Re: [Netconf] Subscription State Notifications (RE: LC on subscribed-notifications-10)

Alexander Clemm <> Wed, 06 June 2018 17:56 UTC

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From: Alexander Clemm <>
To: Alexander Clemm <>, Kent Watsen <>, "Eric Voit (evoit)" <>, Alexander Clemm <>
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Thread-Topic: [Netconf] Subscription State Notifications (RE: LC on subscribed-notifications-10)
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Hi Kent, Martin,

please let us know if we can keep it as-is (our preference), or if you insist on removing the extension and going the description text route, in which case we will post another revision.

Is there anything else?

--- Alex

From: Netconf [] On Behalf Of Alexander Clemm
Sent: Thursday, May 31, 2018 2:38 PM
To: Kent Watsen <>; Eric Voit (evoit) <>; Alexander Clemm <>
Subject: Re: [Netconf] Subscription State Notifications (RE: LC on subscribed-notifications-10)

Hi Kent,

sure, the wire behavior is clear.

It just seems to me cleaner and more desirable to me to make the distinction explicit through formal means, rather than relying on description text.  Contrary to SMIv2, YANG does provide the ability to define extensions that allow us to more formally cover this.  Why not take advantage of it – this is one important way in which YANG IMHO is better than SMIv2.  I have one more point to your comment inline, <ALEX2>.

Now, that said, appreciate trying to simplify it; I am not sure this changes complexity either way – as you mention, it all results in the same on-the-wire behavior, the only question is if we want to specify it informally (description text) or formally (YANG-extension).  In any event, at this point, I believe it is more important to bring this to a conclusion that is acceptable to everyone than to one that may be the “best” (and we all have different opininions on what that would be).  If this is the last thing that is holding this up, I will be happy to compromise and spin a new revision without the extension.  Please let us know.

--- Alex

From: Kent Watsen []
Sent: Thursday, May 31, 2018 11:43 AM
To: Alexander Clemm <<>>; Eric Voit (evoit) <<>>; Alexander Clemm <<>>
Subject: Re: Subscription State Notifications (RE: [Netconf] LC on subscribed-notifications-10)

Hi Alex,

No one is suggesting there would be an on-the-wire change.   With or without the extension, the subscription state notifications would still only by sent in the dynamic/configured subscription sessions.  The only discussion is *how* this understanding is conveyed.  Martin and I are of the opinion that it can be conveyed by document-text, without introducing an extension.

As I see it, it makes no difference to server-implementers, as they're going to hard-code it one way or another, but I think it does make a difference to client-implementers, as one approach allows them to hard-code it while the other approach introduces a need for their infrastructure to look for and act on the presence of this extension.  Am I misunderstanding anything?

<ALEX2> Client implementers can hard code it either way.  The presence of this extension (defined just in this module) makes it more explicit that there is behavior that needs to be coded (ensuring that the description text is not simply ignored, which would result in noncompliant implementations).  If your concern is that “now that the extension is there, some other module might try to use it as well”, well, how they choose to model and define their behavior is up to the fictitious other model, and if they do need the same behavior, I would consider it all the more reason not to get on the slippery slope of the description clause path that became one of the demises for SMIv2.

FWIW, my goal is to try to simplify this work where possible, as it is rather complex as it stands.  This (and configurable replay-start-time) seems like a low-hanging item that could be removed with little impact.


On 5/30/18, 8:41 PM, "Alexander Clemm" <<>> wrote:

Apologies for the late reply.

IMHO, option (b) (having an extension) is clearly preferable.  Subscription state notifications are in essence a signaling channel.  It makes a lot of sense to clearly distinguish a signaling channel from general notification/event messages.

The option to make subscription state notifications a part of the regular NETCONF stream is not desirable because:
- It opens up the possibility that subscription state notifications are shared with _any_ subscriber, not just with the “owning” subscriber”.
- It would require subscribers having to explicitly subscribe for subscription state notifications (and allow accidental filtering of those notifications), making this harder to a user.

Option (a) basically involves putting a lot of descriptions into notifications to override “normal” notification behavior. It will not be picked up by tooling and IMHO is more likely to result in incorrect implementations and resulting usability etc issues.  Back in the SMIv2 days this type of thing might have been acceptable, but we moved on to YANG for a reason.  Option (b) is much cleaner.

--- Alex

From: Eric Voit (evoit) []
Sent: Thursday, April 26, 2018 5:51 PM
To: Kent Watsen <<>>; Alexander Clemm <<>>; Alexander Clemm <<>>
Subject: RE: Subscription State Notifications (RE: [Netconf] LC on subscribed-notifications-10)

Does anyone else want to chime in on whether we should:
(a) hard-code filtering rules for specific subscription state notifications, or
(b) have a “subscription-state-notif” extension

More people seem to prefer (b) at this point.  I am good if we close it wither way.


From: Kent Watsen, April 23, 2018 3:19 PM
On 4/18/18, 4:40 PM, "Eric Voit (evoit)" <<>> wrote:

I don’t think anyone has an issue with excluding them from the NETCONF stream, or just sending them to individual receivers.

<KENT> correct

I think Kent’s question is that he is trying to understand the possible downsides of using this extension construct for this purpose.  And specifically, should we permit reuse of this construct beyond the confines of the family of subscription drafts (I.e., will in other YANG models use this extension to exclude items from the NETCONF stream which they shouldn’t).

<KENT> correct

Personally I don’t see a downside in allowing this flexibility under “subscription-state-notif”.  This notification has a very defined purpose plus definition in the YANG model.   And whether or not this extension exists, model makers and implementers can choose exclude certain notifications.  At least this if this extension is used, it would make such exclusions quite a bit more visible.

<KENT> downside is added complexity.  I don't want to add things that aren't absolutely needed.


From: Alexander Clemm, April 18, 2018 3:08 PM
Hi Kent,

I am not sure of what your question is anymore.  The earlier discussion concerned providing explanation regarding why subscription state notifications are not part of the regular NETCONF stream.  This was my attempt at additional explanation.  I am not sure what options we need to discuss at this point.  These issues were closed and IMHO we should not open them again.

The option to make them part of the regular NETCONF stream is not desirable because:
- It would potentially “share” subscription state notifications with any subscriber, not just their own.
- It would require subscribers having to explicitly subscribe for subscription state notifications, making this harder to user.

Hope this clarifies
--- Alex

From: Kent Watsen []
Sent: Tuesday, April 17, 2018 3:05 PM
To: Alexander Clemm <<>>; Eric Voit (evoit) <<>>; Alexander Clemm <<>>;<>
Subject: Re: Subscription State Notifications (RE: [Netconf] LC on subscribed-notifications-10)

Is this the result of the "I will open up a thread now" comment below?
This reads more like a statement than a question.   Please try again,
this time presenting the pros and cons of the various options.

Kent  // contributor

On 4/10/18, 7:17 PM, "Alexander Clemm" <<>> wrote:


regarding the question of subscription state notifications that is embedded in the long thread below:

As discussed earlier, subscription state notifications are different from “regular” notifications in that they only apply to the target of a subscription (and should not be subscribable by anyone else).  For this reason, they are not placed onto the NETCONF stream, where they would be subscribable by anyone.

At the same time, they should not require being subscribed to explicitly, but simply be automatically delivered as part of the subscription control channel – automatically “included” with the subscription whose state is being notified.  To denote these specific semantics, the model contains the “subscription-state-notification” extension, by which subscription state notifications are tagged.

--- Alex

From: Netconf [] On Behalf Of Eric Voit (evoit)
Sent: Monday, April 09, 2018 3:32 PM
To: Kent Watsen <<>>; Alexander Clemm <<>>;<>
Subject: Re: [Netconf] LC on subscribed-notifications-10

Hi Kent,

Thanks for the feedback.  Look for thoughts at <Eric2> In-line...

Also everything documented below which made it into the working copy can be seen at:<>

From: Kent Watsen, April 6, 2018 11:33 PM

I apologize for the long delay, but I just got back from PTO.  Please find my comments below (<KENT>), and know that I'm not up to speed on conversations you've been having with others, so please just let me know of the current status of things where applicable.

Kent  // as a contributor

On 3/18/18, 5:53 AM, "Alexander Clemm" <<>> wrote:

Kent, thank you for your thorough review and Eric, thank you for your thorough responses!

I agree that most of these are for the most part very small items and Eric has really answered all of them already.  Just adding some small points on a few items, look for <ALEX>

--- Alex

From: Netconf <<>> On Behalf Of Eric Voit (evoit)
Sent: Friday, March 16, 2018 11:41 AM
To: Kent Watsen <<>>;<>
Subject: Re: [Netconf] LC on subscribed-notifications-10

Hi Kent,

Thanks so much for the detailed review.   Thoughts in-line.  At this point there doesn’t seem to be anything insurmountable...

A working copy draft which embeds / covering the points documented below is at:<>

Also a legend for the comments below:

**** indicates a significant item (others might want to read/chime in).

Blue indicates text which is now in the draft (verbatim).

Orange indicates an open question, where I am asking for feedback before making changes.

Note: where I use colors, the wording should still be fine for those WG members using plain text email clients.

Still pending:

- Martin’s comments

- YANG doctor comments

> Kent Watsen, March 14, 2018 9:52 PM


> Here's my review of this draft.


