A Fundamental Study on Quantitative Methods for Constructing Light-Weight Protocols in High-Speed Networks

本文的研究成果可以分为四类。第一个是高速MAC协议的性能评估，这是研究端到端轻量级协议所必需的。我们分析了DQDB和开槽环的平衡点分析（EPA）。分析了有限缓冲用户的吞吐量和平均分组时延。第二个结果是分析了由高速MAC和轻量级LLC协议组成的两层协议的性能模型。LLC协议被称为快速选择面向连接（FS-CO），也被认为是用于单个层的端到端协议，其中集成了LLC、网络和传输层;它隐式地建立和释放连接。对于卫星网络，我们选择了TDMA-Reservation协议，对于局域网，我们选择了时隙环协议。EPA的研究表明，FS-CO协议在各种流量条件下的性能都优于传统的流量控制协议。第三，研究了基于速率的流量控制方案，该方案在高速网络中是有效的。该方案动态地改变传输速率（包间间隙）取决于数据包队列的长度在缓冲区的distination节点。我们为队列长度设置一个或多个阈值。如果长度超过或福尔斯低于阈值之一，则目的地节点将控制分组发送回源节点以调整传输速率。最后，我们在一个FDDI局域网中测量了TCP和UDP协议下的报文延迟时间。这种测量是为了评估现有传输协议的开销。由此获得的数据在设计轻量级端到端协议中是有用的。

The research results obtained here can be classified into four categories. The first is concerned with performance evaluation of high-speed MAC protocols, which is necessary for studies on end-to-end light-weight protocols. We analyze DQDB and slotted rings by means of the equilibrium point analysis (EPA). The throughput and average packet delay are evaluated for finite-buffered users.The second result is analytical performance modeling of two-layr protocols which consists of a high-speed MAC and a light-weight LLC protocols. The LLC protocol, which is referred to as Fast Select Connection-Oriented (FS-CO), is also regarded as an end-to-end protocol for a single layr into which LLC, network and transport layrs are integrated ; it establishes and releases connections implicitly. As the MAC protocol, we choose TDMA-Reservation for satellite networks and slotted ring for LAN's. It is shown by EPA that the FS-CO outperforms conventional protocols over a wide range of traffic condition.Thirdly, we study rate-based flow control chemes, which is efficient in high-speed networks. The schemes dynamically change the transmission rate (inter-packet gaps) depending on the packet queue length in the buffer of the distination node. We set one or more threshold values for the queue length. If the length exceeds or falls below one of the threshold values, then the destination node sends a control packet back to the source node to adjust the transmission rate. the performance of the schemes is evaluated through simulation for time-varying traflic.Lastly, we measure message delay time in an FDDI LAN under the TCP and UDP protocols. This measurement is taken for the prupose of evaluating overheads of the existing transport protocols. The data thus obtained are useful in designing light-weight end-to-end protocols.