路由表快速查找算法

路由器中路由表查找速度是当前英特网发展的瓶颈之一。归纳了设计中路由表快速查找算法时需考虑的问题,分析并比较了各种典型算法的原理。     

基于并行BP神经网络的路由查找算法

结合Bloom-filter算法和并行反向传播神经网络,提出了一种新的基于并行神经网络的路由查找算法(BFBP)。该算法满足路由查找的需求,只需学习路由条目的网络ID,且易于扩展到IPv6地址查询。研究结果表明,相比于己有的神经网络路由查找方法,该算法需要学习的条目数平均减少了520倍,提高了学习效率,为神经网络应用于路由查找创造了有利条件。     

基于流量分布的高速路由表查找算法

IP路由表查找是实现高性能路由器的主要瓶颈。根据IP业务流量分布特性，在现有的路由表查找技术的基础上，提出了基于流量分布的高速路由表查找算法。     

Link-State-Based Algorithms for Dynamic Routing in All-Optical Networks with Ring Topologies

The increased usage of large bandwidth in optical networks raises the problems of efficient routing to allow these networks to deliver fast data transmission with low blocking probabilities. Due to limited optical buffering in optical switches and constraints of high switching speeds, data transmitted over optical networks must be routed without waiting queues along a path from source to destination. Moreover, in optical networks deprived of wavelength converters, it is necessary for each established path to transfer data from source to destination by using only one wavelength. To solve this NP-hard problem, many algorithms have been proposed for dynamic optical routing like Fixed-Paths Least Congested (FPLC) routing or Least Loaded Path Routing (LLR). This paper proposes two heuristic algorithms based on former algorithms to improve network throughput and reduce blocking probabilities of data transmitted in all-optical networks with regard to connection costs. We also introduce new criteria to estimate network congestion and choose better routing paths. Experimental results in ring networks show that both new algorithms achieve promising performance.     

基于非重叠前缀集合的并行路由查找系统

快速的路由查找机制是高性能路由器设计的关键.最长匹配查找是路由查找的难点所在.本文提出一个并行路由查找系统.它使用一种路由表划分方法,可将路由表中的前缀划分为若干个集合,集合内前缀没有重叠.从而把路由表前缀的最长匹配查找转化为若干个集合内前缀的唯一匹配查找.基于这种方法,本文还提出一个通用的并行路由查找框架,框架适用于大多数路由查找算法.并行查找框架可简化查找算法的设计,提高查找算法的速度.使用二分查找算法,并行查找系统可以达到log₂(2N/B)的查找复杂度 (N为路由表前缀数目,B为大于4的整数).同时,并行查找系统对IPv6也具有很好的扩展性.     

IPv6快速路由查找算法分析与研究

分析了IPv6路由结构的特点,介绍了IPv6中的各种路由查找技术,提出了基于聚集位向量的快速路由查找算法,并对该算法和常用二分查找算法的性能进行了分析比较,实验结果表明该算法较好地提高了查找速度,减少了对内存的消耗.     

基于前缀区间集合的IPv6路由查找算法

对IPv6相关的通用型与特定型路由算法进行了分析,重点研究了以BSR为基础的IPv6路由算法在查找和更新时的不平衡问题,提出了基于前缀区间集合的IPv6路由算法。通过对路由前缀（N）进行范围（K）、集合（M）划分以及更新节点自修复提高查询速度、降低不平衡性的影响,具有O(log2N/K)和O(log2N/K+2M)的查询与更新时间复杂度,空间复杂度为O(K+2N)。实验表明,该算法具有良好的查询性能,降低了更新不平衡性的影响。     

Symmetric routing in DHT overlays

In this paper, we propose to extend the DHT topology to a bidirectional graph to provide a super-peer based lookup algorithm and a scalable search support. We consider routing algorithms for a bidirectional variant of the DHT network and show how the resulting structure extends the search region and provides an efficient resource lookup service at a very little additional cost.     

多维过滤规则无冲突的高速分组分类算法

为了有效地实现防火墙及QoS路由等功能,路由器等网络元素必须能高速地对分组分类.对一维分组分类,已有很多成熟方案,而多维算法由于实现复杂,还没有有效的分类算法.本文对无过滤规则无冲突的数据库进行了研究,提出了基于元组空间多维分组分类算法:元组空间矢量位映射算法.对多维和二维分类在最不利情况下分别进行了性能分析,指出与已有的方案相比,在存贮空间、查找时间等性能上,本文提出的算法是效率最佳的.本文的算法不仅可以由软件实现,也很容易由硬件实现.     

