BGP (border gateway protocol) is widely known for some problems in terms of poor reliability, suboptimal path use, and insufficient support for load balancing because it is a single-path routing protocol. Inter-Domain multipath routing explores the underlying network AS-level path diversity to improve the Internet's reliability, performance, and resource utilization. Thus, inter-domain multipath routing is considered a useful and necessary method to address the problems faced by BGP. This paper surveys current proposals on inter-domain multipath routing protocols and classifies these protocols into three categories: Protocols on a single announcement and multipath forwarding, protocols on multiple announcements and multipath forwarding, and new Internet routing architecture based protocols. They are compared under some different features of path diversity, control message overhead, loop-freeness property, etc. In addition to a review of existing protocols, the challenges in designing new inter-domain multipath routing protocols that could be taken as the future research direction are pointed out.%边界网关协议(border gateway protocol,简称BGP)是当前互联网的核心协议,但是由于BGP是一种单路径路由协议,所以仍存在可靠性差、无法有效使用次优路径以及负载均衡支持较弱等问题.域间多路径路由可以通过发挥底层网络的AS级路径多样性,提高域间路由的可靠性、报文分组转发的总体性能和整个网络资源的利用率.因此,域间多路径路由是解决上述BGP问题的一种有效手段,符合互联网应用不断深入、促进路由技术发展的需求.主要综述域间多路径协议,并将其分为3类:单径通告多路转发协议、多径通告多路转发协议和新型域间多路径路由体系结构提出路径多样性、控制平面和数据平面开销、无环路特性等8项主要路由系统性能指标,并比较、分析了域间多路径路由协议.最后,指出域间多路径路由协议面临的主要挑战和未来的研究方向.
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