Does a Mandatory Price of "Zero" Make Sense for All Carrier and Customer Connections?

Are application domains “customers” of service provider domains, or are app domains “carriers?”  

The definition matters, the Phoenix Center for Advanced Legal & Economic Public Policy Studies argues.

If app domains are customers, then a mandated  “zero price ” (settlement free interconnection regardless of the volume of traffic exchanged) does not square with traditional common carrier thinking about inter-carrier interconnection, which is volume sensitive.

But if app domains are carriers, instead of customers, common carrier regulation also suggests that a mandatory “zero price” for interconnection also violates traditional pricing logic?

Clearly, the bulk of traffic exchanged by app domains and retail customer domains (app providers the former: communications service providers the latter) is downstream from the content domains rather than upstream from the CSP domains, by about a ratio of

6:1, according to Sandvine.