Hi Jan,
Thanks for the review. We have posted the updated https://tools.ietf.org/html/draft-ietf-pim-igmp-mld-yang-11 to address these issues.
Some of the details are in-line below.
Best regards,
- Xufeng
On Thu, Feb 7, 2019 at 11:01 AM Jan Lindblad <janl@xxxxxxxxxx> wrote:
Reviewer: Jan Lindblad
Review result: Ready with Issues
This is my YANG-doctor review of draft-ietf-pim-igmp-mld-yang-10. In the
spring, I did an early review of the -02, and in the early fall a last call
review of the -07 version. The module has progressed significantly since then.
In particular the two main issues with -07 have been fixed, which is great!
There are still a few things that should be looked at, however.
Since some of the current issues are the same as addressed in earlier comments,
I will reuse the numbering from the -07 review, and add a few points at the end:
#3 Top level structures not optional
If-feature statements have been introduced so that an implementor can choose
whether to implement igmp and/or mld separately. This is very good. RFC 8349,
which the current module augments, recommend that the top level containers be
presence containers. This is currently not the case, and I see no reason why
they aren't.
It is also RECOMMENDED that protocol-specific data nodes be
encapsulated in an appropriately named container with presence.. Such
a container may contain mandatory data nodes that are otherwise
forbidden at the top level of an augment.
At this time, there are no mandatory leafs under the top level containers,
which makes this recommendation less of a concern, but if a mandatory leaf is
introduced (e.g. see #9 below), making the top level containers presence
containers will be essential.
[Xufeng]: The node "control-plane-protocol" where the augmentation is applied is a list entry, which can already achieve what a presence container can do. I don't think that we need to make igmp and mld presence containers in this case. The mandatory leaves are already possible because of the list statement.
#4 Unclear meaning of optional leaves
While a lot of default values have been introduced (great!), there are still
many optional configuration leafs with no default value, not mandatory, not
self-evident and no description of what absence signifies. A few words in the
description might be all it takes to fix this.
This happens with many leafs, but a couple of examples:
leaf max-entries {
if-feature global-max-entries;
type uint32;
description
"The maximum number of entries in IGMP or MLD.";
}
If no max-entries is configured, what is the prescribed behavior? Will all
implementations agree that there is no max then? If so, maybe mention that in
the description?
leaf source-policy {
if-feature intf-source-policy;
type leafref {
path "/acl:acls/acl:acl/acl:name";
}
description
"Name of the access policy used to filter sources.
A device can restrict the length
and value of this name, possibly space and special
characters are not allowed.";
}
If no source policy is specified, does that mean there is no policy?
There are many more.
[Xufeng]: We examined the model, and added descriptions to these occasions.
#8 What policy name?
In leaf ssm-map-group-policy, the description begins with "Name of the policy
....". Does this mean that the policy name can be chosen freely, or does the
policy name entered here have to match some policy name specified somewhere
else?
If this name can be chosen freely without considering some other list, it's all
fine.
leaf ssm-map-group-policy {
type string;
description
"Name of the policy used to define ssm-map rules.
A device can restrict the length
and value of this name, possibly space and special
characters are not allowed. ";
[Xufeng]: Yes. In this model, this name can be chosen freely without considering some other list. The model that defines such entries are not yet available, and may be specified by a separate model later. When that happens, the system would need to verify against such a model.
#9 Default for version
Leaf version is given a default of 2; this sounds excellent. This clarifies
what protocol version to use even if the operator doesn't specify. Note that a
default can never be changed, however, so only do this if 2 will feel like a
good number even 10 years from now.
If no suitable default value that withstands time can be selected, another
option is to make it mandatory for the client to configure. Note that in such a
case #3 above becomes very important to resolve.
The authors should
leaf version {
type uint8 {
range "1..3";
}
default 2;
[Xufeng]: The version range is defined as “1..3”, so this model can only be used for the versions of IGMP protocols current already specified by IETF. In the future, if new versions of IGMP protocols are introduced, this model cannot be used as is. We will need to add new features to the model, the version range range will need to be modified, and the default version can be changed at that time.
#10 Inaccurate description or _expression_
In the interface-name leaf, there is a must statement and description which
contradict each other. The must statement requires that the ipv4 container is
configured, while the description says ipv4 should be enabled. It is possible
to configure the ipv4 container but have ipv4/enabled = 'false', so the must
_expression_ only cares whether the ipv4 presence container is configured, not if
it is enabled. Which one reflects the desired behavior?
leaf interface-name {
type if:interface-ref;
must "/if:interfaces/if:interface[if:name = current()]/"
+ "ip:ipv4" {
description
"The interface must have IPv4 enabled.";
If ipv4 needs to be enabled, the must _expression_ should be
must "/if:interfaces/if:interface[if:name = current()]/"
+ "ip:ipv4/ip:enabled = 'true'" {
If ipv4 needs to be configured, the description should say "The interface must
have IPv4 configured (but not necessarily enabled)."
The same logic applies to MLD and ipv6 as well.
[Xufeng]: The intention is the described as the must statement, and the descriptions are not accurate. We have fixed the description as suggested.
