valley free routing?

Siegel, David David.Siegel at
Wed Mar 5 21:48:26 UTC 2014

I can't think of any circumstances where the business "B" would be content transit traffic between A and C without some form of compensation.  That compensation may not involve payment for bits, however.  In theory, the compensation might be derived from something occurring at the application layer, but even in those cases that business relationship is probably not apparent from looking at prefix advertisements.  Business B is probably using b2b user agents, gre encap or some other method that makes both legs look like independent IP flows to network A and B.

Interesting question, though.


-----Original Message-----
From: William Herrin [mailto:bill at] 
Sent: Wednesday, March 05, 2014 2:08 PM
To: Valdis Kletnieks
Cc: nanog at
Subject: Re: valley free routing?

On Wed, Mar 5, 2014 at 4:00 PM,  <Valdis.Kletnieks at> wrote:
> On Wed, 05 Mar 2014 15:23:55 -0500, William Herrin said:
>> 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.
> Assume 3 providers A B and C, where you have a single-homed customer 
> on A and a single-homed customer on C, and A and C don't peer.  
> Traffic may end up going thorugh an A-B peering and a B-C peering. And 
> whether A-B and B-C are a free peering or a paid transit is a business 
> deal, outside the scope of BGP, unless you want to abuse communities...
> Are A and/or C "bad actors" for not peering? Jury is still out on that one.

Hi Valdis,

It's that business deal I want to hear about. When A-B and B-C are free peering but the traffic goes A-B-C for some reason other than a misconfiguration or deliberate abuse. On or off list, I'd like to know about real-life use cases where folks do this on purpose.

Bill Herrin

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

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