Re: Implementations/suggestions for Multihoming IPv6 for DSL sites

[Owen DeLong <owen () delong com>]

On Apr 11, 2011, at 8:15 AM, Luigi Iannone wrote:

> On 11, Apr, 2011, at 15:37 , Owen DeLong wrote:
>
> > On Apr 11, 2011, at 6:30 AM, Luigi Iannone wrote:
> >
> > > On 11, Apr, 2011, at 15:17 , Owen DeLong wrote:
> > >
> > > [snip]
> > > > > > Doing IPv4 LISP on any kind of scale requires significant additional prefixes which at this time doesn't seem so 
> > > > > > practical to me.
> > > > >
> > > > > This is not accurate IMO. To inject prefixes in the BGP is needed only to make non-LISP sites talk to LISP sites. 
> > > > > Even there you can aggressively aggregate, as explained in draft-ietf-lisp-interworking.
> > > > >
> > > > > As long as the LISP deployment progress you can even withdraw some prefixes from the BGP infrastructure and 
> > > > > advertise only a larger aggregate in order for legacy site to reach the new LISP site.
> > > > >
> > > > > Luigi
> > > > Who said anything about BGP? I was talking about the amount of additional IP space needed vs. the
> > > > amount of IPv4 free space remaining.
> > >
> > > Sorry. I misunderstood. 
> > >
> > > But can you explain better? Why should LISP require more IP space than normal IPv4 deployment?
> > >
> > > If you are a new site, you ask for an IP block. This is independent from whether or not you will use LISP.
> > Sure, but, if you also need locators, don't you need additional IP space to use for locators?
>
> No, those are the IP address that you provider gives to your border router.
Right... In addition to my provider independent addresses... That's more address space than is required
if I am not using LISP.

> > > If you are an existing site and you want to switch to LISP why you need more space? you can re-use what you have?
> > Perhaps I misunderstand LISP, but, I though you needed space to use for locators and space
> > to use for IDs if you are an independently routed multi-homed site.
>
> Not exactly. You do not need more space. You re-use what you have. 
Still confused, then. This seems antithetical to what you said above and below...


> > If you are not an independently routed multi-homed site, then, don't you need a set of host IDs
> > to go with each of your upstream locators?
> >
> > As I understand LISP, it's basically a dynamic tunneling system where you have two discrete,
> > but non-overlapping address spaces, one inside the tunnels and one outside.
> >
> > If that's the case, then, I believe it leads to at least some amount of duplicate consumption of
> > IP numbers.
>
> No true. I ask for a PI block that I will use as EID-Prefix, then the locators are part of the address space of my 
> providers.
> There is no duplication.
Right... Ordinarily, without LISP, I get a PI block and use that for EID and the routing is based on the
EID prefix. With LISP, the EID prefix is PI and I use additional PA resources to do the routing locators.
That's what I meant by duplication. There are additional PA resources required on top of the PI in order
to make LISP work.

> > > Or I missed the point again?
> > Or perhaps the complexity of LISP in the details still confuses me, despite people's insistence
> > that it is not complex.
>
> IMHO it is very simple. As any new technology  there is just a learning curve to follow, but for LISP it is not steep 
> ;-)
I'd agree with you if it weren't for the fact I keep thinking I just about understand LISP and then get told
that my understanding is incorrect (repeatedly).

Owen

> Luigi
>
>
> > Owen
> >
> > > thanks 
> > >
> > > Luigi
> > >
> > >
> > >
> > > > Owen