Traditional multi-path routing mechanisms aim to establish complete node or link disjoint paths. However, under some circumstances if multiple paths cannot be established based on the current network topology, the tra...Traditional multi-path routing mechanisms aim to establish complete node or link disjoint paths. However, under some circumstances if multiple paths cannot be established based on the current network topology, the traditional multi-path routing mechanism will degenerate into single path routing mechanism, thus the advantages of multi-path routing cannot be exhibited. To enhance the end-to-end path reliability, an adaptive multi-path routing mechanism with path segment is proposed, in which multi-path can be established at part of the end-to-end path. In this way the reliability of the path can be enhanced. This path segment mechanism can divide the end-to-end path into several short segments, and a parallel forwarding mechanism is proposed for guaranteeing the quality of service of multimedia services over the wireless network. Simulations show that the network performance metrics such as the packet delivery ratio, the end-to-end delay and the number of route discoveries are all improved by using the adaptive multi-path routing mechanism.展开更多
To improve the performance of Ad hoc on-demand multipath distance vector (AOMDV) protocol, we proposed NS-AOMDV which is short for “AOMDV based on node state”. In NS-AOMDV, we introduce node state to improve AOMDV’...To improve the performance of Ad hoc on-demand multipath distance vector (AOMDV) protocol, we proposed NS-AOMDV which is short for “AOMDV based on node state”. In NS-AOMDV, we introduce node state to improve AOMDV’s performance in selecting main path. In route discovery process, the routing update rule calculates the node weight of each path and sorts the path weight by descending value in route list, and we choose the path which has the largest path weight for data transmission. NS-AOMDV also uses the technology of route request (RREQ) packet delay forwarding and energy threshold to ease network congestion, limit the RREQ broadcast storm, and avoid low energy nodes to participate in the establishment of the path. The results of simulation show that NS-AOMDV can effectively improve the networks’packets delivery rate, throughput and normalized routing overhead in the situation of dynamic network topology and heavy load.展开更多
Shutting down a link for the purposes of a scheduled routine maintenance does cause the forwarding path to change. If these changes are not done in a required order will cause not only transient micro loops but also a...Shutting down a link for the purposes of a scheduled routine maintenance does cause the forwarding path to change. If these changes are not done in a required order will cause not only transient micro loops but also an overload in some links. Currently, some ISP operators use a graceful link shutdown procedure by first setting up the Interior Gateway Protocol (IGP) link metric to MAX_METRIC -1 and then shutdown the link. In this paper, we present a Pythagorean Triple Metric Sequence as a method to use to shutdown a link during such network operations. Conducting a link shutdown of any desired link for maintenance purpose is a very delicate duty that requires extreme care to prevent transient loops during such topological changes. We thus wish to demonstrate that there exists a Pythagorean Triple Metric Sequence for any given link that can be used to shutdown a link during the routine maintenance by ISPs.展开更多
As a path vector protocol, Border Gateway Protocol （BGP） messages contain an entire Autonomous System （AS） path to each destination for breaking arbitrary long AS path loops. However, after observing the global ro...As a path vector protocol, Border Gateway Protocol （BGP） messages contain an entire Autonomous System （AS） path to each destination for breaking arbitrary long AS path loops. However, after observing the global routing data from RouteViews, we find that BGP AS Path Looping （BAPL） behavior does occur and in fact can lead to multi-AS forwarding loops in both IPv4 and IPv6. The number and ratio of BAPLs in IPv4 and IPv6 on a daily basis from August 1,2011 to August 31, 2015 are analyzed. Moreover, the distribution of BAPLs among duration and loop length in IPv4 and IPv6 are also studied. Several possible explanations for BAPL are discussed in this paper. Private AS Number Leaking （PANL） has contributed to 0.20% of BAPLs in IPv4, and at least 1.76% of BAPLs in IPv4 were attributed to faulty configurations and malicious attacks. Valid explanations, including networks of multinational companies, preventing particular AS from accepting routes, also can lead to BAPLs. Motivated by the large number of PANLs that contribute to BAPLs, we also study the number and the ratio of PANLs per day in the 1492 days. The distribution of the private AS numbers in all of the PANLs is concentrated, and most of them are located in the source of the AS paths. The majority of BAPLs resulted from PANLs endure less than one day, and the number of BAPLs which are caused by two or more leaked private ASes are much larger than that of BAPLs which are caused by one leaked private AS. We explain for this phenomenon and give some advices for the operators of ASes.展开更多
基金supported by the Hi-Tech Research and Development Program of China (2008AA01A322)the National Natural Science Foundation of China (60772109)
文摘Traditional multi-path routing mechanisms aim to establish complete node or link disjoint paths. However, under some circumstances if multiple paths cannot be established based on the current network topology, the traditional multi-path routing mechanism will degenerate into single path routing mechanism, thus the advantages of multi-path routing cannot be exhibited. To enhance the end-to-end path reliability, an adaptive multi-path routing mechanism with path segment is proposed, in which multi-path can be established at part of the end-to-end path. In this way the reliability of the path can be enhanced. This path segment mechanism can divide the end-to-end path into several short segments, and a parallel forwarding mechanism is proposed for guaranteeing the quality of service of multimedia services over the wireless network. Simulations show that the network performance metrics such as the packet delivery ratio, the end-to-end delay and the number of route discoveries are all improved by using the adaptive multi-path routing mechanism.
