Network-on-chip (NoC) technology enables a new system-on-chip paradigm, the system-on-network-on-chip (SoNoC) paradigm. One of the challenges in designing application-specific networks is modeling the on-chip system behavior and determining on-chip traffic characteristics. A universal object message level model for SoNoC was defined and an object-oriented methodology was developed to imple-ment this model in hardware and software. The model supports "object to core" synthesis and "function in-voking to network" mapping. A case study of an H.263 system verifies the model and methodology. System prototypes are easily built and on-chip traffic can be observed using the SoNoC model to provide real benchmarks for on-chip network design.