[ppml] "Recommended Practices" procedure

Scott Leibrand sleibrand at internap.com
Fri Jun 30 10:49:08 EDT 2006

On 06/30/06 at 10:15am -0400, Marshall Eubanks <tme at multicasttech.com> wrote:

> On Jun 30, 2006, at 9:38 AM, Scott Leibrand wrote:
> > No, I'm not making that assumption.  I'm saying that only your
> > transit-free transit providers need to exchange your route.
> > Everyone else
> How do I determine which of my transit providers are transit-free ?

Ask them?  Ask a trusted third party?  I've never had any problem
getting this information from my transit providers.

> What do I do if one fine day no provider available to me is transit-
> free ?

Then perhaps you should start using PI space.  If you can't, it's a harder
problem to solve, but still doesn't require cooperation of anyone who's
not receiving money (directly or indirectly) from you.

Say you buy your transit from me.  I recommend you get PI space, but you
don't qualify, so I give you a /48 out of my /32, and announce both routes
to all of my transit providers (who accept them, because I'm paying them
to do so).  You also run BGP with another tier 2 ISP.  I exchange your /48
with that ISP, either via a peering link or via a mutual transit provider.
If there are no peering links or mutual transit providers, then I must ask
my transit provider to accept your /48 from your ISP's transit provider,
and vice versa.  Other transit-free NSPs, which don't have either me or
your other ISP as customers, will send your traffic to one of my transit
providers based on my /32, then on to me or your ISP based on your /48.
If either of your ISP links (or the routers terminating them) go down,
then your traffic will be passed along to your other ISP.

The only failure scenario where you lose connectivity is if my network
goes completely offline.  If you believe the likelihood of such an event
is higher than your risk tolerance, then you should use PI space, or get
your PA space from someone with a network less likely to catastrophically


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