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Re: [RAM] Incremental Deployment of LISP




El 30/03/2007, a las 22:47, Ross Callon escribió:

At 07:19 PM 3/30/2007 +0200, Eliot Lear wrote:
Hi Fred,
You seem to be assuming that the mapping will be driven by
the first packet out the door; I'm not assuming that at all.
For inter-site communications, there will always be an initial
FQDN-to-locator resolution before a session starts, and the
mapping can be done then before any packets are sent.

Sorry, Yes. I had my head in LISP, where really there is no end host interaction. I think that's a good thing, in as much as it becomes deployable faster due to a smaller set of processors being touched. But in a context, say, like HIP, you would want to do that exact resolution for a HIT.


Eliot

This is beginning to hint at something that I have wondered about for a while:

It seems to me that there could be cases where a router (perhaps
in a private network, or a CE router, or perhaps even a PE router)
receives some packets that already use a PA address, and some
that are using a PI address and that need to be encapsulated.
For example this might occur because deployment of LISP is not
precisely equally rapid in each private network, or is not equally
rapid in each site within a larger private network.

How is a router supposed to know which packets are using an
address that is available in the global BGP top-level routing table
(such as a PA address), and which packets are using an address
that needs to be mapped?

I think this heavily depends on what scenario you are considering

in LISP 1 doesn't matter, since both identifiers and locators are routable
So, if you do have an alternative locator for the identifier, then tunnel, else, forward directly


similar in LISP 1.5

In LISP 2 and 3 the issue you are considering needs to be considered imho

probably it will induce additional latency, since you probably want to check if the dest address is an identifier.

in LISP 3 it depends wheter you are using the push or pull model

if you have all the identifier to locator database available, then you can check on it to verify if the destination is a identifier and which are the locators

if you don't have it, well, then you need to make a query and find out, which will take additional delay



Is the thought to partition the address space? The only other
solution that I have thought of is to have strictly controlled
topology (so that there is a clear boundary where the mapping
is done).


yes, this is what HIP people have done, they defined a prefix for the ORCHIDs which are the identifier.


probably hip people can expand on this one, but i think it was mostly for allowing transparent support for upper layers

Regards, marcelo


Thanks, Ross

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