A path-finding algorithm for loop-free routing

A loop-free path-finding algorithm (LPA) is presented; this is the first routing algorithm that eliminates the formation of temporary routing loops without the need for internodal synchronization spanning multiple hops of the specification of complete or variable-size path information. Like other previous algorithms, the LPA operates by specifying the second-to-last hop and distance to each destination; this feature is used to ensure termination. In addition, the LPA uses an interneighbor synchronization mechanism to eliminate temporary routing loops. A detailed proof of the LPAs correctness and loop-freedom property is presented and its complexity is evaluated. The LPAs average performance is compared by simulation with the performance of algorithms representative of the state of the art in distributed routing, namely an ideal link-state (ILS) algorithm, a loop-free algorithm that is based on internodal coordination spanning multiple hops (DUAL) and a path-finding algorithm without the interneighbor synchronization mechanism. The simulation results show that the LPA is a more scalable alternative than DUAL and ILS in terms of the average number of steps, messages, and operations needed for each algorithm to converge after a topology change     

Self-configuring loop-free alternates with high link failure coverage

A change in network topology triggers the re-convergence process of routing protocols. The re-convergence time of current routing protocols (e.g. OSPF) is constrained by the possibility of having transient loops due to the independent calculation of shortest paths between routers affected by a network failure. Several IP Fast-ReRoute (IPFRR) schemes have been developed to pro-actively calculate and install alternate forwarding entries almost instantaneously once a topology update message is received, without causing temporary micro-loops. The IPFRR scheme which has been used most extensively so far makes use of Loop-Free Alternates (LFA). While these are easy to configure, LFAs still require manual configuration, and the resulting ratio of covered link failures is only about 60 to 70 percent. This paper presents a logical extension of the Loop-Free Alternate concept, proposes a self-configuring scheme to populate the corresponding alternate entries, and evaluates the performance of the scheme with respect to coverage, configuration time and path length in a simulation environment.     

A protocol for scalable loop-free multicast routing

In network multimedia applications such as multiparty teleconferencing, users often need to send the same information to several (but not necessarily all) other users. To manage such one-to-many or many-to-many communication efficiently in wide-area internetworks, it is imperative to support and perform multicast routing. Multicast routing sends a single copy of a message from a source to multiple receivers over a communication link that is shared by the paths to the receivers. Loop-freedom is an especially important consideration in multicasting because applications using multicasting tend to be multimedia and bandwidth intensive, and loops in multicast routing duplicate looping packets. We present and verify a new multicast routing protocol, called multicast Internet protocol (MIP), which offers a simple and flexible approach to constructing both group-shared and shortest-paths multicast trees. MIP can be sender-initiated or receiver-initiated or both; therefore, it can be tailored to the particular nature of an application's group dynamics and size. MIP is independent of the underlying unicast routing algorithms used. MIP is robust and adapts under dynamic network conditions (topology or link cost changes) to maintain loop-free multicast routing. Under stable network conditions, MIP has no maintenance or control message overhead. We prove that MIP is loop-free at every instant, and that it is deadlock-free and obtains multicast routing trees within a finite time after the occurrence of an arbitrary sequence of topology or unicast changes     

Distributed, scalable routing based on vectors of link states

We have present a new method for distributed routing in computer networks and internets using link-state information. Link vector algorithms (LVA) are introduced for the distributed maintenance of routing information in large networks and internets. According to an LVA, each router maintains a subset of the topology that corresponds to adjacent links and those links used by its neighbor routers in their preferred paths to known destinations. Based on that subset of topology information, the router derives its own preferred paths and communicates the corresponding link-state information to its neighbors. An update message contains a vector of updates; each such update specifies a link and its parameters. The LVA can be used for different types of routing. The correctness of the LVA is verified for arbitrary types of routing when correct and deterministic algorithms are used to select preferred paths at each router and each router is able to differentiate old updates from new. The LVA are shown to have better performance than the ideal link-state algorithm based on flooding and the distributed Bellman-Ford algorithm     

On-demand coding-aware routing in wireless Mesh networks

Network coding,which exploits the broadcast nature of wireless medium,is an effective way to improve network performance in wireless multi-hop networks,but the first practical wireless network coding system COPE cannot actively detect a route with more coding opportunities and limit the coding structure within two-hop regions.An on-demand coding-aware routing scheme(OCAR)for wireless Mesh networks is proposed to overcome the limitations specified above by actively detecting a route with more coding opportunities along the entire route rather than within two-hop regions.Utilizing more coding opportunities tends to route multiple flows 'close to each other' while avoiding interference requires routing multiple flows 'away from each other'.OCAR achieves a tradeoff by adopting RCAIA as routing metric in route discovery,which is not only coding-aware but also considers both inter and intra flow interference.Simulation results show that,compared with Ad-hoc on-demand distance vecfor routing(AODV)and AODV+COPE,OCAR can find more coding opportunities,thus effectively increase network throughput,reduce end to end delay and alleviate network congestion.     

