Re: [CCAMP] Yangdoctors last call review of draft-ietf-ccamp-mw-yang-05 capitals

["t.petch" <[e-mail]>]

Top posting and tweaking the subject line slightly since I am picking up
one minor point only

> There are a couple of identities with capitals. Consider changing to
all lowercase; that is the YANG convention.
>
>   identity E1 {
>   identity STM-1 {
> [Amy] will fix it.
> [Jonas] OK.

Disagree!  If I see e1 I will probably think exponent - if I see E1, I
know exactly what is intended, in a wide range of contexts.  YANG
guidelines allows
"Upper-case characters, the period character,
   and the underscore character MAY be used if the identifier represents
   a well-known value that uses these characters.  "
and I think that E1 and STM-1 fall within that MAY.

I see
identity client-signal-OC3_STM1
in
draft-ietf-ccamp-otn-tunnel-model-01
and
identity STM-1 {
in
draft-fioccola-ccamp-l1csm-yang-01

so I think that CCAMP needs to decide between STM-1 and STM1 - the
former works for me - and then tell the YANG doctors that that is how it
is:-) YMMV

Tom Petch

----- Original Message -----
From: "Jonas Ahlberg" <[e-mail]>
To: "Jan Lindblad" <[e-mail]>


> Hi Jan & Amy,
> See comments & questions in green [Jonas2].
> Regards
> JonasA
>
> From: Jan Lindblad <[e-mail]>
> Sent: den 11 juni 2018 15:29

