A method for implementing external route calculation for router

Abstract

This invention discloses a method for realizing outer route computation of a router which declares an array in the router and sets array items of forwarding-address storing the fifth or the seventh LSA, next hop and route distance route information. If the router needs to compute outer route according to a certain LSA, it looks for the related array items in the array according to the forwarding-address in the said LSA and to get related information from said array directly and compute said outer route if so, otherwise it looks for the related next hop and the route distance information set in the array item and to compute the outer route. It can get the related information only by looking for array with little information to increase efficiency of computing outer routes.

Description

technical field [0001] The present invention relates to a network link state routing protocol (Open Shortest Path First, OSPF), more precisely relates to a method for realizing router external route calculation. Background technique [0002] OSPF is a protocol that uses the link state algorithm (SPF) to select the optimal route. Each router generates link state information around itself to form a link state advertisement (Links State Advertisement, LSA). All LSAs are displayed on the entire network. Each router calculates routing information based on all LSAs it receives. [0003] If an OSPF-based autonomous system needs to be connected to an external routing system, the autonomous system boundary router (ASBR) in the autonomous system needs to import external routes. Specifically, the ASBR in the autonomous system imports routes generated by other protocols in the router. Generate an LSA describing the route from this autonomous system to this external routing system. If ...

AI Technical Summary

Problems solved by technology

[0006] 1) As the network grows, the number of Type 5 or Type 7 LSAs generated by ASBR will become larger and larger, and may even reach as many as hundreds of thousands. Type 5 or Type 7 LSAs that need to be calculated by routers There will also be a lot, and there may be millions of routes in the routing table. Therefore, when a router calculates external routes, it needs to traverse such a complicated routing table to calculate each LSA, and the calculation amount will be very large.

[0007] 2) If it is necessary for the router to recalculate all routes and add the routes to the routing table due to network oscillations, etc., it will take a lot of time. At this time, if there is a message to be forwarded, but there is no corresponding route in the routing table , the message can only be discarded, which affects the forwarding of the message

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