> I'm aware that there may be some overlap with recent messages from Rob and

> Martin.  Please respond to them anyways, if only to explain the resolution

> made.


> BTW, when I make an open-ended question, what I'm many times looking for

> is draft-text that answers the question.  Yes, I want to know the answer but,

> more importantly, I want the answer recorded in the draft.


> PS: I'm prioritizing reviewing all three drafts over trying to reply to responses

> from earlier reviews.


> Thanks,

> Kent // contributor (but revving-up for shepherd write-up)



> <chair-hat> Authors, can you please start planning a presentation to review any

> of the larger open issues during the meeting in London? </chair-hat>

Will do

> Title: the word "custom" is throwing me, what does it mean?  I see the word in

> the Abstract and similar text in the Introduction.  In total, the substring

> "custom" appears six times in the draft, all in the Title, Abstract, and

> Introduction, so the word doesn't seem to carry much weight in the body of

> the draft itself.  Is there a better word?  Perhaps "Subscriber-specific" or

> "Receiver-specific"?   Or maybe you want to say "Customized Subscriptions to a

> Publisher's Event Streams"?

Both paths work.  I switched it to:

Customized Subscriptions to a Publisher's Event Streams

<KENT> fine

> Abstract: The first sentence has three issues: first, there's the

> custom/subscriber-specific comment from before; second, the word

> "capabilities" in the first sentence is unclear (if you mean NETCONF/yang-

> library capabilities, this document does not define any); and third, the word

> "operations" is ambiguous, the draft uses this word sometimes to mean RPCs,

> but other times not.  Putting it all together, maybe this is better?


>    This document defines mechanisms enabling subscriber-specific

>    subscriptions to a publisher's event streams.

Based on Robert's comments on add the YANG Data model, I morphed your proposal to:

This document defines mechanisms and a YANG Data Model enabling subscriber-specific subscriptions to a publisher's event streams.

<KENT> first, "data model" shouldn't be capitalized here.  That said, I question if "YANG data model" is needed at all, since "mechanisms" is even more general, and saying both seems like a mouthful.  Perhaps the two could be turned around. something like "This document defines a YANG data model and associated mechanisms enabling…"?

<Eric2>  Your text is adopted.

> Also, in the last sentence, s/Effectively/Combined/ and s/request/request for/?


<KENT> thx

> Introduction: Similar issues with the first sentence as with the Abstract.  Also,

> missing is a statement regarding this draft's compatibility to NMDA (see

> rfc6087bis)

Replicated the first sentence of the abstract to the introduction.  Also added a final sentence to the Intro which says:

The YANG model in this document conforms to the Network Management Datastore Architecture defined in [I-D.ietf-netmod-revised-datastores].

<KENT> thx, but be sure to also replicate any change to the Abstract from above to the Introduction again…

<Eric2>  Your text is adopted.

> Motivation:


>   How about this?

>   OLD: There are various [RFC5277] limitations, many of which have been

>        exposed in [RFC7923] which needed to be solved.

>   NEW: Various limitations in [RFC5277] are discussed in [RFC7923].

>        Resolving these issues is the primary motivation for this work.


<KENT> thx

>   s/document includes/document include/


<KENT> thx

>   in the 2nd bullet, remove "statically"?  the word "static" hardly appears...


<KENT> thx

>   in the 3rd bullet point: would appending "in progress" be okay?


<KENT> thx

> Terminology: I think you want to use this one:


>       The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL



>       "MAY", and "OPTIONAL" in this document are to be interpreted as

>       described in BCP 14 [RFC2119] [RFC8174] when, and only when, they

>       appear in all capitals, as shown here.


<KENT> thx

>   For the "Configured subscription" term, I think that replacing "a

>   configuration interface which" with "configuration that" is clearer.

>   If necessary, we could import the term "configuration" from the

>   revised-datastores draft.

I have added the following:

Configuration: defined in [I-D.draft-ietf-netmod-revised-datastores]

Configuration datastore: defined in [I-D.draft-ietf-netmod-revised-datastores]

Configured subscription: A subscription installed via configuration into a configuration datastore.

This addresses the reboot persistence subsystem question (which came up in Robert's review) by more tightly coupling the terms to the revised datastore work.   Let me know if there are still concerns.

<KENT> works for me

>   For the "Event" term, remove the parenthesis and spell out "e.g."?

How about:

Event: An occurrence of something that may be of interest. Examples include, a configuration change, a fault, a change in status, crossing a threshold, or an external input to the system.

<KENT> better, but I don't think the first comma is needed…

<Eric2> Comma removed.

>   Remove the term "NACM", since it only appears in the Security

>   Considerations section.


<KENT> thx

>   For the "Notification message" term, is the beginning important?

>   Maybe s/A set of transport encapsulated information/Information/?


<KENT> thx

>   For the "Publisher" term, why is "Subscription" capitalized?  Is it

>   (and all other terms) capitalized consistently throughout the draft?

Very early iterations of these drafts had all terminology capitalized.  Earlier reviews resulted in downshifting the terms because it hindered readability.   The large "S" is likely something left over which got missed.   It is now a lower case 's'.

<KENT> thx

>   For the "Stream" term, I'm wondering if this should be renamed "Event

>   stream" (matching what's in the title), and then search/replace instances

>   of just "stream" with "event stream" everywhere else in the document.

>   This seems better, less ambiguous.


We went back and forth on this.  The term is used so often that always saying "event stream" just made the document more cumbersome to read.  In the end, RFC-5277 used both in the terminology, in a similar way.  For example:

In RFC 5277: "stream" appears 104 times, and "event stream" 47 times.

In this doc: "stream appears 297 times, and "event stream"  39 times.

As using both terms made things more humanly readable, and it seemed ok for RFC-5277, we choose that path.   Let me know if *not* adding event before every use of the word stream is ok with you.

<ALEX> Yes, we had multiple discussions on this.  “Stream” certainly seems more general.  If anything, we could discuss replacing some instances of “event stream” with “stream”, but I think in general from the context it is clear what was meant.  I don’t feel strongly either way.  </ALEX>

 <KENT> when it comes to terms in technical documentation, I have found that being annoyingly long-winded and yet completely unambiguous is a win.  I would personally do it, but I'm okay with getting others opinions and going with the WG consensus.

<Eric2>  To make thing unambiguous, and to progress towards closure, I converted to “event stream”.  You can see the results in:<>

>   For the "Subscribed event records" term, I recommend removing it, as

>   it only appears three times in the draft and, besides, you already have

>   the "Event record" term.

Done.   (Re-reading, I don't think anything is lost by removing the term either.)

<KENT> thx

>   For the "Subscriber" term, shouldn't you have a 2nd sentence like in

>   the "Receiver" term?

Added the same sentence to the receiver term.

<KENT> thx

>   Since the tree diagrams are scattered throughout the document, it would

>   be good to add the following here:


>      Tree diagrams used in this document follow the notation defined in

>      [I-D.ietf-netmod-yang-tree-diagrams].


<KENT> thx


> Solution Overview


>   what does "instantiated" mean in the 1st paragraph.  suggest removing

>   if not needed.

It just meant "which exists".  Removed.

<KENT> thx

>   in (1), s/RPC/an RPC/.  Also, is "wants" the right word, maybe "is able"?

Made: "is able"

<KENT> thx

>   same with "wish" in the next sentence.

Made "is not able"

<KENT> thx

>  Also, in the last sentence,

>   s/ which would have been accepted/ that, had they been present, would

>   have enabled the dynamic subscription request to be accepted/?


<KENT> thanks

>   in (2), s/a configuration interface/configuration/.


<KENT> thx

>  Also, replace "this

>   capability" with "configured subscriptions", and maybe append "based on

>   the use of a YANG feature"?

Made it:

Support for configured subscriptions is optional, with its availability  advertised via a YANG feature.

<KENT> thx

>   "For connection-oriented stateful transport" : s/For/For a/ or

>   s/transport/transports/?

Chose: transports

<KENT> thx

>   Looking at "Also note that transport specific transport drafts based

>   on this specification MUST detail the life cycles of both dynamic and

>   configured subscriptions." - do the netconf-event-notifications and

>   restconf-event-notifications drafts do this?

Yes.   It is in non-normative text, but the flow diagrams in both drafts' appendices do this.

<KENT> okay

>   Last paragraph, s/The publisher/A publisher/


<KENT> thx

> Relationship to RFC-5277:


>   In the first bullet point, the "data model" for what, configuration

>   or a notification?   (same issue is in the last bullet point as well)

As there is no configuration of RFC-5277 subscriptions, it was for the notifications.  So I made the bullet:

the data model in this document replaces the Notification Management Schema of [RFC5277], Section 3.4.

<KENT> how about this instead?  "the data model in this document replaces the notification management schema described in Section 3.4 of [RFC5277]."

<Eric> Further tweaking of the wording happened with Martin.   Including your suggestion above, it now says:

“the data model in this document is used instead of the data model in Section 3.4 of [RFC5277]  for the new operations.”

And I made the last bullet:

a publisher MAY implement both the Notification Management Schema and RPCs defined in [RFC5277] and this new document concurrently,...

