随着P2P分布式存储的研究深入,处在不同网络的节点间建立连接受到网络地址转换(network address translator,NAT)限制.现有的UDP对NAT的简单穿越(simple traversal of UDP through NAT,STUN)方案,不能满足P2P分布式存储对数据传输质量...随着P2P分布式存储的研究深入,处在不同网络的节点间建立连接受到网络地址转换(network address translator,NAT)限制.现有的UDP对NAT的简单穿越(simple traversal of UDP through NAT,STUN)方案,不能满足P2P分布式存储对数据传输质量的要求,并且由于对称型NAT的广泛使用,节点间数据传输必须经过服务器中继转发,中继服务器成为系统瓶颈.提出采用基于UDP的数据传输(UDP-based data transfer,UDT)协议的改进STUN方案,可以保证数据传输可靠性,同时基于端口预测的NAT穿越策略,不需要服务器中继即可实现在对称型NAT后的节点间建立P2P直连.展开更多
NAT(网络地址转换)设备的出现有效缓解了IPv4地址的不足问题,但同时限制了很多P2P(点对点)应用软件的使用。目前由于NAT设备的复杂性以及最新STUN(Session Traversal Utilities for NAT)协议的出现,造成了很多早期的TCP穿越方案不再适...NAT(网络地址转换)设备的出现有效缓解了IPv4地址的不足问题,但同时限制了很多P2P(点对点)应用软件的使用。目前由于NAT设备的复杂性以及最新STUN(Session Traversal Utilities for NAT)协议的出现,造成了很多早期的TCP穿越方案不再适用。为了更有效地穿越现有的NAT,基于最新STUN协议和NAT类型分类方法,借助端口预测技术,文章提出TCP穿越NAT的解决方案,并解决hairpin问题。展开更多
The effect that climatic changes can exert on parasitic interactions represents a multifactor problem whose results are difficult to predict. The actual impact of changes will depend on their magnitude and the physiol...The effect that climatic changes can exert on parasitic interactions represents a multifactor problem whose results are difficult to predict. The actual impact of changes will depend on their magnitude and the physiological tolerance of affected organisms. When the change is considered extreme （i.e. unusual weather events that are at the extremes of the historical distribution for a given area）, the probability of an alteration in an organisms＇ homeostasis increases dramatically. However, factors determining the altered dynamics of host-parasite interactions due to an extreme change are the same as those acting in response to changes of lower magnitude. Only a deep knowledge of these factors will help to produce more accurate predictive models for the effects of extreme changes on parasitic interactions. Extreme environmental conditions may affect pathogens directly when they include free-living stages in their life-cycles and indirectly through reduced resource availability for hosts and thus reduced ability to produce efficient anti-parasite defenses, or by effects on host density affecting transmission dynamics of diseases or the frequency of intraspecific contact. What are the consequences for host-parasite interactions？ Here we summarize the present knowledge on three principal factors in determining host-parasite associations; biodiversity, population density and immunocompetence In addition, we analyzed examples of the effects of environmental alteration of anthropogenic origin on parasitic systems because the effects are analogous to that exerted by an extreme climatic change [Current Zoology 57 （3）： 390405, 2011].展开更多
文摘随着P2P分布式存储的研究深入,处在不同网络的节点间建立连接受到网络地址转换(network address translator,NAT)限制.现有的UDP对NAT的简单穿越(simple traversal of UDP through NAT,STUN)方案,不能满足P2P分布式存储对数据传输质量的要求,并且由于对称型NAT的广泛使用,节点间数据传输必须经过服务器中继转发,中继服务器成为系统瓶颈.提出采用基于UDP的数据传输(UDP-based data transfer,UDT)协议的改进STUN方案,可以保证数据传输可靠性,同时基于端口预测的NAT穿越策略,不需要服务器中继即可实现在对称型NAT后的节点间建立P2P直连.
文摘NAT(网络地址转换)设备的出现有效缓解了IPv4地址的不足问题,但同时限制了很多P2P(点对点)应用软件的使用。目前由于NAT设备的复杂性以及最新STUN(Session Traversal Utilities for NAT)协议的出现,造成了很多早期的TCP穿越方案不再适用。为了更有效地穿越现有的NAT,基于最新STUN协议和NAT类型分类方法,借助端口预测技术,文章提出TCP穿越NAT的解决方案,并解决hairpin问题。
文摘The effect that climatic changes can exert on parasitic interactions represents a multifactor problem whose results are difficult to predict. The actual impact of changes will depend on their magnitude and the physiological tolerance of affected organisms. When the change is considered extreme （i.e. unusual weather events that are at the extremes of the historical distribution for a given area）, the probability of an alteration in an organisms＇ homeostasis increases dramatically. However, factors determining the altered dynamics of host-parasite interactions due to an extreme change are the same as those acting in response to changes of lower magnitude. Only a deep knowledge of these factors will help to produce more accurate predictive models for the effects of extreme changes on parasitic interactions. Extreme environmental conditions may affect pathogens directly when they include free-living stages in their life-cycles and indirectly through reduced resource availability for hosts and thus reduced ability to produce efficient anti-parasite defenses, or by effects on host density affecting transmission dynamics of diseases or the frequency of intraspecific contact. What are the consequences for host-parasite interactions？ Here we summarize the present knowledge on three principal factors in determining host-parasite associations; biodiversity, population density and immunocompetence In addition, we analyzed examples of the effects of environmental alteration of anthropogenic origin on parasitic systems because the effects are analogous to that exerted by an extreme climatic change [Current Zoology 57 （3）： 390405, 2011].
