Addressing plan exercise for our IPv6 course

Sun Jul 25 03:25:14 UTC 2010

On Sat, 24 Jul 2010 10:57:49 -0700
Owen DeLong <owen at delong.com> wrote:

> 
> On Jul 24, 2010, at 9:40 AM, Brandon Butterworth wrote:
> 
> >>> Enterprises of non-trivial size will likely use RFC4193 (and I
> >>> fear we will notice PRNG returning 0 very often) and then NAT it to
> >>> provider provided public IP addresses.
> > 
> > Eventually ARIN (or someone else will do it for them) may create a site
> > you can register your address and know that it really is unique
> > among participating registrants. Random is fine, unique is better.
> > 
> > Such a site would be the seed for when (if) we come up with the tech
> > for everyone to have PI and lose all the restrictions imposed so far.
> > 
> SIXXS already has such a registry with a pretty low adoption rate.
> 

And I think that is good news. The fd00::/8 range is not defined as
guaranteed globally unique. I'm concerned that the SIXXS registry could
imply to those people who have used it, that it is. They may think that
because that registry exists, and that they've used it, that address
space it now theirs, and nobody else is allowed to use it. Once somebody
perceives ownership of something they believe is unique, I think they
commonly won't listen to reason about their actual lack of global
ownership.

fc00::/8 is for guaranteed globally unique ULAs.

> I still fail to see any advantage whatsoever to this approach and I think
> that the limited number of sites that implement it is unlikely to get
> continued support from ISVs.
> 
> >>> I'm just hoping that we'll at least
> >>> see 1:1 NAT instead of NAPT being used.
> > 
> > I think that will be a common PI alternative. If people really don't
> > want NAT then we shouldn't provide reasons for it to exist.
> > 
> > RFC4193 seems to be the best enterprise plan. They can link to other
> > enterprises and change ISPs easily or multihome. They are not beholden
> > to any ISP or numbering authority. The global table doesn't explode.
> > 
> I agree that easier to get PI addresses is a better alternative. I will support
> policy initiatives to do that. RFC4193 remains an utterly horrible idea
> and NATing it to the public internet remains even worse.
> 

Well I think RFC4193 is a great idea. I don't want my home network
addressing to be bound to having a commercial arrangement with an ISP,
or having an active Internet connection. I can also use the ULA prefix
as a simple designator of trusted verses untrusted traffic sources in
firewall rules. I see those advantages equally applicable to enterprise
or ISP networks.

Then again, I'm happy with the idea of multiple addresses on an
interface, and source address selection. They're not much different to
those issues in IPv4, such as unnumbered interfaces on routers,
designated source addresses for router SNMP traps etc., or source
address selection for policy routing.

> >> Why on earth would you do that? Why not just put the provider-assigned
> >> addresses on the interfaces along side the ULA addresses? Using ULA
> >> in that manner is horribly kludgy and utterly unnecessary.
> > 
> > Enterprises tend to want only one identifier to manage per device and
> > that it be unique and mostly permanent.
> > 

That's IPv4 thinking showing though. People fundamentally don't want
change when they don't know of or understand the benefits they will
gain. ULAs are an overhead, but they also provide benefits that can't
be achieved with global address space assigned by an ISP. (I don't
accept the PI argument, because it isn't feasible for residential
networks).

> Right... That identifier is the EUI-64 which is both permanent and unique.
> The prefix changes when you switch providers, but, that's mostly not
> particularly horrible since there are tools to make that easier for the
> bulk of internal hosts.
> 
> > With several PA and ULA on each device, links to ISPs and other
> > enterprises, the combinations of addresses and paths to manage flows
> > and security over become too hard (if it's not simple it's probably not
> > secure). Every device becomes a router and firewall and the staff who
> > manage those aren't cheap.
> > 
> Actually, if you set things up correctly, most of the security stuff to manage
> is about the same because you hairpin the stuff that doesn't need filtration
> at a point before it hits the packet filters.
> 
> >>> This is to facilitate easy and cheap way to change provider. Getting PI
> >>> address is even harder now, as at least RIPE will verify that you are
> >>> multihomed, while many enterprises don't intent to be, they just need low
> >>> cost ability to change operator.
> >>> 
> >> Why is that easier/cheaper than changing your RAs to the new provider and
> >> letting the old provider addresses time out?
> > 
> > And changing all the ACLs based on the old providers addresses
> > 
> Mostly this is a pretty straight forward copy->search->replace
> problem with prefix changes that can be done with the equivalent
> of an s/x/y/g construct.
> 
> > And allowing for all the 5 - 15 year old kit that predates this and
> > won't be upgraded (we have that problem with NT embedded in systems
> > with 10year+ refresh cycle)
> > 
> That kit won't support IPv6, so, I fail to see the relevance. Any kit that supports
> IPv6 supports this.
> 
> Owen
> 
> 