<KENT> hmmm, is there an easier way to say this?  perhaps: " a publisher MAY implement both [RFC5277] and this new document concurrently,…"

<Eric>  As RFC5277’s notification capability is still always used, some modifier is needed to show what actually can and cannot be used together between the drafts.  Not sure how to simplify more.

>   The 4th bullet point isn't true (see Event Streams below)


I believe that it is true.   See discussion below.

<KENT> okay, I'll wait for the discussion below…

> Solution:


>   Can you add a paragraph here to introduce what all is in Section 2,

>   how it's organized, or whatever might be helpful?

<KENT> no response to this comment?

<Eric2>  I should have pointed out that comments very early in the review cycle had me pull the introduction of Section 2 just above into Section 1.3 “Solution Overview”.    So placing details here initially seemed redundant.

So to cover your request, I just added to the beginning of Section 2: “Per the overview provided in Section 1.3, this section details the overall context, state machines, and subsystems which may be assembled to allow the subscription of events from a publisher.”

> Event Streams:


>   The 2nd paragraph says "except for where it has been explicitly

>   indicated that this the event record MUST be excluded from the

>   NETCONF stream".  This is a redefinition of what RFC5277 says,

>   has this been discussed?  How is this done (syntax/text)?  Has

>   it been done already?


<ALEX> I believe it is true by virtue of the fact that we are not defining the NETCONF stream anywhere in this document.  You can refer to the NETCONF stream by name.  The NETCONF stream simply refers to the stream defined in RFC 5277.

Note that in an earlier revision we were using identityrefs and identities to refer to stream.  At that point, we were defining a NETCONF stream as part of the datamodel here (even then, referring to the definition of RFC 5277).  However, the WG decided to take it out and have a reference by string.  We were also defining other streams at that point, but again the WG decided to remove the definition of streams as part of the model, leaving it to implementations to introduce arbitrary streams.  (As a side note, I would not be surprised if at some point in the future there will be an attempt to standardize the definition of new streams).


Subscription state change notifications as per Section 2.7 are explicitly excluded from anyone but the target receiver.   Since the notifications are per-receiver, they cannot be placed into any NETCONF stream (for either RFC-5277 or subscribed-notifications).  And as they are excluded from the NETCONF stream, I do not see an issue with the Bullet 4 comment above.

To make this clearer in the draft text, here is some proposed/tweaked text for the start of Section 2.7...

Subscription state notifications are unlike other notifications in that they are never included in any stream.  Instead, they are inserted (as defined in the section below) within the sequence of notification messages sent to a particular receiver.  Subscription state notifications cannot be filtered out...

<KENT> this is better for s2.7, but my concern is here in 2.1.  perhaps instead of " except for where it has been explicitly indicated that this the event record MUST be excluded from the NETCONF stream", you mean "except for the subscription state notifications described in Section 2.7."???

<Eric2> Made this change.  Text now says:

There is only one reserved event stream name within this document: "NETCONF".  The "NETCONF" event stream contains all NETCONF XML event record information supported by the publisher, except for the subscription state notifications described in Section 2.7.  Among these included NETCONF XML event records are individual YANG 1.1 notifications described in section 7.16 of [RFC7950].  Each of these YANG 1.1 notifications will be treated as a distinct event record.

>   s/treated a distinct/treated as a distinct/


<KENT> thx

> Event Stream Filters


>   The 1st and 2nd sentences seems to be at odds with each other.


I don't believe they are at odds.  But I can tweak the wording.   How about making the second sentence:

A match on a filter always results in an action upon a complete event record. Information is never stripped from within an event record prior to that event record being encapsulated within a notification message.

<KENT> I like it

> QoS


>   What does " MUST work identically" mean?

>   is HTTP a mandatory  transport?

>   RFC 7540 Section 5.3.3 talks about a PRIORITY frame,

>   which is  defined in Section 6.3 of that draft.  How is this

>   suppose to work in a transport-agnostic way?


It would be excellent if we can adopt the a subset of prioritization types in HTTP2 without having to redefine the details of the algorithm in this document.  I believe this is possible, but I understand that you want refined wording to make sure this is accomplished explicitly.  Proposed are two snippets of revised text which hopefully accomplishes this:

Snippet 1:

Dequeuing of notification messages across independent subscriptions to a receiver SHOULD be allocated bandwidth proportionally based on each subscription's weight.  For more information on the proper treatment, see stream dependency weighting within RFC 7540, section 5.3.2.

<KENT> fine

Snippet 2

If a subscription has a dependency, then any buffered notification messages containing event records selected by the parent subscription SHOULD be dequeued prior to the notification messages of the dependent subscription.  If notification messages have dependencies on each other, the older notification message MUST go first.  For more information on the proper treatment to stream dependency as described within [RFC7540], section 5.3.1.  If a dependency included within an RPC references a subscription which does not exist or is not visible to that subscriber, that dependency may be silently removed.

<KENT> also fine

Also HTTP is not mandatory.  In fact with the text change, the reference to RFC-7950 now becomes informative rather than normative.

<KENT> good

> Dynamic Subscriptions


>   s/RPC/RPCs/


<KENT> thx

>   Please provide more detail about how extensibility is accomplished,

>   or an example showing the augmentation occurring.


Rather than talk about how augmentation might be done in theory, it should be cleaner to the reference to YANG-Push augmentations.  So I added the following sentence...

For examples of such augmentations, see the RPC augmentations within [I-D.ietf-netconf-yang-push]'s YANG model.

<KENT> I generally shy away from upward refs, but yang-push is an informative ref, so I'll blink on this one.

>   For all the subsections, should the title be s/Subscription/Dynamic

> Subscription/?


<KENT> thx

> Dynamic Subscription State Model


>   What does "asserted" mean?  - remove/replace?


<KENT> thx

>   I'm confused by the diagram and subtitle's use of the word "receiver",

>   when the first sentence of the paragraph above says that the SM is for

>   the publisher...

This is for the Publisher: the publisher must maintain the state of whether a receiver is currently active or suspended.

I changed the title to: "Publisher's state for a dynamic subscription" which should help here.   Other reviewers requested the addition of the word receiver to the states themselves.  This is so people could make a 1:1 correlation with the states of the configured subscription state machine.

<KENT>title is better, though maybe "Publisher's state for a receiver's dynamic subscription" would be better?  (not sure)

<Eric2> I kind of like the simplicity of the current text.  Will change if you have a very strong preference.

>   Only two notifications?

Only two notifications indicate a change in the state of the subscription.

<KENT> okay, but then can you add somewhere that only two notifications are represented because they're the only ones indicating a change in the state of the subscription?

<Eric2> Text now says:

The two state change notifications "subscription-suspended" and "subscription-resumed" are shown.  These are under the control of a publisher. These are the only two state change notifications which indicate a change in state of a dynamic subscription.

>   Looking at the graphic, how is the reader to

>   distinguish these as notifications?

Added a * to the two notifications, and text at the bottom of the drawing which says:

* indicates a state-change-notification

<KENT> better, but somehow not satisfying…  Mentally removing these two notifications from the diagram entirely, I notice that there is no other arrow going from ACTIVE to SUSPENDED; it seems like you might need one, perhaps labeled something like "<internal state event>"?  Assuming this is done, could we then remove listing these notifications from the diagram?

<Eric2> My reading of your comment is that you don’t like the identification of the “suspend subscription” transition cause via the “subscription-suspended*” notification.   To clarify, I have removed all state change notifications from the diagram, and described them in the text below...

                        : start :
                            |   .------modify-subscription-------.
                            v   v                                |
                      .-----------.                        .-----------.
           .--------. | receiver  |--suspend-subscription->| receiver  |
       modify-       '|  ACTIVE   |                        | SUSPENDED |
       subscription   |           |<--resume-subscription--|           |
           ---------->'-----------'                        '-----------'
                            |                                    |
                 delete/kill-subscription                   delete/kill-
                            |                               subscription
                            v                                    |
                        .........                                |
                        :  end  :<-------------------------------'

          Figure 1: Publisher's state for a dynamic subscription

Of interest in this state machine are the following:

   o  A publisher may choose to suspend a subscription, this is notified to a subscriber with a "subscription-suspended" state change notification.

   o  A resume subscription state change is notified to a subscriber "subscription-resumed". There are no direct external controls over resuming a subscription other than for a subscriber to attempt the modification of a subscription in a way which reduces the resources consumed.

<KENT> Separately, can you left indent "modify-subscription" a column or two? - it's difficult to read when up against the "receiver ACTIVE" box…

<Eric2> Done, above

>   The last sentence of the last bullet doesn't square with what's in the

>   graphic.  is "modify-subscription" suppose to be bidirectional?

The diagram is correct.    I have changed the sentence to:

There are no direct controls over resuming a subscription other than to attempt a modification of a subscription in a way which reduces the resources consumed.

<KENT> okay

> Establishing a Subscription


>   I take it that the last two sentences of the first paragraph are

>   intended as requirements for transport-bindings.  Is that correct?


>   If so, then please say so.

Morphed to:

The transport selected by the subscriber to reach the publisher MUST support multiple establish subscription RPC requests made within the same transport session.  In addition, the transport MUST support the pipelining of RPC requests made on independent subscriptions.

(As interleave seems to have NETCONF implications, am trying to move ay from that to pipelining which is a general computer science term.)

