Design And Implementation Of The OSPF Non-Stop-Routing Based On Hot-Stand-by Mechanism

With the development of next generation network, multimedia network services, large customer hotline and the virtual private network, users have a high demand on the network reliability. For this purpose, Non-Stop-Forwarding(NSF) is commonly implemented by most routers.But this implementation has a high requirement on the external environment, and it demands that the neighbor routers should have the capability of Graceful-Restart (GR).For this deficiency, the Non-Stop-Routing technology is designed and implemented in the paper, which depends on hot backup mechanism and has a high reliability. By analysis on backup data and order of OSPF (Open Shortest Path First) protocol, it can be ensured that the slave board can take over the work of the main board seamlessly. It can reduce the period to re-obtain the routing and extend the router's uptime to improve the stability of the network.The underlying implement of OSPF NSR from the backup data and the backup mechanism based on OSPF is discussed. For backing up data, there are five categories of data backup solutions according to the division of OSPF data. These solutions are compared from the feasibility and backup efficiency. Then, a solution with the most accurate data and the best performance is chosen. For the backup mechanism, we propose a new hot standby mechanism, which is on the basis of High Ability (HA) channel.This channel improves the backup performance through the HA state machine and the design of buffer. In addition, we also analyze the difference between the traditional hot standby mechanism and the improved hot standby mechanism. Finally, traditional hot backup mechanism performs better when small amount of data are required to backup,but improved hot backup mechanism performs better when large amount of data are required to backup.Besides, the upper OSPF NSR implementation is discussed, which is based on H3C's COMWARE platform. Based on the analysis of OSPF protocol from configuration, interface, neighbors, LSDB and LSA flooding modules, we propose an improvement scheme to achieve OSPF NSR.OSPF NSR in S7500 and S6800 routers and different performance between the traditional hot standby mechanism and the improved hot standby mechanism are verified in the paper. Finally, we summarize some deficiencies in implementation and the NSR implementation in other router protocols such as BGP and IS-IS.