the unhandled namespace approach was 
the simplest and most effective approach discussed to solve the problem.


    2. Section 3.1/Section 3.2
    For Unhandled Object-Level Extension in section 3.1 and Unhandled
    Command-Response Extension in section 3.2, I see Template unhandled 
namespace
    response example for an unsupported command-response extension is same as
    Template unhandled namespace response example for an unsupported 
object-level
    extension, which make me confused, I am wondering how do we distinguish
    Unhandled Object-Level Extension from Unhandled Command-Response Extension 
in
    the XML snippet example. Can you clarify this?

JG - The most important signal is that the client lacks support for a 
particular service defined by the namespace URI, whether it be for a 
unsupported object-level extension or an unsupported command-response 
extension.  A client can leverage the referenced NAMESPACE-URI to map up to the 
type of service defined in the EPP Greeting of the server.  All of the 
object-level extension namespace URIs are identified using an <objURI> element 
in the EPP Greeting and all of the command-response extension namespace URIs 
are identified using a <extURI> element in the EPP Greeting.  

    3. When we say converting from an object response to a general EPP response 
by
    the server, does it mean the [NAMESPACE-XML] variable should be replaced by 
the
    object-level extension XML. Where these [NAMESPACE-XML] variable are stored 
in
    the server? Do we need to maintain the mapping between [NAMESPACE-XML] 
variable
    and object-level extension XML? Can you clarify this?

JG - What's meant by that is an object-level EPP response includes a <resData> 
element containing the object-level extension XML referenced by 
[NAMESPACE-XML].  The object-level extension XML referenced by [NAMESPACE-XML] 
is moved under a <extValue> <value> element, which is not processed by the XML 
parser, and the <resData> element is removed from the response.  From the 
client perspective the response will not look like an object-level extension 
response, but simply as a general EPP response.  Take a look at how the 
transfer query response is formatted in RFC 5731 
(https://tools.ietf.org/html/rfc5731#section-3.1.3 ) and how it's converted in 
the example of section 3.1 
(https://tools.ietf.org/html/draft-ietf-regext-unhandled-namespaces-07#section-3.1).
  The <domain:trnData> element is moved from under the <resData> element to 
under a <extValue> <value> element and the <resData> element is removed.        



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