<KENT> good

>   The tree diagram is not identified as a tree diagram.  Nowhere in this

>   document is the tree-diagrams draft referenced.  This needs to be fixed.

Tree diagram reference added to the definitions section.  And also added as part of each figure name.  And each tree diagram also has text and a hyperlink near it pointing to the YANG model for more details.

<KENT> better

>   Are your tree diagrams dynamically-generated?  - is there any concern

>   that they are out-of-date?

Generated from Pyang.   Manually snipped from the output.  Concerns are discussed more below.   Next drafts I am certainly changing my integration environment.

<KENT> the question more regards if they've been generated (via pyang or whatever) recently…

<Eric2> With the tool Martin pointed me to for automatically generating to a fixed column width, life is much easier now.

>   Since you're not describing the contents of the data model here, the

>   text should say that a complete description of all the nodes is provided

>   in the YANG module, with a reference.

Every tree in the document now has something like:

Below is a tree diagram for "establish-subscription". All objects contained in this tree are described within the included YANG model within <xref target="data_model"/>.

<KENT> good.

>   why is this "establish-subscription-error-stream" yang-data name having

>   "-stream" at the end?  (same issue with the other yang-data).  It's

>   a rather confusing name.  Maybe "-info" would be better?


We have to have a different yang-data structures for hints provided on datastores and on streams.  Because of that -info is not sufficient.   And while it is possible to place stream and datastore at the beginning of the yang-data name, it is kind-of nice to have the error-info hints start off with the same characters.

That said, I have no problem if people want to rename the yang-data both here and in yang-push to:




Is this what you prefer?

<ALEX> I think this can be renamed.  Really, these are hints, not streams.  Maybe call this “establish-event-subscription-info” and “establish-datastore-subscription-info”?


<KENT> I recall this being discussed in London.  What's the current thinking on this?

>   Also, just so I'm clear, each transport-binding needs to indicate if and

>   how the yang-data structs are returned, right?  Where is this done in

>   the netconf-notif and restconf-notif drafts?


<KENT> what about the second question?

<Eric2> In the netconf-notif draft, it is in Section 8.   The text including this is not yet published in Restconf-notif.

> Replay Subscription


>   Should the title being "Replaying Subscriptions", to match the verb

>   tense of the other subsections?

Tweaked to  "Requesting a replay of event records".  Because this is not a new RPC, I figure such differentiation from the other subsections is helpful.

<KENT> fine

>   s/Replay puts no/Supporting replay puts no/ or /The document puts no/?

Chose the " The document puts no "

<KENT> the current sentence doesn't read right, it looks like you accidentally dropped the word "restrictions"…

<Eric2> Yes, I dropped it.  Re-added.

>   Current text says:

>     """

>     The inclusion of a replay-start-time within an "establish-

>     subscription" RPC indicates a replay request.  If the "replay-start-

>     time" contains a value that is earlier than content stored within the

>     publisher's replay buffer, then the subscription MUST be rejected,

>     and the leaf "replay-start-time-hint" MUST be set in the reply.

>     """

>   Why not just start with what you have, prepended by a special "event

>   record" that says there is a gap?


This discussion went around on the alias a few times.  E.g., the thread from mid-October titled " Martin's thoughts on subscribed-notifications"

An underlying design goal of subscribed-notifications and yang-push is to deliver no less than what subscriber explicitly requested.  Especially when YANG-Push is layered in, if we start delivering less for some combination of parameters, we have no certainty that the subscriber is getting what it needs.

For this parameter, if we start replaying more recently than what has been requested, we don't really know if that is what the subscriber wants.  This doesn't give them the chance to reject the subscription while being sent stuff which is not helpful to them without the earlier history.  And you are correct, while we could define a special event record replay actually began on success, we are not delivering on the implicit promise of the subscription "ok".  But by using the no-success result with the included "replay-start-time-hint", we are matching the design paradigm without adding special constructs.

<KENT> I understand what you're saying, but I think that I disagree with the conclusion.  I think that the common case is the receiver wanting to pickup where it left off, or the best the publisher can, and if not lossless, to be informed that there's a gap (and the size of the gap) for its records.  The current logic optimizes for what I think is an unusual case and, assuming it's flipped to be as I'm suggested, such receivers can themselves immediately cancel the subscription as soon as being told that there is a gap.  Besides, by forcing the receiver to have to perform another round-trip, doesn't that potentially increase the size of the gap?

<Eric2>   Yes later dialogs with Martin convinced me exactly that another round-trip can drive churn unnecessarily.   The latest version posted starts replay immediately.   To cover the issue discussed above, there is a new parameter returned *only* if the replay start time has been modified.   This parameter is: “replay-start-time-revision”.

>   OLD: it MAY also be earlier than the current time and MUST

>   NEW: it MAY be earlier than the current time, but MUST


<KENT>better, but you missed removing the word "also"

<Eric2> I don’t see “also” in the current v11.

 <KENT> separately, it looks like to touched the next paragraph (not sure why, but I'm okay with it) and accidentally introduced a typo: "after the after"

<Eric2> corrected before the current v11.

>   "subscribers can perform a get on" - rephrase, and use "RPC" somewhere

Made it:

To assess the availability of replay, subscribers can retrieve the "replay-log-creation-time" and "replay-log-aged-time" objects from the YANG model.

<KENT> better, but maybe s/objects/nodes/?

<eric2>  Based on other comments, it now is: To assess the timeframe available for replay, subscribers can read the leafs  "replay-log-creation-time" and "replay-log-aged-time".

 With that, I don't think RPC is needed.

<KENT> agreed.

> Modifying a Subscription


>   First sentence, no need for the word "previously"


<KENT> thx

>   s/one or multiple times/multiple times -or- any number of times/?

Chose "any number"

<KENT> thx

>   s/via RPC using/via an RPC on/?


<KENT> thx

>   The tree diagram is not identified as a tree diagram.  And since the

>   data model isn't explained, there should be a statement for the reader

>   to look at the YANG module for details, ideally with a hyperlink.

Now done for every tree diagram in the document

<KENT> excellent

> Deleting a Subscription


>   First sentence, no need for the word "previously"


>   Under what conditions could a publisher reject a delete-subscription

>   request?  should there delete-subscription-error-stream hints?


>   The tree diagram is not identified as a tree diagram.  And since the

>   data model isn't explained, there should be a statement for the reader

>   to look at the YANG module for details, ideally with a hyperlink.


>   Last paragraph, no need for the word "previously"


<KENT> thx

> Killing a Subscription


>   Regarding:

>     "This operation MUST be secured so that only connections with

>      sufficiently privileged access rights are able to invoke this RPC."

>   This needs to be in the Security Considerations section and, given

>   that, doesn't need to be here, right?  If you really want it here,

>   then please indicate that such guidance is provided in the SC section.

Moved to Security Considerations

<KENT> thx

>   Replace the paragraph beginning with "The tree structure of" with the

>   actual tree diagram for this RPC..


<KENT> thx

> RPC Failures


>   Please also call-out RESTCONF error handling (RFC8040 Section 7.1).


<KENT> thx

>   The 2nd paragraph is confusing.  mechanism?  how are the 1st and 2nd

>   sentences related? What does the 2nd sentence really mean, esp. wrt.

>   the MUST?

Rewrote the paragraph to:

Specific errors included within this document's YANG model MUST be returned as part of the RPC error response. Following are valid errors which can occur for each RPC:

<KENT> better

>   I can't find any examples of these errors in use.  The

>   netconf-event-notifications draft only has examples for

>   the "establish-subscription-error-datastore" and

>   "modify-subscription-error-datastore" errors.

Figure 10 in the netconf-event-notifications draft works equally for subscribed-notifications, as well as yang-push.   I have identified that example in that document as being relevant to either streams or datastores with the sentence in that draft: "This subscription may have been to either a stream or a datastore."

<KENT> okay…

Here this document, I have added the sentence:

To see a NETCONF based example of an error response from above, see [I-D.draft-ietf-netconf-netconf-event-notifications], Figure 10.

<KENT> good.  Better would be to also have a reference to a RESTCONF-based example.

<eric2> Understood.  Didn’t know how to do that and not introduce a publication dependency.

>   Perhaps the

>   examples in that draft need to be split into examples related

>   to yang-push vs examples related to subscribed-notifications.

As the error mechanisms are identical between the drafts, splitting things in that document might prove more confusing.  That is one reason I identify the error response as being identical for streams and datastores above.   Perhaps additional examples, git repositories, or applications located outside the drafts?

<KENT> maybe, dunno, I'd have to look at that draft again…

 > Configured Subscriptions


>   1st paragraph: s/configuration interface/configuration/g  (two cases)


<KENT> thx

>   the note under the 3rd bullet point seems unnecessary but, if keeping

>   it, then just say that receivers are unaware of the existence of any

>   other receivers.

Done.  Used your proposed text.

<KENT> thx

>   s/In addition to subscription/In addition to the subscription/

>   s/as described in/described in/


<KENT> thx

>   where is the tree diagram for the configuration data model?!


It is in the section "Subscriptions Container".  It seemed better to introduce the state machines before getting into the details of the tree.  But if you really want to have it early, it certainly can be moved up.

So do you want it moved here, or is a reference to the later section sufficient?

