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

Ladislav Lhotka <lhotka@nic.cz> Thu, 18 April 2019 07:40 UTC

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From: Ladislav Lhotka <lhotka@nic.cz>
To: Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>, Kristian Larsson <kristian@spritelink.net>
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Date: Thu, 18 Apr 2019 09:40:33 +0200
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Subject: Re: [netmod] 6991bis: address-with-prefix-length
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Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>; writes:

> On Wed, Apr 17, 2019 at 09:35:51PM +0200, Kristian Larsson wrote:
>> 
>> I wonder though, isn't ipX-address-and-prefix-length the clearer name, or if
>> we do want to shorten then ipX-address-and-plen. I think Martin stated the
>> case for ipX-address-and-prefix but that is IMHO not the way this is
>> typically perceived by people.
>> 
>> 1.2.3.4/24
>> ^^^^^^^----- ipv4 address
>>        ^^^-- ipv4 prefix length
>> 
>> now, taking the prefix-length you know that 1.2.3 is the prefix but does
>> that mean the above is an IPv4 address and a prefix? Or is it just that you
>> can infer the prefix from the above? It's just different ways of looking at
>> it. My experience tells me ipX-address-and-prefix-length is the clearer way
>> of conveying what this is.
>>
>
> I guess this is somewhat subjective. The prefix length is the number
> used to convey what the prefix is. So you are effectively defining an
> address and the prefix that this address belongs to. ;-)

Strictly speaking, what is being defined by the number is a subnet mask.

>
> Given that we already have ip-prefix (which does as well use a prefix
> length to convey what the prefix is), it seems ip-address-and-prefix
> is more consistent with the existing RFC 6991 definitions. Being
> consistent with what we have was the main reason for me to prefer
> ip-address-and-prefix.

I am not in favour of adding this type. Having ip-prefix next to
ip-address-and-prefix is confusing. Moreover, the most natural use for
this type would be the address specification in the "ietf-ip" module,
but we already have two leaves there: ip and prefix-length.

Lada

>
> /js
>
> -- 
> 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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-- 
Ladislav Lhotka
Head, CZ.NIC Labs
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