BCP38 is hard, was TWC (AS11351) blocking all NTP?

Chuck Anderson cra at WPI.EDU
Tue Feb 4 22:36:18 UTC 2014

On Tue, Feb 04, 2014 at 10:18:21PM -0000, John Levine wrote:
> I was at a conference with people from some Very Large ISPs.  They
> told me that many of their large customers absolutely will not let
> them do BCP38 filtering.  ("If you don't want our business, we can
> find someone else who does.")  The usual problem is that they have PA
> space from two providers and for various reasons, not all of which are
> stupid, traffic with provider A's addresses sometimes goes out through
> provider B.  Adding to the excitement, some of these customers are
> medium sized ISPs with multihomed customers of their own.
> I don't know BGP well enough to know if it's possible to send out
> announcements for this situtation, this address range is us, but don't
> route traffic to it.  Even if it is, not all of the customers do BGP,
> some are just stub networks.
> If we could figure out a reasonable way (i.e., one that the customers
> might be willing to implement) to handle this, it'll make BCP38 a lot
> more doable.

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