In computer networks, especially in large-scale local area networks (LANs) or wide area networks (WANs), the management of routers has become increasingly complex. In order to improve the reliability and performance of the network, many mechanisms have been devised to optimize the communication between routers. One of the important concepts is DR (Designated Router) and BDR (Backup Designated Router). This article will introduce you to these two concepts and how they work in networking.
The concept of DR and BDR:
In a large network, there are a large number of routers, and they need to communicate with each other to know the topology and status of the network. However, if all routers communicate with each other, the control information in the network will be overloaded, which will affect the performance of the network. In order to avoid this situation, a routing protocol called OSPF (Open Shortest Path First) was developed, which introduced the concepts of DR and BDR.
DR is a role on a multipoint link (such as Ethernet), and it is responsible for collecting and distributing routing information. The BDR is a backup DR that can seamlessly take over its role in case the primary DR fails. Other routers are called DROTHERs and they communicate with DR and BDR to send routing information to them.
working principle:
When an OSPF network is established, each router is in the DROTHER state by default. As the network grows, they will elect a DR and a BDR. This election process is based on router priority and router ID. The router ID is usually a unique identifier on the router, which can be an IP address.
Once the election is complete, the DR is responsible for collecting routing information from DROTHER and combining this information into a Link State Database (LSDB). Next, the DR sends the summary information of the LSDB to other routers so that they can understand the topology status of the network. The BDR takes over its role when the DR is unavailable to ensure the continuity of the network.
There is also tight synchronization between DR and BDR. If DR fails, BDR will immediately take over its role to avoid data loss. Once the original DR returns to normal, it will resume the role of DR, and the BDR will return to the backup state.
Advantage:
The introduction of DR and BDR brings many advantages, especially in large-scale networks:
Reduced Control Traffic: By allowing only the DR and BDR to communicate with DROTHER, the traffic of control information in the network is reduced, improving overall performance.
High reliability: The backup mechanism of DR and BDR ensures the smooth transition of the network when the main router fails, reducing the possibility of network interruption.
Simplified router management: By communicating with DR and BDR with a limited number of routers, network management becomes simpler and easier to monitor and maintain.
Reduce resource consumption: Since only DR and BDR need to process a large amount of routing information, other DROTHERs consume less resources, enabling routers to use resources more effectively.
In short, in complex computer networks, DR and BDR, as part of the OSPF protocol, play a vital role. They contribute significantly to network performance by reducing control traffic, improving network reliability, simplifying router management, and optimizing resource consumption. By understanding how DR and BDR work, we can better understand the network mechanisms that operate behind the scenes to better design, maintain and manage modern complex networks.