Re: [pim] [yang-doctors] Optional key support?

[Andy Bierman <[e-mail]>]

On Sun, Oct 28, 2018 at 4:51 AM, Acee Lindem (acee) <[e-mail]> wrote:

> Hi Andy,
>
>
>
> *From: *Andy Bierman <[e-mail]>
> *Date: *Wednesday, October 24, 2018 at 2:44 PM
> *To: *Acee Lindem <[e-mail]>
> *Cc: *"Robert Wilton -X (rwilton - ENSOFT LIMITED at Cisco)" <
> [e-mail]>, Martin Bjorklund <[e-mail]>, Xufeng Liu <
> [e-mail]>, "[e-mail]" <
> [e-mail]>, "[e-mail]" <[e-mail]>, "
> [e-mail]" <[e-mail]>, "[e-mail]" <
> [e-mail]>, YANG Doctors <[e-mail]>, "
> [e-mail]" <[e-mail]>, "pete.mcallister@metaswitch.
> com" <[e-mail]>, "[e-mail]" <[e-mail]>
> *Subject: *Re: [yang-doctors] Optional key support?
>
>
>
>
>
>
>
> On Wed, Oct 24, 2018 at 11:35 AM, Acee Lindem (acee) <[e-mail]>
> wrote:
>
>
>
>
>
> *From: *Andy Bierman <[e-mail]>
> *Date: *Wednesday, October 24, 2018 at 2:29 PM
> *To: *Acee Lindem <[e-mail]>
> *Cc: *"Robert Wilton -X (rwilton - ENSOFT LIMITED at Cisco)" <
> [e-mail]>, Martin Bjorklund <[e-mail]>, Xufeng Liu <
> [e-mail]>, "[e-mail]" <
> [e-mail]>, "[e-mail]" <[e-mail]>, "
> [e-mail]" <[e-mail]>, "[e-mail]" <
> [e-mail]>, YANG Doctors <[e-mail]>, "
> [e-mail]" <[e-mail]>, "pete.mcallister@metaswitch.
> com" <[e-mail]>, "[e-mail]" <[e-mail]>
> *Subject: *Re: [yang-doctors] Optional key support?
>
>
>
>
>
>
>
> On Wed, Oct 24, 2018 at 11:18 AM, Acee Lindem (acee) <[e-mail]>
> wrote:
>
> Lada, Andy,
>
>
>
> I guess I’m missing something in this discussion. Why is a key leaf with a
> defaulted value any more complex to deal with than a leaf with an
> explicitly specified value? I just don’t get it…
>
>
>
>
>
> If YANG-next ever turns into YANG 1.2 we can discuss the complexities of
> list instantiation and protocol interactions at that time.
>
> A YANG default is the value that is implemented if no value is provided by
> the client.
>
> It means the server MUST fully implement the leaf value semantics as if
> the client provided the default value.
>
> IMO this is not the same thing at all as a missing key that is supposed to
> mean "key not applicable".
>
>
>
> And I believe the default value for a key leaf would satisfy the
> requirement… Hopefully w/o the complexities of an N/A key.
>
>
>
>
>
>
>
> So the problem to be solved is that it is too much of a burden on the
> client to provide
>
> the default key leaf value?  It is not as if it can be ignored.  Retrieval
> of the list
>
> entry will include all the keys.
>
>
>
> In some cases (like the case of protocols), the key isn’t applicable. So,
> semantically it is confusing for the client. We could restrict the key
> default to keys subsequent to the first.
>
>
>
> Edits on the candidate datastore become more complex.
>
> Is that missing key going to be provided in a subsequent edit before the
> commit?
>
>
>
> I can see your point here. We’d need to define the behavior and I’d say
> “no”, if a default key is changed, it is a separate list entry.
>
>
>


I agree default for a key leaf is fine if it works this way.
The list instance is set when it is created.
The protocol should have an explicit "rename" operation in order to change
a key leaf.



> Thanks,
>
> Acee
>
>
>


Andy


>
>
> Thanks,
>
> Acee
>
>
>
>
>
>
>
> Andy
>
>
>
>
>
> Thanks,
>
> Acee
>
>
>
>
>
> Andy
>
>
>
>
>
> *From: *Andy Bierman <[e-mail]>
> *Date: *Wednesday, October 24, 2018 at 1:31 PM
> *To: *"Robert Wilton -X (rwilton - ENSOFT LIMITED at Cisco)" <
> [e-mail]>
> *Cc: *Acee Lindem <[e-mail]>, Martin Bjorklund <[e-mail]>,
> Xufeng Liu <[e-mail]>, "[e-mail]" <
> [e-mail]>, "[e-mail]" <[e-mail]>, "
> [e-mail]" <[e-mail]>, "[e-mail]" <
> [e-mail]>, YANG Doctors <[e-mail]>, "
> [e-mail]" <[e-mail]>, "pete.mcallister@metaswitch.
> com" <[e-mail]>, "[e-mail]" <[e-mail]>
> *Subject: *Re: [yang-doctors] Optional key support?
>
>
>
>
>
>
>
> On Wed, Oct 24, 2018 at 8:56 AM, Robert Wilton <[e-mail]> wrote:
>
> It looks like the final reason that it was not accepted was because the
> change was regarded as being too big for YANG 1.1.  As such, it seems
> reasonable for this issue to be on Yang.next and considered again.
