Re: [Netconf] comments on draft-ietf-netconf-subscribed-notifications-12
Martin Bjorklund <mbj@tail-f.com> Fri, 15 June 2018 08:49 UTC
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Date: Fri, 15 Jun 2018 10:49:29 +0200
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To: evoit@cisco.com
Cc: alexander.clemm@huawei.com, alex@clemm.org, j.schoenwaelder@jacobs-university.de, netconf@ietf.org
From: Martin Bjorklund <mbj@tail-f.com>
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Subject: Re: [Netconf] comments on draft-ietf-netconf-subscribed-notifications-12
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"Eric Voit (evoit)" <evoit@cisco.com> wrote: > > From: Martin Bjorklund, June 14, 2018 2:40 PM > > > > "Eric Voit (evoit)" <evoit@cisco.com> wrote: > > > > From: Martin Bjorklund, June 14, 2018 4:22 AM > > > > > > > > Hi, > > > > > > > > Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de> wrote: > > > > > On Wed, Jun 13, 2018 at 03:36:01PM +0000, Eric Voit (evoit) wrote: > > > > > > Each of the terms used are different. While they all are > > > > > > defined in the first > > > > document they are used, let me paraphrase the meanings of the > > > > definitions... > > > > > > > > > > > > Event - something that happened > > > > > > > > > > > > Event record - the recorded details of a single event > > > > > > > > > > > > Update record - one or more datastore node updates > > > > > > > > > > > > <notification> - a structure defined in RFC5277 which is as a > > > > > > wrapper which > > > > contains an event record. A <notification> can exist without any > > > > active subscription. > > > > > > > > > > > > "notification" statement - a structure defined in RFC-7950 > > > > > > section > > > > > > 7.16 > > > > which allows the definition of event record types specific to a YANG > > > > module. > > > > The results of the a YANG "notification" statement are encoded in a > > > > <notification>. > > > > > > > > > > Here is where I am getting lost. The RFC 7950 notification > > > > > statement (its not a structure btw) does define the content of a > > notification. > > > > > And notification used to be defined in RFC 6241 as a > > > > > "server-initiated message indicating that a certain event has been > > > > > recognized by the server." Your notion of an event record may come > > > > > from the RFC 5277 format that adds an eventTime etc. but the > > > > > relationship of what is a YANG defined notification and how it > > > > > related to your event record and the <notification> structure is still > > unclear. > > > > > > > > I don't think we should align terminology with 5277. More important > > > > is to align with the current set of documents; 7950 and 6241. > > > > > > Exactly. > > > > > > Note that there was no terms imported from 5277. > > > Subscribed-notifications does define an umbrella term "notification > > > message", and uses Section 2.6 to make the minimal connection > > > necessary to show that an RFC-5277 <notification> is a valid > > > "notification message". BTW: We had text in earlier versions of > > > subscribed-notifications stating the need to support future types of > > > "notification messages" such as those defined in > > > draft-ietf-netconf-notification-messages. However reviewers asked > > > these evolving references to be removed. > > > > > > We do have the option of importing terms from 6241 into the > > > NETCONF-notif document. This would be the right place to do it > > > because in the subscribed-notifications document we want to limit any > > > introduction of NETCONF dependencies. (Maybe NETCONF-notif adds text > > > to say that a "RFC6241 client" maps to subscriber, and "RFC6241 > > > server" maps to publisher?) > > > > 8342 defines the terms "client" and "server" in a transport-agnostic > > way. I > > think we should try to use these terms in new documents, where > > applicable. > > In this document, the term "subscriber" is a special "client". > > Agreed. Terminology section updated per the last email. > > > I am not sure that a "publisher" is always a "server"; this needs to > > be decided. > > I think that within YANG-push, a publisher is a special RFC-8342 > "server". Perhaps what we could add to YANG push in the terminology a > sentence which says "In this document, the term publisher also > includes the role of RFC-8342 server." Can we first agree on the basic terminology in subscribed-notifications? First question: are server and publisher potentially different entites or not? Looking at restconf-notif, it seems to me that the publisher is an HTTP2 client, i.e., a different entity than the RESTCONF server. Is this correct: NETCONF: subscriber is a NETCONF client publisher is a NETCONF server receiver is a NETCONF client RESTCONF subscriber is a RESTCONF client (NOTE 1) publisher is a HTTP2 client receiver is a HTTP2 server UDP subscriber is a NETCONF/RESTCONF client publisher is a UDP client receiver is a UDP server NOTE 1: the RESTCONF server is missing from this picture. It doesn't have a special term... I assume this work is not applicable to CoMI? /martin > However my belief is that we shouldn't do a global cut-and-paste of > "publisher" with some new term for this intersection to use throughout > the document. This could end up being confusing. For example, if we > define a new term like "YANG-push publisher" a reader of the YANG > model would need to jump back and forth between the definitions of > "publisher" and "YANG-push publisher" knowing that both are equally > valid in this context. > > > > > If subscribed-notifications is transport-independent, it should > > > > probably not talk too much about <notifcation> etc; this should go > > > > into the transport docs. > > > > > > In general, this is what is done. In subscribed-notifications, the > > > only place <notification> is mentioned at all is section 2.6. If > > > necessary, we could move this section to NETCONF-notif, but that would > > > leave no transport independent framing for the notifications. I guess > > > it is possible to live without that, but it would leave the > > > subscribed-notifications feeling incomplete. > > > > If subscribed-notifications is transport independent, it should not > > have the > > NETCONF-specific text in 2.6. > > RESTCONF also refers to RFC-5277's <notification>. See section 6.4. > So there is precedent and adoption for reuse of the transport element > beyond NETCONF. > > So while pulling this section out and placing it within NETCONF-notif > is possible, it would mean either replicating this information > RESTCONF-notif, or forcing RESTCONF-notif to await the completion of > draft-ietf-netconf-notification-messages. > > > 2.6 also says: > > > > In all cases, a single transport session MUST > > be capable of supporting the intermixing of RPCs and notifications > > from different subscriptions. > > > > This applies to NETCONF, but not for the UDP transport, and I suspect > > not for > > the HTTP transport either? > > Agreed. This statement is now removed. > > > > I suspect a similar > > > thought process drove the inclusion of <notification> within RFC-6020 > > > and then RFC-7950. > > > > No; for various reasons YANG was initially positioned as a data > > modelling > > language for NETCONF only. Hence all text about how to map YANG to > > NETCONF and XML. > > > > > > 7950 says that the "notification" statement defines a notification. > > > > As Juergen pointed out this term is not defined in the terminology > > > > section, but nevertheless the term is used. > > > > > > > > Does the WG now want to introduce a new term for what the > > > > "notification" > > > > statement defines? > > > > > > It certainly might make sense to have a future update of RFC-7950 with > > > something like this. I spend a bit of time trying to understand the > > > connection of YANG notification statement with <notification>. Having > > > this be better defined would be helpful. > > > > > > > It seems to me that the term "event record" is being proposed for > > > > this. > > > > > > An event record is not necessarily a YANG notification, as the event > > > record's payload might not be driven by the result of a YANG > > > statement. > > > > I don't get this. Can you give an example of when an event record is > > not > > defined as a YANG "notification"? > > Another way to put this is that the event record within the > <notification> might not be encoding YANG data. For examples, all the > <notification> within RFC5277 were defined before the availability of > YANG. > > > > > The answer to this question will have a big impact on the rest of > > > > the terminology. > > > > > > As event record has a larger scope than what can come from a YANG > > > notification statement, my suggestion would be for the revision of > > > RFC-7950 to import "event record", and then specify a new subtype term > > > (maybe "YANG event record"?). If that term works, a YANG event record > > > could then be an event record where the contents are populated by the > > > results of the YANG notification statement. > > > > > > > > > Notification message - a message intended for a specific > > > > > > subscription > > > > receiver which includes one or more <notification>. A notification > > > > message will have undergone any security/content filtering on > > > > embedded <notification> as appropriate for that receiver. > > > > > > > > > > So how does this fit Figure 1 of RFC 6241? This figure indicates > > > > > that <notification> is a message as seen from the messages layer. > > > > > You are saying a notification message is something else that > > > > > includes one or more <notification>s. Yes, I know that the diagram > > > > > in RFC 5277 is different but the diagram in RFC 6241 is the newer one. > > > > > > > > This confuses me as well. > > > > > > The requirement for the bundling of many events is being driven by > > > large data center telemetry. It is unclear at this point whether > > > NETCONF will be a transport used in this environment. > > > > > > If NETCONF does care about this environment, and does want to support > > > something like draft-ietf-netconf-notification-messages, I do think > > > tweaks to RFC-6241 will be needed. > > > > Yes, somehow. > > Ok > > Eric > > > > For example what is the definition > > > of <notification> within 6241, Figure 1 (right now point RFC-5277 > > > isn't explicitly mentioned.). Must this figure only be interpreted as > > > a RFC 5277 <notification>? Can the figure also mean a > > > draft-ietf-netconf-notification-messages "message"? > > > > RFC 6241 says that <notification> is defined in RFC 5277. (ok, > > there's an error > > in there, and it points to 5717, but there's an errata for that). > > > > > > How much of this do we have to define in this document, and how much > > > > should go into the transport docs? > > > > > > Beyond what I describe above, impacts would be to new/updated > > > transport drafts. Plus an update to subscribed-notifications section > > > 2.6 to indicate that a new transport independent <notification> > > > construct exists. > > > > Ok. > > > > > > /martin > > > > > > > > > > Eric > > > > > > > /martin > > > > > > > > > > > > > > Per the discussion below, I see an update record being a > > > > > > specialized type of > > > > event record. For YANG push, the 'event' is driven by the update > > > > trigger: i.e., > > > > either the expiration of a periodic timer (for periodic > > > > subscriptions), or a change to the datastore (on-change > > > > subscription). > > > > > > > > > > > > > > > > I am missing a definition what an Update record is. It is surely > > > > > not in this email. Anyway, if there are changes to architectural > > > > > concepts, it would be nice to find them in a coherent well explained > > section. > > > > > > > > > > /js > > > > > > > > > > -- > > > > > Juergen Schoenwaelder Jacobs University Bremen gGmbH > > > > > Phone: +49 421 200 3587 Campus Ring 1 | 28759 Bremen | Germany > > > > > Fax: +49 421 200 3103 <https://www.jacobs-university.de/> > > > > > > > > >
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Tianran Zhou
- Re: [Netconf] comments on draft-ietf-netconf-subs… Martin Bjorklund
- Re: [Netconf] comments on draft-ietf-netconf-subs… Tianran Zhou
- Re: [Netconf] comments on draft-ietf-netconf-subs… Alexander Clemm
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Martin Bjorklund
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Kent Watsen
- Re: [Netconf] comments on draft-ietf-netconf-subs… Andy Bierman
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Kent Watsen
- Re: [Netconf] comments on draft-ietf-netconf-subs… Kent Watsen
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Juergen Schoenwaelder
- Re: [Netconf] comments on draft-ietf-netconf-subs… Henk Birkholz
- Re: [Netconf] comments on draft-ietf-netconf-subs… Martin Bjorklund
- Re: [Netconf] comments on draft-ietf-netconf-subs… Juergen Schoenwaelder
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Martin Bjorklund
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Martin Bjorklund
- Re: [Netconf] comments on draft-ietf-netconf-subs… Martin Bjorklund
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Juergen Schoenwaelder
- Re: [Netconf] comments on draft-ietf-netconf-subs… Alexander Clemm
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Juergen Schoenwaelder
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Martin Bjorklund
- Re: [Netconf] comments on draft-ietf-netconf-subs… Juergen Schoenwaelder
- Re: [Netconf] comments on draft-ietf-netconf-subs… Alexander Clemm
- Re: [Netconf] comments on draft-ietf-netconf-subs… Kent Watsen
- [Netconf] comments on draft-ietf-netconf-subscrib… Martin Bjorklund
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Martin Bjorklund
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)
- Re: [Netconf] comments on draft-ietf-netconf-subs… Martin Bjorklund
- Re: [Netconf] comments on draft-ietf-netconf-subs… Eric Voit (evoit)