<KENT> as I recall reading this section, all the previous 2.x sections had tree diagrams and I found it rather odd that there wasn't one here, nor is there any reference to where one can be found.  Perhaps you can add a forward-reference to s3.3, but forward-references are discouraged.  Do we need to rearrange sections to make this right?

<Eric2> I placed a two forward references in v11.  One is to Figure 20 for the tree, the other is to the YANG model.

>   I don't understand the last bullet point.  First, I'm having trouble

>   parsing the implicit parentheses..  Next, the last sentence seems

>   complicated, maybe just say "unless directed otherwise, the

>   notification messages MUST egress the publisher's default

>   interface towards the receiver."?

Used your text.  Done.

<KENT> thx

<Eric2> Based on further comments on the various options, broke specific parameters to bulleted text.  Your text is still used.

> Configured Subscription State Model


>   A better first sentence is needed, something introducing that there

>   exists a state machine for each configured subscription, and states

>   that there are three states (VALID, INVALID, and CONCLUDED), etc.

>   Also should state where this state machine is maintained (publisher,

>   receiver, both?)

Now says:

Below is the state machine for a configured subscription on the publisher.  This state machine describes the three states (VALID, INVALID, and CONCLUDED), as well as the transitions between these states. Start and end states are depicted to reflect configured subscription creation and deletion events.

<KENT> better (ps: the last part, "Start and end states are depicted to reflect configured subscription creation and deletion", isn't there)

<Eric2> Good catch.  Not sure where that went.  Re-added.

>   s/publisher evaluation/evaluation by the publisher/?


<KENT> thx

>   Please move text regarding how to interpret the diagram (uppercase,

>   dashed boxes, parantheses, etc.) into a preamble or postamble element.

Added underneath the diagram.  See diagram below.

<KENT> thx

>   s/itself might itself/itself might/

>   s/in no longer/is no longer/


<KENT> thx

>   The first paragraph under the diagram doesn't match what the diagram

>   shows.  Looking at the diagram, I also see two possible sequence of

>   transitions that get VALID to INVALID, but I'm unsure how they relate

>   to the two mentioned in the text..

Updated paragraph text as per below.  Hopefully it is clearer now.

<KENT> yes

>  The text should call out which

>   parts of the diagram it's referring to.  Many times I number labels

>   in diagrams and then, under the diagram, provide a more thorough

>   explanation for each number.

Added numbers within the diagram, and added text references as per below:

<KENT> better


: start :-.

:.......: |

     create  .---modify-----..----------------------------------.

          |  |               |                                  |

          V  V          .-------.         .......         .---------.

 .----[evaluate]--no--->|INVALID|-delete->: end :<-delete-|CONCLUDED|

 |                      '-------'         :.....:         '---------'

|----[evaluate]--no-.      ^                ^                 ^

 |        ^          |      |                |                 |

yes       |          '->unsupportable      delete           stop-time

 |      modify         (subscription-   (subscription-   (subscription-

 |        |             terminated*)     terminated*)      concluded*)

 |        |                 |                |                 |

 |       (1)               (2)              (3)               (4)

|   .---------------------------------------------------------------.

'-->|                         VALID                                 |



dotted boxes: subscription creation and deletion events

dashed boxes with uppercase letters: valid states for a subscription

[evaluate]: decision point on whether the subscription is supportable

(*): resulting subscription state change notification

Also the text below now says:

A valid subscription may become invalid on one of two ways.  First, it may be modified in a way which fails a re-evaluation.  See (1) in the diagram. Second, the publisher itself might determine that the subscription is no longer supportable.  See (2) in the diagram.  In either case, a "subscription-terminated" notification is sent to any active or suspended receivers.  A valid subscription may also transition to a concluded state via (4) if a configured stop time has been reached.  In this case, a "subscription-concluded" is sent to any active or suspended receivers.  Finally, a subscription may be deleted by configuration (3).

<KENT> better

>   Is it "any active or suspended receivers" or "any receivers for an

>   active or suspended subscription"?

The current wording is correct.  A configured subscription is never suspended.  It can be INVALID, or it can be ACTIVE and all its receivers suspended.  But in the second case, at least the receivers get subscription-suspended notifications.

<KENT> okay

>   s/During any times a/When a/?

<KENT> you didn't say you did this one, but I see that you did, thx.

>   Regarding "Below is the state machine for each receiver of a configured

>   subscription." - where is this state machine maintained, on the publisher

>   or on the receiver?

Updated the title to show it is a Publisher state model.

<KENT> did you?  I see " Receiver state for a configured subscription", which seems misleading

<Eric2> Tweaked to “Receiver state for a configured subscription on a Publisher”

>   why is "receiver" in each box?

To drive home the idea that this state machine was for each individual receiver, rather than for the subscription as a whole..

<KENT> okay, I guess, I don't know, it seems confusing, but I see that you explain it in the legend, so that's better…

>   Again, you might look to having a

>   preamble or postamble to describe the syntax used in the diagram.

Per figure below, added the legend as a postamble:

<KENT> thx

>   1st paragraph below diagram: s/to connecting/to "connecting" -or- to


Now says CONNECTING.   And all receiver states moved to uppercase.

<KENT> good

>   Regarding "and event records are not being dropped due to a publisher

>   buffer overflow" - this seems like it's from out of nowhere.  If not

>   normative, then maybe delete?


It is normative.  This is needed to maximize the number of concurrent subscriptions without enforcing continuous transport keep-alive overhead when no event records are being passed, as well as to not prematurely declare a subscription as suspended while there is a chance that transport may be established before event records do get lost.    This allows a configured subscription’s receiver to exist across an intermittent connection, and the receiver can remain active on the publisher as long as events aren’t being lost.  While this can be done with NETCONF, it is probably more likely to be seen in practice with HTTP connections.

Based on that, I rephrased the words above so that it doesn’t feel from out of nowhere.  See the text below the updated figure below...

 <KENT> thx

>   This text is again difficult to reconcile with the diagram.  I again

>   recommend numbering labels and then describe the numbers below.


<KENT> thx


     |                         VALID                                   |

     |   .----------.                           .--------.             |

     |   | receiver |------------------timeout->|receiver|             |

     |   |CONNECTING|<------------------reset---|TIMEOUT |             |

     |   |          |<-transport---.            '--------'             |

     |   '----------'  loss,reset  |                                   |

     |      (1)          |         |                                   |

     |  subscription-   (3)        |                                   |

     |  started*    .--------.     |                       .---------. |

     |       '----->|        |     '--------------------(3)|         | |

     |              |receiver|(2)-subscription-suspended*->|receiver | |

     | subscription-| ACTIVE |                             |SUSPENDED| |

     |   modified*  |        |<--subscription-resumed*,----|         | |

     |        '---->'--------'    subscription-modified*   '---------' |



   dashed boxes which include the word 'receiver' show the possible

   states for an individual receiver of a VALID configured subscription.

   * indicates a state change notification

Individual receivers are moved to an ACTIVE state when a "subscription-started" state change notification is successfully passed to that receiver (1). Configured receivers remain ACTIVE if both transport connectivity can be verified to the receiver, and event records are not being dropped due to a publisher buffer overflow. The result is that a receiver will remain ACTIVE on the publisher as long as events aren’t being lost, or the receiver cannot be reached.  However if there is buffer overflow, or the publisher cannot generate events for a receiver, the receiver MUST be suspended (2).  In addition, a configured subscription's receiver MUST be moved to CONNECTING if transport connectivity cannot be achieved, or if the receiver is reset via configuration operations (3).

<KENT> yes, better, esp. w/ the numbering

>   s/ mechanisms described above is/ mechanisms described above are/

>   What does this mean, how are mechanisms mirrored for RPCs and

>   notifications?


<KENT> thx

>   Regarding " provides an example of such an extension" - which section?

Revised text to:

The YANG model [I-D..ietf-netconf-yang-push] Section 4.1,  provides many such extensions, this includes the augmentation of "/sn:modify-subscription/sn:input/sn:target".

<KENT> better, but:

1) I didn't review yang-push, but I hope that someone pointed out that section 4.1 needs to point to section 5 and, additionally perhaps section 5 should be moved to section 4.5…

<Eric2>   I think you are suggesting that the YANG push tree model in 4.1 needs to point to the YANG model section number.  And that perhaps the YANG model section itself shouldn’t be in an independent top level section, but rather fall into section 4.     I have no issues with that.   **Alex, do you want to update, this should be a very minor update?

2) sentence structure needs help, how about:  "For instance, the YANG module defined in Section 5 of [I-D..ietf-netconf-yang-push]  augments "/sn:modify-subscription/sn:input/sn:target".  ???

<Eric2> Adopted your text.

> Creating a Configured Subscription


>   1st paragraph: let the first sentence be its own paragraph as with

>   the other 2.5.x sections.

>   For the remainder, I think this is the

>   3rd time that the draft has discussed the differences between

>   configured and dynamic subscriptions.  Please eliminate unnecessary

>   redundancy.  Factor out into another section if needed.

I agree that the following paragraph can be deleted.

There are two key differences between the new RPCs defined in this document and configuration operations for subscription creation. Firstly, configuration operations install a subscription without question, while the RPCs are designed to the support negotiation and rejection of requests. Secondly, while the RPCs mandate that the subscriber establishing the subscription is the only receiver of the notification messages, configuration operations permit specifying receivers independent of any tracked subscriber.

