Subject: Re: [lisp] #5: LISP protocol version is alive and kicking

From: [email-masked] (Noel Chiappa)
Date: Mon, 21 Sep 2009 18:40:58 -0400 (EDT)

> From: "Darrel Lewis (darlewis)" <[email-masked]>

    >> a general problem with square routing (i.e. packets from site A to B
    >> flow from ITR a1 to ETR b1, packets back from B to A flow via ITR b2
    >> and ETR a2) ... the b2 ITR doesn't have the mapping, either.
    >> ...
    >> I suspect the only answers are painful (e.g. better co-ordination
    >> between all the xTRs at a site - which we might need anyway, for other
    >> reasons).

    > To me, all of this discussion makes TTL ... based versioning better and
    > better. It works, and keeps all of this complexity out of the protocol.

My brain clearly isn't working well today, but I'm missing something here. I
guess I don't see how having the ability to detect stale mappings helps you
with the problem I mentioned above?

(And we _have_ to pick some different terminology - header 'versioning' and
mapping 'versioning' are just _too_ similar.)

If b2 never got a mapping for A (because it got neither user-traffic which it
could glean a mapping for A from, nor a Map-Request with piggybacked
information for A), how is it going to get a mapping for A unless either i)
it talks to its fellow ETR b1, or ii) it goes through a mapping-resolution
cycle on A?

	Noel

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From: "Darrel Lewis (darlewis)" <[email-masked]>
Date: Mon, 21 Sep 2009 15:43:28 -0700

> it talks to its fellow ETR b1, or ii) it goes through a 

Right it goes through a mapping resolution cycle.  This is a feature.
The ETR can then use clock sweep if the "header version" changes and it
wants to have ITRs re-learn and see the new information.

-Darrel