Subject: Re: [lisp] #16: map versioning/data plane consensus call

From: [email-masked] (Noel Chiappa)
Date: Thu, 17 Sep 2009 11:35:38 -0400 (EDT)

> From: Sam Hartman <[email-masked]>

    > The chairs believe that we'd need to see somewhat more support for a
    > specific proposal than we've seen for map versioning to date in
    > order to adopt that proposal.

Well, I think we're a ways from that point, yet; the proposal has not yet
received in-depth scrutiny from the WG, and I suspect that in such a
process, a number of changes would likely happen. (I know a number of
people, including me, would prefer an automatic 'fingerprint' to a version
number, for instance.)

Also, the whole area of discovering and dealing with out-dated mappings has
yet to be systematically analyzed. (For instance, what happens if a packet
gets to an xTR which is no longer a valid xTR for the destination EID? That
should be easy to detect, and relatively easy - module DoS concerns - to fix,
but I don't think there's anything in the spec about it yet.) And of course we
don't have a lot of real experience yet, to guide us in that systematic
analysis.

    > If we did receive sufficient support to adopt something as a WG
    > draft, assigning the flag would be easy.

Exactly.

    > The question of whether something belongs in the data plane seems to
    > be all over the map.

For good reason, though.

On the one hand, in high-end boxes (which is where the majority of LISP
packets will be handled, if it succeeds) doing control functions in the
data plane is usually a major PITA - the overall box architecture just
isn't set up for it.

On the other hand, doing it in the control plane makes it impossible to
piggyback these functions on existing traffic - and with the fan-outs we
expect to see in LISP, the overhead of dedicated control traffic for these
functions is a lot of traffic. (Although I do think the concern over this
might be a bit exaggerated... although that's quite possibly true of a lot
of the other concerns that are expressed without much actual experience to
guide us.)

    > I think we may be revisiting the question of what belongs in the
    > data plane when we get more data.

Sounds like a plan....

	Noel