>
>
>
> My objection to it was that it had a huge impact on the protocols and the
> implementations.
>
> The added complexity is not worth it.
>
>
>
> It is not that hard to define a value that indicates "not really used".
>
> That is not the same as "use the default".  Doing this in an elegant way
>
> instead of ad-hoc requires coordinated solutions in YANG, protocols, and
> servers.
>
>
>
> There are probably lots of complex YANG text changes because the concept
> of an
>
> instance (and an instance-identifier) is so different. Also augment,
> leafref,
>
> and other cross-model dependencies are impacted.
>
>
>
>
>
> Thanks,
> Rob
>
>
>
>
>
>
>
> Andy
>
>
>
>
> On 24/10/2018 15:53, Acee Lindem (acee) wrote:
>
> Read through the discussion and it is a shame we can't converge on a
> solution. Is YANG 1.0 compatibility the major issue?
> Thanks,
> Acee
>
> On 10/24/18, 1:48 AM, "yang-doctors on behalf of Martin Bjorklund" <
> [e-mail] on behalf of [e-mail]> wrote:
>
>      Andy Bierman <[e-mail]> wrote:
>      > Hi,
>      >
>      > It has been discussed before.
>      > It is already allowed for config=false nodes so the change would be
> to
>      > allow config=true nodes
>      > to have no keys.
>      >
>      > Each time it comes up, somebody mentions that
>      > (a) NETCONF/RESTCONF has no mechanism to delete all list entries
>      > (b) The client cannot create more than 1 entry. How does the server
> know
>      >      the next entry is a different instance or replacing the first
> instance?
>           I don't think these were the reasons.  See the proposal that was
> on
>      the table for 1.1:
>           http://svn.tools.ietf.org/svn/wg/netmod/yang-1.1/issues.
> html#sec-10
>           and the discussion:
>           https://mailarchive.ietf.org/arch/browse/netmod/?gbt=1&index=
> bwacmVipuJMakMFjDXXCZMXCTAA
>                     /martin
>                > What is the use-case for a config list without keys?
>      >
>      >
>      > Andy
>      >
>      >
>      > On Tue, Oct 23, 2018 at 2:16 PM, Reshad Rahman (rrahman) <
> [e-mail]>
>      > wrote:
>      >
>      > > <Changed subject>
>      > >
>      > >
>      > >
>      > > Hi Xufeng,
>      > >
>      > >
>      > >
>      > > I don’t know if this has been discussed for yang-next but it
> doesn’t seem
>      > > to be in the yang-next list. I believe optional keys were
> discussed for
>      > > YANG1.1, maybe others on the YD list remember…
>      > >
>      > > https://github.com/netmod-wg/yang-next/issues
>      > >
>      > >
>      > >
>      > > In this case, I believe it would have been useful to have that
>      > > functionality.
>      > >
>      > >
>      > >
>      > > Regards,
>      > >
>      > > Reshad.
>      > >
>      > >
>      > >
>      > > *From: *Xufeng Liu <[e-mail]>
>      > > *Date: *Tuesday, October 23, 2018 at 4:39 PM
>      > > *To: *"Reshad Rahman (rrahman)" <[e-mail]>
>      > > *Cc: *"[e-mail]" <[e-mail]>, Mahesh Sivakumar <
>      > > [e-mail]>, Stig Venaas <[e-mail]>,
> Guofeng <
>      > > [e-mail]>, Anish Peter <[e-mail]>, "
>      > > [e-mail]" <[e-mail]>, Liuyisong <
>      > > [e-mail]>, Pete McAllister <
> [e-mail]>, "
>      > > [e-mail]" <[e-mail]>
>      > > *Subject: *Re: [yang-doctors] [pim] Yangdoctors last call review
> of
>      > > draft-ietf-pim-igmp-mld-yang-07
>      > >
>      > >
>      > >
>      > > Hi Reshad and All,
>      > >
>      > >
>      > >
>      > > Do you think that it would be useful to eventually extend YANG
> spec to
>      > > allow an optional key with a default value? That would allow the
> user not
>      > > to enter the extra empty string, and make the model more user
> friendly.
>      > >
>      > >
>      > >
>      > > Thanks,
>      > >
>      > > - Xufeng
>      > >
>      > >
>      > >
>      > > On Fri, Oct 19, 2018 at 11:02 AM Reshad Rahman (rrahman) <
>      > > [e-mail]> wrote:
>      > >
>      > > Hi Xufeng,
>      > >
>      > >
>      > >
>      > > I think we should go with the solution proposed by Chris
> (attached) when
>      > > we last discussed this. I realize it’s not ideal but IMO it’s
> better than
>      > > other proposals.
>      > >
>      > >
>      > >
>      > > Regards,
>      > >
>      > > Reshad.
>      > >
>      > >
>      > >
>      > > *From: *yang-doctors <[e-mail]> on behalf
> of Xufeng
>      > > Liu <[e-mail]>
>      > > *Date: *Friday, October 19, 2018 at 9:21 AM
>      > > *To: *"[e-mail]" <[e-mail]>
>      > > *Cc: *Mahesh Sivakumar <[e-mail]>, Stig Venaas
> <
>      > > [e-mail]>, Guofeng <[e-mail]>, Anish Peter <
>      > > [e-mail]>, "[e-mail]" <
> [e-mail]>,
>      > > Liuyisong <[e-mail]>, Pete McAllister <
>      > > [e-mail]>, "[e-mail]" <[e-mail]>
>      > > *Subject: *Re: [yang-doctors] [pim] Yangdoctors last call review
> of
>      > > draft-ietf-pim-igmp-mld-yang-07
>      > >
>      > >
>      > >
>      > > Hi Jan,
>      > >
>      > >
>      > >
>      > > Thanks for reviewing.
