That's path validation.

Anyway, the diameter of the Internet is only about 4 to 5 AS hops.
Tier 1's only care about the radius, which is mostly 1, 2 or 3 AS hops.

Given such short AS paths, RPKI can provide a good level of protection already.
If the attacker originates a route prepended by the legitimate AS, then his 
AS-PATH will
be longer than that of the legitimate route in the large majority of the 
Internet.
But only if each AS that registers a ROA advertises every prefix matched by the 
ROA.
If it does not, then another AS can easily steal the prefix like you said.

If you need to protect a prefix that you don't advertise then put ASN 0 into 
the ROA for it.
Then nobody can advertise it.

Thanks,
Jakob.

From: Sidrops [mailto:[email protected]] On Behalf Of Christopher Morrow
Sent: Friday, January 13, 2017 2:05 PM
To: Marco Marzetti <[email protected]>
Cc: Randy Bush <[email protected]>; [email protected]; GMO Crops <[email protected]>; 
Job Snijders <[email protected]>
Subject: Re: [Sidrops] [GROW] I-D Action: 
draft-ietf-sidrops-route-server-rpki-light-00.txt



On Fri, Jan 13, 2017 at 4:54 PM, Marco Marzetti 
<[email protected]<mailto:[email protected]>> wrote:
<rant>
Every time one suggests a change related to the IXPs world we spend
days arguing if it affects the neutrality and how.
Do we really need that?
</rant>

Anyway, i can't see why IXPs can blackhole traffic (if the destination
requests it), but cannot do the same with prefixes.
After all if a prefix is invalid the owner requested it to be verified
by the other parties.

I think part of job's point (and randy's in a way) is that you actually don't 
know if:
  192.168.0.0/23<http://192.168.0.0/23> AS1 AS3 AS8

is valid, even if you see a ROA:
192.168.0.0/16<http://192.168.0.0/16> AS8 max-len /23

... because there's nothing that keeps AS-ME from sending AS-JOB a route with 
AS8 prepended on the as-path.

I suggest to default to drop and, if possible, to switch to announce
with community if the peer requests it (for instance someone may want
to collect invalid routes for analysis).

i think you are describing implementations that the IXP may choose... I don't 
know that this draft needs to specify that at all.

-chris


On Fri, Jan 13, 2017 at 10:20 PM, Randy Bush 
<[email protected]<mailto:[email protected]>> wrote:
>> Adding [email protected]<mailto:[email protected]> for reality check.
>
> no comment :)
>
> when you choose to use a route server [0], you have out-sourced much of
> your policy and operational responsibilities.  seems to me that whether
> this includes security decisions is a contract between the user and the
> route server.
>
> so i might tell the server to drop invalids.  if i do not take that
> (configurable, i presume) option, having the server mark them seems
> helpful.
>
> randy
>
> --
>
> 0 - i suspect none of job, carlos, or i do.  so this is the experts
>     telling other people what they should do. :)
>
> _______________________________________________
> GROW mailing list
> [email protected]<mailto:[email protected]>
> https://www.ietf.org/mailman/listinfo/grow



--
Marco

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