On 3/1/18 10:57 AM, Todd Crane wrote:
> Question:
> Since we cannot count on everyone to follow BCP 38 or investigate their 
> abuse@, I was thinking about the feasibility of using filtering to prevent 
> spoofing from peers’ networks.
> With the exception of a few edge cases, would it be possible to filter 
> inbound traffic allowing only packets with source addresses matching the 
> peer’s BGP announcement?  Theoretically it should be a two way street to any 
> address I can receive from, thus if I can’t send to it, I shouldn't be 
> receiving from it. I realize this is not currently a feature of any router 
> (to my knowledge), but could it be implemented into some NOSs fairly easily 
> and jerry-rigged into others for the time being.
you can build ACLs from IRR objects  just like you can build prefix
lists. for customers this is just as feasible as controlling what routes
you accept from them.

unlike URPF strict  this will not cause an outage every time a prefix is
withdrawn but traffic continues to flow (which is a normal and healthy
part of doing maintenance).

on the other hand it means your prefix lists will have to be rather up
to date and your peers will likely have to be very up to date with their
customers. since failures for inclusion will cause black holes.

you can't do this on on and MLPE exchange where you export routes unless
you want to cause an outage everytime a new peer is added.

there is also the problem of the number of cam slots these IP acls chew up.

bgpq3 -P AS-FOO
> This would allow us to peer with OVH et al, and not worry as much. 
> Furthermore, whereas BCP 38 is reliant upon everybody, this could 
> significantly reduce amplification attacks with even just a handful of 
> adopters.
The source addresses of attack traffic associated with for example
memcached (and in fact virtually all reflection attacks) are not spoofed.
> —Todd
>> On Feb 28, 2018, at 6:52 PM, Job Snijders <j...@ntt.net> wrote:
>> On Tue, Feb 27, 2018 at 09:52:54PM +0000, Chip Marshall wrote:
>>> On 2018-02-27, Ca By <cb.li...@gmail.com> sent:
>>>> Please do take a look at the cloudflare blog specifically as they
>>>> name and shame OVH and Digital Ocean for being the primary sources
>>>> of mega crap traffic
>>>> https://blog.cloudflare.com/memcrashed-major-amplification-attacks-from-port-11211/
>>>> Also, policer all UDP all the time... UDP is unsafe at any speed.
>>> Hi, DigitalOcean here. We've taken steps to mitigate this attack on
>>> our network.
>> NTT too has deployed rate limiters on all external facing interfaces on
>> the GIN backbone - for UDP/11211 traffic - to dampen the negative impact
>> of open memcached instances on peers and customers.
>> The toxic combination of 'one spoofed packet can yield multiple reponse
>> packets' and 'one small packet can yield a very big response' makes the
>> memcached UDP protocol a fine example of double trouble with potential
>> for severe operational impact.
>> Kind regards,
>> Job

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