>      > >
>      > > For #1, as discussed, there is no other better solution at the
> moment.
>      > > What would you suggest?
>      > >
>      > > Thanks.
>      > >
>      > > - Xufeng
>      > >
>      > >
>      > >
>      > > On Fri, Oct 19, 2018 at 4:25 AM Jan Lindblad <[e-mail]>
> wrote:
>      > >
>      > > Feng,
>      > >
>      > >
>      > >
>      > > Hi Jan,
>      > >
>      > >
>      > >
>      > > We updated  draft-ietf-pim-igmp-mld-yang according to the
> comments #2 ~
>      > > #7, while Xufeng and you had discussed about comment #1.
>      > >
>      > > Please review the draft, thanks a lot.
>      > >
>      > > https://www.ietf.org/id/draft-ietf-pim-igmp-mld-yang-08.txt
>      > >
>      > >
>      > >
>      > > Good. I looked through the points #2-#7 and find that the work
> group have
>      > > understood and fixed those issues. #1 still remains to be
> resolved. I can
>      > > do a full re-review of the module once that one has been resolved
> as well..
>      > > Are there any outstanding questions on how to fix #1?
>      > >
>      > >
>      > >
>      > > Best Regards,
>      > >
>      > > /jan
>      > >
>      > > --
>      > >
>      > > *Jan Lindblad*, [e-mail], [phone]
>      > >
>      > > Solutions Architect, Business Development, Tail-f
>      > >
>      > > Tail-f is now a part of Cisco
>      > >
>      > >
>      > >
>      > >
>      > >
>      > > Feng
>      > >
>      > >
>      > >
>      > > -----Original Message-----
>      > >
>      > > From: Jan Lindblad [mailto:[e-mail] <[e-mail]>]
>      > >
>      > > Sent: Monday, August 13, 2018 10:35 PM
>      > >
>      > > To: [e-mail]
>      > >
>      > > Cc: [e-mail]; [e-mail]; draft-ietf-pim-igmp-mld-yang.
> [e-mail]
>      > >
>      > > Subject: Yangdoctors last call review of
> draft-ietf-pim-igmp-mld-yang-07
>      > >
>      > >
>      > >
>      > > Reviewer: Jan Lindblad
>      > >
>      > > Review result: On the Right Track
>      > >
>      > >
>      > >
>      > > This is my YANG-doctor review of draft-ietf-pim-igmp-mld-yang-07.
> In the
>      > > spring, I did an early review of the -02 version.
>      > >
>      > >
>      > >
>      > > Most of the comments from the earlier review are still valid. In
> some ways
>      > > the document has progressed since -02, in many it has not, and in
> a few it
>      > > has deteriorated. In my judgement, the document is not ready for
> last call.
>      > > Many fundamentally important questions are still unresolved. Here
> are my
>      > > review comments in rough falling order of importance.
>      > >
>      > >
>      > >
>      > > #1 Improper augment of /rt:routing/rt:control-plane-protocols
>      > >
>      > >
>      > >
>      > > Quoted from section 3.1:
>      > >
>      > >    This model augments the core routing data model "ietf-routing"
>      > >
>      > >    specified in [RFC8349].  The IGMP model augments "/rt:routing/
>      > >
>      > >    rt:control-plane-protocols" as opposed to augmenting
> "/rt:routing/
>      > >
>      > >    rt:control-plane-protocols/rt:control-plane-protocol", as the
> latter
>      > >
>      > >    would allow multiple protocol instances, while the IGMP
> protocol is
>      > >
>      > >    designed to be enabled or disabled as a single protocol
> instance on
>      > >
>      > >    a network instance or a logical network element.
>      > >
>      > >
>      > >
>      > > The description above, and the actual augment statements in the
> YANG
>      > > module violate the principles described in RFC 8349, the
> ietf-routing.yang
>      > > module it augments. In RFC 8349, section 5.3.  Control-Plane
> Protocol, the
>      > > proper way of augmenting the routing module is described. The
> fact that
>      > > this is a singleton protocol instance doesn't change this.
> Section 5.3
>      > > describes singleton cases as well.
>      > >
>      > >
>      > >
>      > > Guofeng: Xufeng has discussed with Jan about the comment, and it
> is closed.
>      > >
>      > >
>      > >
>      > > #2 Incorrect vendor refinement model
>      > >
>      > >
>      > >
>      > > Quoted from section 2.2:
>      > >
>      > >    For the same reason, wide constant ranges (for example, timer
>      > >
>      > >    maximum and minimum) will be used in the model.  It is
> expected that
>      > >
>      > >    vendors will augment the model with any specific restrictions
> that
>      > >
>      > >    might be required. Vendors may also extend the features list
> with
>      > >
>      > >    proprietary extensions.
>      > >
>      > >
>      > >
>      > > This is not acceptable. The principle suggested does not foster
>      > > interoperability and useful standards. It is also not possible to
> do what
>      > > the paragraph suggests in YANG. This was pointed out in the -02
> review, and
>      > > a suggestion was given there on how to address the problem.
