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Re: IPv6 adoption

On Sun, 16 Jul 2000, Mika Liljeberg wrote:

> I landed into the middle of this thread, when it dropped onto the
> the IPv6 list, so forgive me if I miss the point (I'm not even sure
> which way you're arguing there), but...

I'm just trying to say that a 128 bit address space is isn't really too
large, but probably about the right size.
> Anyway, having aggregatable addresses is simply a matter of
> assigning addresses so that they are tied to network topology.
> The routing information doesn't actually eat up any "extra bits"
> in the addresses.

Well, it does make the address larger than it technically needs to be.
With 64 bits you can represent enough devices (indeed, IPv6 already
assumes this, since that is the interface ID length). But adding another
64 bits makes it alot easier and faster to route - which is the point :>

> Err... I have no idea why you mention this. The idea behind automatic
> tunneling is simply that you can connect isolated IPv6 subnets together
> through an IPv4 network without having to configure tunnels manually. 

Simply a neat example of how useful it is to have routing information
embedded in the addresses, instead of tranmitted seperately.

This thread did start because people were complaining that 128 bit
addresess were unecessiarily large.

> Can't do that. There's no guarantee that the interface id has been
> constructed from an Ethernet address and even if it has, the
> destination might be proxied. The router has to do ND as usual.

I was under the impression that link layer resolution ND messages were
only for use in unusual cases, not for general use on ethernet? 

It seems to me that if you do use ND for each IP then you will end up with
rather low IP utilization - of the 2^64 addresses that are delivered to a
router, maybe about 10000 would fit in the neighbour cache of a router? 

I don't see the problem with proxies, if they are able to do the
equivilant of 'proxy arp' then they can just as easially listen for
multiple MACs (like a switch).

> Why wouldn't it work? It couldn't possibly be worse than IPv4. Five years 
> ago, when CIDR was introduced in a hurry, Internet backbone routers were
> on the brink of collapse. Now they are applying the same principle in 
> IPv6 and suddenly it's not a good idea? 

I didn't say it wouldn't work, just that it wasn't known how well it would
work. You can't really say how well it will do as it scales up beyond
where IPv4 is now. In any event, I understand IPV6 is also supposed to be
improved from what CIDR is, the question is how much.


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