RMTP(reliable multicast transport protocol)是一种通过修复服务器(repair server)本地恢复来提供可靠性的组播协议.对改进的RMTP协议的时延性能进行建模分析.推导了数据包自发送主机发出到成功地被一个随机选择的接收主机接收之间的...RMTP(reliable multicast transport protocol)是一种通过修复服务器(repair server)本地恢复来提供可靠性的组播协议.对改进的RMTP协议的时延性能进行建模分析.推导了数据包自发送主机发出到成功地被一个随机选择的接收主机接收之间的平均时延公式.分析表明,随着丢失率的增长,RMTP的时延性能恶化点将迅速下降;随着每个修复服务器下连接尾链路数量的增加,RMTP的时延性能恶化点也将下降.但是,随着尾链路总数量的增加而保持每个修复服务器连接的尾链路数量不变,RMTP的时延性能的变化很小.仿真结果较好地验证了分析的有效性.展开更多
As a scalable QoS(Quality of Service)architcture,DiffServ(Differentiated Service)mainly consists of two components:taffic conditioning at the edge of the DiffServ domain and simple packet forwarding inside the DiffSer...As a scalable QoS(Quality of Service)architcture,DiffServ(Differentiated Service)mainly consists of two components:taffic conditioning at the edge of the DiffServ domain and simple packet forwarding inside the DiffServ domain.DiffServ has many advantages such as flexbility,scalability and simplicity.But when providing, AF (Assured Forwarding) services ,DiffServ has some problems such as unfairness among aggregated flows or among micro-flows belonging to an aggregated flow.In this paper,a feedback mechanism for AF aggregated flows is proposed to solve this problem.Simulation results show that this mechanism does improve the performance of DiffServ.Firt,it can improve the fairness among aggregated flows and make DiffServ more friendly toward TCP (Transmision Control Protocol)flows.Second,it can decrease the buffer requirements at the congested router and thus obtain lower delay and packet loss rate.Third,it also keeps almost the same link utility as in normal DiffServ,Einally,it is simple and easy to be implemented.展开更多
Most existing multicast protocols adopt a static retransmission scheme(unicast or multicast) to retransmit lost packets.In the mobile multicast environment,static multicast retransmission mode may lead to congestion i...Most existing multicast protocols adopt a static retransmission scheme(unicast or multicast) to retransmit lost packets.In the mobile multicast environment,static multicast retransmission mode may lead to congestion in the receivers' wireless interfaces,while static unicast mode may result in great network load.Both static unicast and multicast retransmission modes will cause a performance loss.This paper logically divides the mobile multicast network into fixed and mobile parts,and focuses on the mobile part.Then this paper analyzes the retransmission costs when multicast or unicast mode is chosen.Two main parameters are used to compare their efficiencies:the average air-interface utilization of each receiver and the average network load.Based on the results of analysis,two new algorithms,called NLPA(Network Load Priority Algorithm)and AUPA(Air-interface Utilization Priority Algorithm)are presented.Finally,simulation results conclude that,with proper parameters,both NLPA and AUPA can dynamically alternate between unicast and multicast retransmission modes acording to the conditions of network and receiver,and avoid congestion in receivers' wireless interfaces as well as great network load,with a better use of network and terminal resources.展开更多
文摘RMTP(reliable multicast transport protocol)是一种通过修复服务器(repair server)本地恢复来提供可靠性的组播协议.对改进的RMTP协议的时延性能进行建模分析.推导了数据包自发送主机发出到成功地被一个随机选择的接收主机接收之间的平均时延公式.分析表明,随着丢失率的增长,RMTP的时延性能恶化点将迅速下降;随着每个修复服务器下连接尾链路数量的增加,RMTP的时延性能恶化点也将下降.但是,随着尾链路总数量的增加而保持每个修复服务器连接的尾链路数量不变,RMTP的时延性能的变化很小.仿真结果较好地验证了分析的有效性.
文摘As a scalable QoS(Quality of Service)architcture,DiffServ(Differentiated Service)mainly consists of two components:taffic conditioning at the edge of the DiffServ domain and simple packet forwarding inside the DiffServ domain.DiffServ has many advantages such as flexbility,scalability and simplicity.But when providing, AF (Assured Forwarding) services ,DiffServ has some problems such as unfairness among aggregated flows or among micro-flows belonging to an aggregated flow.In this paper,a feedback mechanism for AF aggregated flows is proposed to solve this problem.Simulation results show that this mechanism does improve the performance of DiffServ.Firt,it can improve the fairness among aggregated flows and make DiffServ more friendly toward TCP (Transmision Control Protocol)flows.Second,it can decrease the buffer requirements at the congested router and thus obtain lower delay and packet loss rate.Third,it also keeps almost the same link utility as in normal DiffServ,Einally,it is simple and easy to be implemented.
文摘Most existing multicast protocols adopt a static retransmission scheme(unicast or multicast) to retransmit lost packets.In the mobile multicast environment,static multicast retransmission mode may lead to congestion in the receivers' wireless interfaces,while static unicast mode may result in great network load.Both static unicast and multicast retransmission modes will cause a performance loss.This paper logically divides the mobile multicast network into fixed and mobile parts,and focuses on the mobile part.Then this paper analyzes the retransmission costs when multicast or unicast mode is chosen.Two main parameters are used to compare their efficiencies:the average air-interface utilization of each receiver and the average network load.Based on the results of analysis,two new algorithms,called NLPA(Network Load Priority Algorithm)and AUPA(Air-interface Utilization Priority Algorithm)are presented.Finally,simulation results conclude that,with proper parameters,both NLPA and AUPA can dynamically alternate between unicast and multicast retransmission modes acording to the conditions of network and receiver,and avoid congestion in receivers' wireless interfaces as well as great network load,with a better use of network and terminal resources.
