空间延迟/中断容忍网络的接触图路由研究综述

Survey on Contact Graph Routing for Space Delay/Disruption Tolerant Networks

基于覆盖协议和存储-携带-转发范式的延迟/中断容忍网络(delay/disruption tolerant network,简称DTN)被认为是应对空间环境挑战(如长延迟、间歇性连接等)的有效解决方案.接触图路由(contact graph routing,简称CGR)是一种利用空间DTN网络拓扑的先验知识来计算路径的动态路由算法.首先介绍了CGR的基本原理和算法过程,并给出了相关术语的定义及相应计算公式;然后,从路由环路避免、计算效率、路由准确性、拥塞控制、机会性扩展和异常处理方面总结了现有的CGR改进工作;接下来概述了已经进行的评估DTN协议栈和CGR适用性的代表性实测实验,并通过GEO/MEO/LEO卫星网络仿真实验,对比评估了CGR算法与多层卫星路由算法(multi-layered satellite routing algorithm,简称MLSR)的性能差异;最后给出了CGR的未来发展方向,包括扩展块CGR(CGR-extension block,简称CGR-EB)和缓存CGR(cache-CGR,简称C-CGR)整合、机会CGR、CGR向大型网络的扩展、服务质量保障CGR和接触计划描述方法改进等.

Delay/Disruption Tolerant Networks (DTNs), which are based on an overlay protocol and the store-carry-forward paradigm, are considered as a promising solution to cope with the challenges imposed by space environment, such as long delay, intermittent connectivity, etc. Contact Graph Routing (CGR) is a dynamic routing algorithm which can compute routes by taking advantage of a priori knowledge of the space DTN topology. In this paper, the basic principles and algorithm procedures of the CGR are introduced, and the definitions of the associated terminologies and corresponding formulas are given, firstly. Then, the existing enhancements of the CGR are summarized in terms of routing loops avoidance, computational efficiency, routing accuracy, congestion control, opportunistic extension, and exception handling. Next, the representative real test experiments that have been conducted to evaluate the applicability of the DTN protocol stack and CGR, are outlined, and the performance differences between the CGR algorithm and the multi-layered satellite routing algorithm (MLSR) are evaluated by GEO/MEO/LEO satellite network simulation. Finally, the future developments of CGR are given, including the integration of CGR-extension block (CGR-EB) and cache-CGR (C-CGR), opportunistic CGR, CGR extension to large network, CGR-Quality of service (QoS) provision, enhancement of contact plan description method, etc.