1. Introduction to OSPF
When referring to OSFP, we have to start with RIP. RIP uses the number of hops to calculate the optimal path to the destination network, which is not suitable for practical applications. It is more reasonable to measure network quality by network bandwidth and link delay.
The maximum number of hops supported by RIP is 16, which cannot be used to build a large-scale network. The convergence speed of RIP is slow, and RIP will suppress the information update of unreachable routes, the original route will become invalid, and the new route will not be updated until the suppression time is over.
The update cycle of RIP is long, if a router goes offline suddenly, it will take a long time for other routers to find out.
RIP uses broadcasting to send all routing information. The larger the network scale, the larger the network resources occupied by routing information.
Therefore, RIP routing is not suitable for large-scale networks, and OSPF protocol solves these problems and is widely used.
OSPF is an acronym for Open Shortest Path First, translated as Open Shortest Path First. OSPF is an autonomous system internal routing protocol based on link state (Link State), used to replace the RIP protocol, and the common one is OSPFv2. Unlike distance vector protocols, link state protocols use the shortest path first algorithm (Shortest Path First, SPF) to calculate and select routes. This type of routing protocol is concerned with the status of network links or interfaces, such as up, down, IP address, mask, bandwidth, utilization, and delay. Each router advertises the known link status to other routers, so that each router on the network has the same understanding of the network structure. Then, the router uses the SPF algorithm to calculate and select routes based on this.
The OSPF protocol uses multicast to send protocol packets, saving resources and reducing interference to other network devices.
In short, compared with RIP, the OSPF protocol has greater expansion, fast convergence, safety and reliability, and uses incremental routing updates to ensure routing synchronization and reduce network resources.