Next generation routers

As the broadband access technologies, such as DSL, cable modem, and gigabit Ethernet, are providing affordable broadband solutions to the Internet from home and the enterprise, it is required to build next generation routers with high-speed interfaces (e.g., 10 or 40 Gb/s) and large switching capacity (e.g., multipetabit). This paper first points out the issues of building such routers, such as memory speed constraint, packet arbitration bottleneck, and interconnection complexity. It then presents several algorithms/architectures to implement IP route lookup, packet classification, and switch fabrics. Some of the functions, such as packet classification, route lookup, and traffic management, can be implemented with emerging network processors that have the advantages of providing flexibility to new applications and protocols, shortening the design cycle and time-to-market, and reducing the implementation cost by avoiding the ASIC approach. Several proposed algorithms for IP route lookup and packet classification are compared in respect to their search/update speeds and storage requirements. Different efficient arbitration schemes for output port contention resolution are presented and analyzed. The paper also surveys various switch architectures of commercial routers and switch chip sets. At the end, it outlines several challenging issues that remain to be researched for next generation routers     

High-speed IP routing with binary decision diagrams based hardware address lookup engine

With a rapid increase in the data transmission link rates and an immense continuous growth in the Internet traffic, the demand for routers that perform Internet protocol packet forwarding at high speed and throughput is ever increasing. The key issue in the router performance is the IP address lookup mechanism based on the longest prefix matching scheme. Earlier work on fast Internet protocol version 4 (IPv4) routing table lookup includes, software mechanisms based on tree traversal or binary search methods, and hardware schemes based on content addressable memory (CAM), memory lookups and the CPU caching. These schemes depend on the memory access technology which limits their performance. The paper presents a binary decision diagrams (BDDs) based optimized combinational logic for an efficient implementation of a fast address lookup scheme in reconfigurable hardware. The results show that the BDD hardware engine gives a throughput of up to 175.7 million lookups per second (Ml/s) for a large AADS routing table with 33 796 prefixes, a throughput of up to 168.6 Ml/s for an MAE-West routing table with 29 487 prefixes, and a throughput of up to 229.3 Ml/s for the Pacbell routing table with 6822 prefixes. Besides the performance of the scheme, routing table update and the scalability to Internet protocol version 6 (IPv6) issues are discussed.     

区域编码标记交换网络性能的研究

着重分析了在RCLS(Region Code Label Switching)体制下路由查表的特点及实现方式,并与IPv4体制进行了对比,构建了两种体制下的查找模型,然后对目前用户所关心的网络性能参数进行了仿真,结果表明,RCLS体制能够获得更好的性能.     

高性能安全路由器中快速路由查找算法的研究与实现

设计快速的路由查找算法是提高路由器整体性能的关键之一.文章在一种基于RAM快速路由查找算法的基础上,根据高性能安全路由器的设计要求,进一步融入Hash链式表以及Trie树查找算法的设计思想,提出了一种可配置的路由查找算法.通过动态配置算法中的评价函数系数,该算法可以适用于多种网络应用环境.     

A novel IP-routing lookup scheme and hardware architecture formultigigabit switching routers

One of the pertinent design issues for new generation IP routers is the route-lookup mechanism. For each incoming IP packet, the IP routing is required to perform a longest-prefix matching on the route lookup in order to determine the packet's next hop. This study presents a fast unicast route-lookup mechanism that only needs tiny SRAM and can be implemented using a hardware pipeline. The forwarding table, based on the proposed scheme, is small enough to fit into a faster SRAM with low cost. For example, a large routing table with 40000 routing entries can be compacted into a forwarding table of 450-470 kbytes costing less than US$30. Most route lookups need only one memory access; no lookup needs more than three memory accesses. When implemented using a hardware pipeline, the proposed mechanism can achieve one routing lookup every memory access. With current 10-ns SRAMs, this mechanism furnishes approximately 100×10⁶ routing lookups/s, which is much faster than any current commercially available routing-lookup scheme     

稀疏城市车载网络中的静态结构动态权重路由

以上海市4 000辆出租车为期两年的GPS数据为依托,设计仅存在于理论意义上的车载网络路由最优算法并对其进行仿真,一方面,最优路由算法的结果揭示了现有路由算法的不足;另一方面,根据最优路由算法的宴际路径特点,设计了基于地图的静态结构动态权重的路由策略来逼近车载网络路由的理论最优性能,这一路由算法相对干传统的地理路由和其变种算法在性能方面有超过50%的提升.     