>
> Jonas,
>
> Thank you for your review and valuable comments.
> I’ve not responded to the latest mail since I have added comments to
some of the items removed in that mail.
> I’ve copied and pasted your comments into this mail instead, in order
to make the thread of comments complete.
>
> I’ve added my comments in green [Jonas].
>
> [janl2] Very good. Sorry for deleting text prematurely ;-)
>
> I would like to ask CCAMP for support with the question about if the
protection group is likely to be reused elsewhere or if it can be merged
with the microwave module again.
>
> Regards
> JonasA
>
> From: Yemin (Amy) <[e-mail]<mailto:[e-mail]>>
> Sent: den 8 juni 2018 11:37
>
> Hi Jan,
>
> Thanks very much for the comments. I found them are quiet useful to
improve the models.
> Please see my reply below in blue.
> The draft co-authors may add more reply to your comments.
>
> BR,
> Amy
> -----Original Message-----
> From: CCAMP [mailto:[e-mail]] On Behalf Of Jan Lindblad
> Sent: Thursday, June 07, 2018 6:18 PM
>
> Reviewer: Jan Lindblad
> Review result: Ready with Issues
>
> YD review of draft-ietf-ccamp-mw-yang
>
> I have now reviewed the YANG modules and corresponding examples of
the -05 version of this draft. I have not read much of the RFC text, so
I can't vouch for how well the text aligns with the model. I find the
proposed modules in good shape. Most of my comments below are alternate
ways of modeling something that the wg may consider, or a few things
where I propose a better option for something that would be acceptable
even as it is. There is a single issue that must be fixed IMO, see #8
below.
>
> Let's start with module ietf-microwave-types.
>
> #1) Consider adding structure to related identities
>
> This module consists mostly of a long list of identities based off of
coding-modulation. If it makes sense that in the future someone might be
interested in doing something with all qam-4096 based identities or
all -strong identities, say, it may make sense to model the identities
as based on each other in a tree style. E.g.
>
>   identity qam-4096 {
>     base coding-modulation;
>     description
>       "4096 QAM coding and modulation scheme.";
>   }
>
>   identity qam-4096-strong {
>     base qam-4096;
>     description
>       "4096 QAM strong coding and modulation scheme.";
>   }
>
>   identity qam-4096-light {
>     base qam-4096;
>     description
>       "4096 QAM light coding and modulation scheme.";
>   }
>
> Or even go to "multiple inheritance" with multiple bases for
identities, e.g.
> for qam-4096 and strong. This would allow future applications to
filter the identities on such criteria. Just a thought.
> [Amy] change to base qam-4096. Multiple bases seem not applicable
here.
> [Jonas] I agree.
>
> #2) Convention to use all lowercase in YANG symbols
>
> There are a couple of identities with capitals. Consider changing to
all lowercase; that is the YANG convention.
>
>   identity E1 {
>   identity STM-1 {
> [Amy] will fix it.
> [Jonas] OK.
>
> Next, let's look at module ietf-interface-protection.
>
> I can't say I understand exactly why this is a separate module. It
publishes a single grouping, which is required by
ietf-microwave-radio-link, and as far as I understand would probably
never be used anywhere else. When the grouping is used a single time in
ietf-microwave-radio-link, it is immediately refined.
> Would probably reduce the clutter by merging the two modules and
resolving the refine.
> [Amy] They were in one model. During the WG discussion, comment was
raised that the interface protection function could be generic and be
used by other technologies in future, so we split the models.
> I’m open to discuss about this.
> [janl] Ok, I didn't quite see how the grouping would be used anywhere
else, but if it indeed is usable elsewhere, having it in a separate
module isn't a bad idea.
> [Jonas] I’m in favor of reverting back to one single module gain,
since it will simplify the model as you mention above. The argument for
breaking it out into a separate module is that it can be used elsewhere.
I’m doubtful if it ever will be, but here I think we need input from the
rest of the community (at least from the CCAMP WG).
>
>
> #3) Config true leaf name status
>
> I find it counter-intuitive that a leaf called status (or state) is a
configuration item. I had to re-read the model several times to get my
head around the fact that this is indeed meant to be config true.
Perhaps consider a name change?
>
>       leaf status {
> [Amy] status should be config false.
> [Jonas] Correct. Our mistake.
>
> #4) Action external-commands
>
> There is a single action called external-commands (even in plural). It
takes a single argument, which is the name of the operation to execute.
No output. To me, a more natural modeling would be to make each of the
external commands an action, over time possibly with different input and
output.
> [Amy] add output to describe the action result (success, fail,
inprogress). But prefer to use one action.
> Change the name to external-command.
> [janl] Hmm, I don't quite understand your preference for a single
action. I see how this choice closes doors, but no real benefit. This is
no big deal, though, what you have works. Just feels less evolvable for
no reason.
> [Jonas] I’m not quite sure I’ve understood what you propose. Do you
mean that we should replace the single action statement and the list of
identifiers with several action statements:
> action manual-switch-working;
> action manual-switch-protection;
> …
> action clear;
> The reason for using identities was that we wanted to make it easy to
extend the module with additional, potentially vendor specific, commands
by augmentation.
> But maybe there are other ways to handle that in case of using the
alternative approach you suggest.
>
> [janl2] Yes, exactly. Separate actions like this has the advantage
that they can take (different) input and output parameters, and that