>      > >
>      > >
>      > >
>      > > Guofeng: We removed the paragraph above, and put the values
> discussed by
>      > > Mcast Design Team.
>      > >
>      > >
>      > >
>      > >
>      > >
>      > > #3 Top level structures not optional
>      > >
>      > >
>      > >
>      > > Quoted from section 2.3:
>      > >
>      > >    The current document contains IGMP and MLD as separate schema
>      > >
>      > >    branches in the structure. The reason for this is to make it
> easier
>      > >
>      > >    for implementations which may optionally choose to support
> specific
>      > >
>      > >    address families. And the names of objects may be different
> between
>      > >
>      > >    the IPv4 (IGMP) and IPv6 (MLD) address families.
>      > >
>      > >
>      > >
>      > > This problem was also pointed out in the -02 review. The author
> suggests
>      > > that implementing igmp and/or mld is optional. This is not
> reflected in the
>      > > YANG module, however. As currently modeled, both are currently
> mandatory to
>      > > implement. If-feature is used liberally in the module, and could
> be used
>      > > here as well.
>      > >
>      > >
>      > >
>      > > #4 Unclear meaning of optional leaves
>      > >
>      > >
>      > >
>      > > Quoted from section 3.1:
>      > >
>      > >    Where fields are not genuinely essential to protocol
> operation, they
>      > >
>      > >    are marked as optional. Some fields will be essential but have
> a
>      > >
>      > >    default specified, so that they need not be configured
> explicitly.
>      > >
>      > >
>      > >
>      > > In fact, in the current version of the module, every leaf is
> optional
>      > > (except keys, which cannot be optional). It is good to see the
> addition of
>      > > defaults in many cases, but many unclear cases remain. E.g. leaf
>      > > /igmp/global/enable is of type boolean. I understand what true
> and false
>      > > implies for this leaf. But what does it mean if it is not set at
> all?
>      > > Either add a default or describe the meaning in the description.
> Similarly,
>      > > if the leaf version is not set on an igmp or mld interface, or on
> the
>      > > interface-global level, what does that mean?
>      > >
>      > > Add default. require-router-alert? explicit-tracking?
> exclude-lite? Many
>      > > of these are used in NP-containers inheriting all the from the
> root, which
>      > > makes the use of mandatory highly discouraged in the current
> form. If the
>      > > RFC 8349 augmentation principles are followed, the concern around
> mandatory
>      > > falls, and some leafs with no sensible default could be marked
> mandatory
>      > > instead.
>      > >
>      > >
>      > >
>      > > #5 All optional state
>      > >
>      > >
>      > >
>      > > All state data is optional, which means a conforming server could
> very
>      > > well decide not to implement it. E.g. discontinuity-time is
> optional.
>      > > Should a manager count on this being available? A situation where
> every
>      > > leaf is optional is as nice and flexible for server implementors
> as it is
>      > > frustrating and complicated for manager implementors to consume.
> A YANG
>      > > model is an API contract and should consider the needs of both
> sides. The
>      > > way this has been designed reveals that no representation for the
> consumer
>      > > side of this model has been involved in the design. I would
> suggest
>      > > thinking through what is the most essential state data for a
> manager, and
>      > > make some leafs mandatory.
>      > >
>      > >
>      > >
>      > > #6 Abundant copy-paste
>      > >
>      > >
>      > >
>      > > There is abundant repetition in the YANG module. leaf version is
> defined 2
>      > > times for igmp with identical definitions, and two more for mld
> with
>      > > identical definitions. leaf enable is defined once for the
> interface
>      > > global-level, and with identical definition on the interface
> local level.
>      > > leaf last-member-query-interval, query-interval and half a dozen
> other
>      > > leaves are defined twice with identical definitions.
>      > >
>      > >
>      > >
>      > > #7 Leaf interface in the rpc clear*groups on line 1124, 1094 has
> type
>      > > string.
>      > >
>      > > Should be a leafref? Describe what values are valid. #8 Leaf
> group-policy,
>      > > source-policy on line 486, 527, 624, 689: type string. Should be
> leafref?
>      > >
>      > > Describe what values are valid. #9 Leaf group on line 705, 1101,
> 1131: Is
>      > > any
>      > >
>      > > ipv4/6 address ok, or only a multicast address? Model accordingly.
>      > >
>      > >
>      > >
>      > >
>      > >
>      > >
>      > >
>      > >
>      > >
>      > >
>      > >
>      > >
>      > >
>      > > *From:* pim [mailto:[e-mail] <[e-mail]>]
> *On
>      > > Behalf Of *Jan Lindblad
>      > > *Sent:* Tuesday, September 11, 2018 9:52 PM
>      > > *To:* Xufeng Liu <[e-mail]>
>      > > *Cc:* [e-mail]; ietf <[e-mail]>; [e-mail];
>      > > [e-mail]
>      > > *Subject:* Re: [pim] Yangdoctors last call review of
>      > > draft-ietf-pim-igmp-mld-yang-07
>      > >
>      > >
>      > >
>      > > Xufeng,
>      > >
>      > >
>      > >
>      > > Thanks for the review and valuable comments.
>      > >
>      > >
>      > >
>      > > In regard to item #1, there was a discussion thread among the Yang
>      > > Doctors, authors of RFC 8349, and Routing Area Yang Architecture
> Design
>      > > Team, as attached below.  The discussion occurred during the
> review of a
>      > > draft with the same issue as this one.