I have just removed this.

<KENT> thx

>   Regarding 2nd/3rd paragraphs, how resilient is the solution to the

>   resumption of the underlying transport?  If messages lost in the

>   write-buffer are lost, could the receiver ever be helplessly out

>   of sync without a full restart?

I think we are clean here.  I have updated the text against the diagram per-above which hopefully provides more descriptive text on why the resumption of  underlying transport is covered.

<KENT> I don't understand this response, can you provide more information?

<Eric2>  For a configured subscription, transport can safely come/go as long as events are not lost or delayed because a connection with a receiver is unavailable.   Instead it is whether events are dropped before they can be transmitted.

To support this, the text says:

“However if there is buffer overflow, or the publisher cannot generate notification messages for a receiver, the receiver MUST be moved to SUSPENDED (2).”   The result is that a receiver will know that event records may have been lost if a subscription-suspended and/or subscription-resumed are received.    On such a resume, a subscriber can attempt a replay if it needs the older events.

> Modifying a Configured Subscription


>   s/ ././    ;)


<KENT> thx

> Resetting a Configured Receiver


>   But *how* is it reset? - via a configuration operation?  which one?

>   Should this be part of "Modifying a Configured Subscription"?

Added the sentence:

This is accomplished via the "reset" action within the YANG model at "/subscriptions/subscription/receivers/receiver/reset".

<KENT> thx

> Event Record Delivery


>   First paragraph, last sentence.  I think I commented on similar text

>   before.  Is this a requirement for the transport binding?

Perhaps the word interleave is the wrong choice here, and intermixing is better in this case.  I made that change.

<KENT> okay, but where did the following new paragraph come from?

<Eric2> WG threads/dialogs with Martin.


   - s/passed receiver/passed to the receiver/?

<Eric2> Don’t see that text.  Looks like it was cleaned up already.

>  Do the  netconf-notif and restconf-notif drafts satisfy this requirement?


<KENT> good

> where?

Netconf-notif supports interleaving of requests as described in Section 3.

<KENT> okay

Restconf-notif doesn’t need to explicitly call for pipelining support as it is a basic capability of HTTP.

<KENT> but the question isn't about pipelining.  Even NETCONF supports pipelining, something extra is needed to support "intermixing", right?

<Eric2> Yes.  And we do have that intermixing included in document requirements within this section.   Text says:

“In all cases, a single transport session MUST be capable of supporting the intermixing of RPCs and notifications from different subscriptions.”

I think that change was made after conversations with Martin, so it didn’t come back explicitly via this subthread.

>   2nd paragraph: "able to traverse" --> "not blocked by"?


<KENT> thx

>   Also, for

>   the 3rd sentence, call out the "RPC response" is for dynamic and

>   "state-change notification" is for configured?

Yes.   Made text:

A subscription's events MUST NOT be sent to a receiver until after a corresponding RPC response (in the case of a dynamic subscription) or state-change notification (in the case of a configured subscription) has been passed receiver indicating that events should be expected.

<KENT> good

>   Last two paragraphs, this text needs to be removed,


<KENT> thx

>   or else we might

>   need to block this draft on notification-messages.   What do you mean

>   by " this document will be updated to indicate support".

At some point when notification-messages is complete, this draft should be updated as it is a more robust solution (as a subscription id can be provided for event records provided on streams.)

<KENT> you misunderstood, I know what it means, I was questioning why we'd say such a thing.  Anyway, you removed the paragraph already, so it's no longer an issue.

> Subscription State Notifications


>   OLD

>    In addition to subscribed event records, a publisher MUST send

>    subscription state notifications to indicate to receivers that an

>    event related to the subscription management has occurred.

>   NEW

>    In addition to sending event records to receivers, a publisher MUST

>    also send subscription state notifications when events related to

>    the subscription management has occurred.

>   ???

Done.  (Removed the extra ‘the’)

<KENT> thx

>   2nd paragraph: s/directly//


<KENT> thx

>   Also, I'm unsure about the "subscription-state-notif" extension, how

>   is it expected to be used by a YANG processor?

Per above, it ensures that these YANG notifications if encoded in XML are not placed onto the NETCONF stream.

<KENT> actually, I thought that before it only said that the Subscription State Notifications (s2.7) were not placed into the NETCONF stream???

<Eric2> Subscription state notifications are a type of YANG notification, as they are encoded in the YANG model.  Per the London WG discussion on slide “Question 2”, I believe it easier to mark these.  See next comment below.

>   Perhaps a generic

>   notification-filtering GUI is envisioned whereby the logic could

>   automatically remove these notifications from selection, but coding

>   for this extension has very limited use, as no other drafts are ever

>   likely to define any.  I suppose it does no harm, but I also think

>   that the text sure be clear.  Personally, I'd rather the extension

>   be removed unless there is a good reason to keep it.


The three choices seem to be:
(a) current solution

(b) hardcode the these notifications so none ever go on the NETCONF stream

(c)  make the extension “exclude-from-NETCONF-stream”.  As it is quite possible that other drafts will want to do that.

I am good with any of these.  But the first seems the cleanest, and most self contained.  Let me know it the current doesn’t work for you.

<ALEX> Just to add on:  A reason for the extension (and different solutions were discussed at different points in time) was that since this is a “meta-notification”, it should be treated differently from other notificaitons.  For example, a subscriber should receive these even if not explicitly subscribing to them – they are simply part of the “control protocol” for managing the subscriptions.   They also apply if a subscriber subscribes to something other than the NETCONF stream.


<KENT> yes, Alex, part of the control protocol, this is why I'm thinking maybe Eric's choice (b) is best.  Is this being discussed elsewhere?

<Eric2> We had a discussion on this in London:<>

As there was no comment in the room, I was hoping we had actually had some form of consensus between us on (a).   So I hadn’t spun up a separate question on this yet.

But it seems there is an issue.  I will open up a thread now.

> subscription-started:


>   Regarding the 2nd paragraph, Section implies a contradiction

>   to this statement.


A replay subscription can be set for a configured subscription.  There was some carrier on the NETCONF alias who requested this many months ago.  See also dialogs with Martin.

Looking at your comment, it probably isn’t a good idea to embed this fact within the replay text embedded as part of the dynamic subscription section.

The best way to tease this apart is first to separate any configured subscription context the   This can be done simply by replacing the ‘after the "subscription-started" notification’. With ’ after the after a successful establish-subscription RPC response’.

<KENT> okay, modulus the "after the after" typo.

<Eric2> I can find no “after the after” in v11.  Perhaps I already fixed this.

And then to be more explicit that this is supported, we could add move contradicting statement into a new section 2.5.6 where it would no longer appear contradicting.  Replay in a new section looks like this:

2.5.6 Replay for a Configured Subscription

It is possible to place a start time on a configured subscription.  This enables functionality like immediately streaming boot log information off of a publisher immediately after restart.

<KENT> "immediately used twice, suggest removing first instance.  Actually, this needs a rewrite, perhaps "This enables streaming of logged information immediately after restart." ???

<Eric2> Adopted your text.

When any such configured subscription receivers become ACTIVE, buffered event records (if any) will be sent immediately after the “subscription-started” notification.  The first event sent will be the most recent following the latest of four different times: the "replay-log-creation-time", "replay-log-aged-time", "replay-start-time", or the most recent publisher boot time.

<KENT> I don't understand the 2nd sentence here

<Eric2>   Rewrote to: “The leading event record sent will be the first event record subsequent to the latest of four different times: the "replay-log-creation-time", "replay-log-aged-time", "replay-start-time", or the most recent publisher boot time.”

All other replay functionality remains the same as with dynamic subscriptions as described in Section

<KENT> I'm not sure I like having to look at and trying to figure out what this means.  Can you make this more explicit or, since 5.6 is pretty small, copy the parts into this section?

<Eric2> I initially had all the text in  But this hid the fact that you can do replay on a configured subscription.  So your comment above lead to this section being introduced.  Which is a good thing.   But as is not very small, to me it feels like repeating all that text here might be overkill.

The good news is that all of this is consistent with text is already reflected in the YANG model.

<KENT> thankfully!

>   The tree diagram is not identified as a tree diagram.  And since the

>   data model isn't explained, there should be a statement for the reader

>   to look at the YANG module for details, ideally with a hyperlink.


<KENT> thx

>   Why is all this sent to the receiver?  Doesn't it already know the

>   protocol and encoding?  What about the other parts?  Which parts

>   are actually useful?

The complete state of the subscription is sent, which can also be useful for debugging.  But beyond that, based on what I am hearing from the CBOR people, even the protocol and encoding might be different between.

<KENT> okay

> subscription-modified


>   1st paragraph: the same parameters, or data model / tree diagram?

>   Also, is "provided" the right word?  Maybe it would be better to

>   have the tree diagram itself, even though only the name changes?

Provided the full tree.   It does chew up space, but that is not really an issue.

<KENT> thx

>   Last two paragraphs, why put "First" and "Second" when they are

>   bullet points.  Maybe you want to use a numbered-list or otherwise

>   rephrase these?

Made a numbered list

<KENT> thx

>   Last paragraph, the last sentence doesn't flow with the first.

>   It seems as if it was copy/pasted from somewhere else.  Is this

>   intended to be a normative statement here?

