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

"Rob Wilton (rwilton)" <rwilton@cisco.com> Tue, 02 April 2019 16:44 UTC

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From: "Rob Wilton (rwilton)" <rwilton@cisco.com>
To: tom petch <ietfc@btconnect.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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Date: Tue, 2 Apr 2019 16:44:12 +0000
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Subject: Re: [netmod] 6991bis: address-with-prefix-length
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Hi Tom,

But having joined this thread midway through, I thought that what was being described was an ip-prefix.

I wonder how many folks will mistakenly think that "ip-address-prefix" means "ip-prefix"?

Thanks,
Rob


> -----Original Message-----
> From: tom petch <ietfc@btconnect.com>
> Sent: 02 April 2019 17:34
> To: Rob Wilton (rwilton) <rwilton@cisco.com>om>; Martin Bjorklund <mbj@tail-
> f.com>; j.schoenwaelder@jacobs-university.de
> Cc: netmod@ietf.org
> Subject: Re: [netmod] 6991bis: address-with-prefix-length
> 
> ----- 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
> > > > >
> > > > >
> > > > >
> > > >
> > --------------------------------------------------------------------
> > > > > ----
> > > > > --------
> > > > >
> > > > >
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> > > > >
> > > > > _______________________________________________
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> > > >
> > > > --
> > > > 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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