they can be access controlled separately using NACM. This way different
operators could have/not have access to different operations. Future
standard or vendor modules could still augment whatever additional
actions they like to the same location in the tree.
> [Jonas2] OK I understand and I see the advantage of this approach.
Amy, should we consider change to this or are there other benefits with
the original approach?
>
> Finally, we have module ietf-microwave-radio-link.
>
> #5) Use derived-from when comparing identities
>
> It's more future-proof and more likely to be interoperable if you use
proper XPATH functions to determine kinship than using plain equality
>
>   augment "/if:interfaces/if:interface" {
>     when "if:type = 'mw-types:radio-link-terminal'";
>
> is better written as
>
>   augment "/if:interfaces/if:interface" {
>     when "derived-from-or-self(if:type,
'mw-types:radio-link-terminal')";
>
> This allows future sub-typing (sub-classing) of radio-link-terminal,
i.e. new identities that are based on radio-link-terminal to reflect
some special kind of RLT. It also improves chances of interoperability.
> [Amy] will adopt this.
> [Jonas] Agree.
>
> #6) Blank id reasonable?
>
> Leafs that function as an id usually do not have defaults. Does a
blank id make sense here? If it does, maybe it would make more sense to
leave it without a default and explain what happens if not set in the
description instead? Or mark it as mandatory if it has to be set.
>
>     leaf id {
>       type string;
>       default "";
> [Amy] remove default. Add mandatory.
> [Jonas] I think that the name of the attribute could be misleading. It
’s not a formal id of the terminal, it is a text string that is used by
an optional system feature in a far-end RLT (on the opposite end of the
microwave link) to verify that the correct two RLTs (far-end and
near-end) are connected.
> I don’t think we should make it mandatory. I would suggest to leave it
without default and clarify the consequences in the description.
>
> #7) Use derived-from when comparing identities (again)
>
>     leaf-list carrier-terminations {
>       type if:interface-ref;
>       must "/if:interfaces/if:interface[if:name = current()]"
>          + "/if:type = 'mw-types:carrier-termination'" {
>
> is better written as
>
>       must "derived-from-or-self(/if:interfaces/if:interface[if:name =
>       current()]"
>          + "/if:type, 'mw-types:carrier-termination')" {
>
> It is possible to write this in a more compact way, but there's
nothing wrong with the above.
>
>       must "derived-from-or-self(deref(current())/.."
>          + "/if:type, 'mw-types:carrier-termination')" {
> [Amy] will adopt this.
> [Jonas] Agree.
>
> #8) Badly broken frequency duplex config
>
> If you read the descriptions in these related leafs:
>
>     leaf tx-frequency {
>       type uint32;
>       units "kHz";
>       mandatory true;
>       description
>         "Selected transmitter frequency.";
>     }
>    leaf rx-frequency {
>       type uint32;
>       units "kHz";
>       description
>         "Selected receiver frequency.
>          Overrides existing value in duplex-distance.
>          Calculated from tx-frequency and duplex-distance if
>          only duplex-distance is configured.
>          Must match duplex-distance if both leaves are
>          configured in a single operation.";
>     }
>
>     leaf duplex-distance {
>       type uint32;
>       units "kHz";
>       description
>         "Distance between Tx & Rx frequencies.
>          Used to calculate rx-frequency when
>          rx-frequency is not specifically configured.
>          Overrides existing value in rx-frequency.
>          Calculated from tx-frequency and rx-frequency if only
>          rx-frequency is configured.
>          Must match rx-frequency if both leaves are configured
>          in a single operation.";
>     }
>
> It appears that the author intends the system to fill in the value for
one of these leaves based on the value set for the other. This is a big
no-no. A system should never alter its own configuration, or automation
flows (which is the whole purpose with YANG and NETCONF, remember) will
break. Also, the validity of the configuration should not depend on how
many operations are used to inject it.
>
> I find this a serious flaw that must be fixed before the module can be
released.
>
> I propose fixing it like this:
>
>     leaf tx-frequency {
>       type uint32;
>       units "kHz";
>       mandatory true;
>       description
>         "Selected transmitter frequency.";
>     }
>     choice freq-or-distance {
>       leaf rx-frequency {
>         type uint32;
>         units "kHz";
>         description
>           "Selected receiver frequency."
>       }
>       leaf duplex-distance {
>         type uint32;
>         units "kHz";
>         description
>           "Distance between Tx & Rx frequencies."
>       }
>     }
>
> If you would like to have read-only computed values accessible in the
model, maybe you could add:
>
>     leaf actual-rx-frequency {
>       type uint32;
>       units "kHz";
>       description
>         "Computed receiver frequency."
>       config false;
>     }
>     leaf actual-duplex-distance {
>       type uint32;
>       units "kHz";
>       description
>         "Computed distance between Tx & Rx frequencies."
>       config false;
>     }
>
> Many other ways of doing this properly are also possible. Let me know
if you'd like to discuss options.
> [Amy] I think choice is a good way to model those leafs. I suggest to
use it.
> That’s the real value of YANG doctors! Thanks.
> [Jonas] Thanks for your help. We have discussed this a lot without
finding a good solution. I agree that we should use it.
> The only question I have is the name of the attributes. Should the
attribute used for configuration or the attribute showing the resulting
be called rx-frequency?
