28 prioritization obviously regulates rates—the rates paid by edge providers; it insists that the incremental rate for assured or enhanced quality of service must be zero. Although I cannot claim that the parties’ exposition of the technology is clear to me, it seems evident that the factors affecting quality of delivery to a consumer include not only whatever service characteristics go into promised (and delivered) speed at the consumer end but also circumstances along the route. “Paid peering” (discussed below) would be unintelligible if it were otherwise. With these background points in mind, I turn to the Commission’s treatments of “unjust” and “unreasonable” under §§ 201 and 202. Its principal discussions of the concept have occurred in the context of § 202(a), which bars “any unjust or unreasonable discrimination in charges, practices. . . ,” etc. Section § 201(b), relied on by the Commission here, is very similar but does not include the word “discrimination.” § 201(b) (“All charges, practices, classifications, and regulations for and in connection with such communication service, shall be just and reasonable, and any such charge, practice, classification, or regulation that is unjust or unreasonable is declared to be unlawful . . . .”) The Order’s language explaining its view of § 201(b) doesn’t mention this difference, so evidently the Commission’s interpretation doesn’t rely on it. The Commission’s decisions under § 202 have plainly recognized the permissibility of reasonable rate differences. In In re Dev. of Operational, Tech. & Spectrum Requirements for Meeting Fed., State & Local Pub. Safety Agency Commc'n Requirements Through the Year 2010, 15 F.C.C. Rcd. 16720 (2000), for example, the Commission issued an order declaring that premium charges for prioritized emergency mobile services were not unjust and unreasonable. In full accord with the usual understanding of rate regulation, the