In message <174561.1312807...@turing-police.cc.vt.edu>, valdis.kletni...@vt.edu writes: > --==_Exmh_1312807411_38980P > Content-Type: text/plain; charset=us-ascii > > On Mon, 08 Aug 2011 10:15:17 +0200, Mohacsi Janos said: > > > - Home users - they usually don't know what is subnet. Setting up > > different subnets in their SOHO router can be difficult. Usually the > > simple 1 subnet for every device is enough for them. Separating some > > devices into a separate subnets is usually enough for the most > > sophisticated home users. If not then he can opt for business service.... > > You don't want to make the assumption that just because Joe Sixpack doesn't > know what a subnet is, that Joe Sixpack's CPE doesn't know either. > > And remember that if it's 3 hops from one end of Joe Sixpack's internal net t > o > the other, you're gonna burn a few bits to support heirarchical routing so yo > u > don't need a routing protocol. So if Joe's exterior-facing CPU gets handed a > /56 by the provider, and it hands each device it sees a /60 in case it's a > device that routes too, it can only support 14 devices. And if one of the > things that got handed a /60 is a wireless access point or something, it's on > ly > going to be able to support 15 or so subnets. So a simple topology of only a > half dozen devices can burn up 8 bits of subnet addressing real fast. Yes, yo > u > can conserve bits by being more clever, but then you probably need an IGP of > some sort....
Which is why CPE devices shouldn't do heirarchical assignment by default. PD supports multiple upstream requests. -- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: ma...@isc.org