> config-rx-frequency & rx-frequency   v.s.   rx-frequency &
actual-rx-frequency
>
> [janl2] I used actual-rx-frequency because you had some other leafs
called actual-...
>
> Yet another possibility could be to model it like this (pseudo YANG):
>
> leaf tx { ... }
> choice freq-or-dist {
>   container by-frequency {
>     leaf rx { ... }
>     leaf dist { config false; }
>   }
>   container by-distance {
>     leaf dist { ... }
>     leaf rx { config false; }
>   }
> }
>
> I.e. three leaves with the same names, just different paths (since the
container names differ) and different configness. I think my initial
proposal is a little cleaner, tho, which is why I went with that one
earlier. Or you could move the actual-... leaves into the choice, so
that only the one that's meaningful exists.
>
> [Jonas2] I think that your first proposal has a benefit of always
providing access to the actual configuration through the same leafs (and
path) (tx-frequency, actual-rx-frequency, actual-duplex-distance,
independent of how they have been configured.
> One use-case we have discussed is that an operator uses
duplex-distance for the initial configuration of the rx-frequency and
then in a second step fine tuning it by setting the rx-frequency
directly. Would that work with a choice statement, i.e. that you first
choose duplex-distance and then in a subsequent operation overrides that
and choose rx-frequency?
>
> #9) Check that lower threshold is less than upper threshold
>
> Would it make sense to add a must statement checking that the lower
threshold is less than (or equal?) to the upper threshold?
>
>     leaf atpc-lower-threshold  {
>       when "../power-mode = 'atpc'";
>       type power {
>         range "-99..-30";
>       }
>       units "dBm";
>       mandatory true;
>       description
>         "The lower threshold for the input power at far-end
>          used in the ATPC mode.";
>       reference "ETSI EN 302 217-1";
>     }
>     leaf atpc-upper-threshold  {
> [Amy] can add the must statement.
> [Jonas] Good!
>
> #10) Choice more convenient
>
> There are a few leafs that act as discriminators for when clauses in
other leafs. Such constructs might be a little smoother when modeled as
a choice instead. I'll take one and show as an example. This power-mode
construct:
>
>     leaf power-mode {
>       type enumeration {
>         enum rtpc {
>           description
>             "Remote Transmit Power Control (RTPC).";
>           reference "ETSI EN 302 217-1";
>         }
>
>         enum atpc {
>           description
>             "Automatic Transmit Power Control (ATPC).";
>           reference "ETSI EN 302 217-1";
>         }
>       }
>       mandatory true;
>       description
>         "A choice of Remote Transmit Power Control (RTPC)
>          or Automatic Transmit Power Control (ATPC).";
>     }
>
>     leaf maximum-nominal-power {
>       type power {
>         range "-99..40";
>       }
>       units "dBm";
>       mandatory true;
>       description
>         "Selected output power in RTPC mode and selected
>          maximum output power in ATPC mode. Minimum output
>          power in ATPC mode is the same as the system
>          capability, available-min-output-power.";
>       reference "ETSI EN 302 217-1";
>     }
>
>     leaf atpc-lower-threshold  {
>       when "../power-mode = 'atpc'";
>       type power {
>         range "-99..-30";
>       }
>       units "dBm";
>       mandatory true;
>       description
>         "The lower threshold for the input power at far-end
>          used in the ATPC mode.";
>       reference "ETSI EN 302 217-1";
>     }
>     leaf atpc-upper-threshold  {
>       when "../power-mode = 'atpc'";
>       type power {
>         range "-99..-30";
>       }
>       units "dBm";
>       mandatory true;
>       description
>         "The upper threshold for the input power at far-end
>          used in the ATPC mode.";
>       reference "ETSI EN 302 217-1";
>     }
>
> could be modeled as:
>
>     choice power-mode {
>       container rtpc {
>         description
>           "Remote Transmit Power Control (RTPC).";
>         reference "ETSI EN 302 217-1";
>         leaf maximum-nominal-power {
>           type power {
>             range "-99..40";
>           }
>           units "dBm";
>           mandatory true;
>           description
>             "Selected output power.";
>           reference "ETSI EN 302 217-1";
>         }
>       }
>       container atpc {
>         description
>           "Automatic Transmit Power Control (ATPC).";
>         reference "ETSI EN 302 217-1";
>
>         leaf maximum-nominal-power {
>           type power {
>             range "-99..40";
>           }
>           units "dBm";
>           mandatory true;
>           description
>              "Selected maximum output power. Minimum output
>              power is the same as the system
>              capability, available-min-output-power.";
>           reference "ETSI EN 302 217-1";
>         }
>
>         leaf atpc-lower-threshold  {
>           type power {
>             range "-99..-30";
>           }
>           units "dBm";
>           mandatory true;
>           description
>             "The lower threshold for the input power at far-end
>              used in the ATPC mode.";
>           reference "ETSI EN 302 217-1";
>         }
>         leaf atpc-upper-threshold  {
>           type power {
>             range "-99..-30";
>           }
>           units "dBm";
>           mandatory true;
>           description
>             "The upper threshold for the input power at far-end
>              used in the ATPC mode.";
>           reference "ETSI EN 302 217-1";
>         }
>       }
>       mandatory true;
>       description
>         "A choice of Remote Transmit Power Control (RTPC)
>          or Automatic Transmit Power Control (ATPC).";
> }
>
> [Amy] Choice is a better way. Is it possible to further refine your
