Networks communication offer a whole of services very diversified as well for industrialists,banks, research and recently in medicine and for remote control. To this large useof networks are added constraints of performances, safety and quality of service which servicesuppliers must respect. Thus, the study of networks performances and their precise modelingare important steps to evaluate the several links influences on the data which cross transmissionlines. In order to evaluate the influence of the communication networks on data transmission,we propose first to model and then to study a TCP/IP transmission line subjected to congestioncontrol protocols and merged in the Internet external environment. The tool of modeling usedis hybrid Petri nets. A model was established thanks to which all dynamics can be observed atall the levels of transmission (the buffers load, flows decrease at the entry of the routers, flowsseparation in routers, priorities, data storage, delays, losses, etc). This detailed model also allowedus to visualize what are the effects of the line and protocols parameters changes on thetransmission evolution: a large simulations panel was thus carried out in order to visualize thesevarious performances. At last, a work of losses detection time improvement was carried out.