一种安全的Ad Hoc On-demand路由协议

由于Ad Hoc网络固有的弱点,设计安全、有效的Ad Hoc路由协议是困难的.本文从新的角度设计了一个简单、安全的On-demand路由协议.在路径请求和响应阶段,源节点和目的节点的身份分别被隐藏,只有那些位于目的节点选择的最优路径上的节点可以获得完整的路由信息,从而产生有效的前向和反向路径.同时,一个公开的单向Hash函数可以利用隐藏的路由信息构建单向Hash链用于路由信息的认证,从而不需要预先的共享密钥.在一次路由计算中,只有源节点和目的节点需要进行一次非对称密码运算.     

面向确定性网络的按需智能路由技术

确定性网络需要保证不同应用在时延、丢包率、抖动、吞吐量和可靠性等方面的确定性传输需求。针对应用的差异化、确定性的网络传输需求,提出了一种面向确定性网络的按需智能路由学习框架 OdR,在OdR框架下提出一种基于深度强化学习的按需智能路由算法OdR-TD3,OdR-TD3算法可以根据应用流量的确定性QoS需求生成路由策略,以满足确定性网络应用的需求。通过网络仿真实验评估,在确定性应用的QoS需求达成率上,OdR-TD3算法相较DV算法和SPF算法,具有显著的优势。     

一种基于分时的LEO卫星网络无环路由算法

在分析传统卫星网络路由算法的基础上，提出一种基于分时的LEO卫星网络无环路由算法(DTRA)。针对卫星在各时间片之间进行路由表切换时可能出现的路由环问题，算法采用平滑路由表切换策略消除由于切换前后网络状态信息不一致而产生环路的可能性，保证分组在任何时刻都能够沿无环最短时延路径被转发。同时，DTRA也能够通过使用无环备份路径处理可能出现的链路拥塞、节点失败等突发情况。通过复杂性分析可知，算法只需较小的星上存储开销和星上处理开销，而无需星问通信开销。仿真实验结果也表明算法能够提供数据最优传送，具有较好的端到端时延性能。     

Capacity of interconnected ring communication systems with unique loop-free routing (Corresp.)

{em Capacity} is defined for a given distribution of offered traffic as the maximum rate with which packets can be sent with finite delay through the network by appropriate routing. It is shown how capacity depends on the traffic characteristics and on the topology of ring communication systems interconnected so as to provide unique loop-free routing. First, the traffic conditions are given under which the capacity of a {em single ring} attains its maximum and its minimum. For the case of {em uniform traffic} it is shown that the capacity is equal to twice the minimum capacity. Then it is shown that, for uniform traffic, the capacity relative to a single ring communication system can be increased by as much as33.3or80percent when the stations are split up into two or three separate rings, respectively, interconnected to give unique loop-free routing. Exact formulas are given for the capacity of systems with an arbitrary number of stations split up into an arbitrary number of separate rings interconnected to give unique loop-free routing. Finally, it is shown that connecting {em local rings} through a star network with a central switching node is particularly useful when stations can be segregated into local groups of stations which often communicate with stations from the same local group but only rarely with stations from the other groups. Exact formulas are given to calculate the capacity of such interconnected ring communication systems.     

On-demand SIR and bandwidth-guaranteed routing with transmit power assignment in ad hoc mobile networks

In this paper, we propose a novel on-demand quality-of-service (QoS) routing protocol, SBR [signal-to-interference (SIR) and bandwidth routing], which explicitly fulfills both SIR and bandwidth requirements from different multimedia users in ad hoc mobile networks. With SBR, bandwidth reservation is made by allocating time slots and SIR reservation is ensured by assigning adequate powers at the intermediate nodes between a source and a destination. The power-assignment method used in SBR supports finding routes that satisfy the SIR requirements as well as reduces the level of prevailing interference that necessarily occurs in multiple-access wireless networks. SBR also has a new backup capability of establishing multiple paths, even for a single connection, when the route search cannot find a single path that supports the QoS requirements, which contributes to reducing the probability of call denials in constructing the route due to a lack of suitable paths. Extensive simulations show that SBR significantly reduces the ratio of unsuccessful calls with modest routing overhead.     

