The Gorgon's Knot. Was: Re: Verio Peering Question

Fri Sep 28 18:40:59 UTC 2001

At 06:17 PM 9/28/2001 +0000, Joseph T. Klein wrote:

 >Find a way to provide reliable multi homing without massive route
 >table growth and you fix many things.

We have, and every backbone is implementing it today, including 
Verio.  Namely, give people who need to muti-home a /24, and let them 
announce that /24 from their own ASN.

Simple, elegant, scalable (although not infinitely, but what is?), and 
working today.  However, if all backbones took Verio's advice and filtered, 
this solution would no longer be workable.

So, you may not fault them for taking a stance, but I do fault them for 
taking a stance and then acting in direct contradiction to that stance.

 >A more NANOG centric discussion may be to understand how many providers
 >would have problems given larger route tables. We all don't have routers
 >that can easily chew through a 100,000+ line BGP table.

Then you are in trouble, since the current table is already slightly over 
100K prefixes.

And most core routers at big networks (cisco GSRs, Juniper M###'s), can 
handle many more.  (Lots of core routers already do - internal tables are 
frequently much larger than the global table.)

 >How much can we give to individual entities without endangering the
 >common good?

That is not really the question being discussed.  Right now we are deciding 
*which* entities we can give the freedom to announce what they please.

Verio's "stance" does not prohibit networks or providers with large 
allocations to announce whatever they want.  Also, many companies, schools, 
providers, etc., have very large IP allotments for which they would not 
qualify today (e.g. Apple, IBM, GE, MIT, etc. all have /8s.)  The filtering 
policy does not affect these companies' & providers' announcements in the 
slightest.

Only the new companies, the ones starting small and following the "rules" 
by not wasting space or asking for more than they really need, are hurt by 
this policy.

In fact, one of the possible affects of this policy is the depletion of IP 
space at a much faster rate.  For instance, companies with /24s on their 
NAT boxes and 1000s of employees would suddenly want - and qualify for - 
larger allocations to allow them to multi-home.  Even if they only got a 
/20 for the NAT box, that would still increase IP address depletion rates 
alarmingly.

Not to mention all the other companies & providers who would claim they 
need a /20 from the start, when they only need a /24 or less.

Personally, I am far more afraid of running out of IP space than I am of 
router vendors not being able to handle 250K routes in a few 
years.  (Juniper and cisco both claim they can do it today.  I know Zebra 
can do it today on a single processor fast Pentium III box with a gig of 
RAM.  Not exactly bleeding edge technology.)

So, how much good does filtering do?  And how much damage?

 >Joseph T. Klein                                         +1 414 915 7489

--
TTFN,
patrick