>      > >
>      > >
>      > >
>      > > I see, didn't know. Good. If this has been discussed to
> conclusion, then
>      > > you should of course go with that decision.
>      > >
>      > >
>      > >
>      > > As mentioned earlier, there are a few other singleton protocols
> mapped
>      > > into this structure, e.g. static. I think it would make sense to
> treat this
>      > > the same. Principle of least astonishment.
>      > >
>      > >
>      > >
>      > > Best Regards,
>      > >
>      > > /jan
>      > >
>      > >
>      > >
>      > >
>      > >
>      > > ================================
>      > >
>      > > 原始邮件
>      > > 发件人：XufengLiu <[e-mail]>
>      > > 收件人：Acee Lindem (acee) <[e-mail]>Christian Hopps <
> [e-mail]>Martin
>      > > Bjorklund <[e-mail]>
>      > > 抄送人：张征00007940;[e-mail] <[e-mail]>
>      > > 日 期 ：2018年02月20日 22:30
>      > > 主 题 ：RE: [yang-doctors] How to restrict to have
>      > > singlecontrol-plane-protocol instance
>      > > Using "" as the name is better, but I am not sure that it is good
> enough.
>      > > When we use ConfD to translate the model to a command line, if
> the option
>      > > "tailf:cli-expose-key-name" is not used, we will have:
>      > >
>      > > edit routing control-plane-protocols control-plane-protocol type
> msdp name
>      > > ''"
>      > >
>      > > If the option "tailf:cli-expose-key-name" is used, we will have:
>      > >
>      > > edit routing control-plane-protocols control-plane-protocol msdp
> ''"
>      > >
>      > > I am pretty sure that we would get a bug report on this, asking
> what is
>      > > the purpose to have: name ''", and requesting a suppression on
> the term,
>      > > but we do not have a good way to achieve.
>      > >
>      > > As a comparison, the option #3 will give:
>      > >
>      > > edit routing control-plane-protocols msdp
>      > >
>      > > This is the only acceptable solution so far. When a model is not
> usable by
>      > > the end-user, other considerations (such as augmentation
> convenience) will
>      > > not matter.
>      > >
>      > > Thanks,
>      > > - Xufeng
>      > >
>      > > > -----Original Message-----
>      > > > From: Acee Lindem (acee) [mailto:[e-mail]]
>      > > > Sent: Monday, February 19, 2018 1:35 PM
>      > > > To: Christian Hopps <[e-mail]>; Martin Bjorklund <
>      > > [e-mail]>
>      > > > Cc: Xufeng Liu <[e-mail]>; [e-mail];
> yang-
>      > > > [e-mail]
>      > > > Subject: Re: [yang-doctors] How to restrict to have single
> control-plane-
>      > > > protocol instance
>      > > >
>      > > >
>      > > >
>      > > > On 2/19/18, 5:02 AM, "Christian Hopps" <[e-mail]>
> wrote:
>      > > >
>      > > >
>      > > >     Martin Bjorklund <[e-mail]> writes:
>      > > >
>      > > >     > Hi,
>      > > >     >
>      > > >     > "Acee Lindem (acee)" <[e-mail]> wrote:
>      > > >     >> All,
>      > > >     >>
>      > > >     >> As seems to be the modus operandi for YANG issues, we
> have 3
>      > > separate
>      > > > opinions as to how a protocol only supporting a single instance
> should be
>      > > > realized.
>      > > >     >>
>      > > >     >>   1. Augment the existing control plane protocols list
> (RFC
>      > > 8022BIS)
>      > > >     >>   and specify in the description text that only a single
> instance
>      > > is
>      > > >     >>   supported.
>      > > >     >>   2. Augment the existing control plane protocols list
> (RFC
>      > > 8022BIS)
>      > > >     >>   and use a YANG 1.1 must() restriction as discussed by
> Martin and
>      > > >     >>   Lada.
>      > > >     >>   3. Augment the container one level up from the list for
>      > > singleton
>      > > >     >>   protocols (suggested by Xufeng).
>      > > >
>      > > >     > But I think there was also a proposal to require the
> single
>      > > instance
>      > > >     > to have a well-known name - but maybe this proposal is no
> longer on
>      > > >     > the table.
>      > > >
>      > > >     I actually liked this solution; however, instead of picking
> an
>      > > arbitrary "well-
>      > > > known" value for name, I would specify the 0 length string
> instead. I
>      > > think that
>      > > > reinforces the idea that this isn't actually a named instance.
> :)
>      > > >
>      > > >        augment "/rt:routing/rt:control-plane-protocols/"
>      > > >              + "rt:control-plane-protocol" {
>      > > >           when "derived-from-or-self(rt:type, 'msdp:msdp') and
> rt:name =
>      > > ''"  {
>      > > >           container msdp {
>      > > >
>      > > > One benefit of this solution is that it solves Xufeng's issue
> of what
>      > > the client uses
>      > > > as the instance name.
>      > > >
>      > > >
>      > > >     Thanks,
>      > > >     Chris.
>      > > >
>      > > >     >
>      > > >     >
>      > > >     > /martin
>      > > >     >
>      > > >     >
>      > > >     >> and #3. For #3, one determent would be that the control
> plane
>      > > protocols
>      > > > are in a location other than where they were originally
> envisioned and I
>      > > don't
>      > > > relish pulling RFC8022BIS off the RFC queue to document.
