Software-defined networking(SDN)makes network agile and flexible due to its programmable approach.An extensive network has multiple domains in SDN for the scalability and performance of the network.However,the inter-d...Software-defined networking(SDN)makes network agile and flexible due to its programmable approach.An extensive network has multiple domains in SDN for the scalability and performance of the network.However,the inter-domain link is also crucial for the stability of the entire network on the data plane layer.More than one inter-domain connection enhances the scalability of the data plane layer.However,it faces a reachability problem with the principal root,which causes forwarding loops and packet drops in the network,thereby degrading network performance.The proposed solution is a multiple controller architecture;however,this approach increases the complexity and affects network performance.Thus,in this study,we propose a framework that avoids forwarding loops and packet drops without the synchronization of multiple-domain controllers in the network using an avoid loop with test packet scheme.Moreover,we collect the link status for improved routing and load balancing for the upcoming flow across inter-domain links to prevent congestion and increase throughput in real time.Our proposed methodology can significantly reduce the controller workload against multiple controller architecture,minimize flow setup latency,and improve throughput.展开更多
During convergence,after a link state change in traditional networks with a distributed control plane,packets may get caught in transient forwarding loops.Such loops can be avoided by imposing a certain order among th...During convergence,after a link state change in traditional networks with a distributed control plane,packets may get caught in transient forwarding loops.Such loops can be avoided by imposing a certain order among the routers in updating their forwarding information bases(FIBs),but it requires some form of coordination among routers.As an alternative,a progressive link metric increment method has been proposed for loop-free forwarding without ordered FIB updates,but it takes longer to converge to the target state.In this paper,we show that the order of updates rarely matters for loop-free convergence when the failure inference-based fast reroute(FIFR)scheme with interface-specific forwarding is employed for dealing with link failures.The key insight is to have each router install the traditional interface-independent forwarding entries as soon as they are recomputed during convergence and install the recomputed interface-specific backwarding entries post-convergence.Our evaluation of 280 real and random topologies confirms that the order of updates does not matter with the proposed approach for 17336 out of 17339 links in those topologies.To handle such rare cases where the order matters,it can be coupled with progressive link metric increments to ensure loop-freedom with unordered FIB updates.Thus,the proposed approach,referred to as FIFR++,makes it possible to achieve disruption-free fast convergence and fast reroute without requiring any modification to the IP datagram and without needing any coordination between routers.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The authors are grateful to the University of Malakand and University ofMalaya for providing fund for this project.The authors are grateful to the Taif University Researchers Supporting Project(number TURSP-2020/36),Taif University,Taif,Saudi ArabiaThis research work was also partially supported by the Faculty of Computer Science and Information Technology,University of Malaya,under Postgraduate Research Grant PG035-2016A.
文摘Software-defined networking(SDN)makes network agile and flexible due to its programmable approach.An extensive network has multiple domains in SDN for the scalability and performance of the network.However,the inter-domain link is also crucial for the stability of the entire network on the data plane layer.More than one inter-domain connection enhances the scalability of the data plane layer.However,it faces a reachability problem with the principal root,which causes forwarding loops and packet drops in the network,thereby degrading network performance.The proposed solution is a multiple controller architecture;however,this approach increases the complexity and affects network performance.Thus,in this study,we propose a framework that avoids forwarding loops and packet drops without the synchronization of multiple-domain controllers in the network using an avoid loop with test packet scheme.Moreover,we collect the link status for improved routing and load balancing for the upcoming flow across inter-domain links to prevent congestion and increase throughput in real time.Our proposed methodology can significantly reduce the controller workload against multiple controller architecture,minimize flow setup latency,and improve throughput.
文摘During convergence,after a link state change in traditional networks with a distributed control plane,packets may get caught in transient forwarding loops.Such loops can be avoided by imposing a certain order among the routers in updating their forwarding information bases(FIBs),but it requires some form of coordination among routers.As an alternative,a progressive link metric increment method has been proposed for loop-free forwarding without ordered FIB updates,but it takes longer to converge to the target state.In this paper,we show that the order of updates rarely matters for loop-free convergence when the failure inference-based fast reroute(FIFR)scheme with interface-specific forwarding is employed for dealing with link failures.The key insight is to have each router install the traditional interface-independent forwarding entries as soon as they are recomputed during convergence and install the recomputed interface-specific backwarding entries post-convergence.Our evaluation of 280 real and random topologies confirms that the order of updates does not matter with the proposed approach for 17336 out of 17339 links in those topologies.To handle such rare cases where the order matters,it can be coupled with progressive link metric increments to ensure loop-freedom with unordered FIB updates.Thus,the proposed approach,referred to as FIFR++,makes it possible to achieve disruption-free fast convergence and fast reroute without requiring any modification to the IP datagram and without needing any coordination between routers.
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.
