在DTN中,节点没有长时间端到端的链接,所以为了在长时间间歇性链接的环境下提供可靠的数据传输,就需要中继节点来进行数据包的存储和转发。充足的缓存空间和能源是保证DTN网络正常运行的关键,而DTN网络节点的分散性使此条件很难实现,因...在DTN中,节点没有长时间端到端的链接,所以为了在长时间间歇性链接的环境下提供可靠的数据传输,就需要中继节点来进行数据包的存储和转发。充足的缓存空间和能源是保证DTN网络正常运行的关键,而DTN网络节点的分散性使此条件很难实现,因此,提出一种基于分组的路由协议(group based protocol for DTN,GBP),它只通过本地信息引导数据包副本到达目的节点,旨在传播少量数据包来减少网络开销。先介绍了GBP协议的原理,然后用ONE(opportunistic network environment)仿真软件对Epidemic协议,Spray and Wait协议,PRoPHET协议,MaxProp协议和GBP协议进行仿真对比,在交付成本、成功投递率、网络平均延时3个方面进行对比分析,得出GBP协议具有更好的性能。最后指出了存在的不足并提出改进措施。展开更多
DTN(delay tolerant network)网络的特点及其采用的保管传输机制使得DTN极易耗尽其有限的网络资源(缓存、带宽等),从而导致网络拥塞,降低网络性能。针对这个问题,在应用增强型PROPHET(probabilistic routing protocol using history of ...DTN(delay tolerant network)网络的特点及其采用的保管传输机制使得DTN极易耗尽其有限的网络资源(缓存、带宽等),从而导致网络拥塞,降低网络性能。针对这个问题,在应用增强型PROPHET(probabilistic routing protocol using history of encounters and transitivity)路由算法的基础上,给出了一种基于归一化混合参数的缓存管理策略。应用这种缓存管理策略的DTN网络会优先丢弃归一化混合参数小的消息,以使节点获得足够接收新消息的缓存空间,从而有效地缓解拥塞。仿真结果表明,基于归一化混合参数的缓存管理策略在消息递交率、开销率及平均时延几个方面的性能表现优于应用传统缓存管理策略。展开更多
Vehicular ad hoc networks (VANETs) are a new emerging recently developed advanced technology that allows a wide group of applications related to providing more safety on roads, more convenience for passengers, self-dr...Vehicular ad hoc networks (VANETs) are a new emerging recently developed advanced technology that allows a wide group of applications related to providing more safety on roads, more convenience for passengers, self-driven vehicles, and intelligent transportation systems (ITS). There are various routing protocol categories used in VANETs, like unicast, multicast, and broadcast protocols. In unicast position-based protocols, the routing decisions are based on the geographic position of the vehicles. This does not require establishment or maintenance of routes but needs location services to determine the position of the destination. Non-delay-tolerant network protocols (non-DTN), also identified as minimum delay protocols, are aimed at minimizing the delivery time of the information. Delay-tolerant protocols (DTN) are used in a variety of operating environments, including those that are subject to failures and interruptions and those with high delay, such as VANETs. This paper discusses the comparison between non-DTN and DTN routing protocols belonging to the unicast delay-tolerant position-based category. The comparison was conducted using the NS2 simulator, and the simulations of three non-DTN routing protocols and three DTN routing protocols were recorded. Simulation results show that the DTN routing protocols outperform in delivery ratio compared to the non-DTN routing protocols, but they lead to more average delay due to buffering, the processing algorithm, and priority calculation. In conclusion, non-DTN protocols are more suitable for the city environment since the distance between nodes is relatively smaller and the variations in the network topology are slower than they are on highways. On the other hand, DTN protocols are more suitable for highways due to the buffering of packets until a clear route to destination is available.展开更多
文摘在DTN中,节点没有长时间端到端的链接,所以为了在长时间间歇性链接的环境下提供可靠的数据传输,就需要中继节点来进行数据包的存储和转发。充足的缓存空间和能源是保证DTN网络正常运行的关键,而DTN网络节点的分散性使此条件很难实现,因此,提出一种基于分组的路由协议(group based protocol for DTN,GBP),它只通过本地信息引导数据包副本到达目的节点,旨在传播少量数据包来减少网络开销。先介绍了GBP协议的原理,然后用ONE(opportunistic network environment)仿真软件对Epidemic协议,Spray and Wait协议,PRoPHET协议,MaxProp协议和GBP协议进行仿真对比,在交付成本、成功投递率、网络平均延时3个方面进行对比分析,得出GBP协议具有更好的性能。最后指出了存在的不足并提出改进措施。
文摘DTN(delay tolerant network)网络的特点及其采用的保管传输机制使得DTN极易耗尽其有限的网络资源(缓存、带宽等),从而导致网络拥塞,降低网络性能。针对这个问题,在应用增强型PROPHET(probabilistic routing protocol using history of encounters and transitivity)路由算法的基础上,给出了一种基于归一化混合参数的缓存管理策略。应用这种缓存管理策略的DTN网络会优先丢弃归一化混合参数小的消息,以使节点获得足够接收新消息的缓存空间,从而有效地缓解拥塞。仿真结果表明,基于归一化混合参数的缓存管理策略在消息递交率、开销率及平均时延几个方面的性能表现优于应用传统缓存管理策略。
文摘Vehicular ad hoc networks (VANETs) are a new emerging recently developed advanced technology that allows a wide group of applications related to providing more safety on roads, more convenience for passengers, self-driven vehicles, and intelligent transportation systems (ITS). There are various routing protocol categories used in VANETs, like unicast, multicast, and broadcast protocols. In unicast position-based protocols, the routing decisions are based on the geographic position of the vehicles. This does not require establishment or maintenance of routes but needs location services to determine the position of the destination. Non-delay-tolerant network protocols (non-DTN), also identified as minimum delay protocols, are aimed at minimizing the delivery time of the information. Delay-tolerant protocols (DTN) are used in a variety of operating environments, including those that are subject to failures and interruptions and those with high delay, such as VANETs. This paper discusses the comparison between non-DTN and DTN routing protocols belonging to the unicast delay-tolerant position-based category. The comparison was conducted using the NS2 simulator, and the simulations of three non-DTN routing protocols and three DTN routing protocols were recorded. Simulation results show that the DTN routing protocols outperform in delivery ratio compared to the non-DTN routing protocols, but they lead to more average delay due to buffering, the processing algorithm, and priority calculation. In conclusion, non-DTN protocols are more suitable for the city environment since the distance between nodes is relatively smaller and the variations in the network topology are slower than they are on highways. On the other hand, DTN protocols are more suitable for highways due to the buffering of packets until a clear route to destination is available.
