the Internet Backbone

Avi Freedman freedman at
Mon Apr 8 20:27:49 UTC 1996

> On Mon, 8 Apr 1996, Avi Freedman wrote:
> > Now, many 2nd level providers that *could* operate default-free choose
> > not to.  Even if you have three or more sets of 30k+ routes each, it
> > takes balls to risk dropping packets that your customers want you to 
> > deliver just so that you can have the packet be dropped at your router
> > instead of at your (possibly backup) transit provider's router.
> > 
> > Avi
> 	Can't anyone who takes full routes from any tier 1 provider 
> operate without a default route? And isn't it a reasonable assumption 
> that if you don't have a route somewhere, odds are they don't have a 
> route to you (assuming you do your own BGP routing) and so a default 
> route is mostly pointless anyway?
> 	What am I missing?
> 	DS

Sorry if this thread is taking too much space on NANOG.  I didn't start it;
also, it's been suggested to me that inet-access may be a better forum this.

I'm not sure you're missing anything, but here are some things that we 

a) It can take a minute or so, depending on link speed & router types,
   to load 30k+ routes into a crisco.  Therefore, if you have no default
   route, even though your provider may have routes/connectivity to sites,
   you may drop packets in the meantime.

b) Your provider may in fact have you statically routed even if they speak
   BGP to you, you'd have to check - esp. if you're singly-homed.  Ever since
   mid-last year, the consensus was that localized flapping of connections 
   shouldn't be reflected in all of the routers on the 'net if at all possible.
   (see appropriate pointers on route dampening and inserting Null0 routes)

c) It takes balls to risk dropping customer packets on the bet that just 
   because your provider doesn't have or hasn't told you a route to a 
   destination, they can't get there.  It's a good bet, but not a sure one.


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