>      > > >     >>
>      > > >     >> Thanks,
>      > > >     >> Acee
>      > > >     >>
>      > > >     >> On 2/15/18, 8:39 AM, "Reshad Rahman (rrahman)" <
> [e-mail]
>      > > >
>      > > > wrote:
>      > > >     >>
>      > > >     >>     Hi Xufeng,
>      > > >     >>
>      > > >     >>     I think the intent of 8022bis was to have all
> protocols under
>      > > > /rt:routing/rt:control-plane-protocols/rt:control-plane-protocol.
> I
>      > > agree that
>      > > > forcing a name for a single-instance is cumbersome, but I think
> it is
>      > > too late to
>      > > > change tree hierachy organization at this point.
>      > > >     >>
>      > > >     >>     I will defer to other YDs and 8022bis authors on
> this.
>      > > >     >>
>      > > >     >>     Regards,
>      > > >     >>     Reshad.
>      > > >     >>
>      > > >     >>     On 2018-02-08, 9:48 AM, "Xufeng Liu" <
> [e-mail]>
>      > > wrote:
>      > > >     >>
>      > > >     >>         Hi All,
>      > > >     >>
>      > > >     >>         I feel that such a solution is still not clean
> enough to
>      > > outweigh the
>      > > > simple augmentation to "/rt:routing/rt:control-plane-
> protocols/".
>      > > >     >>
>      > > >     >>         Some considerations are:
>      > > >     >>
>      > > >     >>         - Name management: Neither the operator nor the
>      > > implementation
>      > > > wants to deal with the artificial name, whether it is hardcoded,
>      > > user-configured,
>      > > > or system-generated. When we implement such singleton protocol,
> we don't
>      > > > save a name anywhere.
>      > > >     >>         - The complexity of validation: The "when"
> statement is an
>      > > > unnecessary expense to the user and to the implementation,
> especially if
>      > > we
>      > > > need to check all instances.
>      > > >     >>         - Data tree query: If the singleton "MSDP" is
> mixed with
>      > > other protocol
>      > > > instances, it is less obvious or harder to search for.
> Depending on the
>      > > > implementation, it would be worse if the entire list needs to be
>      > > iterated.
>      > > >     >>         - Tree hierarchy  organization: I don't see too
> big a
>      > > problem with "all
>      > > > single-instance protocols under /rt:routing/rt:control-plane-
> protocols
>      > > and all
>      > > > the multi-instance ones under /rt:routing/rt:control-plane-
>      > > protocols/rt:control-
>      > > > plane-protocol". If necessary, some of the names can be
> adjusted.
>      > > >     >>
>      > > >     >>         Thanks,
>      > > >     >>         - Xufeng
>      > > >     >>
>      > > >     >>
>      > > >     >>         > -----Original Message-----
>      > > >     >>         > From: Reshad Rahman (rrahman) [mailto:
> [e-mail]
>      > > ]
>      > > >     >>         > Sent: Thursday, February 8, 2018 9:41 AM
>      > > >     >>         > To: Ladislav Lhotka <[e-mail]>; Martin
> Bjorklund
>      > > <mbj@tail-
>      > > > f.com>;
>      > > >     >>         > Acee Lindem (acee) <[e-mail]>
>      > > >     >>         > Cc: [e-mail];
> [e-mail];
>      > > Xufeng Liu
>      > > >     >>         > <[e-mail]>
>      > > >     >>         > Subject: Re: [yang-doctors] How to restrict to
> have
>      > > single control-
>      > > > plane-
>      > > >     >>         > protocol instance
>      > > >     >>         >
>      > > >     >>         > Thanks for the suggestions. I agree that
> hard-coding
>      > > the name is a
>      > > > bad idea,
>      > > >     >>         > glad that a cleaner way of doing this is
> possible.
>      > > >     >>         > - We can move the must statement up to
> restrict max of
>      > > 1 control-
>      > > > plane-
>      > > >     >>         > protocol instance of type msdp?
>      > > >     >>         > - Acee/Lada, should a note be added to section
> 5.3 of
>      > > 8022bis
>      > > > regarding how
>      > > >     >>         > to enforce single instance? How much of a
> concern is the
>      > > > performance
>      > > >     >>         > impact in this specific case?
>      > > >     >>         >
>      > > >     >>         > Regards,
>      > > >     >>         > Reshad.
>      > > >     >>         >
>      > > >     >>         > On 2018-02-08, 7:02 AM, "Ladislav Lhotka" <
>      > > [e-mail]> wrote:
>      > > >     >>         >
>      > > >     >>         >     On Thu, 2018-02-08 at 12:39 +0100, Martin
> Bjorklund
>      > > wrote:
>      > > >     >>         >     > "Acee Lindem (acee)" <[e-mail]>
> wrote:
>      > > >     >>         >     > > Hi Lada,
>      > > >     >>         >     >
>      > > >     >>         >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > > On 2/8/18, 4:42 AM, "yang-doctors on
> behalf of
>      > > Ladislav
>      > > > Lhotka"
>      > > >     >>         > <yang-docto
>      > > >     >>         >     > [e-mail] on behalf of
> [e-mail]>
>      > > wrote:
>      > > >     >>         >     >
>      > > >     >>         >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     On Thu, 2018-02-08 at 09:20 +0100,
> Martin
>      > > Bjorklund wrote:
>      > > >     >>         >     >
>      > > >     >>         >     > >     > Hi,
>      > > >     >>         >     >
>      > > >     >>         >     > >     >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > "Reshad Rahman (rrahman)" <
>      > > [e-mail]> wrote:
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > Hi YDs,
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > MSDP YANG authors want to
> enforce
>      > > single-instance of
>      > > > MSDP
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > control-plane protocol. The
> when
>      > > “rt:type =
>      > > > ‘msdp’“ allows
>      > > >     >>         > multiple
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > control-pane-protocol
> instances as long
>      > > as they have
>      > > > different
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > rt:name. The only workaround I
> thought
>      > > of is to have a
>      > > > when
>      > > >     >>         >     > statement
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > on the name in the top level
> container..
