CSMA / CD simulation code, Gigabit Ethernet previous versions used to compete for a unified approach, in order to decide on the right of media access, which relates to the backoff algorithm. OPNET environment can be achieved through the experience card.-CSMA/CD simulation code, Gigabit Ethernet previous versions used to compete for a unified approach, in order to decide on the right of media access, which relates to the backoff algorithm. OPNET environment can be achieved through the experience card.