Reliability, security, scalability and QoS (Quality-of-Service) have become key issues as we envision the future Internet. This paper presents the "Cognitive Packet Network (CPN)" architecture in which intelligent peer-to-peer routing is carried out with the help of "smart packets" based on best-effort QoS goals. Since packetized voice has stringent QoS requirements, we then discuss the choice of a "goal" and "reward" function for this application and present experiments we have conducted for "voice over CPN". Its performance is detailed via several measurements, and the resulting QoS is compared with that of the IP routing protocol under identical conditions showing the gain resulting from the use of CPN.