>      > > This would still
>      > > > multiple
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > control-plane-protocol
> instance of type
>      > > msdp but
>      > > > restricts the
>      > > >     >>         > name
>      > > >     >>         >     > to
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > a fixed name (msdp-protocol in
> this
>      > > case) for the top level
>      > > > msdp
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > container to exist. Any
> suggestions on
>      > > how to do this
>      > > > better?
>      > > >     >>         >     >
>      > > >     >>         >     > >     >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > Hard-coding a name like this is
> IMO a bad
>      > > idea.
>      > > >     >>         >     >
>      > > >     >>         >     > >     >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > Better would be to simply state
> in text
>      > > that there MUST
>      > > > only be one
>      > > >     >>         >     >
>      > > >     >>         >     > >     > instance of this type.
>      > > >     >>         >     >
>      > > >     >>         >     > >     >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > But you can also add a must
> statement
>      > > that enforces this:
>      > > >     >>         >     >
>      > > >     >>         >     > >     >
>      > > >     >>         >     >
>      > > >     >>         >     > >     >    augment
> "/rt:routing/rt:control-plane-
>      > > protocols/"
>      > > >     >>         >     >
>      > > >     >>         >     > >     >          +
> "rt:control-plane-protocol" {
>      > > >     >>         >     >
>      > > >     >>         >     > >     >       when
> 'derived-from-or-self(rt:type,
>      > > "msdp:msdp"'  {
>      > > >     >>         >     >
>      > > >     >>         >     > >     >      container msdp {
>      > > >     >>         >     >
>      > > >     >>         >     > >     >        must
> 'count(/rt:routing/rt:control-
>      > > plane-protocols/'
>      > > >     >>         >     >
>      > > >     >>         >     > >     >           + '
>      > > rt:control-plane-protocol['
>      > > >     >>         >     >
>      > > >     >>         >     > >     >           + '
>      > > derived-from-or-sel(../rt:type, "msdp:msdp")])
>      > > > <=
>      > > >     >>         >     > 1'";
>      > > >     >>         >     >
>      > > >     >>         >     > >     >
>      > > >     >>         >     >
>      > > >     >>         >     > >     >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > In general, you should be
> careful with
>      > > the usage of "count",
>      > > > since it
>      > > >     >>         >     >
>      > > >     >>         >     > >     > will loop through *all*
> instances in the
>      > > list every time.  If
>      > > > the list
>      > > >     >>         >     >
>      > > >     >>         >     > >     > is big, this can have a
> performance
>      > > impact.
>      > > >     >>         >     >
>      > > >     >>         >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     Instead of count(), it is possible
> to use
>      > > the so-called
>      > > > Muenchian
>      > > >     >>         >     > method:
>      > > >     >>         >     >
>      > > >     >>         >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >         container msdp {
>      > > >     >>         >     >
>      > > >     >>         >     > >           must
> "not(../preceding-sibling::rt:
>      > > control-plane-
>      > > > protocol["
>      > > >     >>         >     >
>      > > >     >>         >     > >              +
> "derived-from-or-self(rt:type,
>      > > 'msdp:msdp')])";
>      > > >     >>         >     >
>      > > >     >>         >     > >           ..
>      > > >     >>         >     >
>      > > >     >>         >     > >         }
>      > > >     >>         >     >
>      > > >     >>         >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     It basically states that the
>      > > control-plane-protocol containing
>      > > > the
>      > > >     >>         >     > "msdp"
>      > > >     >>         >     >
>      > > >     >>         >     > >     container must not be preceded
> with a
>      > > control-plane-
>      > > > protocol entry
>      > > >     >>         > of
>      > > >     >>         >     > the
>      > > >     >>         >     >
>      > > >     >>         >     > >     msdp:msdp type (or derived).
>      > > >     >>         >     >
>      > > >     >>         >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > > This looks like an elegant solution.
>      > > >     >>         >     >
>      > > >     >>         >     >
>      > > >     >>         >     > "elegant" as in "less obvious" ;)  It
> has the
>      > > same time complexity
>      > > > as
>      > > >     >>         >     > the count() solution.
>      > > >     >>         >
>      > > >     >>         >     It should be faster on the average - it
> has to scan
>      > > only preceding
>      > > > siblings of
>      > > >     >>         >     the MSDP protocol instance whereas count()
> always
>      > > has to check
>      > > > *all*
>      > > >     >>         > protocol
>      > > >     >>         >     instances.
>      > > >     >>         >
>      > > >     >>         >     It is true though that in XSLT this
> technique can
>      > > be made
>      > > > considerably
>      > > >     >>         > more
>      > > >     >>         >     efficient by using indexed keys.
