Delay analysis of a worst-case model of the MetaRing MAC protocol with local fairness
چکیده
The MetaRing is a Medium Access Control (MAC) protocol for Gigabit LANs and MANs with cells removed by the destination stations (slot reuse). Slot reuse increases the aggregate throughput beyond the capacity of single links but may cause starvation. In order to prevent this the MetaRing MAC protocol includes a fairness mechanism. Two types of fairness algorithms have been proposed: "global" and "local". The MetaRing analyzed in the paper implements the local fairness algorithm specified in [CHE93]. In order to reduce the complexity we have identified a simplified model which can be analytically solved and yet still provides useful information on network performances. This model represents a worst case scenario in which network congestion is stressed, i.e. no station, apart from a specific station (tagged station), ever has an empty queue. The model proposed can be represented by a discrete time discrete state Markov chain of M/G/1-Type and hence the matrix analytical methodology has been used to solve it. Our analysis focuses on the average access delay experienced by the tagged station as a function of the offered load. The results show that average access delay remains bounded for values of offered load less than or equal to 90%. Furthermore, the average access delay depends on the number of interfering stations and on the protocol parameter Qr.