文摘To improve the performance of Ad hoc on-demand multipath distance vector (AOMDV) protocol, we proposed NS-AOMDV which is short for “AOMDV based on node state”. In NS-AOMDV, we introduce node state to improve AOMDV’s performance in selecting main path. In route discovery process, the routing update rule calculates the node weight of each path and sorts the path weight by descending value in route list, and we choose the path which has the largest path weight for data transmission. NS-AOMDV also uses the technology of route request (RREQ) packet delay forwarding and energy threshold to ease network congestion, limit the RREQ broadcast storm, and avoid low energy nodes to participate in the establishment of the path. The results of simulation show that NS-AOMDV can effectively improve the networks’packets delivery rate, throughput and normalized routing overhead in the situation of dynamic network topology and heavy load.
文摘Shutting down a link for the purposes of a scheduled routine maintenance does cause the forwarding path to change. If these changes are not done in a required order will cause not only transient micro loops but also an overload in some links. Currently, some ISP operators use a graceful link shutdown procedure by first setting up the Interior Gateway Protocol (IGP) link metric to MAX_METRIC -1 and then shutdown the link. In this paper, we present a Pythagorean Triple Metric Sequence as a method to use to shutdown a link during such network operations. Conducting a link shutdown of any desired link for maintenance purpose is a very delicate duty that requires extreme care to prevent transient loops during such topological changes. We thus wish to demonstrate that there exists a Pythagorean Triple Metric Sequence for any given link that can be used to shutdown a link during the routine maintenance by ISPs.
基金Supported by the National Basic Research Program of China under Grant No.2003CB3148020(国家重点基础研究发展计划(973))the National Natural Science Foundation of China under Grant No.90204005(国家自然科学基金)
基金supported by the National Natural Science Foundation of China(Nos.61772307 and 61161140454)the National Key Basic Research and Development(973) Program of China(Nos.2013CB329105 and 2009CB320500)
文摘As a path vector protocol, Border Gateway Protocol （BGP） messages contain an entire Autonomous System （AS） path to each destination for breaking arbitrary long AS path loops. However, after observing the global routing data from RouteViews, we find that BGP AS Path Looping （BAPL） behavior does occur and in fact can lead to multi-AS forwarding loops in both IPv4 and IPv6. The number and ratio of BAPLs in IPv4 and IPv6 on a daily basis from August 1,2011 to August 31, 2015 are analyzed. Moreover, the distribution of BAPLs among duration and loop length in IPv4 and IPv6 are also studied. Several possible explanations for BAPL are discussed in this paper. Private AS Number Leaking （PANL） has contributed to 0.20% of BAPLs in IPv4, and at least 1.76% of BAPLs in IPv4 were attributed to faulty configurations and malicious attacks. Valid explanations, including networks of multinational companies, preventing particular AS from accepting routes, also can lead to BAPLs. Motivated by the large number of PANLs that contribute to BAPLs, we also study the number and the ratio of PANLs per day in the 1492 days. The distribution of the private AS numbers in all of the PANLs is concentrated, and most of them are located in the source of the AS paths. The majority of BAPLs resulted from PANLs endure less than one day, and the number of BAPLs which are caused by two or more leaked private ASes are much larger than that of BAPLs which are caused by one leaked private AS. We explain for this phenomenon and give some advices for the operators of ASes.
