[Python-Dev] PEP 3144 review.

[R. David Murray]

On Mon, 28 Sep 2009 at 22:32, Antoine Pitrou wrote:
> Le lundi 28 septembre 2009 à 22:11 +0200, "Martin v. Löwis" a écrit :
>>
>> That's not the question that was asked, though - the question asked
>> was "Under what circumstances would I want to specify...". I hope
>> most people agree that it is desirable to be able to specify a network
>> not just by its network address.
>
> To me it makes no sense to "specify a network not just by its network
> address", because by definition a prefix + mask is all that
> characterizes a network: that's all you need to specify it entirely.
> Adding a "base address" would be like adding a "port number" attribute
> to the Address class: it's abusing an existing class by adding
> irrelevant information.
>
> I may be mistaken, but it seems to me that, in the IP world, nowhere
> does such a "network + host" hybrid appear. You find networks (prefix +
> mask) in routing protocols, and host addresses in applicative protocols.

You do find "address plus mask" when specifying an IP address for an
interface.  This is a shorthand for specifying the IP address plus the
network, since the network can be derived from the IP plus the mask.
But it is a _shorthand_, it isn't an entity in its own right.  There is
no such thing as "a network that has an IP", there is only an
_interface configuration_ that has an IP _and_ an associated network.

--David