[Python-Dev] PEP 3144 review.

DrKJam drkjam at gmail.com
Sat Sep 26 23:57:00 CEST 2009

2009/9/26 Daniel Stutzbach <daniel at stutzbachenterprises.com>

> On Sat, Sep 26, 2009 at 2:07 PM, DrKJam <drkjam at gmail.com> wrote:
>> The current version of the PEP and reference implementation do not mention
>> or deal with IPv4 classful addressing (A, B, C, D and E). It would be good
>> to know if any of this (admittedly older yet no less important)
>> functionality is going to be supported. If the library is to concentrate
>> solely on classless addressing (i.e. CIDR) please can this be stated in
>> future revisions of the PEP.
> Classful addressing was deprecated more than 15 years ago!
> Quoting RFC 4632: "With the full deployment of CIDR on the Internet, such
> scenarios are no longer operationally relevant."

Interesting as evidence of classful IPv4 behaviour seems fairly pervasive in
current IP stacks and software that supports IPv4 addressing (e.g.
PostgreSQL inet and cidr data types).

Here's an excerpt from the 'ifconfig' man page (taken from an Ubuntu 9.04
install) :-
netmask addr

Set the IP network mask for this interface. This value defaults to the usual
class A, B or C network mask (as derived from the interface IP address). but
it can be set to any value.

The point being that you can't always assume /32 implicitly for all use

Here is how IP addresses without an explicit prefix or netmask are currently
handled :-

>>> import ipaddr
>>> ipaddr.IPv4Network('')

It may not be something we want to support (you could always force the end
user to specify a prefix or netmask explicitly). This is fair enough, but
let's indicate that it's a considered choice. Somewhere in the PEP text is
might be a good place for treatment of this topic.

> --
> Daniel Stutzbach, Ph.D.
> President, Stutzbach Enterprises, LLC <http://stutzbachenterprises.com>
> "The plumage don't enter into it. It's stone dead."
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