The M/G/1 queueing system with multiclass customer arrivals, fixed feedback, and first come first served policy is considered, where different classes of customers have different arrival rates, service-time distributions, and feedback numbers. The joint probabifity generation function of queue size of each class and the Laplace-Stieltjes transform of the total sojourn time of a customer in each class are presented, which extended the results obtained by Choi B D. The mean queue size of each class and mean total sojourn time of a customer in each class are obtained with this result. The results can be used in computer and communication networks for their performance analysis.
After analyzing the features of the Parlay application server（AS）, which provides many services with different time constraints in the next generation network（NGN）, a selfadapted overload control algorithm implemented in Parlay AS is proposed. In this algorithm, the service process module in parlay AS uses the earliest deadline first （EDF） serving rule to serve messages, and the overload control mechanism, using the Leaky Bucket algorithm to control message flows, is triggered by estimating the queue waiting time of a newly arriving message. By simulation it shows that this algorithm is a simple, easy-to-use, and available algorithm.
针对IMS(IP Multimedia Subsystem)中已注册用户的重注册过程,提出了一种改进的快速重注册方法。由于已注册用户的UE(User Equipment)已经记录归属地S-CSCF(Serving-Call Session Control Function)的地址信息,因此在重注册过程中,通过在REGISTER消息中携带S-CSCF的路由信息,让REGISTER消息直接从拜访地的P-CSCF(Proxy-Call Session Control Function)转发到归属地的S-CSCF,可以有效地减少重注册延时。分析结果显示,改进的快速重注册过程要优于标准重注册过程和已有的一些改进过程。同时,它对网络的改动较小,容易实现。
