[Python-Dev] PEP 3144: IP Address Manipulation Library for the Python Standard Library (original) (raw)

"Martin v. Löwis" martin at v.loewis.de
Sat Sep 26 20:19:16 CEST 2009

I think using .network and .broadcast are pretty well understood to be the [0] and [-1] of the network address block. I don't think we want to start creating new terms or access patterns here.

+1 on leaving .network and .broadcast as-is (including returning a IPvXAddress object). -1. I think 'network.number' or 'network.zero' is a lot clearer than 'network.network'. Maybe '.broadcast' would be okay, as long as it can be adjusted for those unusual, or maybe even only hypothetical, networks where it is not the [-1]. Real life example: network with a /31 mask. There are only two hosts: 0 and 1 first host configures the other's host as broadcast address and vice versa. NOTE - broadcasts are different here!

This is RFC 3021. IIUC, it does not support directed broadcast; only link-local broadcast can be used on that link.

So ISTM that .broadcast should raise an exception on a /31 network. Any installation that configures the partner as the broadcast address is broken (somebody correct me if I'm wrong).

Another real life examples include /32 networks on PPP. Just a point-to-point. No need for broadcasts and networks, a host just have one IP address and send all traffic via point-to-point link, no addressing is required there. This is a working dialup configuration, it works for me, it works for you, probably. It is not weird, it is common, it is used for PPPoE, for ADSL, for dialup.

So where is that defined?

Regards, Martin

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