Mobile computing: where's the tofu?
Mobile computing: where's the tofu?
复制标题
移动计算：豆腐在哪里？
DOI：
10.1145/583973.583980
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
M. Satyanarayanan
中科院分区：
文献类型：
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作者：
M. Satyanarayanan
另一种描述移动的计算约束影响的方法是检查它们对经典客户端-服务器模型的影响。在这个模型中，少量的可信服务器站点构成了数据的真正家园。可以从大量不受信任的客户端站点高效、安全地访问这些数据。缓存和预读等技术可用于提供良好的性能，而端到端身份验证和加密传输可用于保护安全性。这个模型被证明对可扩展性特别有价值[6]。实际上，客户机-服务器模型将一个大型分布式系统分解为一个变化相对缓慢的小核心，以及一个更大、静态程度更低的客户机外围。从安全和系统管理的角度来看，系统的规模似乎是核心的规模。但从性能和可用性的角度来看，处于外围的用户几乎可以获得独立的服务，应对移动性的限制要求我们重新思考这种模式。客户机和服务器之间的区别可能必须暂时模糊，从而形成图2所示的扩展客户机-服务器模型。客户端的资源限制可能要求通常在客户端上执行的某些操作有时在资源丰富的服务器上执行。相反，为了科普不确定的连接，客户端有时需要模拟服务器的功能。当然，从性能和可用性的角度来看，这些都是对经典客户机-服务器模型的短期偏离。从长远来看，
Another way to characterize the impact of mobile computing constraints is to examine their effect on the classic client-server model. In this model, a small number of trusted server sites constitute the true home of data. Efficient and safe access to this data is possible from a much larger number of untrusted client sites. Techniques such as caching and read-ahead can be used to provide good performance, while end-to-end authentication and encrypted transmission can be used to preserve security. This model has proved to be especially valuable for scalability [6]. In effect, the client-server model decomposes a large distributed system into a small nucleus that changes relatively slowly, and a nmch larger and less static periphery of clients. From the perspectives of security and system administration, the scale of the system appears to be that of the nucleus. But from the perspectives of performance and availability, a user at the periphery receives almost standalone service.Coping with the constraints of mobility requires us to rethink this model. The distinction between clients and servers may have to be temporarily blurred, resulting in the extended client-server model shown in Figure 2. The resource limitations of clients may require certain operations normally perfolrned on clients to sometimes be performed on resource-rich servers. Conversely, the need to cope with uncertain connectivity requires clients to sometimes emulate the functions of a server. These are, of course, short-term deviations from the classic client-server model for purposes of performance and availability. From the longer-term