valley free routing?

William Herrin bill at
Fri Mar 7 02:56:38 UTC 2014

On Thu, Mar 6, 2014 at 9:23 PM, Matthew Petach <mpetach at> wrote:
> On Wed, Mar 5, 2014 at 12:23 PM, William Herrin <bill at> wrote:
>> Can anyone tell me about a situation in which a route which was not
>> valley free was not a result of a misconfiguration or a bad actor? For
>> those who don't recall the terminology, a network path is valley free
>> if it crosses exactly zero or one free peering links when traveling
>> between the two endpoints.
> Isn't that the way most of the IPv6 internet ran
> for many years?   ISP A -> 6939 <- ISP B,
> settlement-free connections all around?  It's
> what established 6939 as the core of the
> IPv6 internet.

Hi Matthew,

By peering I mean a link on which the two participants offer and
accept substantially fewer routes than "the rest of the Internet."
Usually only the routes for each participant's respective customers.
The clever folks at HE provided full IPv6 transit as a loss leader
which enhanced their market position (put them on the map quite
frankly). That's not a "valley" in this context.

I'm really intrigued by the multiple reports of RENs creating a sort
of shadow network where other RENs are permitted to cross their
internal backbone at no cost but not access their general Internet
transit. That does seem to be a valley. Is anybody outside the
Research and Education industry doing this sort of thing?

Bill Herrin

William D. Herrin ................ herrin at  bill at
3005 Crane Dr. ...................... Web: <>
Falls Church, VA 22042-3004

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