域名解析系统DNS(Domain Name System)是互联网的一项核心服务,用于将域名和IP地址相互映射,使用户不用专门记忆网站的IP,通过域名就可以方便地访问互联网。文中主要介绍了在Linux系统下使用BIND9建立智能DNS系统,来实现安全、高效、低...域名解析系统DNS(Domain Name System)是互联网的一项核心服务,用于将域名和IP地址相互映射,使用户不用专门记忆网站的IP,通过域名就可以方便地访问互联网。文中主要介绍了在Linux系统下使用BIND9建立智能DNS系统,来实现安全、高效、低成本的域名解析服务。在此基础上,结合企业具体情况,研究实现了域名镜像、双主DNS、链路健康探测等功能。最后对动态DNS探测、多数据中心的DNS体系实现进行了展望。展开更多
Network planning, analysis and design are an iterative process aimed at ensuring that a new network service meets the needs of subscribers and operators. During the initial start-up phase, coverage is the big issue an...Network planning, analysis and design are an iterative process aimed at ensuring that a new network service meets the needs of subscribers and operators. During the initial start-up phase, coverage is the big issue and coverage in telecommunications systems is related to the service area where a bare minimum access in the wireless network is possible. In order to guarantee visibility of at least one satellite above a certain satellite elevation, more satellites are required in the constellation to provide Global network services. Hence, the aim of this paper is to develop wide area network coverage for sparsely distributed earth stations in the world. A hybrid geometrical topology model using spherical coordinate framework was devised to provide wide area network coverage for sparsely distributed earth stations in the world. This topology model ensures Global satellite continuous network coverage for terrestrial networks. A computation of path lengths between any two satellites put in place to provide network services to selected cities in the world was carried out. A consideration of a suitable routing decision mechanism, routing protocols and algorithms were considered in the work while the shortest paths as well as the alternate paths between located nodes were computed. It was observed that a particular satellite with the central angle of 27°can provide services into the diameter of the instantaneous coverage distance of 4081.3 Km which is typical of wide area network coverage. This implies that link-state database routing scheme can be applied, continuous global geographical coverage with minimum span, minimum traffic pattern and latency are guaranteed. Traffic handover rerouting strategies need further research. Also, traffic engineering resources such as channel capacity and bandwidth utilization schemes need to be investigated. Satellite ATM network architecture will benefit and needs further study.展开更多
This paper constructs a new spectrum of networks by means of the matrix of link-state ofthe network,which can reveal the characteristics of the correlation between the degrees of the network.Also,the computation of th...This paper constructs a new spectrum of networks by means of the matrix of link-state ofthe network,which can reveal the characteristics of the correlation between the degrees of the network.Also,the computation of this spectrum of networks is usually more feasible and more efficient due tothe much lower order of its matrix of link-state than its adjacent matrix in practice.Some estimatesfor the bounds of the key eigenvalues in the spectrum are obtained,the corresponding inequalities arepresented and proved.For the sake of its application,the authors define spectrum of networks in twoways,and all theorems are given in parallel for both kinds of definition.In addition,the authors finda symmetry in the spectrum,which is relative to the characteristic of structure of its network to someextent.展开更多
针对卫星网络动态环境下的高速信息传输、业务类型差异大等特点,提出一种综合考虑各业务QoS(Quality of Service)指标的可靠性分析方法。在卫星通信网络实际运行周期内,通信系统往往处于逐渐劣化过程中,导致卫星的节点和链路除正常工作...针对卫星网络动态环境下的高速信息传输、业务类型差异大等特点,提出一种综合考虑各业务QoS(Quality of Service)指标的可靠性分析方法。在卫星通信网络实际运行周期内,通信系统往往处于逐渐劣化过程中,导致卫星的节点和链路除正常工作和完全失效外,还存在部分失效的工作状态。本文在链路多状态基础上基于最小路集算法(Minimum Path Set Algorithms,MPSA)在不同业务的QoS指标(时延、带宽和丢包率)约束下,得出满足该业务QoS约束的所有可靠路径集,对路径集中路径进行不交化处理得到网络端-端可靠性。研究结果表明,不同业务由于QoS需求的差异导致网络端-端可靠性不同,所提算法与传统算法相比更加符合实际。由于实际卫星网络环境中会采用端-端并行多路径传输(Multi-Path Transmission,MTP),本文在上述研究的基础上,进一步对多路径的端-端可靠性进行了研究,结果表明多路径数据传输可靠性高。展开更多