高速IP路由查找中改善更新性能的方法

现有的高速IP路由查找算法更多地强调路由表的查找,却忽视了路由表的更新。而路由表的更新对整个路由查找算法的性能和实际应用有不可忽视的影响。分段式查找树(Multibittrie)查找算法作为常用的IP路由查找算法,具有算法简单、有效等特点,但是更新速率较慢。作者提出一种在分段式查找树中控制路由表更新时间的方法,此方法能够较大地改善分段式查找树的更新性能。文章对更新性能的改善作了论述。     

SDHT:面向P2P直播系统的高效单跳分布式哈希查找策略

Video data location plays a key role for Peer-to-Peer (P2P) live streaming applications. In this paper, we propose a new one-hop Distributed Hash Table (DHT) lookup framework called Streaming-DHT (SDHT) to provide efficient video data location service. By adopting an enhanced events dissemination mechanism-EDRA+ , the accuracy of routing table at peers can be guaranteed. More importantly, in order to enhance the performance of video data lookup operation without incurring extra overhead, we design a so-called Distributed Index Mapping and Management Mechanism (DIMM) for SDHT. Both analytical modeling and intensive simulation experiments are conducted to demonstrate the effectiveness of SDHT framework. Numerical results show that almost 90% requested video data can be retrieved within one second in SDHT based systems, and SDHT needs only 26% average bandwidth consumption when compared with similar one-hop DHT solutions such as D1HT. This indicates that SDHT framework is an appropriate data lookup solution for time-sensitive network applications such as P2P live streaming.     

改进的TCAM路由更新方法与实现

基于TCAM的硬件路由查找算法能够在一个时钟周期内完成最长前缀匹配．实现快速路由查找和分组转发。但路由表表项的有序性使得更新过程比较复杂从而成为TCAM路由技术发展的瓶颈。根据不同长度前缀表项的分布特性及路由表稳态时的更新规律，优化了路由表的空间分配，并引入了缓冲池的思想．提出了一种改进的路由表更新方法，从而提高路由表更新效率。     

Scalable, Memory Efficient, High-Speed IP Lookup Algorithms

One of the central issues in router performance is IP address lookup based on longest prefix matching. IP address lookup algorithms can be evaluated on a number of metrics—lookup time, update time, memory usage, and to a less important extent, the time to construct the data structure used to support lookups and updates. Many of the existing methods are geared toward optimizing a specific metric, and do not scale well with the ever expanding routing tables and the forthcoming IPv6 where the IP addresses are 128 bits long. In contrast, our effort is directed at simultaneously optimizing multiple metrics and provide solutions that scale to IPv6, with its longer addresses and much larger routing tables. In this paper, we present two IP address lookup schemes—Elevator-Stairs algorithm and logW-Elevators algorithm. For a routing table with$N$prefixes, The Elevator-Stairs algorithm uses optimal$cal O(N)$memory, and achieves better lookup and update times than other methods with similar memory requirements. The logW-Elevators algorithm gives$cal O(log W)$lookup time, where$W$is the length of an IP address, while improving upon update time and memory usage. Experimental results using the MAE-West router with 29 487 prefixes show that the Elevator-Stairs algorithm gives an average throughput of 15.7 Million lookups per second (Mlps) using 459KB of memory, and the logW-Elevators algorithm gives an average throughput of 21.41Mlps with a memory usage of 1259KB.     

Optimized priority based energy efficient routing algorithm for mobile ad hoc networks

Recently more and more research interest focuses on the energy efficient routing in mobile ad hoc networks and many related routing algorithms are reported. In this paper, a new optimized priority based energy efficient routing algorithm is presented and priority is added to the existing routing algorithm according to the residual energy proportion of the nodes. Lower residual energy means lower priority and the nodes with lower priority are less likely to forward packets to other nodes. The algorithm needs no global information of the networks and only a little modification is needed to the existing algorithm, so it is practical to be implemented. The algorithm can improve the performance of routing discovery, routing maintenance and cache management at the same time. Some optimization strategy is taken to reduce the network overhead and the lifetime of the network is much longer and the network with our algorithm can transfer much more effective data. Simulation with NS-2 is done and satisfying results are obtained with this algorithm. The results show that the algorithm is efficient.