>      > > >     >>         >
>      > > >     >>         >     Lada
>      > > >     >>         >
>      > > >     >>         >     >
>      > > >     >>         >     >
>      > > >     >>         >     > However, since the key for the
>      > > control-plane-protocol  list is
>      > > > "type
>      > > >     >>         >     > name", won't it only work if the
> previous sibling
>      > > has a  "name"
>      > > > that
>      > > >     >>         >     > is precedes the one being added?
>      > > >     >>         >     >
>      > > >     >>         >     > For each list entry that has this
> container, the
>      > > expression is
>      > > >     >>         >     > evaluated.  It will scan all preceding
> entries
>      > > and ensure that there
>      > > >     >>         >     > are none with this type.  So the order
> of the
>      > > entries doesn't
>      > > > matter;
>      > > >     >>         >     > if there are two with the same type, one
> of them
>      > > has to be
>      > > > before the
>      > > >     >>         >     > other.
>      > > >     >>         >     >
>      > > >     >>         >     >
>      > > >     >>         >     > /martin
>      > > >     >>         >     >
>      > > >     >>         >     >
>      > > >     >>         >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > > Thanks,
>      > > >     >>         >     >
>      > > >     >>         >     > > Acee
>      > > >     >>         >     >
>      > > >     >>         >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     Lada
>      > > >     >>         >     >
>      > > >     >>         >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > Also note that I use
> derived-from-or-self
>      > > instead of equality
>      > > > for the
>      > > >     >>         >     >
>      > > >     >>         >     > >     > identity.
>      > > >     >>         >     >
>      > > >     >>         >     > >     >
>      > > >     >>         >     >
>      > > >     >>         >     > >     >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > /martin
>      > > >     >>         >     >
>      > > >     >>         >     > >     >
>      > > >     >>         >     >
>      > > >     >>         >     > >     >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > Regards,
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > Reshad.
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >   augment
> "/rt:routing/rt:control-plane-
>      > > protocols/"
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >         +
> "rt:control-plane-protocol" {
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >      when "rt:type = ‘msdp’"  {
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >       description
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >         "….”;
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >     }
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >     description "….";
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >     container msdp {
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >       when "../rt:name =
>      > > ‘msdp-protocol’"  {
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >         description
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >           "….";
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >       }
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >       description "MSDP top
> level
>      > > container.";
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > From: "Reshad Rahman
> (rrahman)" <
>      > > [e-mail]>
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > Date: Monday, February 5, 2018
> at 6:25
>      > > PM
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > To: Xufeng Liu <
> [e-mail]>,
>      > > >     >>         > "[e-mail]"
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > <[e-mail]>
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > Cc: "[e-mail]" <
>      > > [e-mail]>,
>      > > > "Mahesh
>      > > >     >>         > Sivakumar
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > (masivaku)" <
> [e-mail]>,
>      > > > "[e-mail]"
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > <[e-mail]>,
>      > > > "[e-mail]"
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > <pete.mcallister@metaswitch.
> com>,
>      > > > "[e-mail]"
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > <[e-mail]>, "
>      > > [e-mail]"
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > <[e-mail]>,
>      > > "tanmoy.kundu@alcatel-
>      > > >     >>         > lucent.com"
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > <tanmoy.kundu@alcatel-lucent.
> com>,
>      > > >     >>         > "[e-mail]"
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > <[e-mail]>,
> "Acee
>      > > Lindem (acee)"
>      > > >     >>         > <[e-mail]>
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > Subject: Re: Hi all, about the
>      > > modification of MSDP YANG
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > Hi Sandy and Xufeng,
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > I understand that you want
> only 1 MSDP
>      > > instance but I
>      > > > don’t think
>      > > >     >>         >     > that
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > justifies
> /rt:routing/rt:control-plane-protocols.
>      > > If we do
>      > > > that we
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > will end up with all
> single-instance
>      > > protocols under
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > /rt:routing/rt:control-plane-
> protocols
>      > > and all the multi-
>      > > > instance
>      > > >     >>         >     > ones
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > under
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > /rt:routing/rt:control-plane-
>      > > protocols/rt:control-plane-
>      > > > protocol.
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > I am not sure what’s the best
> way to
>      > > enforce single-
>      > > > instance, I can
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > check with the other YDs on
> this topic..
>      > > One way it can be
>      > > > done is
>      > > >     >>         > as
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > follows (I’ve added the when
> statement
>      > > in bold to
>      > > > existing BFD
>      > > >     >>         >     > model),
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > it enforces that the protocol
> name is
>      > > ‘bfdv1’. So multiple
>      > > >     >>         > instances
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > with rt:type=bfd-types:bfdv1
> could be
>      > > created, but only
>      > > > one of
>      > > >     >>         > these
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > instances can have the bfd
> container.
>      > > This is probably not
>      > > > the
>      > > >     >>         > best
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > way but the point is that IMO
> protocols
>      > > have to go under
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > /rt:routing/rt:control-plane-
>      > > protocols/rt:control-plane-
>      > > > protocol.
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > Regards,
>      > > >     >>         >     >
>      > > >     >>         >     > >     > > Reshad.
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >   augment
> "/rt:routing/rt:control-plane-
>      > > protocols/"
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >         +
> "rt:control-plane-protocol" {
>      > > >     >>         >     >
>      > > >     >>         >     > >     > >      when "rt:type =
>
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