IPv6 end user addressing

Valdis.Kletnieks at vt.edu Valdis.Kletnieks at vt.edu
Mon Aug 8 15:35:31 UTC 2011

On Mon, 08 Aug 2011 16:12:00 +0200, Mohacsi Janos said:
>                                              You don't have to count the all 0 and all
> 1 as reserved.... maybe each deeice can see /57 or /58 or /59....
> depending of capabilities your devices....

As I said further down the note - you can conserve bits but then it gets more
complicated.  You don't want to go to a static "subdivide whatever you got 16
ways if you can", you have to get more clever.  Sure, that one device may only
need a /61 right now because there's only 3 devices behind it.  So the upstream
bridge allocates the first /61 to that device, and allocates the next /63 to the next
device that comes online.  Then somebody adds a 4th device to that first router
and now it needs a /60, but you can't just expand the allocation to a /60
because somebody is in the way.  Somebody's gonna have to renumber.

Or you can just say "I can support 16 devices so I need 4 bits of space".  Or
you can bite the bullet and do something more clever.

> I think daisy chaining of CPE routers is bad idea - as probably done in
> several IPv4 home networks. Why would you build several hierarchy into you
> network if it is unnecessary?

Because we're talking Joe Sixpack here - and he can't *spell* hierarchy.  All
he knows is that he's got one box that his cable company sent him, then he
plugged his wireless access point into the cable company box, then he plugged
all the stuff in the media center into a box and connected that box to the
cable company box (He couldn't plug it all into the cable company box because
that only had 4 RJ45's, and one got used for the wireless, and he's got 9(*)
things in the media center that have RJ45s).  You're at 2 levels of heirarchy
already.  Now if he decides to get lazy and not run a cable to the upstairs
bedroom he wants to use as a home office, and gets another box that's really
similar to the on in his media center except it will do wirelesss, he just
added a third level of heirarchy.

And I don't think that's an at all unreasonable scenario.  Feel free to
redesign that network to get rid of one level, let me know what you ended up
doing.  Oh, and explain it in terms Joe Sixpack can understand. ;)

(*) Yes, 9 isn't at all unreasonable - I know plenty of people that have
a Wii, a PS/2, a PS/3, an XBox, a TV that will talk to the Internet, a DVR
that wants to talk to the Internet, and a PC. That's 7 already.

On Tue, 09 Aug 2011 00:18:57 +1000, Mark Andrews said:
> In message <174561.1312807412 at turing-police.cc.vt.edu>, Valdis.Kletnieks at vt.edu
> > half dozen devices can burn up 8 bits of subnet addressing real fast. Yes, you
> > 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.

As I said - you can conserve bits using PD or similar, but then you need a
routing solution - you can use PD to hand out prefixes, but then you still need
routing.  Consider the case above - the wireless box asks for a prefix
delegation, then the media center box asks for one. Then the home office asks
for one - and now you need to make sure there's a way for the stuff behind the
media center box to know that to get to the printer that''s hanging off the
home office box, it has to route to the wireless box.

Anybody got gear that can do that and is ready for Joe Sixpack?

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