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From: D'Arcy J.M. Cain <darcy@druid.net>
To: Greg Smith <gsmith@gregsmith.com>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: Best way to index IP data?
Date: Sat, 12 Jan 2008 01:00:48 -0500
Message-ID: <20080112010048.27678be8.darcy@druid.net> (raw)
In-Reply-To: <Pine.GSO.4.64.0801112136430.23114@westnet.com>
References: <36e682920801101541o7626bbddj428617144240c554@mail.gmail.com>
	<Pine.LNX.4.64.0801111025390.30762@localhost>
	<13179.1200064791@sss.pgh.pa.us>
	<20080111162747.GT5294@mathom.us>
	<24044.1200082058@sss.pgh.pa.us>
	<20080111212703.GU5294@mathom.us>
	<20080111213710.GD8260@alvh.no-ip.org>
	<20080111220235.GX5294@mathom.us>
	<20080111222403.GA7527@crankycanuck.ca>
	<1259C7B1-C948-4326-B827-849C64B61A16@blighty.com>
	<20080111230055.GB7618@crankycanuck.ca>
	<00045B34-A238-46B9-8641-C0A40C5CCCE5@blighty.com>
	<Pine.GSO.4.64.0801112136430.23114@westnet.com>

On Fri, 11 Jan 2008 21:56:38 -0500 (EST)
Greg Smith <gsmith@gregsmith.com> wrote:
> On Fri, 11 Jan 2008, Steve Atkins wrote:
> 
> > You may well need netmasks to configure your interface, but there's 
> > absolutely no need for them to identify an IP endpoint, which is all you 
> > need to identify the destination the packet is going to, and that is the 
> > most common use of IP addresses.
> 
> Technically you can't ever send a packet unless you know both the endpoint 
> and your local netmask.  As the sender, you're obligated to determine if 
> the destination is on your local LAN (in which case you send it there) or 
> if it goes to the gateway.  That's similar to a routing decision, but it's 
> not quite--if you don't have to look in a routing table, it's not actually 
> part of routing.

Not sure what your point is here.  Sure, you need the netmask but not
of every IP address you send to, only for the IP/network that you are
on.  That's a grand total of one netmask per interface that you need to
know.  And you don't store it in your database.

-- 
D'Arcy J.M. Cain <darcy@druid.net>         |  Democracy is three wolves
http://www.druid.net/darcy/                |  and a sheep voting on
+1 416 425 1212     (DoD#0082)    (eNTP)   |  what's for dinner.



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