[ppml] "Recommended Practices" procedure

Scott Leibrand sleibrand at internap.com
Thu Jun 29 18:04:19 EDT 2006

On 06/29/06 at 5:15pm -0400, Jason Schiller (schiller at uu.net)...:

> Although somewhat difficult, the problem isn't getting each of the
> customer's upstream ISPs to send the more specifics between their peering
> sessions, the customer is presumably paying their upstream ISPs to carry
> these routes.


> The problem is getting all the other default free ISPs to carry the
> route.  Sources that buy transit from someone other than the customer's
> upstream ISPs will be dependent on the upstream ISP that provided the PA
> IP space, unless they also carry the more specifics.

I would maintain that getting other default free ISPs to carry the
deaggregated PA /48 is beneficial, for traffic engineering and routing
optimization, but unnecessary in most cases for reachability.

The only case in which it would be insufficient would be if the provider
who allocated the addresses went totally offline (stopped originating
their /32) or partitioned their network in such a way that they were
unable to reach *any* of the peering links to the customer's other
provider.  (Remember, they're accepting the /48 from the other provider,
presumably over all their peering links, so that's a lot of diverse

I would argue that if you need resilience against that kind of failure,
you should be using PI space, not PA.  Even in the IPv4 world, PA
multihomers can experience issues when the provider who allocated them the
space has issues affecting their announcement of the aggregate.


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