proposal?
> Since maximum-nominal-power will be used by both RTPC and ATPC, how
about to move it out of the choice, then use maximum-nominal-power in
the choice? Like this:
>         leaf maximum-nominal-power {
>           type power {
>             range "-99..40";
>           }
>           units "dBm";
>          mandatory true;
>           description
>              "Selected maximum output power. Minimum output
>              power is the same as the system
>              capability, available-min-output-power.";
>           reference "ETSI EN 302 217-1";
>         }
>
>     choice power-mode {
>       container rtpc {
>         description
>           "Remote Transmit Power Control (RTPC).";
>         reference "ETSI EN 302 217-1";
>
>         use maximum-nominal-power;
>       }
>       container atpc {
>         description
>           "Automatic Transmit Power Control (ATPC).";
>         reference "ETSI EN 302 217-1";
>
>         use maximum-nominal-power;
>
>         leaf atpc-lower-threshold  {
>           type power {
>             range "-99..-30";
>           }
>           units "dBm";
>           mandatory true;
>           description
>             "The lower threshold for the input power at far-end
>              used in the ATPC mode.";
>           reference "ETSI EN 302 217-1";
>         }
>         leaf atpc-upper-threshold  {
>           type power {
>             range "-99..-30";
>           }
>           units "dBm";
>           mandatory true;
>           description
>             "The upper threshold for the input power at far-end
>              used in the ATPC mode.";
>           reference "ETSI EN 302 217-1";
>         }
>       }
>       mandatory true;
>       description
>         "A choice of Remote Transmit Power Control (RTPC)
>          or Automatic Transmit Power Control (ATPC).";
>     }
>
> [janl] Yes, this is certainly very reasonable. I placed the
maximum-nominal-power inside the choice because the description string
was giving the leaf different interpretations in each case. In that case
I felt it better to have separate leaves with clear descriptions. If you
feel the leaf can be shared between the options with a clear definition
of its meaning, this is reasonable.
> [Jonas] One purpose of the mode attribute was to show if the
carrier-termination was configured for RTPC or ATPC, but I guess the
same can be achieved by looking for which container, rtpc or atpc, has
been instantiated.
>
> [janl2] Yes, that's the idea.
> [Jonas2]. Good!
>
> I suggest that we go for Jan’s proposal since the attribute has
different meaning in the two cases. One purpose of the
>
> #11) Choice more convenient (again)
>
> Same thing again for
>
>     leaf coding-modulation-mode {
> [Amy] will update it.
> [Jonas] OK, see above.
>
> #12) Unusual exponential notation
>
> Do you really mean 10e-9 (=10*10^-9 =10^-8), or do you mean the more
traditional notation 1e-9?
>
>       leaf ber-alarm-threshold {
>         type enumeration {
>           enum "10e-9" {
> [Amy] should be 1e-9. Need to confirm with the co-authors.
> [Jonas] Yes, we mean 10^-9, 10^-8, …, 10^-1.
>
> [janl2] A perpahs simpler way to model this would be to only keep the
part that contains information, i.e. as
>
> leaf ber-alarm-threshold {
>   type int8 {
>     range -9..-1;
>   }
>   default -6;
>   description "Specification of at which BER as a power of 10 an alarm
should be raised. 10^-6 is the default.";
>   reference "ETSI EN 302 217-1";
> }
>
> #13) Separate module with grouping, used a single time with refine
>
> Module ietf-interface-protection defines a grouping
(protection-groups), which is used a single time, yet is refined when it
is used below. As noted before comment #3, I find this way of laying out
the YANG unnecessarily hard to read and understand, for no clear
benefit.
>
>   container radio-link-protection-groups { ....
>     uses ifprot:protection-groups {
>
>       refine protection-group/members {
>         must "/if:interfaces/if:interface[if:name = current()]"
>            + "/if:type = 'mw-types:carrier-termination'" {
>
> Also, as noted in comment #7, the must statement is better written
using derived-from-or-self. This applies regardless of the current
refine statement is kept, or if the must statement moves to the actual
leaf-list it applies to.
> [Amy] Will update the must statement.
> [Jonas] If I remember correctly, I think it was done with the ambition
that it should be made generic so that other interface technologies
could use the same protection module. In case, we revert back to one
single module I suggest that we also simply the structure as Jan
suggests.
>
> Appendix A.1 & A.2
>
> Besides the actual YANG modules, there are also a couple of examples
in Appendix A.1 and A.2. I tried to use them and uncovered a couple of
issues.
>
> #14) Config false leaf in config example
>
> Both examples list
>
>         "tx-oper-status": on
>
> This is a config false item, which could never be part of a
configuration message (and it also lacks comma at the end).
> [Amy] will remove it.
> [Jonas] OK
>
> #15) Wrong type in example
>
> Both examples list
>
>         "coding-modulation-mode": 0,
>
> 0 not a legal value, should be "single" to match the rest of the
example data.
> [Amy] will fix it.
> [Jonas] OK
>
> #16) Missing mandatory parameter
>
> Both examples lacks leaf maximum-nominal-power, which is mandatory
according to the YANG, so the transaction fails to validate.
> [Amy] will add it.
> [Jonas] OK
>
> #17) Examples perhaps a tad basic
>
> The examples are demonstrating only a small part of the module
functionality. A bigger example, e.g. including xpic with interface
pointers might be useful.
>
> Feel free to reach out to me to discuss any of this. Thank you.
> [Amy] will add additional example.
> [Jonas] Good suggestion. Amy, let’s what configuration to show.
>
>
> Best Regards,
> /jan
>
>