不完全活动的分组交换格点网络模型的行为

Behavior of a Packet-Switched Lattice Network Model with Inactive Sites

针对Overlay分组交换体系结构的拓扑和路由,利用元胞自动机的模型,研究了拓扑结构上微小的不一致性对网络临界流量行为的影响.在早期的拓扑均一的元胞自动机分组交换网络模型中,相变是全局一致发生的,而临界流量和网络自由延迟成反比.而在不完全活动的元胞网络模型中,网络全局临界流量行为随节点活动概率降低而恶化.不活动元胞的存在事实上造成了格点空间上元胞排队状态的分化,这意味着拓扑的不一致性导致网络中某些位置形成固有的薄弱点,相比其它位置更容易陷入拥塞.

Re-considering basic principles of topology and routing is significant to overlay architectures. In this paper, impacts of topological asymmetry to the critical traffic behavior are studied in a Cellular Automata model with inactive cells. Previous approaches showed that phase-transition happened globally in regular Cellular Automata networks and the critical traffic was inversely proportional to the free delay. In the model proposed here, however, the global critical traffic becomes much worse as there are a significant number of inactive sites. The asymmetry in topology differentiates the queuing states of the cells over the lattice space, and therefore, it causes a set of fixed vulnerable points, is much more easier to be congested than elsewhere. For an overlay architecture, improvement of the free delay is significant when the critical traffic achieves the inverse-proportional law, but the topological asymmetry makes it less effective. Fortunately, the observation inspires that the vulnerability of a network can be predicted in order that necessary actions are taken at the vulnerable points on the application leyer.