针对Zigbee无线传感器网络在移动过程和恶劣环境中严重的丢包率和链路失效问题,通过分析AODVjr算法和AODV多径路由算法(AOMDV),提出了一种基于链路状态感知的Zigbee多径路由算法Link State AwareAOMDV Junior(S-AOMDVjr).S-AOMDVjr算法...针对Zigbee无线传感器网络在移动过程和恶劣环境中严重的丢包率和链路失效问题,通过分析AODVjr算法和AODV多径路由算法(AOMDV),提出了一种基于链路状态感知的Zigbee多径路由算法Link State AwareAOMDV Junior(S-AOMDVjr).S-AOMDVjr算法在路由发现过程中可以根据链路通信质量建立多条路径,路由维护过程中采用AODVjr改进的KEEP ALIVE信息进行维护,该信息包含当前链路的通信质量,当链路质量下降至预警阀值时及时通知源节点切换至备用路径,从而降低由于链路失效造成的路由延时.仿真结果表明与AOMDV、AODVjr算法相比,S-AOMDVjr的平均传输时延有所降低,并提高了分组投递率,从而提高了网络性能.展开更多
文摘域名解析系统DNS(Domain Name System)是互联网的一项核心服务,用于将域名和IP地址相互映射,使用户不用专门记忆网站的IP,通过域名就可以方便地访问互联网。文中主要介绍了在Linux系统下使用BIND9建立智能DNS系统,来实现安全、高效、低成本的域名解析服务。在此基础上,结合企业具体情况,研究实现了域名镜像、双主DNS、链路健康探测等功能。最后对动态DNS探测、多数据中心的DNS体系实现进行了展望。
文摘Network planning, analysis and design are an iterative process aimed at ensuring that a new network service meets the needs of subscribers and operators. During the initial start-up phase, coverage is the big issue and coverage in telecommunications systems is related to the service area where a bare minimum access in the wireless network is possible. In order to guarantee visibility of at least one satellite above a certain satellite elevation, more satellites are required in the constellation to provide Global network services. Hence, the aim of this paper is to develop wide area network coverage for sparsely distributed earth stations in the world. A hybrid geometrical topology model using spherical coordinate framework was devised to provide wide area network coverage for sparsely distributed earth stations in the world. This topology model ensures Global satellite continuous network coverage for terrestrial networks. A computation of path lengths between any two satellites put in place to provide network services to selected cities in the world was carried out. A consideration of a suitable routing decision mechanism, routing protocols and algorithms were considered in the work while the shortest paths as well as the alternate paths between located nodes were computed. It was observed that a particular satellite with the central angle of 27°can provide services into the diameter of the instantaneous coverage distance of 4081.3 Km which is typical of wide area network coverage. This implies that link-state database routing scheme can be applied, continuous global geographical coverage with minimum span, minimum traffic pattern and latency are guaranteed. Traffic handover rerouting strategies need further research. Also, traffic engineering resources such as channel capacity and bandwidth utilization schemes need to be investigated. Satellite ATM network architecture will benefit and needs further study.
基金supported by the Key Project for Fundamental Research of STCSM under Grant No. 06JC14057
文摘This paper constructs a new spectrum of networks by means of the matrix of link-state ofthe network,which can reveal the characteristics of the correlation between the degrees of the network.Also,the computation of this spectrum of networks is usually more feasible and more efficient due tothe much lower order of its matrix of link-state than its adjacent matrix in practice.Some estimatesfor the bounds of the key eigenvalues in the spectrum are obtained,the corresponding inequalities arepresented and proved.For the sake of its application,the authors define spectrum of networks in twoways,and all theorems are given in parallel for both kinds of definition.In addition,the authors finda symmetry in the spectrum,which is relative to the characteristic of structure of its network to someextent.
文摘针对卫星网络动态环境下的高速信息传输、业务类型差异大等特点,提出一种综合考虑各业务QoS(Quality of Service)指标的可靠性分析方法。在卫星通信网络实际运行周期内,通信系统往往处于逐渐劣化过程中,导致卫星的节点和链路除正常工作和完全失效外,还存在部分失效的工作状态。本文在链路多状态基础上基于最小路集算法(Minimum Path Set Algorithms,MPSA)在不同业务的QoS指标(时延、带宽和丢包率)约束下,得出满足该业务QoS约束的所有可靠路径集,对路径集中路径进行不交化处理得到网络端-端可靠性。研究结果表明,不同业务由于QoS需求的差异导致网络端-端可靠性不同,所提算法与传统算法相比更加符合实际。由于实际卫星网络环境中会采用端-端并行多路径传输(Multi-Path Transmission,MTP),本文在上述研究的基础上,进一步对多路径的端-端可靠性进行了研究,结果表明多路径数据传输可靠性高。
文摘针对Zigbee无线传感器网络在移动过程和恶劣环境中严重的丢包率和链路失效问题,通过分析AODVjr算法和AODV多径路由算法(AOMDV),提出了一种基于链路状态感知的Zigbee多径路由算法Link State AwareAOMDV Junior(S-AOMDVjr).S-AOMDVjr算法在路由发现过程中可以根据链路通信质量建立多条路径,路由维护过程中采用AODVjr改进的KEEP ALIVE信息进行维护,该信息包含当前链路的通信质量,当链路质量下降至预警阀值时及时通知源节点切换至备用路径,从而降低由于链路失效造成的路由延时.仿真结果表明与AOMDV、AODVjr算法相比,S-AOMDVjr的平均传输时延有所降低,并提高了分组投递率,从而提高了网络性能.
