[netconf] Re: Default statements on udp-client-server groupings

Andy Bierman <andy@yumaworks.com> Tue, 17 September 2024 17:21 UTC

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From: Andy Bierman <andy@yumaworks.com>
Date: Tue, 17 Sep 2024 10:21:11 -0700
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To: Kent Watsen <kent+ietf@watsen.net>
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Subject: [netconf] Re: Default statements on udp-client-server groupings
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On Mon, Sep 16, 2024 at 4:12 PM Kent Watsen <kent+ietf@watsen.net> wrote:

> Hi Alex,
>
> Please see inline below.
>
> K.
>
>
> On Sep 16, 2024, at 4:42 AM, Alex Huang Feng <alex.huang-feng@insa-lyon.fr>
> wrote:
>
> Dear Kent and Andy,
>
> Thank you for the provided feedback.
>
> Here a few comments about udp-groupings:
> - When I meant user, I meant YANG module’s writer or designer, which can
> be a IETF contributor or not.
> - I agree with Andy that the default port on the generic grouping should
> be removed.
>
>
> The above sentence is hard to parse because 1) there’s more than one port
> (local vs remote) and 2) there’s more than one grouping (i.e., client vs
> server).
>
> Did you mean “I agree with Andy that the default *remote-port* in the
> ietf-[tcp/udp]-client-grouping should be removed.”?   This is what I agreed
> to, and was able to get the RFC Editor to fix in RFC9643-to-be (i.e., the
> tcp-client-server draft)
>
>
> Personally, I would remove all of them, just for the fact that by having
> them we are limiting the scope of usage of this generic grouping.
> Maybe adding a section (or text) explaining that service models SHOULD
> define (or prioritize) having a default port request within the YANG module
> would be useful? See proposal below
> Because I can see a user/designer wanting to implement a YANG module with
> a “mandatory" port but unable to do so because of this “default” statement.
>
>
> Here I think you are referring to having the client's and server’s
> *local-port* to NOT be "default 0”.
>
> On one level, I agree with you.  i.e., it can always be added by a
> consumer, and it prevents the local-port from being “mandatory true".
>
> On the flip-side, every socket-level API I’ve used has always defaulted
> the client’s local-port to “0” (meaning that it’s a wildcard, and the OS
> gets to choose), and I’ve never seen a client not default its local-port to
> 0.   As for servers, one might think that the local-port should always
> default to its well-known/assigned value.
>
>
> Proposed text:
> NEW:
> The "remote-port" and "local-port" leaves are defined without any
>     "default" or "mandatory" statements in the "udp-client-grouping"
>     grouping.  YANG models using this grouping SHOULD refine the grouping
>     with a "default" statement, usually with the port allocated by IANA,
>     or a "mandatory" statement, if the ports needs to be always present.
>
> Diff:
> https://author-tools.ietf.org/diff?doc_1=draft-ietf-netconf-udp-client-server-03&url_2=https://raw.githubusercontent.com/netconf-wg/udp-client-server/master/draft-ietf-netconf-udp-client-server-04.txt
>
> Better this way?
>
>
> I think that it’s fine.
>
> As written above, such can always be added by consuming modules.
>
>
> Regarding udp-notif:
> - Personally I am not against having a default IANA port for UDP-Notif. I
> actually asked for it on the -13 iteration.
> But from the feedback received on the ML [1] and the last IETF meeting
> [2], the conclusion was that a port is not needed because an operator
> already needs to configure the IP address where the collector is located.
> I also see the same use case on the NC/RC Call home RFC. Even though a
> default port is defined, the operator still needs to configure the IP
> address of the NC client on the network management system...
>
> [1]
> https://mailarchive.ietf.org/arch/msg/netconf/gP5AApWL0Ha8uey9yIQvBlqOJ7A/
> [2] https://datatracker.ietf.org/doc/minutes-120-netconf-202407251630/
>
>
> It’s true that it’s not a “first contact” situation, but many times
> Operators want a port for firewalls, wireshark, etc.   And if we’re lucky,
> udp-notif will be very popular, easily justifying its allocation.
>
>
The main purpose for YANG defaults is ease of use.
If there are less things to configure then the device is easier to use.
Without a default port then this parameter becomes mandatory to configure.



> Looking at the numbers, I see a 50/50 split in proponents of the two
> choices.  This is far from WG consensus (not to mention weak participation).
>
> The minutes [2] show Rob suggesting asking a designated expert.  This is
> what we should do.
>
> Kent
>
>
Andy