基于星形网实现交换式多兆位数据服务（SMDS）的研究

【作者】 于萌；

【导师】 逯昭义；

【作者基本信息】 青岛大学 ， 计算机软件与理论， 2007， 硕士

【摘要】 交换式多兆位数据服务(SMDS)是一种高速、无连接的分组交换服务，可接续大量的分布资源，在互联的LAN、工作站和计算机系统之间进行高速分组交换，并且具有吞吐量大和传输延迟小的特点，能够在任意类型的网络上透明实现，但是目前支持SMDS的网络是IEEE802.6 DQDB(分布式队列双总线)网络。虽然应用DQDB实现SMDS的网络技术已经相当成熟，但是本课题在分析SMDS体系结构和DQDB协议后发现，由于DQDB协议自身的不完善，以及在综合业务网络环境下对超大信息量服务质量(QoS)的要求不断提高，SMDS服务网络的双总线结构明显不能完全适应。为此，亟待对SMDS网络协议进行改进。比较了各种网络拓扑结构后，本文提出了一种性能更优越的网络系统，以双星网替代双总线的DQDB来实现SMDS。由于多星网(包括双星网)支持的SMDS服务对于任意的猝发信息都能在尽可能短的时间内让其通过中心结点，从而尽可能快速地通过以使空闲出交换通道，让后续信息畅通。从理论上讲，这种情况相当于运行在轻负载状态下。为了评价该系统的性能，文章首次在SMDS所要求的条件——轻负载条件下，对双星网支持的SMDS进行了解析评价和模拟实验。模拟实验表明，当用多星网替代DQDB实现SMDS服务时，能比较理想地交换猝发信息，更好地为综合业务网络服务。这一问题的解决为多星网应用于SMDS的设计提供了理论依据。更多还原

【Abstract】 Switched Multi-megabit Data Service (SMDS) is a high-speed, connectionless, packet switched, network service that operates over public data networks. It is intended to meet this emerging demand for high throughput and low delay between customers’ LANs, computer systems, and advanced work stations. It can be implemented transparently over any type of network, but the IEEE P802.6 Distributed Queue Dual Bus (DQDB) was chosen as the basis for SMDS Interface Protocols at present.Although the technology of DQDB SMDS is already quite to be mature, we analyze DQDB agreement and find that DQDB SMDS has some insufficiencies because of DQDB agreement being imperfect and the request of quality of service being unceasingly enhanced in the integrated service network. Therefore, there is need for improvement in the SMDS network agreement. A new network system that would have better properties is presented in this paper—the double-star network.SMDS that is supported by the multi-star network (including the double-star network) can make accident information go through the central point in very short time so that obtains the idle exchange channel as soon as possible. The double-star network is regarded as operating under the condition of light load in this kind of situation. For evaluating the performance of the new system, the mathematical modeling of the system is studied under the condition of light load, which is requested in SMDS, for the first time in this paper. The simulation experiment shows that the double-star network could successfully exchange accident information and expand the system to serve for the synthesis service network when it replaces DQDB to implement SMDS. The result of this paper can give academic reference value to multi-star network applicable to SMDS.更多还原