Re: [RRG] Not moving the problem to the global mapping system

[Robin Whittle <rw@firstpr.com.au>]

Hi Brian,

You wrote, in part:

> I can't say how much I agree with this. If the mapping system
> degenerates into a reachability-driven routing system, we might
> just as well switch to two layers of BGP immediately.
> 
> I would suggest turning this into a concrete goal, such as:
> 
> <strawman>
>
> The update rate in the mapping system should be at least
> two orders of magnitude less than the update rate in
> the BGP4 system, at any point in time.
>
> </strawman>

This might be a reasonable goal or constraint if it was assumed that
the map-encap's mapping system was as costly and problematic (with
problems like convergence time, amplification of changes due to
routers flapping, making half-baked decisions based on limited
information, unfair burden of costs etc.) as BGP is today.

There are good reasons why BGP has to do what it does today.

A map-encap system is a totally different thing, and its mapping
distribution system need have no resemblance whatsoever to BGP.

The map-encap schemes other than Ivip try to avoid the mapping
distribution system being involved in reachability changes.  Ivip
takes the opposite approach, which has various benefits as mentioned
in the recent thread:

   Moving the problem to the global mapping system - fast-push

      http://psg.com/lists/rrg/2008/msg01137.html
      http://psg.com/lists/rrg/2008/msg01139.html
      http://psg.com/lists/rrg/2008/msg01143.html

Ivip's mapping distribution system is much more efficient than BGP,
and there is a fee per update.  So there is no (or much less)
"tragedy of the commons" problem which lies at the heart of the
routing scaling problem we are trying to solve.

Ivip is a map-encap scheme which violates what I think are the
implicit assumptions behind your strawman text: that mapping changes
in the mapping distribution system are at least as burdensome - due
to intrinsic costs and probably the unfair distribution of costs -
as updates are in BGP today.  So I don't think proposals such as
Ivip should be constrained as you suggest.

  - Robin


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