Re: exponential route prefix growth, was: Re: The Cidr Report

[Thomas Marshall Eubanks <tme () 21rst-century com>]

John Todd wrote:

> Take a look at:
>
> http://www.fox-den.com/routes/
>
> This is a plot of routes v. paths on a router that peers with or at
> least sees the tables from a few large upstreams.  Please ignore the
> large gaps in the chart where I <ahem> did some configuration that
> was contrary to the correct functioning of my statistics collection.
> This is a crude measurement, but it's useful for trending.  I'm sure
> someone at CAIDA has done better research than my stupid-simple MRTG
> graphs, but I haven't seen theirs mentioned yet so I'll throw my $.02
> in first.
>
> What is interesting in the growth difference between the two growth
> patterns.   An interesting trend shows; there is a much larger
> increase in the number of paths than in the number of routes.  I
> would assume that this indicates a growth in the interweaving of
> networks, or at least the interweaving of transit providing
> relationships.  I suspect the interweaving of interconnections is
> growing at a similar rate, but proof of this is invisible with only a
> few BGP perspectives.

I don't see that, at least in RELATIVE growth. In your "Yearly" graph,

number of routes at start = 64 K, number at end = 84 K, ratio = 1.31

number of paths at start = 192 K number at end = 252 K, ratio = 1.31

so both have grown by ~ 31 % in the last year. I don't see how this shows that
networks are changing - wouldn't the naive model be
growth in routes is proportional to growth in paths, which is what  these
data show ?

I am not saying that the networks aren't getting more interweaved - just
that I don't see how these graphs support that belief.


                                   Regards
                                   Marshall Eubanks

> Perhaps the more vital piece of information in this discussion is not
> the sudden growth of routes, but the growth of paths.  The
> de-aggregation of routes (though I have done no research to prove
> this) seems to me simply a response to redundancy/load distribution
> issues introduced by current route selection algorithms.  I think
> we're identifying one of the symptoms, but not the root cause of the
> growth in routes.  * It seems that we should be saying that there is
> a growth in paths, not _just_ routes, and path growth with current
> implementation methodologies and reasoning implies route growth. *
>
> We come back to "BGP only works the way most people expect it to in a
> multi-home situation when you de-aggregate a route from one of your
> upstreams and announce it all the time to all your peers."  Yes,
> there are many other reasons that one would de-aggregate and
> re-announce either back into the primary with the aggregate or
> others; however, I think that the (obvious) basic reasoning for the
> bulk of path/route announcements is redundancy and load sharing.
>
> The demand for "always on" backup ("announce all the time even in
> directions in which you pad the path") and cost efficiency ("we're
> paying for that second line, so we'd better get some use out of it")
> lead to increase in paths that need to be visible, and thus routes
> that need to be visible.
>
> Why in the last year has this been so large?  You've got me there,
> but I'll take a swing at it.  Probably something to do with the
> collapsing prices of bandwidth, the dispersion of BGP know-how (or
> the "how to set up BGP for your enterprise for dummies" books/FAQs,
> at least,) and the sudden expectation that all Internet traffic is
> mission-critical and mustmustmust always be available.  The bubble of
> hype is finally moving down the hose and causing operational issues
> such as this.
>
> It's the nature of the beast; as complexity grows... complexity
> grows.  So how does this get solved?   The complex solutions of
> multi-provider NAT are possible, but practically impossible in a
> business environment where FUD rules the day.  This is really a
> matter best discussed after at least 6 hours of deep thought, which
> is about 5:55 short of what has occurred for this message.  :)
>
> JT


   T.M. Eubanks
   Multicast Technologies, Inc.
   10301 Democracy Lane, Suite 410
   Fairfax, Virginia 22030
   Phone : 703-293-9624
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   e-mail : tme () on-the-i com

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