Re: [netmod] 6991bis: address-with-prefix-length

tom petch <ietfc@btconnect.com> Tue, 02 April 2019 16:34 UTC

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From: tom petch <ietfc@btconnect.com>
To: "Rob Wilton (rwilton)" <rwilton@cisco.com>, Martin Bjorklund <mbj@tail-f.com>, "j.schoenwaelder@jacobs-university.de" <j.schoenwaelder@jacobs-university.de>
CC: "netmod@ietf.org" <netmod@ietf.org>
Thread-Topic: [netmod] 6991bis: address-with-prefix-length
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Subject: Re: [netmod] 6991bis: address-with-prefix-length
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----- Original Message -----
From: "Rob Wilton (rwilton)" <rwilton@cisco.com>
Sent: Tuesday, April 02, 2019 4:37 PM
> > -----Original Message-----
> > From: netmod <netmod-bounces@ietf.org> On Behalf Of Martin Bjorklund
> > Sent: 02 April 2019 13:47
> >
> > Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de> wrote:
> > > If you go back ~20 messages, my proposal was ip-address-prefix,
> > > ipv4-address-prefix, and ipv6-address-prefix.
> >
> > Do we agree that this type really specifies two values in one?  If
so I think the
> > "and" is useful.
>
> Isn't an "IP prefix" made up of an "IP address" and a "prefix length"?

No; that is the point.  A prefix is not an address.  What we specifying
here is an address and an address mask, except that now we can use a
shorthand for the mask since the one bits of the mask are contiguous and
left justified (which they used not to be:-).

Including 'and' in the identifier of this type may be semantically more
accurate but IMHO just clutters up the identifier, makes it longer,
harder to type, read and do anything else with.

'ipv6-address-prefix'

is quite long enough (if not too long).

Tom Petch

>
> So, I think that the names above are probably right, or otherwise if
you want the "and" then perhaps it should be
"ip-address-and-prefix-length" - which seems clunky?
>
> Thanks,
> Rob
>
>
> >
> > Also note that the current text in RFC 6991 says:
> >
> >      The ipv4-prefix type represents an IPv4 address prefix.
> >
> > so having a type ipv4-address-prefix for something that is not
(only) an
> > "ipv4 address prefix" is imo confusing.
> >
> >
> > /martin
> >
> >
> >
> >
> > >
> > > /js
> > >
> > > On Tue, Apr 02, 2019 at 11:13:09AM +0000, tom petch wrote:
> > > > ----- Original Message -----
> > > > From: "Jeff Tantsura" <jefftant.ietf@gmail.com>
> > > > To: <netmod@ietf.org>rg>; "Kristian Larsson"
<kristian@spritelink.net>
> > > > Sent: Monday, April 01, 2019 11:09 PM
> > > >
> > > > What Kristian has proposed makes sense, in favor.
> > > >
> > > > <tp>
> > > >
> > > > Yes, I support this idea and we should be able to come up with a
> > > > more user-friendly name;  address-prefix or address-length ?
> > > >
> > > > Tom Petch
> > > >
> > > > p.s.
> > > >
> > > >    identifier          = (ALPHA / "_")
> > > >                          *(ALPHA / DIGIT / "_" / "-" / ".")
> > > >
> > > > Cheers,
> > > > Jeff
> > > > On Apr 1, 2019, 1:09 PM -0700, Kristian Larsson
> > > > <kristian@spritelink.net>et>, wrote:
> > > > > Hello Mahesh,
> > > > >
> > > > > On 2019-04-01 21:40, Mahesh Jethanandani wrote:
> > > > > >
> > > > > > > On Apr 1, 2019, at 10:29 AM, Martin Bjorklund
<mbj@tail-f.com>
> > > > wrote:
> > > > > > >
> > > > > > > I know that this type is convenient, esp. if you use it
for
> > > > > > > manual input, but I wonder if it really is good practice
to
> > > > > > > squeeze two values into one.
> > > > > >
> > > > > > Agree. The combination makes sense for CLI, but for modeling
the
> > > > address and prefix should be separate.
> > > > >
> > > > > Okay, then why do we have an ip-prefix data type at all? With
the
> > > > > same line of argument you apply, it should be split up.
> > > > >
> > > > > So you're the third person bringing up CLI. I don't get this
at
> > > > > all. I don't see how CLI are different from everything else.
This
> > > > > is about
> > > > data
> > > > > modeling and data modeling is about expressing the world in a
data
> > > > > modeling language. It's like painting a picture but instead of
a
> > > > > brush you have a schema language like YANG. What do you see?
> > > > > Express it. It doesn't matter if the purpose is a CLI, a web
page
> > > > > or just exposing it via NETCONF for another system to consume.
> > > > >
> > > > > I think address-and-prefix-length is natural. JUNOS uses this
format.
> > > > XR
> > > > > uses this format (for IPv6 at least). Nokia SROS uses this
format.
> > > > >
> > > > > We have written a bunch of models where the lack of this IMHO
> > > > > makes
> > > > them
> > > > > less elegant. I'd like for there to be an IETF standard data
type
> > > > > to make those models more elegant.
> > > > >
> > > > > Kind regards,
> > > > > Kristian.
> > > > >
> > > > > _______________________________________________
> > > > > netmod mailing list
> > > > > netmod@ietf.org
> > > > > https://www.ietf.org/mailman/listinfo/netmod
> > > >
> > > >
> > > >
> > >
> --------------------------------------------------------------------
> > > > ----
> > > > --------
> > > >
> > > >
> > > > > _______________________________________________
> > > > > netmod mailing list
> > > > > netmod@ietf.org
> > > > > https://www.ietf.org/mailman/listinfo/netmod
> > > > >
> > > >
> > > > _______________________________________________
> > > > netmod mailing list
> > > > netmod@ietf.org
> > > > https://www.ietf.org/mailman/listinfo/netmod
> > >
> > > --
> > > Juergen Schoenwaelder           Jacobs University Bremen gGmbH
> > > Phone: +49 421 200 3587         Campus Ring 1 | 28759 Bremen |
Germany
> > > Fax:   +49 421 200 3103
<https://www.jacobs-university.de/>
> > >
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> > >
> >
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