Yes it is a normative statement, and it is in the correct place.

I added text to smooth the transition.  It now is this:

While this state change will be most commonly used with configured subscriptions, with dynamic subscriptions, there is also one time this notification will be sent. A "subscription-modified" state change notifications MUST be sent if the contents of a filter identified by a "stream-filter-ref" has changed.

<KENT> better

> subscription-terminated


>   1st paragraph, 1st sentence: -e a/The publisher/A publisher/ and

>   also s/the pushing of/pushing/?


 <KENT> thx

>   1st paragraph: "Such a decision may be made for" - should this

>   be "A publisher may terminate a subscription for" ?


 <KENT> thx

>   1st paragraph, for the "first type of reason": does the subscription

>   terminate when the first or last referenced objects are no longer

>   accessible?

This refers to any either any leafref going missing, or the subscription-id being removed.  More in next comment

>  BTW, what do you mean by "via the YANG model", aren't

>   these instance objects in <operational>?

I have updated the text in this section to be much more explicit to cover the intent.  The section now says

   A publisher MAY terminate pushing subscribed event records to a
   receiver.  This notification indicates that no further notification
   messages should be expected from the publisher.  A publisher may
   terminate a subscription for the following reasons:

   1.  Configuration which removes a configured subscription, or a "kill-
       subscription" RPC.  These are identified via the reason "no-such-

   2.  A referenced filter is no longer accessible.  This is identified
       by "filter-unavailable".

   3.  The stream referenced by a subscription is no longer accessible
       by the receiver.  This is identified by "stream-unavailable".

   4.  A suspended subscription has exceeded some timeout.  This is
       identified by "suspension-timeout".

Each of the reasons above correspond one-to-one with a "reason" identityref specified within the YANG model.

<KENT> good

>   1st paragraph, what do you mean by " Identities within the YANG model"?

>   Can the text be more clear that it is referring to the "reason"

>   identityref in the tree diagram?

Text attempted just above.

<KENT> okay

>   The tree diagram is not identified as a tree diagram.


<KENT> thx

>   last paragraph: remove "established".  Also, the first 2 sentences would

>   benefit moving to singular, as plural leads to some ambiguity.


<KENT> thx

Note: a subscriber can terminate an existing subscription via a "delete-subscription" RPC. In such a case, no "subscription-terminated" state change notification is sent.

<KENT> good

> subscription-suspended


>   Please replace the 2nd paragraph with the actual tree diagram, and then

>   speak to that.


<KENT> thx

   This notification indicates that a publisher has suspended the

   sending of event records to a receiver, and also indicates the

   possible loss of events.  Suspension happens when capacity

   constraints stop a publisher from serving a valid subscription.  The

   two conditions where is this possible are "insufficient-resources"

   and "unsupportable-volume".  These conditions are encoded within the

   reasons.  No further notification will be sent until the subscription

   resumes or is terminated.

   Below is a tree diagram for "subscription-suspended".  All objects

   contained in this tree are described within the included YANG model

   within Section 4.

       +---n subscription-suspended

          +--ro identifier    subscription-id

          +--ro reason        identityref

        Figure 11: subscription-suspended notification tree diagram

<KENT> good

> subscription-resumed


>   The tree diagram is not identified as a tree diagram.

Updated.  As are all other tree diagrams now..

<KENT> thx

> subscription-completed


>   Please replace the 2nd paragraph with the actual tree diagram, and then

>   speak to that.

Updated.  As are all other tree diagrams now..

<KENT> thx

> replay-completed


>   2nd paragraph: s/ If subscription/ If a subscription/ and s/which/that/


<KENT> thx

>   Please replace the last paragraph with the actual tree diagram, and then

>   speak to that.

Done as identical to above.

<KENT> thx

> Subscription Monitoring


>   1st paragraph: s/Container/The container/.


<KENT> thx

>   How can container "subscriptions" (config true) contain entries for

>   dynamic subscriptions?  Are you assuming in <operational>?

Updated the start of paragraph 1 to:

In the operational datastore, the container "subscriptions" maintains the state of all known subscriptions.

<KENT> thx

Updated paragraph 2 to:

Each subscription is represented as a list element.  While many subscription objects are "config true", dynamic subscriptions are only included within the operational datastore. Operational information which may be monitored includes receiver counter information, the state...

<KENT> thx

>   Also,

>   does it include configured subscriptions that are currently not

>   active for whatever reason?

Yes.   First paragraph above uses the word ‘all’.

<KENT> but if not active, aka operational, why are they in the operational datastore?  This needs to be explained.

<Eric2> Two thoughts.  First, a configured subscription can be VALID without having any ACTIVE receivers. Second, the status of a configured subscription is a “config false” element which includes both the INVALID and CONCLUDED states that are not configurable.  (text below)

Also, maybe you need to be more explicit than just having "all" …

<Eric2> You are correct, some more detail is needed.  And more description of the counters is needed.  I shook things up.  Here is what it says now:

In the operational datastore, the container "subscriptions" maintains the state of all dynamic subscriptions, as well as all configured subscriptions.  Using datastore retrieval operations, or subscribing to the "subscriptions" container via [I-D.ietf-netconf-yang-push] allows the state of subscriptions and their connectivity to receivers to be monitored.

Each subscription in the operational datastore is represented as a list element. Included in this list are event counters for each receiver, the state of each receiver, as well as the  subscription parameters currently in effect. The appearance of the leaf "configured-subscription-state" indicates that a particular subscription came into being via configuration.  This leaf also indicates if current state of that subscription is VALID,  INVALID, and CONCLUDED.

To understand the flow of event records within a subscription, there are two counters available for each receiver.  The first counter is "pushed-notifications" which shows the quantity of events actually identified for sending to a receiver.  The second counter is "excluded-notifications" which shows event records not sent to receiver.  "excluded-notifications" shows the combined results of both access control and per-subscription filtering.  For configured subscriptions, counters are reset whenever the subscription is evaluated to VALID (see (1) in Figure 8).

Dynamic subscriptions do not appear outside of the operational datastore, and are removed from the operational datastore once they expire (reaching stop-time) or when they are terminated.

>   You mention NETCONF's <get> (wait, I

>   thought this draft was suppose to be transport agnostic), but not

>   NMDA's <get-data>, so it make me wonder if this paragraph regards

>   the contents of <running> or <operational>...

Yes, we want to make it want to make it agnostic.  So it now says:

Using datastore retrieval operations , or subscribing to...

<KENT> better

>   The 2nd paragraph would make more sense if I was looking at a tree

>   diagram.  But then I realize that this would be the same tree-diagram

>   that should've been presented in Configured Subscriptions.

The tree is in the subscriptions container section just below.  I will gladly reference it wherever it ends up.

<KENT> you already need to be referring to it regardless.  As for where it is, see my previous comment on this topic

<Eric2> References to Figure 20 has been made.   If the tree must be moved up, it can be.   I think it fits better where it is.

> Advertisement


>   The second paragraph seems to be mostly NETCONF specific and

>   therefore belongs in the netconf-binding draft.

Good point.  Moved the first sentence to the end of that draft’s “Compatibility with RFC-5277's create-subscription” section.

<KENT> thx

>   In a transport-

>   agnostic draft, maybe only features should be discussed?

Makes sense

<KENT> did you do this, or is this entire paragraph missing now?

<Eric2> I did this.   Current section “Compatibility with RFC-5277's create-subscription” of NETCONF-notif says:

If a publisher supports this specification but not subscriptions via [RFC5277], the publisher MUST NOT advertise "urn:ietf:params:netconf:capability:notification:1.0".

> YANG Data Model Trees


>   s/top level YANG Data Node containers/protocol-accessible nodes/


<KENT> thx

>   " If you would rather see" - please use more formal language.

Made it:

For tree diagrams of state change notifications,

<KENT> thx

> Event Streams Container


>   1st paragraph, last sentence: perhaps rephrase as "This enables

>   clients to discover what streams a publisher supports."?


<KENT> thx

>  BTW, is

>   the " and against which subscription is allowed" part important,

>   if so, why?

Not really.  I was just trying to highlight that different clients might have visibility for different streams.  As this is implicit, I just dropped it and used your text.

<KENT> thx

>   This tree-diagram does not match what I generate.  This indicates

>   that the tree diagrams are not being dynamically-generated.  I

>   strongly suggest updating your build script to dynamically generate

>   the tree diagrams.  We cannot afford to have them be out of alignment.

At the WG request, I segmented the YANG tree into different sections.  However I do not have the tooling which automatically extracts portions of the YANG tree.

Is there a git repository which recommends a continuous integration for sub portions of a YANG tree?  For future drafts, I have certainly built a strong desire for such a continuous integration environment.

<KENT> I have my own tooling using Makefiles and shell scripts to dynamically generate and include the tree diagrams every build.  You should be looking to create similar now, for this draft (not next drafts).   Again, we cannot afford for these things to get out of alignment, and these drafts still have a way to go yet…

<Eric2> I have not seen automated tooling from pyang which pulls individual RPCs and Notification Trees into extracts.  Not finding a way to do this with –tree-path, I tried guessing.  But didn’t get there.   As the majority of my trees are RPCs and Notifications, I don’t see a fully automated solution available as yet.