On-demand routing and channel assignment in multi-channel mobile ad hoc networks

The capacity of mobile ad hoc networks is constrained by the intra-flow interference introduced by adjacent nodes on the same path, and inter-flow interference generated by nodes from neighboring paths. By assigning orthogonal channels to neighboring nodes, one can minimize both types of interferences and allow concurrent transmissions within the neighborhood, thus improving the throughput and delay performance of the ad hoc network. In this paper, we present three novel distributed channel assignment protocols for multi-channel mobile ad hoc networks. The proposed protocols combine channel assignment with distributed on-demand routing, and only assign channels to active nodes. They are shown to require fewer channels and exhibit lower communication, computation, and storage complexity, compared with existing approaches. Through simulation studies, we show that the proposed protocols can effectively increase throughput and reduce delay, as compared to several existing schemes, thus providing an effective solution to the low capacity problem in multi-hop wireless networks.     

基于节点接入能力的ad hoc网络按需路由协议

基于802.11协议MAC层重传策略,提出一个衡量节点接入能力的参数CAM(capacity of access to medium),以体现节点周围信道的繁忙程度及其抢占信道能力。在此基础上,联合MAC层和网络层进行跨层设计,提出了一个拥塞感知路由CAOR(congestion aware on-demand routing)协议。仿真表明:该协议能够在降低开销的前提下,显著增加网络吞吐量,并降低平均端到端的时延。     

Investigating quality routing link metrics in Wireless Multi-hop Networks

In this paper, we propose a new Quality Link Metric (QLM), “Inverse Expected Transmission Count (InvETX),” in Optimized Link State Routing (OLSR) protocol. Then, we compare performance of three existing QLMs which are based on loss probability measurements: Expected Transmission Count (ETX), Minimum Delay (MD), and Minimum Loss (ML) in Static Wireless Multi-hop Networks (SWMhNs). A novel contribution of this paper is enhancement in conventional OLSR to achieve high efficiency in terms of optimized routing load and routing latency. For this purpose, first we present a mathematical framework, and then to validate this frame work, we select three performance parameters to simulate default and enhanced versions of OLSR. The three chosen performance parameters are throughput, Normalized Routing Load, and End-to-End Delay. From the simulation results, we conclude that adjusting the frequencies of topological information exchange results in high efficiency.     

A link contact duration-based routing protocol in delay-tolerant networks

Delay Tolerant Networks (DTNs) provide message delivery services to users via intermittently connected nodes. In DTNs, routing is one of the most challenging issues since end-to-end connectivity between nodes may not be available most of the time. Although many routing protocols for DTNs have been proposed, they do not achieve satisfactory performance, since they exploit only some of the network characteristics. In this paper, we present a new DTN routing protocol, called the Link Contact Duration-based Routing Protocol (LCD). Like existing protocols, LCD uses the disconnect duration of a link between two nodes to find the routing path with the shortest end-to-end delay. In addition, LCD uses the contact duration of a link and the number of buffered messages to deliver as many messages as possible in a short time. Our simulation results show that LCD has better performance than existing DTN routing protocols.     

一种基于链路稳定的能量有效AODV路由协议

在移动自组网中,减少移动节点电池能量消耗,延长网络总的使用时间,成为路由协议性能优劣的一个很重要的指标.本文介绍了一种关于节点能量估价PCF(Power Cost Function)的计算方法,它动态地反映了节点能量的剩余和使用情况,能够成功找到一条路径上的能量瓶颈节点.并且基于移动预测思想,综合考虑路径的总能耗最小和能量瓶颈节点的PCF两种情况,提出了基于链路稳定的能量有效AODV路由协议E-AODV(An Energy-efficient AODV routing protocol based on link stability).模拟结果表明E-AODV协议比AODV路由协议具有更好的能量效率,它延长了节点的生存时间,提高了数据包的到达率.     

