Full routes needed at sites? [Re: RIR bashing, was: Routing table size?]

[Pekka Savola <pekkas@netcore.fi>]

Let's change the subject as there seems to need some discussion..

On Mon, 13 Oct 2003, masataka ohta wrote:
> > I personally see the situation where I would get two
> > independent ISP's, eg a cable and ADSL provider. They don't
> > have to know anything about eachother. The only thing they do
> > is that they each route a prefix from and to me as delegated out
> > of their TLA. My boxes thus would get 2 prefixes.
> 
> And, you want to have 2 exit routers, if you want to avoid a single
> point of failure.
> 
> Then, you want to have full route in your site to choose the best
> exit router for each destination.
> 
> Or, you may develop a complex protocol on hosts and exit routers
> that a host first query exit routers (multiple ones, of course)
> to choose a source address and routers between the host and
> the exit routers perform source address based routing (or,
> the host may use tunneling to the exit routers), even in which
> case, the exit routers must have a global routing table.
> 
> This is why the global routing table should be reasonably small.

I fail to see a strict *requirement* for the global routing table even at 
border routers.

A typical customer (at least the kind of I imagine using something like 
this) would be one connecting to two operators operating in the same 
region.   The global connectivity would be more or less the same.  Sure, 
there could be differences and optimizations of dozens of milliseconds, 
but that wouldn't be a major problem.

More likely than not, having just two default routes would be "good 
enough".  If one wanted more granularity than that, adding the prefixes 
directly connected to each ISPs to be explicitly preferred through that 
ISP could optimize the scenarios quite a bit.

Remember -- the ISPs *do* inter-connect locally these days, except in 
some developing areas.  And in that case, the choice of the ISP for 
outbound packets really don't matter much at all, as long as it just 
works..

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings