Analysis of three contention protocols in distributed real-time systems

The probability of a station/node failing to deliver packets before their deadlines, called the probability of dynamic failure, P _dyn, and the ∈-bounded delivery time, which is defined as the time period between the arrival of a packet and its delivery with probability greater than 1-∈, are important performance parameters for the communication subsystems of a distributed real-time system. The parameters are derived and are used to evaluate the token passing protocol, the token ring scheduling protocol, and the P_i-persistent protocol and a priority-based variation thereof. The communication subsystem equipped with different contention protocols as embedded Markov chains is modeled. The probability distributions of the access delay are then derived, from which P_dyn and T_∈ can be calculated. Using P_dyn and I_∈ as indices, the performances of these contention protocols are evaluated and compared over a wide range of traffic