Moralism: mobility prediction with link stability based multicast routing protocol in MANETs

In recent research, link stability is getting tremendous attention in mobile adhoc networks (MANETs), because of several impediments that occur in a reliable and robust network. Link stability metric is used to improve network performance in terms of end-to-end delay, data success delivery ratio (DSDR) and available route time (ART). Energy consumption, bandwidth and communication delay of major concern in ad hoc networks. A high mobility of MANET nodes reduces the reliability of network communication. In a dynamic networks, high mobility of the nodes makes it very difficult to predict the dynamic routing topology and hence cause route/link failures. Multicast in MANETs is an emerging trend that effectively improves the performance while lowering the energy consumption and bandwidth usage. Multicast routing protocol transmits a packet to multicast a group at a given time instant to achieve a better utilization of resources. In this paper, node mobility is considered to map better their movement in the network. So, the links with long active duration time can be identified as a stable link for route construction. Variation in signal strength is used to identify whether the direction of the node is towards or away from estimating node. We consider signal strength as QoS metric to calculate link stability for route construction. Efforts are made to identify the link with highly probable longer lifetime as the best suitable link between two consecutive nodes. We predict the movement time of nodes that define the route path to the node destination. Exata/cyber simulator is used for network simulation. The simulation results of the proposed routing protocol are compared with on-demand multicast routing protocol and E-ODMRP, which works on minimum hop count path. Analysis of our simulation results has shown improvement of various routing performance metrics such as DSDR, ART, routing overhead and packet drop ratio.     

Epidemic routing based on adaptive compression of vectors: efficient low‐delay routing for opportunistic networks based on adaptive compression of vectors

In the study of routing in opportunistic networks, we find that there are some redundant overhead when the existing epidemic‐based routing algorithms exchange summary vectors (SVs) and request vectors (RVs), and store SVs. To address this issue, we propose an efficient low‐delay routing algorithm, epidemic routing based on adaptive compression of vectors (ERACV). Our proposed algorithm adaptively shortens the length of SVs and RVs by compressing the same bit sequences, optimizes the mechanism of exchanging SVs and RVs, and improves the order of transmitting data packets. Theoretical analysis verifies the effectiveness of ERACV in decreasing redundant overhead and packet delay. Simulation results show that ERACV reduces SVs’ storage and control overheads by at least 18.0% and 35.8%, respectively, as well as decreases the average end‐to‐end delay of data packets by more than 2.5%, as compared with epidemic routing algorithm and message transmission control scheme. Copyright © 2013 John Wiley & Sons, Ltd.     

基于连接质量和节点相关度的机会网络路由

提出利用连接质量估计节点间消息成功转发的概率,并证明了节点间相关度越高,消息转发率越高。在此基础上,提出基于连接质量和节点相关度的机会网络路由机制。路由计算节点转发效用值时,综合了连接质量和节点相关度;消息转发时,不断向相对于目的节点转发效用值高的节点转发消息。仿真结果表明,与传统路由相比,在消息送达率相同的前提下,该路由消息延迟更小、消耗的总能量更少。     

低轨卫星星座快速响应链路损毁路由算法

设计高效弹性的卫星路由算法是未来低轨(Low Earth Orbit, LEO)卫星通信技术的一个重要发展方向。为解决低轨卫星星座网络中星间链路发生故障后存在的传输中断和数据安全问题,提出了一种低轨卫星星座快速响应链路损毁路由算法(Quick-response Link Destruction Routing Algorithm for LEO Satellite Constellation, QRLDRA)。QRLDRA以星座可预测拓扑作为星间路由计算基础,增加星地回传路由设计,快速将星间链路异常回传至地面计算中心处理;引入多优先级动态队列,根据节点链路状态调整星间链路不同数据传输的优先级;综合路由计算、路由上注、链路检测等功能,完成对拓扑变化的及时响应。通过仿真实验与传统算法的比较发现,所提算法有效提高了数据端到端传输的成功率,为用户业务服务质量(Quality of Service, QoS)提供了可靠保障。     

一种新型IP数据链网络路由算法模型

针对无线数据链网络,提出了一种新型的基于分层结构的IP路由算法模型,满足至少3种异构数据链网络的集成要求.仿真结果表明,该模型可有效支撑基于链路带宽、传输时延、链路质量等多种QoS的路由算法设计,为无线数据链网络层IP路由协议和算法设计提供了理论框架和实现指导.