valley free routing?

Joel Maslak jmaslak at
Thu Mar 6 01:18:39 UTC 2014

I have worked for the middle network when I was responsible for a
government network - typically we were the middle network.  Logic was it
was good for citizens for us to essentially act like a peering exchange for
certain types of entity (who also typically were government affiliated).
One I can think of was to allow a full mesh of video education between
various institutions - it was the right thing to do for all entities
involved and I facilitated it through the network I was affiliated with.

You might also think about the circumstance of two government
subcontractors working on a common project or interfacing with each other's
systems on behalf of a common customer.  The middle network is paying each
end to connect to the middle but is providing reverse transit between them
(I.E. the end entities are paid to transit the middle!), although the
contracts aren't exactly phrased to say that!  A lot of time, this may be
done with static routes, but it could easily be done with BGP and the end
effect is the same.

I have never heard the term valley free.  Where does it come from?
On Mar 5, 2014 1:25 PM, "William Herrin" <bill at> wrote:

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

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