> Event Stream Filters Container


>   "and validated" - is this needed, since *all* configuration is validated?


>   s/ which/ that/


<KENT> thx

>   "referenced and used" - is there a difference?  - can you just use one?

Now just referenced

 <KENT> thx


> Subscriptions Container



>   This tree-diagram does not match what I generate.  This indicates

>   that the tree diagrams are not being dynamically-generated.  I

>   strongly suggest updating your build script to dynamically generate

>   the tree diagrams.  We cannot afford to have them be out of alignment.

I would love to have fully generated scripts.   That is hard for a few reasons here:

(a) The automatically generated trees are getting mangled because they are so wide.  Especially with yang-push, the automatic trees must all be fixed manually each time.

<KENT> pyang already supports folding and pathing, what else are you doing?  Sometimes I need to tweak the pyang output, but I scripted that too and make it part of my build scripts

<Eric2> Martin taught me how to fold/path.  So that is a welcome fix.

(b) I have no insights on how to pull portions of a tree into a XML document.   Is there a tool site which provides this?

<KENT> my Makefiles call a shell script to do the insertions…

<Eric2>  My environment has certainly shown itself to be insufficient.  If WG requires Makefiles rather than what many of us use (yes, I really built most of this via NOTEPAD++, and I know there are multiple others doing this), then the WG should document expected toolsets to be used.  Note that based on my pain here that I do have my eye on an alternative tooling after these 3 drafts complete WGLC.  If there is a lull subsequent review cycles, perhaps I will convert if my experiences with the next set of drafts work.

The delta I see is “rw” vs “ro”.  Fixed now.   I have brought in the current tree.

<KENT> better, but not a lasting fix

<Eric2> Would the NETMOD WG be willing to put together a wiki of the development tool recommendations?    As a user, I know it would be welcomed.

> Data Model


>   I going to skip this part, for now at least, as I assume the YANG

>   Doctor will scrutinize it.




> Implementation Considerations


>  s/ For a deployment/To support deployments/


<KENT> thx

>  s/split subscription/it is recommended to split subscription"


 <KENT> thx

>  is " unlikely" the right word?  doesn't it eliminate the concern altogether?

Yes it does solve it.

That way it eliminates the possibility of collisions if…

<KENT> thx

>  Regarding the 2nd-half of the 1st paragraph, is it necessary for

>  interoperability reasons for this draft to define how to split the

>  subscription identifiers into static and dynamic parts.

Not necessary, just a best practice.

>   Is the

>  normative text needed here?  Maybe just describe the current

>  approach as a possible way to go about doing it?  - I think it

>  achieves the same goal without using normative text.

Agree.  Text now says:

A best practice is to use lower half the "identifier" object’s integer space when that "identifier" is assigned by an external entity (such as with a configured subscription). This leaves the upper half of subscription identifiers available to be dynamically assigned by the publisher.

<KENT> thx

>  For the 2nd paragraph, this sounds like normative text from earlier

>  in the document.  If so, then is it needed here again?

No.  Deleted.

<KENT> thx

>  For the 3rd paragraph, I'm not sure if the second sentence needs to

>  be said at all, but at least s/SHOULD/should/ so it's not normative.

Made it non-normative

<KENT> thx

> Security Considerations


>   Regarding the 1st paragraph, aren't *all* operations (configuration

>   or RPCs) always authenticated and authorized?

Yes.   Deleted as redundant.

<KENT> thx

>   Please restructure to follow, in part, the template provided here:


Restructured to this:

5.3.  Security Considerations

   The YANG module specified in this document defines a schema for data

   that is designed to be accessed via network management protocols such

   as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer

   is the secure transport layer, and the mandatory-to-implement secure

   transport is Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer

   is HTTPS, and the mandatory-to-implement secure transport is TLS


   The NETCONF Access Control Model (NACM) [RFC6536bis] provides the

   means to restrict access for particular NETCONF or RESTCONF users to

   a preconfigured subset of all available NETCONF or RESTCONF protocol

   operations and content.

   There are a number of data nodes defined in this YANG module that are

   writable/creatable/deletable (i.e., config true, which is the

   default).  These data nodes may be considered sensitive or vulnerable

   in some network environments.  Write operations (e.g., edit-config)

   to these data nodes without proper protection can have a negative

   effect on network operations.  These are the subtrees and data nodes

   and their sensitivity/vulnerability:

   Container: filters

   o  stream-subtree-filter: updating a filter could increase the

      computational complexity of all referencing subscriptions.

   o  stream-xpath-filter: updating a filter could increase the

      computational complexity of all referencing subscriptions.

   Container: subscriptions

   o  address: can be used to attempt to send traffic to an unwilling


   o  dependency: can force important traffic to wait behind the


   o  dscp: can send traffic with a higher priority marking that


   o  encoding: none

   o  identifier: can overwrite an existing subscription configured by

      another entity.

   o  port: none

   o  protocol: none

   o  purpose: none

   o  replay-start-time: can be used to push very large logs, wasting


   o  source-address: address might not be able to reach a receiver.

   o  source-interface: interface might not be able to reach a receiver.

   o  source-vrf: can push subscribed traffic into a virtual network

      which might not contain receivers able to see the subscribed


   o  stop-time: none

   o  stream: none

   o  stream-filter-ref: none

   o  stream-subtree-filter: a complex filter can increase the

      computational resources for this subscription.

   o  stream-xpath-filter: a complex filter can increase the

      computational resources for this subscription.

   o  weighting: placing a large weight can overwhelm the dequeuing of

      other subscriptions.

   Some of the readable data nodes in this YANG module may be considered

   sensitive or vulnerable in some network environments.  It is thus

   important to control read access (e.g., via get, get-config, or

   notification) to these data nodes.  These are the subtrees and data

   nodes and their sensitivity/vulnerability:

   Container: streams

   o  name: if access control is not properly configured, can expose

      system internals to those who should have no access to this


   o  replay-support: if access control is not properly configured, can

      expose logs to those who should have no access.

   Container: subscriptions

   o  pushed-notifications: will show the amount of events a particular

      subscriber actually received from a stream.

   o  excluded-notifications: will show the results of access control,

      and how many event records have been filtered out.

   Some of the RPC operations in this YANG module may be considered

   sensitive or vulnerable in some network environments.  It is thus

   important to control access to these operations.  These are the

   operations and their sensitivity/vulnerability:

   RPC: all

   o  If a malicious or buggy subscriber sends an unexpectedly large number

       of RPCs, the result might be an excessive use of system resources on the

       publisher just to determine that these subscriptions should be declined. In

       such a situation, subscription interactions MAY be terminated by

       terminating the transport session.

   RPC: delete-subscription

   o  No special considerations.

   RPC: establish-subscription

   o  Subscriptions could overload a publisher's resources.  For this

      reason, Publishers MUST ensure that they have sufficient resources

      to fulfill this request or otherwise reject the request.

   RPC: kill-subscription

   o  The "kill-subscription" RPC MUST be secured so that only

      connections with administrative rights are able to invoke this


   RPC: modify-subscription

   o  Subscriptions could overload a publisher's resources.  For this

      reason, Publishers MUST ensure that they have sufficient resources

      to fulfill this request or otherwise reject the request.

<KENT> better, though I'm unsure the "none" nodes need to be listed.

 <Eric2> The template text  “These are the subtrees and data nodes and their sensitivity/vulnerability” appears to make the list of all node mandatory.  As this was not your intent, I pulled the “none” out.

>   Regarding the 2nd and 3rd paragraphs, this sounds good, but isn't

>   this behavior already defined by the draft?  (or should be?)

Yes they are.   I actually refined / incorporated these points in the template above.  As this is what the template appears to be asking to have.

<KENT> thx

>   Regarding the 4th paragraph, why would the publisher need to the

>   terminate the transport session?  wouldn't it have started to

>   reject dynamic subscriptions when it became overloaded?  Or is

>   this trying to say something specific about dropping the transport

>   session as a club?  ;)

Yes, as a club.  Moved this up into the template as part of “RFC: all” and fixed the text to show why the club might need to be used

<KENT> thx

>   Re: the 5th paragraph, this is better than the 1st paragraph, but

>   may not be needed if following the template.

Agree.  This is redundant, and the point is covered as per the template above.

<KENT> thx

>   Re: the 6th paragraph, I'm surprised that requirements for transport-

>   bindings wasn't discussed before in its own section.  It seems like

>   a new thing here, that a receiver's transport might not be secure.

>   I'm okay with and support this, btw, as its sometimes better to

>   offload devices thru the use of a local collector node, for which

>   encryption may not be needed...

Agree with your comments.

<KENT> but where's the change?  Shouldn't this have been discussed

previously in the draft somewhere?

<Eric2> The vast majority of transport binding discussions are addressed in the transport document.  So I see this as guidance to a documenter of a transport document.  Perhaps that is unnecessary for this document, and the paragraph should be removed.  I would be fine with that.

>   Re: the 7th paragraph, this was said before also, right?

Correct, removed.

<KENT> thx

>   Re: 2nd to last paragraph, what is the " very-secure" tag?

Removed, and the overall points moved up into template.  As for the very-secure tag, Andy had mentioned that a few years ago.   It looks like it wasn’t standardized.

<KENT> gotcha

<Eric2>  Thanks again for your time on this.  I see these as good additions...