An important issue for providing better guarantees of Quality of Service (QoS) to applications is QoS rout-ing. The task of QoS routing is to determine a feasible path that satisfies a set of constraints while maintaining high u-tilization of network resources. For the purpose of achieving the latter objective additional optimality requirementsneed to be imposed. In general, multi-constrained path selection problem is NP-hard so it cannot be exactly solved inpolynomial time. Accordingly heuristics and approximation algorithms with polynomial or pseudo-polynomial timecomplexity are often used to deal with this problem. However, many of these algorithms suffer from either excessivecomputational complexity that cannot be used for online network operation or low performance. Moreover, they gen-erally deal with special cases of the problem (e. g. , two constraints without optimization, one constraint with opti-mization, etc. ). In this paper, the authors propose a new efficient algorithm (EAMCOP) for the problem. Makinguse of efficient pruning policy, the algorithm reduces greatly the size of search space and improves the computationalperformance. Although the proposed algorithm has exponential time complexity in the worst case, it can get verygood performance in real networks. The reason is that when the scale of network increases, EAMCOP controls effi-ciently the size of search space by constraint conditions and prior queue that improves computational efficiency. Theresults of simulation show that the algorithm has good performance and can solve effectively multi-constrained opti-mal path (MCOP) problem.
1 引言目前的Internet网络中,一个会话的数据分组可以通过不同的传输路径到达目的节点,而且不同任务分组公平地共享网络资源,例如,链路带宽、交换缓冲区等。这种结构不能支持多媒体数据和实时数据传输。多媒体业务需求的日益增长推动了现有多媒体应用的进一步发展,这也对新一代网络提出了新的要求。服务质量(QoS,Quality of Services)的概念已经用于定量和定性地描述服务的提供者和服务的接受者之间协商的服务性能。服务质量可以由一些特定的参数来描述,服务的提供者允许服务的使用者在建立连接时对各种服务参数指定希望的、可接受的最低限度值。
及时传输有服务质量(QoS, Quality of Service)要求的多媒体信息对于集成服务的宽带网络发展提出了新的挑战。QoS路由算法的优劣直接影响网络服务质量,而由于链路信息的不及时更新必将造成网络链路信息的非精确性。本文提出了一种在非精确网络状态信息下基于改进的Bellman-Ford算法的随机QoS路由算法Random_link_S0N0,该算法采用随机策略来平衡网络负载和改善网络性能。通过网络模拟器的测试,该算法具有良好的性能指标,同时减少了处理和协议的额外开销。
