Re: Yangdoctors last call review of draft-ietf-pim-igmp-mld-yang-07

Xufeng Liu <xufeng.liu.ietf@gmail.com> Sat, 08 September 2018 17:47 UTC

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From: Xufeng Liu <xufeng.liu.ietf@gmail.com>
Date: Sat, 08 Sep 2018 13:47:04 -0400
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Subject: Re: Yangdoctors last call review of draft-ietf-pim-igmp-mld-yang-07
To: janl@tail-f.com
Cc: yang-doctors@ietf.org, ietf <ietf@ietf.org>, pim@ietf.org, draft-ietf-pim-igmp-mld-yang.all@ietf.org
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Hi Jan,

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.

Thanks,
- Xufeng

================================
原始邮件
发件人：XufengLiu <Xufeng_Liu@jabil.com>
收件人：Acee Lindem (acee) <acee@cisco.com>Christian Hopps
<chopps@chopps.org>Martin
Bjorklund <mbj@tail-f.com>
抄送人：张征00007940;yang-doctors@ietf.org <yang-doctors@ietf.org>
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:acee@cisco.com]
> Sent: Monday, February 19, 2018 1:35 PM
> To: Christian Hopps <chopps@chopps.org>; Martin Bjorklund <mbj@tail-f.com>
> Cc: Xufeng Liu <Xufeng_Liu@jabil.com>; zhang.zheng@zte.com.cn; yang-
> doctors@ietf.org
> Subject: Re: [yang-doctors] How to restrict to have single control-plane-
> protocol instance
>
>
>
> On 2/19/18, 5:02 AM, "Christian Hopps" <chopps@chopps.org> wrote:
>
>
>     Martin Bjorklund <mbj@tail-f.com> writes:
>
>     > Hi,
>     >
>     > "Acee Lindem (acee)" <acee@cisco.com> 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)" <rrahman@cisco.com>
> 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" <Xufeng_Liu@jabil.com>
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:rrahman@cisco.com]
>     >>         > Sent: Thursday, February 8, 2018 9:41 AM
>     >>         > To: Ladislav Lhotka <lhotka@nic.cz>; Martin Bjorklund
<mbj@tail-
> f.com>;
>     >>         > Acee Lindem (acee) <acee@cisco.com>
>     >>         > Cc: yang-doctors@ietf.org; zhang.zheng@zte.com.cn;
Xufeng Liu
>     >>         > <Xufeng_Liu@jabil.com>
>     >>         > 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" <lhotka@nic.cz>
wrote:
>     >>         >
>     >>         >     On Thu, 2018-02-08 at 12:39 +0100, Martin Bjorklund
wrote:
>     >>         >     > "Acee Lindem (acee)" <acee@cisco.com> wrote:
>     >>         >     > > Hi Lada,
>     >>         >     >
>     >>         >     > >
>     >>         >     >
>     >>         >     > > On 2/8/18, 4:42 AM, "yang-doctors on behalf of
Ladislav
> Lhotka"
>     >>         > <yang-docto
>     >>         >     > rs-bounces@ietf.org on behalf of lhotka@nic.cz>
wrote:
>     >>         >     >
>     >>         >     > >
>     >>         >     >
>     >>         >     > >     On Thu, 2018-02-08 at 09:20 +0100, Martin
Bjorklund wrote:
>     >>         >     >
>     >>         >     > >     > Hi,
>     >>         >     >
>     >>         >     > >     >
>     >>         >     >
>     >>         >     > >     > "Reshad Rahman (rrahman)" <
rrahman@cisco.com> 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)" <
rrahman@cisco.com>
>     >>         >     >
>     >>         >     > >     > > Date: Monday, February 5, 2018 at 6:25 PM
>     >>         >     >
>     >>         >     > >     > > To: Xufeng Liu <Xufeng_Liu@jabil.com>,
>     >>         > "zhang.zheng@zte.com.cn"
>     >>         >     >
>     >>         >     > >     > > <zhang.zheng@zte.com.cn>
>     >>         >     >
>     >>         >     > >     > > Cc: "anish.ietf@gmail.com" <
anish.ietf@gmail.com>,
> "Mahesh
>     >>         > Sivakumar
>     >>         >     >
>     >>         >     > >     > > (masivaku)" <masivaku@cisco.com>,
> "guofeng@huawei.com"
>     >>         >     >
>     >>         >     > >     > > <guofeng@huawei.com>,
> "pete.mcallister@metaswitch.com"
>     >>         >     >
>     >>         >     > >     > > <pete.mcallister@metaswitch.com>,
> "liuyisong@huawei.com"
>     >>         >     >
>     >>         >     > >     > > <liuyisong@huawei.com>, "
xu.benchong@zte.com.cn"
>     >>         >     >
>     >>         >     > >     > > <xu.benchong@zte.com.cn>,
"tanmoy.kundu@alcatel-
>     >>         > lucent.com"
>     >>         >     >
>     >>         >     > >     > > <tanmoy.kundu@alcatel-lucent.com>,
>     >>         > "zzhang_ietf@hotmail.com"
>     >>         >     >
>     >>         >     > >     > > <zzhang_ietf@hotmail.com>, "Acee Lindem
(acee)"
>     >>         > <acee@cisco.com>
>     >>         >     >
>     >>         >     > >     > > 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 = 'bfd-types:bfdv1'"
{
>     >>         >     >
>     >>         >     > >     > >       description
>     >>         >     >
>     >>         >     > >     > >         "This augmentation is only valid
for a control-plane
>     >>         >     > protocol
>     >>         >     >
>     >>         >     > >     > >          instance of BFD (type
'bfdv1').";
>     >>         >     >
>     >>         >     > >     > >     }
>     >>         >     >
>     >>         >     > >     > >     description "BFD augmentation.";
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > >     container bfd {
>     >>         >     >
>     >>         >     > >     > >       when "../rt:name = 'bfdv1'"  {
>     >>         >     >
>     >>         >     > >     > >         description
>     >>         >     >
>     >>         >     > >     > >           "This augmentation is only
valid for a control-plane
>     >>         >     > protocol
>     >>         >     >
>     >>         >     > >     > >            instance of BFD (type
'bfdv1').";
>     >>         >     >
>     >>         >     > >     > >       }
>     >>         >     >
>     >>         >     > >     > >       description "BFD top level
container.";
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > > From: Xufeng Liu <Xufeng_Liu@jabil.com>
>     >>         >     >
>     >>         >     > >     > > Date: Monday, February 5, 2018 at 9:38 AM
>     >>         >     >
>     >>         >     > >     > > To: "zhang.zheng@zte.com.cn"
> <zhang.zheng@zte.com.cn>
>     >>         >     >
>     >>         >     > >     > > Cc: "Reshad Rahman (rrahman)" <
rrahman@cisco.com>,
>     >>         >     >
>     >>         >     > >     > > "anish.ietf@gmail.com" <
anish.ietf@gmail.com>,
> "Mahesh
>     >>         > Sivakumar
>     >>         >     >
>     >>         >     > >     > > (masivaku)" <masivaku@cisco.com>,
> "guofeng@huawei.com"
>     >>         >     >
>     >>         >     > >     > > <guofeng@huawei.com>,
> "pete.mcallister@metaswitch.com"
>     >>         >     >
>     >>         >     > >     > > <pete.mcallister@metaswitch.com>,
> "liuyisong@huawei.com"
>     >>         >     >
>     >>         >     > >     > > <liuyisong@huawei.com>, "
xu.benchong@zte.com.cn"
>     >>         >     >
>     >>         >     > >     > > <xu.benchong@zte.com.cn>,
"tanmoy.kundu@alcatel-
>     >>         > lucent.com"
>     >>         >     >
>     >>         >     > >     > > <tanmoy.kundu@alcatel-lucent.com>,
>     >>         > "zzhang_ietf@hotmail.com"
>     >>         >     >
>     >>         >     > >     > > <zzhang_ietf@hotmail.com>
>     >>         >     >
>     >>         >     > >     > > Subject: RE: Hi all, about the
modification of MSDP YANG
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > > Hi Sandy,
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > > Thanks for the updates.
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > > In RFC8022bis, the rt:type is defined
under
>     >>         >     >
>     >>         >     > >     > >
/rt:routing/rt:control-plane-protocols/rt:control-plane-
> protocol.
>     >>         > If
>     >>         >     >
>     >>         >     > >     > > we augment
/rt:routing/rt:control-plane-protocols, the
> “when”
>     >>         >     >
>     >>         >     > >     > > statement will not be valid, because it
cannot find the
> rt:type. I
>     >>         >     >
>     >>         >     > >     > > don’t think that we need the “when”
statement. The
> container
>     >>         > with
>     >>         >     >
>     >>         >     > >     > > “presence” will serve the purpose of the
identity. We can
> simply
>     >>         >     > take
>     >>         >     >
>     >>         >     > >     > > out the “when” statement and the
definition of the MSDP
> identity.
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > > Thanks,
>     >>         >     >
>     >>         >     > >     > > - Xufeng
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > > From: zhang.zheng@zte.com.cn
> [mailto:zhang.zheng@zte.com.cn]
>     >>         >     >
>     >>         >     > >     > > Sent: Monday, February 5, 2018 3:36 AM
>     >>         >     >
>     >>         >     > >     > > To: Xufeng Liu <Xufeng_Liu@jabil.com>
>     >>         >     >
>     >>         >     > >     > > Cc: rrahman@cisco.com;
anish.ietf@gmail.com;
>     >>         > masivaku@cisco.com;
>     >>         >     >
>     >>         >     > >     > > guofeng@huawei.com;
> pete.mcallister@metaswitch.com;
>     >>         >     >
>     >>         >     > >     > > liuyisong@huawei.com;
xu.benchong@zte.com.cn;
>     >>         >     >
>     >>         >     > >     > > tanmoy.kundu@alcatel-lucent.com;
> zzhang_ietf@hotmail.com
>     >>         >     >
>     >>         >     > >     > > Subject: RE: Hi all, about the
modification of MSDP YANG
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > > Hi Xufeng and Reshad,
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > > I am sorry for forgetting the point. I
updated the YANG
> model.
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > > If no one has comments on it I'd like to
submit the new
> version. :-)
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > > Thanks,
>     >>         >     >
>     >>         >     > >     > >
>     >>         >     >
>     >>         >     > >     > > Sandy
>     >>         >     >
>     >>         >     > >     > > 原始邮件
>     >>         >     >
>     >>         >     > >     > > 发件人：
>     >>         > <Xufeng_Liu@jabil.com<mailto:Xufeng_Liu@jabil.com>>;
>     >>
================================

On Mon, Aug 13, 2018 at 10:34 AM Jan Lindblad <janl@tail-f.com> wrote:

> 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.
>
> #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.
>
> #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.
>
>
>

Yangdoctors last call review of draft-ietf-pim-ig… Jan Lindblad
RE: Yangdoctors last call review of draft-ietf-pi… Guofeng
Re: Yangdoctors last call review of draft-ietf-pi… Xufeng Liu
Re: Yangdoctors last call review of draft-ietf-pi… Jan Lindblad
Re: [yang-doctors] Yangdoctors last call review o… Martin Bjorklund
Re: [yang-doctors] Yangdoctors last call review o… Reshad Rahman (rrahman)
RE: [pim] Yangdoctors last call review of draft-i… Guofeng