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

这里得到的研究结果可以分为四类。首先是高速MAC协议的性能评估，这是研究端到端轻量级协议所必需的。采用平衡点分析法（EPA）对DQDB和开槽环进行了分析。对有限缓冲用户的吞吐量和平均数据包延迟进行了评估。第二个结果是由一个高速MAC协议和一个轻量级LLC协议组成的两层协议的分析性能建模。LLC协议，被称为快速选择连接导向（FS-CO），也被认为是一个单一的端到端协议，其中集成了LLC、网络和传输层；它隐式地建立和释放连接。作为MAC协议，我们对卫星网络选择TDMA-Reservation协议，对局域网选择槽环协议。EPA表明，FS-CO在广泛的交通条件下优于传统协议。第三，我们研究了在高速网络中有效的基于速率的流量控制方案。该方案根据区分节点缓冲区中的数据包队列长度动态改变传输速率（包间间隙）。我们为队列长度设置一个或多个阈值。如果长度超过或低于其中一个阈值，则目的节点向源节点发送控制报文以调整传输速率。通过对时变交通的仿真，对方案的性能进行了评价。最后，我们测量了TCP和UDP协议下FDDI局域网中的消息延迟时间。采取这种度量是为了评估现有传输协议的开销。由此获得的数据对于设计轻量级的端到端协议非常有用。

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.