标题： 增量与优化的网络设计 显示英文标题

标题： Incremental Versus Optimized Network Design

摘要： 尽管网络拓扑设计问题通常被研究为一种“从零开始”的优化问题，但在实际中，大多数服务提供商和企业网络都是随着时间的推移逐步设计的。这个进化过程是由底层参数和约束（“环境”）的变化驱动的，并且旨在最小化每次环境变化后的修改成本。在本文中，我们首先提出了增量设计方法（三种变体），并将其与更传统的优化设计方法进行了比较，后者的目标是使总网络成本最小化。我们在两种网络扩展模型（随机和渐进）下评估了增量设计的成本开销和可演化性，从成本、拓扑相似性、延迟和鲁棒性等方面比较了增量网络和优化网络。我们发现，尽管增量设计有一些成本开销，但这种开销不会随着网络规模的增长而增加。此外，只要网络扩展因子小于临界值，演化现有网络比“从零开始”设计网络要便宜。 显示英文摘要

摘要： Even though the problem of network topology design is often studied as a "clean-slate" optimization, in practice most service-provider and enterprise networks are designed incrementally over time. This evolutionary process is driven by changes in the underlying parameters and constraints (the "environment") and it aims to minimize the modification cost after each change in the environment. In this paper, we first formulate the incremental design approach (in three variations), and compare that with the more traditional optimized design approach in which the objective is to minimize the total network cost. We evaluate the cost overhead and evolvability of incremental design under two network expansion models (random and gradual), comparing incremental and optimized networks in terms of cost, topological similarity, delay and robustness. We find that even though incremental design has some cost overhead, that overhead does not increase as the network grows. Also, it is less costly to evolve an existing network than to design it "from scratch" as long as the network expansion factor is less than a critical value.