Implementations/suggestions for Multihoming IPv6 for DSL sites

Owen DeLong owen at delong.com
Mon Apr 11 10:26:32 CDT 2011


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
>>>> 
>>> 
>> 
> 




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