Design and Implementation of High Availability Routers

• Main Authors: Tsai, Chia-Tai, 蔡嘉泰
• Other Authors: Jan, Rong-Hong
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/29614005655363604028

博士 === 國立交通大學 === 資訊科學與工程研究所 === 99 === How to optimally allocate redundant routers for high availability (HA) networks is a crucial task. In this dissertation, a 5-tuple availability function, A(M, N, λ, μ, δ), is proposed to determine the minimum required number of standby routers to meet the desired availability (ρ) of an HA router, where M and N are the numbers of active routers and standby routers, respectively, and λ, μ, and δ are a single router’s failure rate, repair rate, and failure detection and recovery rate, respectively. We have derived the availability function, and analytical results show that the failure detection and recovery rate (δ) is a key parameter for reducing the minimum required number of standby routers of an HA router. Thus, we also propose a High Availability Management (HAM) middleware, which was designed based on an open architecture specification, called OpenAIS, to achieve the goal of reducing takeover delay (1/δ) by stateful backup. We have implemented an HA Open Shortest Path First (HA-OSPF) router, which consists of two active routers and one standby router, to illustrate the proposed HA router. Experimental results show that the takeover delays of the proposed HA-OSPF router were reduced by 6%, 37.3%, and 98.6% compared to those of the industry standard approaches, the Cisco-ASR 1000 series router, the Juniper MX series router, and the VRRP (Virtual Router Redundancy Protocol) router, respectively. In addition, we have also implemented the HA-OSPF router on an ATCA (Advanced Telecom Computing Architecture) platform, which can provide an industrial standardized modular architecture for an efficient, flexible, and reliable router design. Based on our ATCA-based platform with 1/δ = 217 ms for a software failure and 1/δ = 1066 ms for a hardware failure, along with the router module data, 1/λ = 7 years and 1/μ = 4 hours, obtained from Cisco, the availabilities of the proposed ATCA-based HA-OSPF router are 99.99999905% for a software failure and 99.99999867% for a hardware failure. Therefore, the experimental results have shown that both our proposed ATCA-based and PC-based HA-OSPF routers can easily meet the requirement of carrier-grade availabilities with five-nine. In addition, in contract to the industry routers, the proposed HA router, which was designed based on an open architecture specification, is more cost-effective, and its redundancy model can be more flexibly adjusted.