North American Network Operators Group

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  • From: John W. Stewart III
  • Date: Thu Nov 14 19:01:43 1996

reasonable questions.  my general reaction to your message
is that the irr could be used for more things than it is
currently *if* the information were more accurate.  it's
logical to ask "do we *need* those 'more things?'"  one
argument is "apparently not, because the internet is
working without them."  but at the same time, as the net
continues to grow and the routing continues to become more
complex (e.g., with increasing layers of aggregation),
having a database of routing information and tools which
can analyze that routing information seems like A Good

i come from a provider which believes in the irr.  but at
this point i think we "believe in it" for what we use it
for:  route-filtering our bgp customers in order to provide
a sanity check before passing those routes onto the global
internet.  we think that's important, and we think that by
doing this we are being a responsible member of the global
internet routing system (especially given our size)

it *is* worth noting that we have local-use stuff in our
registry to do two things.  first is automatic config of
static routes.  second is to track all of our bgp peers (in
a lot more practical detail than either inet-rtr objects or
as-in/as-out/interas-in/interas-out attributes in aut-num
objects).  so we most definitely "believe in" those uses as

we are interested in some of the uses of the irr that others
have proposed and are using (e.g., curtis has proposed some
interesting uses, and the raconfig tool is actively being
used by at least one provider), though we haven't yet chosen
to dedicate resources to those uses ourselves

so having said all of that, what's an irr violation?  for us
an "irr violation" would be that for some reason we're not
accepting a route from a customer.  in those cases that
customer calls us and we work with them to fix the problem.
the important point being that we think our use of the
registry, even if considered a "violation" by some stats-
collection system elsewhere on the net, results in our AS
being a more stable part of the global routing system

so working to get rid of "violations" is a good thing
because it might usher in some other very helpful uses of
the registry.  but in the meantime, keep in mind that even
though one person may call an irr entry a "violation"
because of the way *they* use the irr, other people may be
using that entry to help keep the routing system stable

my US$0.02


 > Ok, this is in follow up to a discussion Bill Woodcock, John Hawkinson,
 > Kim Claffy and I had on the IPNMoo (or CAIDAnce or whatever it's called) 
 > regarding the IRR. This discussion led me to ask a bunch of questions. I'd
 > like to present these questions for discussion, and share a few of my
 > comments. 
 > How accurately does the IRR represent the actual routing policy of the
 > various participating networks and of the Internet as a whole? 
 > Well, according to the IRR Violations statistics at
 >, not very well. 
 > Since MAE-East is the "most important" (don't even start on that one) 
 > exchange on the Internet, let's look at the very few datapoints available.
 > 10187 IRR violations at MAE-East on 11/13/96
 >  9873 IRR violations at MAE-East on 11/12/96
 > There is no data available on the web page for any other days. 
 > Barring all of the obvious flames about the "if's" involved (number of
 > data points, statistical methodology, what constitutes a violation,
 > multiple violations, Merit stats don't mean anything, etc.) this doesn't
 > look real good. If there are about 42000 paths in the "default-free" 
 > routing table (this part we know), and every last one of them is
 > registered in the IRR (which isn't true), ~25% of the routes on the
 > Internet do not jive with the IRR, according to these Merit stats. 
 > Obviously, this calculation isn't exactly statistically sound, but it's
 > something to think about.  The fact that there are so many if's is kind of
 > the point, too. If you don't trust Merit stats, whose? Is there anything
 > else available to base any sort of conclusions on? I know of at least one
 > example of a reported "IRR violation" that isn't, so there could certainly
 > be (many) more. Anyone from Merit care to explain how these stats are
 > collected, and/or if they should be considered accurate? There's nothing
 > on the web pages concerning IRR violation statistic collection methodology
 > so far as I can tell.
 > To quote the eloquent folks at Merit:
 > "Maintaining accurate IRR information is important as several providers
 > base their router configurations on IRR information. Incorrect IRR data
 > may result in loss of connectivity. 
 > The IRR also provides a valuable source of information for analysis and
 > debugging tools."
 > How many providers are basing their policy solely on IRR information? Are
 > these providers (if they exist) at all concerned with the notion that (if
 > the RA statistics on IRR violations are at all useful) they may not be
 > able to get to up to 25% of the Internet at any one time? Might the IRR be
 > more harmful than goodful if it's actually used to generate router
 > config's by any small group of providers, and not by everyone? (Unless you
 > think segmentation is good). Is the IRR more valuable as a "source of
 > information for analysis and debugging tools" than as a source of
 > information to base routing policy on?  I would say apparently so. Is the
 > IRR supported?  Well, as far as I can tell almost everyone that should be
 > participating (in some form) is.  Is it supported in the sense that
 > everyone that is participating is commited to maintaining accurate
 > information? I would say apparently not. Is it supported in the sense that
 > it is actually used for anything other than "analysis and debugging"? (And
 > what sort of useful analysis can be done with data that is 25% bad
 > anyhow?) I don't know. Should the IRR be used for anything presumed to be
 > "actually useful"? Well, I certainly wouldn't rely (solely) upon it. How
 > about you? If the IRR were useless would it break the Internet? Nope. 
 > Could the IRR improve the Internet if it were used by everyone? Maybe. 
 > Should the IRR exist? I think yes. 
 > This whole "discussion" begs a lot of other questions. Adressing them is 
 > "beyond the scope of this document". :)
 > To be Scott Bradner for a moment, here's a disclaimer. 
 > I don't have large sums of grant money to do statistics, and I have to
 > rely on people who do, so don't complain about how terrible my stat is.  I
 > know many (all?) of these questions have been brought up before. I believe
 > there is interest in discussion, and so I have brought them up again. If
 > you don't want to talk about it, don't. These bits will not break your
 > network (well, unless you're <insert anyones favorite congested network
 > here>). 
 > Brian
 > ___                                                   
 >     Brian Merritt 	         [email protected]
 > ___ Principal Network Engineer   GetNet International 
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  • References:
    • IRR Brian Merritt